1.1. General

This is one of a series of cases arising out of the tragic accident on the Piper Alpha oil platform which occurred on the evening of 6 July 1988. As is well known the oil platform in question, located in an oilfield in the North Sea about 110 miles north-east of Aberdeen, was destroyed in an explosive conflagration with considerable loss of life. 166 persons lost their lives as a result of the accident either through being on board the platform or through being involved in rescue operations. Of those killed 159 were British and of the balance only one was an American citizen, he being from Texas. 62 of those aboard the platform survived the accident but many of these suffered varying degrees of injury or trauma. The accident was the worst disaster in the history of the British off-shore oil industry. The pursuers in each of the said cases are Elf Enterprise Caledonia Limited who are the successors to the owners and operators of the platform at the time of the incident. Following upon the accident the families of deceased victims and the survivors combined in various ways to present their claims against the platform operators and in particular they indicated that they were proposing to litigate their claims against the pursuers’ predecessors in Texas. The reason for this selection of Texas as a prospective forum to litigate claims, arising from an event largely involving British victims and occurring in Scottish waters, was that it was conceived that the Texas legal system was materially the most favourable which was potentially available for the pursuit of such claims both in relation to its Jury procedures and in quantification of damages. Negotiations took place throughout the autumn of 1988 between the pursuers’ predecessors and the representatives of the victims’ interests and eventually settlement terms were agreed and then implemented. The validity of the claimants’ assertion that a Texas court would accept jurisdiction in litigating their claims was a critical issue but compromise was reached on the assumption that the level of damages finally offered and accepted represented an approximate mid-point between the assumed Texas level of damages and the assumed Scottish one. This basis of settlement was referred to by the parties as a "mid-Atlantic formula". The relatively prompt settlement of claims is clearly to be applauded on humanitarian grounds but the question of who bears the ultimate responsibility for the monies paid to claimants raises contentious issues which have given rise to the present litigations. The operators of the platform employed a certain number of their own employees but most persons on board the platform at the time of the accident were in fact employees of various contractors who had arrangements with the operators to carry out specialist work tasks. Thus for example drilling, diving and catering work on the platform was conducted on behalf of the operators by specialist contractors. The contractors had each entered into contracts in connection with the work they had to perform and these contracts provided that in certain circumstances the contractors were to indemnify the operating parties in the event that damages had to be paid to those contractors’ employees as a result of incidents occurring while they were working on the platform. At the time of the accident there were 226 persons on board the platform. Of these 165 died and 61 survived. Of the persons who died 31 were employees of the Operators and 134 were employees of one or other of the contractors. There were also two persons killed while working on a rescue craft. Of the survivors 6 were employed by the Operators and 55 employed by contractors. There are 146 actions in the present series of cases and these are each directed against contractors who employed persons killed or injured in the accident and in respect of whom monies have been paid by way of damages and expenses to claimants under the settlement terms to which I have previously alluded. The pursuers claim that the defenders in each case are bound in terms of their contract to indemnify the pursuers for the monies paid out under the settlement. It is claimed by the pursuers that they were bound to compensate the victims or their relatives and that the sums that were payable under each settlement were reasonable. In the actions the pursuers are seeking to recover not only the sums paid to claimants as actual damages but also sums of expenses paid to the claimants in respect of legal expenses said to have been necessarily incurred in pressing home their claims including expenses incurred for representation at the Cullen Inquiry. The defenders for their part deny that they have any liability under the alleged indemnities. This puts in sharp focus the cause of the accident and any attribution of fault therefor. It also raises questions concerning the construction of the indemnity provisions in the contractors’ contracts. There is also a major dispute between the parties about the reasonableness of the damages and expenses paid out to claimants by the 0perators. The defenders contend that the Operators over-estimated the likelihood that a Texas court would have accepted jurisdiction in the cases and in any event that a Jury sitting in Texas would not have awarded (or been allowed to award) the high levels of damages on which the operators based their settlement offer. The level of expenses paid out is also queried. Lastly but not least the defenders advanced an argument that the pursuers had misconceived the present actions for indemnity and that the appropriate procedure following upon the settlement should have been actions by their insurers for contribution. The dispute between the parties in the various actions (which I have merely outlined above) gave rise to a multiplicity of complex questions as the considerable length of the Proof denotes.

At the commencement of the Proof I was informed by Counsel that the 146 actions before the Court largely raised the same questions. It was therefore proposed that seven of the actions which illustrated such differences as there were between the cases should proceed on a test case basis, and that Proof in these actions be conjoined. These seven actions, (which include the present action), were said to focus all the issues which arise in the other actions and I was asked to sist these other actions. Since there were no objections to these proposals I agreed to give effect to them. The seven actions which went to Proof were the cases against London Bridge Engineering Limited (employers of the deceased Robert Carroll), Northern and Industrial & Marine Services Limited (employing the deceased John Duncan), British Telecommunications P.L.C. (employing the deceased Graham Gill Whyte) , Wood Group Engineering Contractors Limited (employing the deceased Michael O’Shea), Eastman Christensen Limited (employing the deceased Neil Pyman), Kelvin International Services Limited (employing the deceased William John Cowie), and Stena Offshore Limited (employing the injured party Andrew Murray Carroll).

1.2 The Parties

The pursuers in all these actions are Elf Enterprise Caledonia Ltd. This company were formerly known inter alios as Occidental Petroleum (Caledonia) Ltd (hereinafter referred to as OPCAL). OPCAL were registered in England and had their principal place of business in London with further places of business in Scotland. In 1988 at the time of the accident OPCAL were the Operators of the Piper Alpha and Claymore oil production platforms as well as the Flotta terminal to which the oil was pumped. In 1988 OPCAL were a member of a large international group of companies known as the Occidental Group. Since the accident OPCAL has been acquired from Occidental by a French company known as Elf Enterprises and this no doubt explains the changes in the name of the company. Before a company can explore for or develop a North Sea oilfield it requires a licence to do so from the Government. By licence no. P220 dated 28 April 1972 the Secretary of State for Trade and Industry granted licence to four companies namely Occidental Petroleum (UK) Ltd. (hereinafter referred to as OPUK), Getty Oil International (England) Ltd., Allied Chemical (Great Britain) Ltd, and Thomson Scottish Associates Ltd. By 1988 the four last mentioned companies had transformed themselves into Texaco, Union Texas Petroleum and Thomson North Sea Ltd. respectively . The said licence was granted to relate to a number of exploration blocks including the block where Piper Alpha was eventually situated, namely the Piper Field. OPUK was another Occidental subsidiary and was a British Company (which attribute was needed to secure a licence). However the company was at that time effectively a nominee for an American company of the Group which provided the finance required. The said American company was Occidental of Britain Ltd. ( hereinafter referred to as OBI). They were registered under the laws of California and had a place of business in London. By a Deed of Variation dated 3 October 1974 Licence no. P220 was restricted to the Piper Field and it was agreed that a licence for the residual fields should be granted to OPCAL (and the three other companies who were licensees under the original licence). Moreover OPCAL and the said three licensee companies were by further licences given permission to lift oil from the Claymore field and from other blocks. All these oil fields were located in the United Kingdom sector of the North Sea in the Scottish area. On 28 July 1982 a further Deed of Variations was entered into by the relevant parties with reference to licence no. P220 with a view to amending certain model clauses. By an agreement dated 1 January 1984 Occidental Petroleum (Great Britain) Ltd., the holding company of OPCAL, sold to OPCAL the share capital of OPUK and indeed on that date OPCAL took over their whole interest in the Piper Field. The effect of a series of arrangements entered into at that time was that OPCAL became the representative of the Occidental interests in the North Sea and in particular acquired Occidental’s rights and liabilities in the Piper Field. On 1 March 1984 OPCAL were named in the licence for the Piper Field in place of OPUK. In 1977 the original four licensees entered into a Joint Venture Operating Agreement (the JVOA) in terms of which OBI were to act as Operators of the Piper Alpha platform on behalf of all the licensees whose respective interests in the operations were also defined. OBI were also "throughput parties" in the original JVOA. Throughput agreements were arrangements which enabled American companies to provide finance to British companies for North Sea oil development and obtain oil income in return. The parties to the JVOA were defined as "Participants". On 1 March 1984 the participants were parties to what is described as a "Novation Agreement" which related to the JVOA and this was made to operate retrospectively from 1 January 1984. In terms of this Novation Agreement OPCAL by agreement with the interested parties took over the former interests under the JVOA of OBI and OPUK and became Operators of the Piper Alpha platform on behalf of the Participants. A similar Joint Operating Agreement had been entered into in 1977 making OPCAL the Operators on behalf of the licensees of Claymore and by a further agreement on 27 July 1986 the effect of this was clarified. By the date of the accident in 1988 the Participants were OPCAL (successors to the original interest of OPUK), Texaco Britain Ltd (successors to the original interest of Getty Oil International (England) Ltd.), Union Texas Petroleum Ltd (successors to the original interest of Allied Chemical (Great Britain) Ltd.), and Thomson North Sea Ltd. (successors to the original interest of Thomson Scottish Associates Ltd.). Since the disaster Thomson North Sea Ltd have been taken over to become Lasmo (TNS) Ltd. At the date of the accident the said four Participants jointly owned the Piper Alpha platform as well as their joint interest in the licence and oil concession. Their respective shares in the Piper Alpha operations were as follows; OPCAL’s share was 36.5%, Texaco’s share was 23.5%, Union Texas Petroleum’s share was 20%, and Thomson’s share was 20%. In effect in operating the platform OPCAL were acting as agents for the other three Participants as well as looking after their own interest in the operations. In terms of the JOAV they had authority on behalf of the Participants to enter into such contracts as were necessary for the operations. Provision was made for the way in which the operations were to be supervised. Each participant had a right to its participation percentage of the petroleum recovered and the costs and expenses of the operations were to be borne by the participants on the basis of these percentages. The liabilities of the Participants were declared by the JOAV to be several and not joint. It was further declared that there was no intention to create a partnership. English law was to apply to the Agreement and there was an agreement to submit to the English Courts. In relation to the Piper Alpha platform the Operators had authority to enter into the relevant contracts on behalf of all the Participants but a requisite of approval was reserved for contracts of value over £5 million. There was a lack of precision in the evidence as to when the relevant platforms came on stream and began producing but Piper Alpha was certainly in production by the end of 1976 and Claymore by the end of 1977.

OPCAL pursues each of the actions on its own behalf and on behalf of the other Participants. They do this in terms of a contract entered into between the Participants in l987 which is governed by the law of Scotland and which provides that OPCAL as Operators should pursue all claims under the relevant indemnities on behalf of all the Participants. The respective claim of each Participant to any indemnity monies recovered is to be determined by their said participation percentage. The defenders are each contractors who at the time of the accident were employing a particular victim in respect of which a claim under the indemnities is made.

1.3 The Operations

By July 1988 when the accident happened OPCAL had developed important interests in the North Sea. They had discovered two major Oilfields, built the platforms needed to support them (Piper Alpha and Claymore), and constructed the necessary pipelines to the shore. OPCAL had a terminal in the Orkney Islands namely the Flotta Terminal. They had extensive related offices at Aberdeen, a warehouse facility at Peterhead and a helicopter facility at Aberdeen Airport. When I come to consider the Contracts entered into with the Contractors, it will be seen that there are references to "Operations envisaged herein" and the significance of the operations which I have just described derives from the defenders’ submissions that these are the backbone of the operations which OPCAL were conducting at the time when they entered into these contracts. These operations are to be distinguished from the contractual responsibilities of the contractors which are described as the "Work" and are detailed in the contracts as the "workscope". It is interesting to note that Mr Joseph Snape occupied a function until shortly before the accident which could generally be described as Managing Director of OPCAL (although it was designated by a variety of descriptions) and when he gave his evidence he did not list the sale of oil as being part of OPCAL’s North Sea operations. This may be significant when I come to consider the question of Texas jurisdiction. The outline of the management structure on Piper Alpha is set out in number 13/62 of process. In this production the references to "operations" have a more generalised meaning and refer to the production processes on the Piper Alpha platform. In effect the personnel who are described as production personnel operate the process and ensure that the oil and gas flow. Thus a person in the Divers section would not be considered as being part of the operations team. On the other hand the defenders contend, and I think that they are right, that on the platform everyone working there is ultimately responsible to an OPCAL supervisor. The Offshore Installation Manager (OIM) is the person in overall control of the platform. In respect of the Maintenance of equipment the hierarchy is the Superintendent, Deputy Maintenance Superintendent, and Lead Maintenance Hand. The technicians below the Lead Maintenance Hand are the Maintenance Technicians and other relevant personnel such as electricians. For Safety there is a Safety Supervisor, a Lead Safety Officer (vacant when the accident occurred), OPCAL’s safety operators and the Contractor’s Safety Operators. The most significant personnel are of course the Production personnel for apart from safety they would take over if anything went wrong. Moreover they were OPCAL’s own employees. Under the OIM there was an Operations Superintendent, a Deputy Operations Superintendent, Lead Production Operators, and the actual Operators. Of course there were also many employees of the various contractors on the platform but subject to the overall supervision of the permanent production staff. In fact there was no dispute that OPCAL’s management and staff structures affecting Piper Alpha were as set out in numbers 13/62 and 12/ 209 of process. As Mr Snape observed "This was our business, we take the oil out and export it". Ancillary services were generally provided by contractors brought on to the platform.

With regard to the management structure it can be seen that OPCAL had a Chairman and Chief Executive Officer. At the time of the accident this post was held by Mr Brading. He was based in London and had wider responsibilities than just OPCAL’s North Sea Operations. He was not a full time executive officer of OPCAL and the most senior full time executive manager until very shortly before the accident was Mr Snape. In fact he had been replaced by a Mr Schultz just before the accident. He had been, before being transferred to another post in the Occidental Group about 1 July 1988, the person in charge of the production of oil and exploration. In that regard he also had the ultimate responsibility for health and safety. In the management structure certain posts are identified as "senior management" and others as "line management". The company’s safety procedures were set out in a document described as the General Safety Procedures Manual (number 12/405 of process). There was some discussion in the evidence as to the provenance of this Manual but I think it was accepted that insofar as the accident goes it was a safety manual regulating the relevant procedures at the time of the accident. This manual provides Under the heading "Safety Meetings" that meetings of Senior Management shall be held at least quarterly to discuss matters relating to safety performance. The President and Managing Director (the post occupied by Mr Snape) was to chair these meetings. The concept of "senior management" appeared to have been relatively fluid but for the purposes of the said meeting it certainly extended to cover Mr Gordon, the Loss Prevention Manager. It would seem that the OIM did not generally attend these meetings. It was policy to keep safety distinct from operations. The Manual also provides that each line manager is responsible for identifying the statutory health and safety requirements relevant to his operations and to ensure that activities under his control are conducted in accordance with these requirements. Included in the line managers’ responsibilities are control and direction over all operations within their jurisdiction, to ensure adequate measures for the safety of all personnel including those of Occidental, contractors and visitors, and the reliability of operations. In terms of the Manual another responsibility of line management was declared to be the "Developing and maintaining adequate procedures for the safe control of operations, and monitoring their effectiveness in preventing injury and loss". A booklet on safety was allegedly issued to those coming onto the platform but just how effective it was in content is difficult to say.

Mr Snape’s evidence was that line management would start with him. It would run through the Vice President of Operations and insofar as relating to production operations , down to the Production and Pipeline Manager and then the Production and Pipelines Superintendent. From there the line would descend to the OIM and then down their chain of management. Apart from Production the line would go to the Drilling Manager for Drilling and to the Marine Operations Manager for Diving operations just to give two examples as to how line management might diverge. The Flotta terminal had its own manager. In Production, line management stops before the production operators. The same would apply to the Maintenance technicians. These groups had nobody to manage. The witnesses Todd and Sneddon (who were Maintenance Superintendent and Operations Superintendent respectively) indicated in evidence that they had never been instructed to monitor the permit to work system that was the safety control procedure. This may or may not be accurate because each of these men would presumably not be anxious to adopt a position where there might be an attempt to saddle them with responsibility for any deficiencies in the permit to work procedures. In any event clearly they each had responsibilities for the permits to work and the reference to monitoring is simply a requirement to take reasonable steps to check the system from time to time and see that it is working properly. It would be surprising if persons at their levels did not know that this would be part of their responsibility. It was of course claimed by the defenders that there was a flagrant and continuing failure to monitor the permit to work system and I shall deal with this later.

There was no doubt that OPCAL were in control of the platform and its operations and thus were deemed to be the owners of the platform under the Mineral Workings (Offshore Installations) Act 1971. Moreover the management and control which OPCAL had of the platform was direct. Ownership of the platform in the statutory sense which is different from ownership of a concession to work the oil as the participants had. Indeed OPCAL were also concession owners. OPCAL as the deemed owner of the platform and also as the actual Operators had statutory obligations for safety. This is a heavy responsibility for it is plain beyond doubt that an Oil Platform is a dangerous place unless careful and proper safety precautions are taken. The platform holds contained under pressure large quantities of gas and liquid hydrocarbon material which is explosive, very flammable and most dangerous if control of it is lost. Mr Snape described the operations as being "potentially hazardous". This was well recognised before the accident. The said Act provides that the platform shall be under the charge of an Offshore Installation Manager appointed by the owner. He had the overall right to regulate the platform just as a Master controls his ship. He has statutory authority over persons on the platform in connection with matters connected with safety, health, or welfare. Under section 5(4) of the said Act it is an offence not to obey the lawful command of an OIM. He also has the duty not to permit the installation to be used in any manner which would endanger the installation and the owner of the installation has a duty to ensure that he complies with this obligation.

The Offshore Installations (Operational Safety, Health and Welfare) Regulations 1976 were enacted in terms of the Act. Under Regulation 32(1) the owner, the concession owner, and the OIM have duties to ensure that the provisions of the regulations are complied with. Regulation 32(2) lays duties on employers and employees in relation to work on or near an offshore installation to ensure that the employee complies with the Regulations insofar as they impose a duty on him or expressly prohibit a specified act. In the case of a contractor he, of course, under this scheme only incurs liability for the activities of his own employee. The Operators on the other hand have a comprehensive duty to see that the regulations are observed. The contractors it should be noted are obliged to insure in respect of their own interest. Regulation 32(3)(a) provides that it shall be the duty of every person on or near an offshore installation not to do anything likely to endanger the safety or health of himself or other persons or to render any equipment unsafe. The defenders made a point extremely important to their case to the effect that the pursuers have no possibility of invoking that regulation unless the cause of the accident is established. Regulation 5 imposes a duty of general maintenance of equipment on the operator. If a flange had not been fitted properly there could be a breach of this regulation. The defenders submitted that if the only source of the defenders’ liability was a res ipsa loquitor situation that would not establish a breach of the Regulations. I think this is probably right. Regulation 30 provides that the OIM shall appoint a sufficient number of competent persons to be responsible for the control and safety of certain specified matters which are essentially matters likely to create dangers. Regulation 3 provides specifically for work permits. Essentially the provision requires that persons doing certain work shall require written permission from a person responsible for the work. In the Operators’ permit to work system it is clear that the designated authority (who issues the permit) is the person authorised to grant permits. As we shall see the designated authority was the Lead Production Operator. Regulation 30(2) provides checks to ensure that those carrying out certain work are themselves competent or closely supervised. Thus the OIM has the ultimate responsibility for safety on the platform and he exercises his function by delegating to competent persons.

In practice the platform was under the direct control of the OIM. There was only one OIM on the platform at a time so that if for any reason he was not available his responsibilities would devolve upon the Operations Superintendent. The Operations Superintendent reports to the OIM and is responsible for the safe production of oil and gas on the platform. This of course involved the responsibility of seeing that personnel were doing their jobs safely and properly. However the persons who had immediate and direct responsibility for supervising the production process were the Lead Production Operators. The Lead Production Operator in charge of production on the night of the accident was Robert Vernon and although he had recourse to senior managers if required he had to make the immediate decisions about the production process. Thus although he had immediate control when he was on duty he was just one in the ranks of line management. The defenders attempted to make much of Mr Vernon’s responsibilities and contended that Mr Vernon was the person who effectively represented the company in respect of the running of the process at the time of the accident. He certainly was the person "with hands on the job" at the time. As Mr Snape said "the supervisor and the designated authority is the one in overall control of what is going on in the operation". The Lead Production Operator could in an emergency shut down the plant and indeed even the Control Room Operator had an Emergency Shut Down button that he could use if necessary. Indeed after the explosion, the Control Room Operator, Mr Bollands, pressed this shut down button. However the shutting down of process was expensive and involved various subsequent problems so that it would not be done lightly.

In the light of the foregoing Mr Snape maintained that it was essentially the operations staff who caused the platform to function and everyone else was really there for support. Mr Snape also said that a function of the Permit to Work procedures was to ensure that a designated authority coming on duty was made aware of what had been happening on the previous shift. In respect of the specialist contractors the designated authority would still have the responsibility in a general sense for monitoring and supervising them and keeping them informed of the workload. The OPCAL safety personnel also monitor the contractors’ activities.

OPCAL engaged contractors upon contractual terms that obliged the contractors’ employees to comply with the requirements of the OPCAL’s Operations Manual. The contractors employees were also bound to observe the requirements of OPCAL’s General Safety Procedures Manual and of course as we have seen this incorporated the procedures for the Permit to Work system. OPCAL retained the right to stipulate not only which work was to be performed by the contractors’ employees but also how such work was to be performed. The Operators retain an ultimate control over the personnel the contractors may use and they could remove such personnel. The details of the work to be performed were set out in Schedules attached to the contracts. Indeed the work was most closely specified. The times to be worked by contractor’s personnel are specified as are provisions for overtime. The contracts provide that the work of the contractors shall be subject to inspection and approval by the Operators. The contractors are to provide competent and skilled personnel. The form of the Contract in the case against BT was somewhat distinctive but the contracts in the other cases illustrate the points I have been making. The point that the defenders were at pains to emphasise was that in the contracts there was a clear distinction between the Operator’s operations and the carefully defined workscopes which delineate the work the contractor has to perform. Although the Score contract is not one of these in the seven indemnity cases dealt with in the proof it is obviously a significant contract since it sets out the obligations Score had undertaken in respect of valve maintenance. Score of course were specialist contractors. The Contract was produced and is Number 12/366 of process. In paragraph 3 of page 3 of 9 in the first section of the contract there is a heading "Scope of Work". It is there declared that the work involves inspection, refurbishment, testing and re-certification at any part of the OPCAL operations which are both onshore and offshore. There is therefore a specific distinction made in the contract between "operations" and "work". The contract also provided that Score’s labour force and valve crew shall be responsible to OPCAL’s Maintenance Superintendent on-board Piper. It has to be noted that until the day before the accident the Maintenance Superintendent had been Mr Todd. He was due to be replaced by Mr Barry Clark but it seems that for some unknown reason Mr Clark did not arrive on the platform. On the other hand the Maintenance Superintendent had a deputy. OPCAL had once again reserved for themselves the right to supervise and control the work. They specified that the contractors’ employees attained a reasonable standard of competence and reserved the right to have anyone who was not competent removed. The scheme is clearly that the contractors are responsible for the proper carrying out of the work but their work is subject to overall control and inspection by OPCAL.

It has to be noticed that given the considerable standards expected by the Contract in respect of their work there seems no doubt that in general Score worked to a reasonable standard. They had been on the platform for valve maintenance work during March, June, and July 1988. Their work during that time was wholly acceptable to OPCAL’s Maintenance Superintendent, Mr Todd. During the periods in question Mr Rankin and Mr Sutton had been on the platform for Score acting as valve fitters.

As well as a safety Manual OPCAL had a Operations Manual (number 12/3 of process) and this had been revised as at February 1986. The purpose of this manual was to provide guidance for operators in the field in respect of the equipment and its operation. The Engineering Department also used it as a reference document. It was divided into 9 sections namely Platform Construction, Platform Loads, System Description, Procedures, Drilling, Diving, Safety Equipment, Communications and Miscellaneous. The document contains much detailed information about fire and gas detection and also hazard classification. Obviously practice and procedures developed because I heard evidence of approved practices that were not in strict accordance with the Manual.

The General Safety Procedures Manual had been introduced in October 1987 (number 12/405 of process) to supersede a 1982 Manual. It dealt with the institution, monitoring and control of safety policy for offshore operations as well as details for personnel safety, safe operational procedures, control of maintenance procedures and the control and use of hazardous substances. There was also a statement of OPCAL’s Health and Safety policy. Some aspects of the 1982 Manual continued in force such as the arrangements for safety auditing which were not repeated in 1987. As has been noted already this Manual deals among many other matters with the Permit to Work procedures. The Manual confirms that OPCAL at least aspired to maintain a tight control over anything that happened on the platform that might affect safety.

The defenders asked me to make findings in terms of a summary they gave me and given that the matters that concerned them seem perfectly clear it may be helpful to summarise certain of the findings that I can make in respect of this chapter. First, the Piper Alpha platform was placed in the North Sea in order to take hydrocarbon mixture from beneath the sea-bed, process it and export it. Second, the operations performed on the platform were inherently dangerous and hazardous. Third, the Piper Alpha platform was at all material times operated by OPCAL. Fourth, OPCAL were the deemed owners of the platform in terms of the Mineral Workings (Offshore Installations) Act 1971. Fifth, OPCAL in their capacity as Operators, had the management and control of the platform. Sixth, the core process of making oil and gas flow was performed by OPCAL’s Operations Group. Seventh, while the Operations Group were the ones operating the platform others were required for the support functions. OPCAL relied mostly on the employees of contractors for these support functions. Eighth, OPCAL engaged contractors upon a basis that entitled OPCAL to stipulate not only what jobs were to be performed by the contractor but how such jobs were to be performed. Ninth, OPCAL engaged such contractors upon a basis that entitled OPCAL to impose such supervision and guidance of a contractor’s work as it saw fit to furnish. Tenth, OPCAL had direct management supervision of all work performed on the platform whether performed by their own employees or contractor’s employees. Eleventh, all personnel on the platform, whether OPCAL’s employees or contractors’ employees, were bound to perform work in accordance with the OPCAL’s Operations Manual under the OPCAL General Safety Procedures Manual. Twelfth, all personnel on the platform, whether OPCAL’s employees or contractor’s employees were bound to perform all their work on the platform under regulation by OPCAL’s Permit to Work system which gave OPCAL control of any task which they regarded as other than routine and non-hazardous. I do not regard any of these findings as difficult to make.

As is generally well known shortly after the Piper Alpha disaster a Public Inquiry was held by the Honourable Lord Cullen. This began at Aberdeen on 19 January 1989 and the evidence at the inquiry lasted 125 days. Some of the contractors who are defenders in the present seven test actions were represented at the inquiry for their interests. I was told in evidence by Mr George Smith that the inquiry was in two parts and that in part one the circumstances surrounding the accident were investigated whereas part two was concerned with recommendations as to possible future safety measures. From time to time during the Proof before me the evidence of a witness was tested by his being asked if he has told the same story in evidence at the Inquiry. However I was not shown the final Report nor told of its conclusions. Thus except in a very general sense I am not aware of Lord Cullen’s conclusions. Nor am I aware of the basis of his analysis of the incident. Except for a few matters of detail I do not know the evidence which was before the Cullen inquiry but clearly the present proof was differently focused and more extensive in scope. Certainly there were witnesses in this case who did not appear at the Cullen Inquiry and others who had reviewed their positions since the Inquiry. The findings of Lord Cullen’s inquiry did not enter into my own consideration of the circumstances of the accident and I am not aware of the extent by which my own findings may coincide with or differ from Lord Cullen’s views. I mention this because the findings of the Cullen Inquiry aroused much interest when they were first published so that it may be important to emphasise that this Opinion is not in any sense a review of these findings.

The structure of the Piper Alpha platform was relatively complex. Detailed evidence of it was given by the pursuers’ witness, Mr Konrad Wottge, (whose evidence lasted 18 days) and apart from certain limited areas his evidence was unchallenged. At the time of giving his evidence Mr Wottge was Vice-President operations for Occidental Columbia which job involved responsibility for the production operations of that company in Columbia. He had been transferred to Columbia from Aberdeen in 1991 until which time he had been in the employment of Occidental International & Production Company as a facility engineer. Much of his work was connected with the operations of OPCAL. He held a B.Sc. in civil engineering and also had other professional qualifications in engineering. He had spent all his working life as an engineer in the oil industry (working on - and offshore in a variety of countries) and I was impressed by the high level of his practical knowledge of his area of expertise. He came to work in the North Sea in 1976 and was assigned to work with OPCAL. His position eventually was that of Facilities Engineering Manager and that was the position he enjoyed at the time of the accident in 1988. His responsibilities included all plant and pipelines downstream of the wellhead. It included the overall structure of the platforms and the network of pipelines. He was also responsible for the Flotta Terminal facility. Originally he had visited the Piper Alpha platform frequently, sometimes spending weeks aboard, but as his responsibilities developed he would visit the platform about once every two months. Initially the plant on Piper Alpha had experienced certain operational problems and Mr Wottge had been involved in sorting these out. He had prepared a Report and Glossary (number 12/1 of process) which he spoke to in his evidence. He also illustrated his evidence with a number of detailed drawings and schematics. The schematics were prepared under Mr Wottge’s direction. He claimed that his Report represented a general description of the design and operation of the Piper platform and associated pipelines and I think this contention was on the whole well justified. He also spoke to the Piper Alpha Operations Manual (number 12/3 of process ). This was issued to persons who had been working on the platform to give them operational instructions how to operate the individual items of equipment including data on the relevant structures of the platform. His evidence was also illustrated by two models which were in court, by photographs of the original model and by photographs of the platform (12/8 of process). Mr Wottge spoke to the general accuracy of the models (although they could show nothing like all the detail on the platform) and they were used to give a picture of the general features of areas of the platform for experiments carried out by the pursuers’ experts. The original model had been built for various practical purposes like training operators but once the platform was running it was donated to Aberdeen University. After the disaster it was retrieved and formed the basis of the models in court (12/6 and 12/7 of process) although these did not contain as much fine detail as the original. The scale of the model is 1 to 33. A further model in court of the whole platform (12/5 of process) is 1 to 100 scale. Photographs numbers 69/1 and 69/2 of process also show certain details of the original model and were relied upon by Mr Wottge but have to be regarded with a degree of care since they became inaccurate in certain minor respects as the modules were developed. However they show that there was much more pipework in the Modules than the reconstructed models show. In fact I found the models in court were useful for illustrative purposes in relation to evidence being given but not much else. However Dr Davies used the models for his experiments but in any event I think his results were intended to be no more than approximate. Certainly at best that is how I would have regarded them. The photographs 69/1 and 69/2 were not in court when Mr Wottge gave his evidence (and the remaining photographs of the original model were never produced). Therefore he could not be examined about them but I do not think this could bear on the outcome of the proof. It should also be noted that the defenders did not seek to recover documents relating to the structure of the platform or models from the pursuers. Since photographs of the platform (number 12/8 of process) were taken at different dates they too have to be regarded with some care. At best the problems about models and photographs concern matters of detail since witnesses who had been working on the platform at the time of the accident seemed happy to accept them as being representative of what they were describing. Occasionally when a witness thought that matters had changed since a photograph he said so.

In his evidence Mr Wottge relied on a number technical drawings and reports. A point was made that he was not always asked to identify the sources of particular passages in his report. It is possible that he had relied upon documents not lodged in the proof. This was said to cast a degree of shadow over his reliability. However considering that the platform was an immensely complicated structure and that Mr Wottge was in the witness box for many weeks I do not think the pursuers could have expected him to consider every detail in the report comprehensively. The defenders had ample opportunity to challenge him about any detail that concerned them. He was very familiar with the general structure of the platform and had obviously compiled his Report with care. A substantial number of documents of a technical nature were lodged in process. The defenders say that a drawing only has evidential value if it reflects accurately the position on the platform at the time of the accident. That statement is probably unexceptional. The defenders contended that insofar as some of these documents were copies they could have been authenticated under Section 6 of the Civil Evidence (Scotland) Act 1988. This was not done. However I am happy to accept that in compiling his Report Mr Wottge relied wholly or largely on technical Documents which formed part of the Company’s general records. If the defenders thought that he may not have done so they were of course free to examine him in detail about this. In any event most of these technical documents only had illustrative significance.

The defenders made the point that some of the documents produced do not accurately represent the position on the platform. Equipment can be built and then modified rendering original drawings inaccurate. However such inaccuracies on the whole relate to points of detail. Thus production 12/83 purports to be a representation of the B/C firewall. On this there is a representation of a sliding door and in fact there was a hinged door on the actual wall. In some of the drawings relating to fire detectors the location of these had been in error as to the heights of the detectors since on many occasions their position had been adjusted. The defenders pointed out that drawings marked "as built" had more authority than others because they represented the final drawing of the structure after it had been built. It was suggested that very few of the documents produced were marked "as built". For example in relation to the B/C firewall all that was produced was a design drawing, which may have been modified during construction, and not an "as built" drawing. Mr Wottge accepted that even the "as built" documents were not all wholly accurate. The ongoing process of modification, addition, and removal which continued to the date of the accident was not always reflected on the Drawings produced. However Mr Wottge indicated that what he described as "key drawings" were generally kept up-to-date. Drawings were from time to time reviewed for the purposes of structural certification which occurred every five years. It should perhaps be noted that Mr Wottge indicated that he was not aware of any significant changes in the flooring of the Modules having occurred although there was localised strengthening. Nor was he aware of the ceilings being altered. Some of the drawings produced were made after the accident on Mr Wottge’s instructions. The pursuers had a difficult task in respect of proving the detail of the structures on the platform. The platform itself was not available for checking . Some of the records had gone to the bottom of the sea. This the defenders argued just emphasises the uncertainty hanging over the pursuers’ attempt to prove the cause of this terrible accident. What they presented seemed to me on the whole to be the best available evidence of the platform’s structure. Insofar as details may have been doubtful the witnesses speaking to the matters in question were largely able to point these out if they were significant. It should be noted that Mr Wottge claimed that many of the documents produced were used by him as the basis of his work. For example through his work he was very familiar with Module C but if he required detail such as measurements he would often take these from the available documents.

I considered that I was provided with reasonably satisfactory material as to the structure of the platform subject of course to consideration of particular points which the defenders asked me to consider especially and claimed to be significant.

In general I found Mr Wottge to be a very informative witness whose views were worthy of respect. He had a sound personal recollection of the basic structure of the platform and personal knowledge of many of the details. However for some details he had to avail himself of the recorded material available to him after the accident. He had some experience of the production processes but his experience was less extensive than in regard to structural matters. His knowledge of alarms, process controls and trips was also limited.

I was provided with an extensive book of Schematics. I accept that these are only of evidential interest insofar as they are spoken to by witnesses familiar with their contents. They were really lodged to help illustrate the technical evidence. They of course are not to scale and on occasions witnesses pointed out inaccuracies.

The Tartan Field was discovered in 1972 or early 1973 and following thereon the platform was designed and built. The oilfield operated under Licence Block 15/17. The constituent parts of the platform and, in particular, the jacket, deck support frame, and modules were built onshore and later shipped to location on the field. Over the years the platform was changed and modified. By the end of 1980 a Gas Conservation Module had been installed and was in operation. The field was highly productive. Initially the field produced 250,000 barrels of oil per day and that increased to 300,000 barrels during the early years of production. However by July 1988 the production had declined to about 125,000 barrels per day. To accommodate the production from the field Occidental built a pipeline to Flotta on Orkney and installed a process plant there.

The Claymore field was discovered approximately one year after the Piper Field and operated under Licence Block 14/19. The Claymore platform was developed and the field came onstream about November 1977. Oil produced by this field was also exported to the Flotta facility by means of a short pipeline which linked into the pipeline from Piper Alpha to the Flotta Terminal.

The discovery of the Tartan Field post-dated the discovery of the Claymore field. A platform was built which was owned and operated by Texaco North Sea Limited and this came onstream about 1979.

Two years after the Piper Field the Frigg gas field was discovered. Gas produced from this field was exported to the shore through a pipeline and a booster platform known as the Manifold Compression Platform number 1 (otherwise known as MCPO 1). MCPO 1 was operated by Total Oil Marine. The gas produced by both the Piper and the Tartan platforms was also exported ashore by way of MCPO 1.

Subsequently to the discovery of the Claymore field a small field know as the Scapa field was discovered about 7 miles from Claymore. This was exploited by means of a sub-sea production facility. This facility was controlled from the Claymore platform and the oil production from the Scapa field was piped via the Claymore platform to the main oil line and subsequently to Flotta.

The Piper oilfield is situated about 120 miles north-east of Aberdeen. It has an oil reservoir situated about 8,000 feet below the sea level and the water depth at the location is 474 feet. The reservoir covers an area of approximately 12 square miles. The natural pressure of the reservoir is about 3,400 lbs per square inch absolute (psia). The design criterion for production was for a total of 36 wells.

The platform was orientated 43 degrees counter-clockwise from true north so as to coincide with the direction of the most severe wave loading. The longitudinal axis was referred to as "platform north" and other directions referred to in the productions such as east, west, and south are with reference to platform north.

The platform was anchored to the seabed by each of its four corner legs. Around each corner leg was a skirt pile driven into the seabed. The sub-structure from the sea-bed to the surface of the water and up to the 20-foot level was known as the jacket. The deck support frame was attached to the jacket and its purpose was to provide a frame structure to support the deck and the various deck modules that had to be installed. The top part of the deck support frame was known as the 68-foot level (such levels referring to levels above the sea.)

The 84-foot level consisted of four modules A, B ,C, and D. A, B, and C were the main production modules. Module D was the generation and utilities module. These modules as with other structural equipment had all been fabricated onshore.

The next main level up was the 107-foot level which housed inter alia the Mud Module and Storage Module on the west, and the Gas Conservation Module (also known as the G CM or Phase 2 Module) and Utilities module on the east. The 133-foot level contained the pipe deck and the 174-foot level the helideck. The accommodation modules were at the north end of the platform and were at levels ranging from 121 feet to 174 feet.

There were ten jacket legs. On the east side they were numbered from north to south as A1 through to A5. On the north side the legs were numbered from south to north as B1 through to B5.

2.5.1 The West

The west face of the platform is shown in the drawing 12/18 of process and in various aspects in the photographs which are 12/8D, 12/8E, 12/ 8F, 12/8G and 12/8L of process. The western ends of Modules A, B, and C were open. In the said photographs the west crane pedestal is shown at the join of Modules B and C. The Chanter Riser gantry is shown in the photograph 12/8L. The west face of the Dive Package which was mainly at the 64-foot level, substantially below Module B, is also shown in these photographs.

2.5.2 The North

The north face is shown in the drawing 12/15 of process and in the photographs 12/8B and 12/8C of process. The said drawing shows the main oil and gas risers which carried the oil from Piper Alpha to Flotta and other platforms . The 30 inch diameter oil export riser is approximately at the centre of the north face. The 16 inch diameter Claymore Gas Riser is to the west of this and formed part of the gas pipeline linking Piper Alpha and Claymore. At the north west corner of the platform was a Navigational Aid Platform from which point a number of men were able to escape the platform after the accident. The photographs 12/8B and 12/C also show the turbine exhausts of the John Brown Turbines. The orange cabin seen on the north face in photograph 12/E was the Maintenance Superintendent’s office.

2.5.3 The East

As with the western ends the eastern ends of Modules A, B, and C were open on the east face. The crane pedestal on the east is again at the point where Module B joins Module C. The photographs 12/8H and 12/8I of process show the east face and the GCM can be seen above Modules B and C at the 107-foot level. The utility module is adjacent to the GCM to the north. Stairways linked the 107-foot level down past the east face of Module B and down to the 68-foot level. On the east face and to the left was sub-Module D.

2.5.4 The South

The South face elevation of the platform is shown in the drawing which is 12/16 of process whereas the relevant photographs are 12/8C and 12/8 D. The south face is dominated by the east and west flare booms. There is in consequence of these a heat shield on the east, west, and south sides of Module A. The precise location of this is shown on the drawing 12/16 of process. The flare booms were each about 165 feet in length and it was necessary to have two to accommodate changes in wind direction. Each flare boom had two flare tips. Low pressure material flared through the low pressure flare and gasses from high pressure sources flared through the high pressure flare. When passing relatively high rates of gas the flare made a noise and would get bigger. Even in normal operation there would be some variation of flare. When the process was in Phase 1 a greater amount of gas went to flare than was the case with the Phase 2 process. There was a stairway immediately inside the heatshield to the south side of Module A linking the 84-foot level to the 107-foot level. This stairway was about I metre out from the module and there were some structural members between it and the module. Furthermore there were Navigational Aid Platforms at the east and west of the south elevation and particularly the west of these played a part in permitting some men to escape the conflagration.

2.6.1 General Description

The overall layout of the production level ( the 84-foot level) is set-out in the layout drawing 12/108 of process. Since Module A was considered to be the most hazardous module the production modules on the platform were arranged to provide maximum separation between Module A containing the wellheads and Module D containing various utilities and also separation from the Accommodation Modules. Modules A, B, C, and D, were each divided by firewalls referred to respectively as the A/B, B/C, and C/D firewalls and were really set in sequence according to the supposed level of hazard in each. Mr Wottge indicated that gas leaks did from time to time occur in Module C but he said that most of these were very small. The position of any leaks that were not small was not explored. Thus for example I do not know if any previous leaks had given rise to an escape of gas such as could have caused a serious explosion or indeed how and when the leaks had been noted. He gave some examples of situations that could feasibly cause a leak and these included faulty pump seals, valve stem leakage, gasketed joints, leaks at sampling points, operations which breach containment, effects from corrosive fluids, and loose connections at the pulsation dampeners. The potentiality of such leaks was not really explored with Mr Wottge. Nor was he asked if the detection arrangements were such that he would have expected any such leak to be detected. He did not say that leaks had occurred that were not detected until the gas reached dangerous levels. Mr Wottge also indicated that the frequency of recorded leaks in Module C was higher than in B. Thus although Module B had a higher hydrocarbon inventory than C in general there was less chance of it leaking. Of course in Module C there was much more pipework and vibration. It seems that on one occasion there was a serious oil leak on the Claymore platform due to an unexplained failure of a pipe but what this involved and how it was detected are facts that were not explored.

Module A was the wellhead module and that was where the wellheads controlled the flow of hydrocarbons and water produced from the wells. Module B was a production module where inter alia the separation of oil from other fluids took place and where the oil was pumped into the main oil line (the MOL) for transmission onshore. Module C was the gas compression module where some of the gas processing took place. Module D was the generation and utilities module and contained the Control Building, the main generators, the switchgear and other utility systems.

The open ends of Modules A, B, and C, allowed access to personnel and also natural ventilation. The south face of Module A was also open. The east and eastern half of the north face of Module D were also open and this can be seen in the photograph 12/8E of process.

Each module was approximately the same dimension namely 50 feet (15 metres) wide, 24 feet (7.5 metres) high and 150 feet (46 metres) long. The decks and ceilings of Module B were of three-eighths of an inch steel plate throughout. The ceiling of Module C was likewise plated throughout and the deck from the west side to the skids on which the centrifugal compressor stood at the east end of the module. Between the skids in the modules at a height of about 18 inches above the deck floor were walkways consisting of grating and these were to enable personnel to walk between various pieces of equipment. One witness described this as a labyrinth of gratings. There were various estimates by witnesses of the height of grating above the deck but 18 inches to 2 feet seems to represent a fair consensus. In Module B the grating ran throughout the module so that personnel would be walking on grating rather than deck. In relation to Module C there was a considerable amount of grating.

The witness Mr Henderson thought that in the area of the compressors there was also some solid plating above the deck. He observed that there was a considerable amount of cabling underneath the grating. However on this matter I found Mr Henderson rather imprecise and not wholly consistent. The witness Mr Ferguson contradicted Mr Henderson and was firm in recalling that the walkways in Module C were grating. His evidence was not challenged. Certainly on the basis of Mr Wottge’s evidence there was grating on the outside platform adjacent to Module C. This matter of grating could have some bearing on the manner of response of certain detectors. There does not appear to have been a walkway down the south side of Module C. This may be significant because the expert Mr Cubbage bases some of his calculations on the assumption that there was such a walkway.

The floors of Modules B and C were of steel plating and were of substantial construction in order to hold the weight of the heavy equipment that was placed on them. The ceilings of the modules were also made of steel and of substantial construction to hold the weight of any equipment placed on top.

A walkway ran along the west side of the 84-foot level outside Modules A, B, C and D and this passed around the crane pedestal. This walkway passed outboard of the crane pedestal and whether the part of it which also passed inboard of the pedestal was passable is not entirely clear but there seems at least to have been a space. The said walkway also ran past the other faces of the platform.

Firewalls were attached to the trusses between each module. It is important to note that these were not designed as blast protection walls and their function was to localise fire and to prevent it spreading to other modules. They were constructed of light steel plates and material called Durasteel. The fire rating for the A/B and B/C firewalls about 4 to 4.5 hours and the C/D firewall had an extended rating of about 6 to 6.5 hours.

2.6.2 Module A

This module had 36 well slots in three rows of 12. Each well had a wellhead which comprised a number of valves and associated pipework known as a "christmas tree". Associated with each christmas tree was a well safety shutdown panel. Each of these had its own controls to shut the flow from its well and these panels were located on the north side of module adjacent to the firewall. The firewall was in the north separating Module A from Module B.

The water injection system was also located in Module A. This system was required for the re-injection of sea water into the oil reservoir in order to maintain pressure. The sea water pumps were located to the south of the module and the course filters associated with these pumps were located in the south east corner. The de- oxygenation towers, which were part of the system, were located at the south end. Water was extracted from these towers using the three water booster pumps located immediately to the west of the towers. The booster pumps then fed the three water injection pumps and these were located at the west end of the module.

At the north wall to the east of the module there was a Chemical Injection Package. This included a tank which contained compartments of chemicals primarily for the water injection system. The overall length of the tank was 25 feet, the width 10 feet and the height 12 feet.

The heat shield that went round the east, south and west sides of the module was located beyond the walkways which surrounded these sides of the module. It was designed to protect against the radiant heat of the flares and comprised two layers of tightly woven stainless steel mesh. A person in module A could see through the heatshield mesh.

Means of access to the module could be obtained via the east and west face walkways. Stairways to the north side of the module allowed access to the 68-foot level. There was also a stairway going up to the skid deck and down to the 68-foot level on the south face.

The defenders made the point that Module A was extremely congested and so it was but perhaps no more so than say Module C. The defenders make this point to explain why a witness such as Mr Gutteridge may not have seen a breach in the A/B firewall.

2.6.3 Module B

In this module the two main production separators were located in the centre of the module. These were essentially identical and were large cylindrical vessels measuring approximately 11 feet in diameter by 44 feet in length. Their function was to separate the oil, gas, and water extracted from the reservoir. They were fitted with internal baffle plates which deflected the fluid and assisted with the separation process. The fluid separated into three flows by means of gravity separation. These vessels had no moving parts. The water being heavier than the oil settled in the bottom. The oil floated to the top of the liquid level where it flowed over internal weirs and was pumped out of the end of the vessel. The gas being the lightest came out of the top of the vessel. The residence time of the oil within the separator was 2.5 to 3 minutes. The liquid level in the separator was slightly below the centre line of the vessel and gas occupied about 60% of the vessel volume.

Immediately to the west of the separators were the three MOL booster pumps. There was one booster pump for each separator the third serving as a spare. The discharge line from each pump was routed to one of the three metering runs. Each such run consisted of a fiscal turbine meter and associated pipework. The meters themselves were located towards the north of the module approximately 10 feet from the firewall. The metering skid occupied a little more than 50% of the width of the module.

The four MOL pumps were at the west end of the module and indeed could be seen at the west face from outside the module as is demonstrated by photograph 12/8G of process. Moving from north to south these pumps were designated B, A, C, and D (the order being due to their historical development). The configuration of these pumps is shown in the schematic 12/97 of process. The MOL itself had a diameter of 30 inches and was located between the MOL pumps and the metering skid. It penetrated the floor of the module as it made its way downwards and thereafter dropped vertically at a point just below the 68-foot level. It then turned through 90 degrees and was routed in a northerly direction, going slightly to the east beneath the 68-foot level, to the north face of the platform. From there it turned through another 90 degrees angle before descending to the sea-bed. On the MOL at a point before it penetrated the floor in Module B was the emergency shut down valve designated ESV-208. This was a large valve (weighing up to 3 tonnes) and although described in the Operations Manual as working manually it in fact at the time of the accident was set to be closed by an electric motor backed by a pneumatic device. The piping was about 20 inches in diameter and the valve was approximately 36 to 40 inches long and about 36 inches in diameter. The valve was approximately 8 to 10 feet above the floor. It was designed to close in the event of an emergency. It was suggested by the fire engineer Dr Drysdale that this valve may have been damaged by the explosion causing it to fail to close after the accident. The valve because of its special significance was subject to regular checks.

Situated above ESV-208 was the tie-in point for the four inch diameter condensate line. This pipeline came from the condensate injection pumps at the 68-foot level up to Module C and then passed through the B/C firewall to the east of the door in that firewall. Once in Module B it then turned west and ran parallel with the B/C firewall for about 17.5 feet or so. It then turned through 90 degrees and ran south for about 15 feet 10 inches before tying in with the MOL. It was supported on hangers. Mr Wottge was not entirely familiar with the layout of the condensate line. He took his detail on this from a Schematic but as I have indicated it was not proved that these were to scale and indeed it was clear that many were not.

The door on the B/C firewall was about 30 to 40 feet from the western end of Module B. It had been supplied by Durasteel Limited. It had a self-closing mechanism. However there was evidence that during the day shift on 6 July 1988 this door had been partly open to accommodate some work intended for the west end of the Module. One would expect that if the work did not extend into the nightshift then the cables would have been dealt with when the permit was suspended. There was no evidence to suggest that work at the West end of Module B was continuing at the accident. The defenders claimed that no tests had been carried out to determine the quantity of gas that would have had to be released from the door to trigger an alarm at the detector in the C3 zone.

The pig launcher (apparatus used in connection with cleaning-out the MOL) was designated 1-P-103 and was positioned between the MOL pumps and the metering skid along the same axis as the MOL. Its position can be seen by reference to photograph 12/4A or the video 41/21 of process. There was a stairway over the pig launcher which gave access to the main walkway which ran down the southern side of the separators.

The test separator (designated 1-C-109) was to the east of the production separators about midway between the north and south sides of Module B. The vessel had an outside diameter of 7 feet and it was about 20 feet long. To the north of this separator was the condensate knock-out drum (designated 1-C-104) and associated with this, and directly to the west, were two condensate transfer pumps. They were in-line pumps sitting within the pipework. Just to the north of the condensate knock-out drum and near the floor were two pressure control valves , namely PSV 51/1 and 2. These were designed to relieve gas pressure to flare and if necessary this would have happened if a centrifugal compressor failed. However during normal Phase 1 operation no gas passed through these valves. The gas that got to flare at or about the time the compressors failed suggests to me that these pressure valves were functioning properly.

Along the east face of Module B there was a bank of four gas coolers. These were substantial pieces of equipment as can be seen from Photograph 12/4A of process. Between the production separators and the condensate knock-out drum at the east end of Module B were two fuel gas filter separators, one on top of the other. These were horizontal cylindrical vessels and were about 2.5 feet in diameter and 7.5 feet long. Within these vessels were filters through which gas would flow.

To the south of the production separators and along the A/B firewall were the inlet manifolds. There were about 27 flowlines connecting the wellheads in Module A with the main inlet manifold. Each flowline fed into one of the three main manifolds. The manifolds were connected to the production separators and also to the test separator. The total length of the manifolds was about 100 feet running west to east. The main emergency shutdown valves for the manifolds were located in the east end of the manifolds and adjacent to the A/B firewall.

On the floor of the module various items of equipment such as the MOL pumps, the metering runs, and the separators were located on skids. These consisted of beams of substantial construction used to support the equipment placed on them. Each skid formed a bounded area and each such area had a drain which allowed material collected there to be routed to the sump pile which was located at the south east corner of the platform at leg A1 at the 68-foot level. Generally above the skids and about 18 inches to 2 feet above the deck plating there had been placed grating to allow access for personnel to the module and equipment.

Pipes led out of the module and to allow this there were a series of pipe penetrations. Generally these were fitted with collars and were not necessarily sealed. Gaps ranging from quarter of an inch to about three quarters of an inch existed between pipes and collars. Such an unsealed gap existed where the MOL penetrated the floor of the 84-foot level. If escaped oil had collected on the floor of the module at the west end then it could have flowed through the grating and drains to the sump or, if for any reason the sump could not accommodate the quantity of the escape, it could have flowed through the gap at the MOL penetration. The witness Mr Amaira had been at the 68-foot level shortly before the accident and in the vicinity of the MOL but he had not noticed any oil flow. On the other hand the collars round the pipe penetrations had a lip about one and a half to two inches high so that water or oil would not escape through the pipe orifice unless it was deep enough to flow into it. The defenders suggested that it was only in relation to the MOLs that the evidence showed gaps at the pipe orifices. Certainly it is difficult to tell from the evidence if it was only the MOL penetrations which had collars or all penetrations although at one point in his evidence Mr Wottge seemed to suggest that the use of collaring for pipe penetrations was fairly general. I think if a pipe penetration did not have a collar it would be sealed.

The defenders made the point that the north-west corner of this module was a great deal more cluttered than would appear from the model of it in court and this is probably correct.

2.6.4 Module C

Although Module C was open at each end the opening at the east end was restricted by the centrifugal compressors. There were three of these and they were designated A, B, and C running from north to south. Each centrifugal compressor consisted of a compressing machine driven by a gas turbine. The gas turbine had its own air filtration unit. The air filter and part of the gas turbine of each compressor protruded from the eastern end of Module C. The gas turbines required a supply of combustion air. The air filters were used to draw in such air and filter it. Each compressor was located within an enclosure divided into two compartments, one having the gas turbine machine and the other having the compressing machine. The enclosure was approximately 10 feet high 8 to 10 feet in width and 30 feet in length. Each machine had its own exhaust which was on the east face of Module C and extended upwards above the 107-foot level. The ventilation intakes for the compartments again was located on the eastern face of Module C. Each compartment exhausted air into Module C through louvres. In the Operating Manual the suction pressure of these compressors was shown as 190 psig whereas in practice they operated at 140 or 150 psig. The system required about 27,000 standard cubic feet per minute of combustion air and about 8,000 of ventilation air. The combustion air was drawn into each compressor from the outside and was drawn into the machine through the grating outside the end of the skid. About 75% of this air would come from below and depending on ambient conditions some might come from the east or from within Module C. The ventilation air was drawn in outside the east face of Module C towards the south side of each compressor. A centrifugal detector would not trip if it only detected enough gas for a low alarm but would trip if the gas level reached about 50% which is rather less than the level required for a high alarm. The ventilation air is not just for personnel entering the compressor compartment. It is cooling air as well. As I have indicated it escapes from the compartment through a louvre. There was a louvre for each compartment. The first alarm that went off was associated with the southmost compressor. Ventilation air would be continue to be drawn in for about two hours after a compressor had tripped.

To the west of the centrifugal compressors was an equipment package known as the centrifugal compressor skid. This comprised equipment auxiliary to the operation of the compressors and, in particular, suction and discharge scrubbers and discharge coolers for each of the compressors. A scrubber is equipment which alters the velocity of gas flow by altering direction and flow area for the gas stream. The alteration is accomplished by baffles within the scrubber. The equipment in each centrifugal compressor skid was known as a "train" and there was one for each. The area was quite congested because of the quantity of equipment. Indeed this congestion would have caused a sufficient degree of restriction in the event of an explosion in Module C to have created vibration of the platform structure as the rushing gases encountered it.

To the south of the skids were fresh water pumps and coolers of which there were two one on top of the other. Between these coolers and the B/C firewall were two pumps and a vertical vessel associated with fresh water circulating system. Two pressure control valves, namely PCV 1000 A and B, were located towards the east end of Module C between the reciprocating compressors and the centrifugal compressors. These were positioned at floor level.

In the centre of the module there were two reciprocating compressors A and B (A being in the centre of the module and B being to the west). These were motor driven machines the motor on each being to the north and the compressor unit to the south. These were large machines and occupied a substantial portion of the module. Each machine weighed about 70 tons. There were two compressing stages to each machine known as the first stage and the second stage. The west of each compressor was the first stage compression which utilised three cylinders. There was a suction scrubber for the first stage which was to the north of each of the reciprocating compressors. The second stage was to the east and again utilised three cylinders. The second stage suction scrubber was located to the south of each compressor. The control panel for reciprocating compressor A was on the walkway to the north of the compressor. This was designated as panel JCP-020. The control panel for reciprocating compressor B was in a similar position and was designated as panel JCP-021. If for any purpose it was considered necessary to suspend compression each compressor had a facility to unload and recycle gas. The control panels JCP-020 and 021 were those the operator would have required to use if unloading and recycling was effected. The operator would have to operate seven switches on each panel to complete a particular exercise, that is a total of 14 switches. The defenders argued that it may not have been a coincidence that the reciprocating compressors had been recycled about 5 minutes before the accident.

PSV 1000A and PSV 1000B were pressure safety valves for these compressors and when Phase 1 was in operation PSV 1000A was kept partly open to relieve any excess pressure on the compressors. The state in which the valve was kept in Phase 2 is not known.

The pressure safety valve PSV-504 was located close to the second stage suction scrubber of the reciprocating compressor and was approximately 15 to 20 feet above deck level. This valve is shown in red in the photograph of the 84-foot model 12/14B of process. The position of this PSV as shown on the model is only approximate since it had been moved at one stage but it is clear from the evidence that the actual PSV was close to where it is shown to be. The witness Mr Grieve located the PSV to the east and south of reciprocal compressor A. Mr Bollands said that the PSV was on the south-east corner of a reciprocating compressor. Mr A G Clark said the valve was close to the freshwater pump on the south wall of Module C just about level with the walkway. This does not accord with the balance of the evidence. Mr Bagnell located the valve as being between the reciprocating compressors and the centrifugal compressors but nearer to the former. Mr Todd said that it was in Module C just to the east side of the reciprocating compressors. The witness Pirie thought that the valve was just above the reciprocating compressors. There was some minor adjustment of the position of the PSV as between the two models that the pursuers produced and the reasons for this were not adequately explained. The defenders contend that the pursuers should have provided more precise information about the location of the PSV such as may have been available if they had lodged an isometric plan . I am not sure that on the whole these descriptions of the location of PSV 504 are materially different. There was some divergence in the evidence about the height of the PSV. Mr Wottge, Mr Grieve and Mr Bagnell said that the PSV was about 15 feet above deck level. Mr Pirie gave the height as being about 12 to 15 feet above deck level but this could be explained if he was judging the height not from the deck but from the walkway. Mr Wottge had agreed with the suggestion that the PSV was close to the ceiling which in fact would give it a height of about 20 feet rather than 15. Mr Todd placed it in the roof space which would also take it higher than 15 feet. Mr Henderson had placed the valve as being close to the manual isolation valve. This raises the interesting question not explored as to how an operator requiring to open the manual isolation valve obtained access to it. We were also never told what steps had to be taken to unlock this valve which when in a closed position was locked. Whatever precise height the PSV valve had we know that scaffolding was required to have access to it for removal for calibration. We also know that it was located above a walkway. We also are aware where the pipe loop on which PSV 504 was sited was located. We know from the expert Dr Davies who did experiments in relation to PSV 504 that moving it a few metres in one direction or another would not make a material difference to his results. If anything the height was more significant.

At the time of the accident Scaffolding had been erected to obtain access to PSV 504 and the presence of this could have affected the dispersion of any leak from the blind flange attached to the open end of the pipe when the valve was removed for maintenance. We were not given any precise information about the size, layout or composition of this scaffolding and all we know about is that it must have been placed in a position to permit access to the valve work. It also must have been of a sufficient dimension to accommodate at least three men and the dismantled valve. The witness Mr McDonald explained that if the PSV is assumed to be at a height of about 15 feet the scaffolding platform would be at about 12 feet but of course I think it is possible it was rather higher although the height of the PSV was only proved within approximate limits. We also know that if work was interrupted the scaffolding was left in situ. Mr McGregor was able to confirm that when about 9pm on the night of the accident he went to do some work near the reciprocating compressor second stage suction scrubber he was inhibited in doing this work because of scaffolding around it. If this was the same scaffolding as the valve maintenance men were using this evidence gives some additional information about the location of PSV 504.

Adjacent and to the east of PSV - 504 was PSV - 505 and both valves were at about the same height. They were about 2 to 2.5 feet apart. The pipe loop in which PSV - 504 was located ran from north to south. There was a manual isolation valve next to the PSV on the horizontal pipework. This was downstream of the PSV and about 1 foot to eighteen inches away. To the south of reciprocating compressor A were gas coolers E - 103A and B and to the south of compressor B were the gas coolers E - 103 C and D. Next to the western end of the gas cooler E - 103 C was the location of the 4 inch diameter condensate pipeline as it passed through Module C on the way to the point where it was routed through the B/C firewall into Module B.

To the west of the reciprocating compressor was the potable water storage tank. Originally this was circular but that tank was eventually replaced by a square tank. The tank, which is light grey, is shown in the photograph 12/8 G. PCV 501 which let down gas to the Claymore pipeline was located to the west of the reciprocating compressors. There were instrument control panels for the MOL pumps to the south and west of the potable water storage tank. There were four separate such instrument control panels and these were constructed from light weight sheet panelling, each having an access door to allow maintenance personnel access to the instrumentation. North of the potable water tanks were two vertical cylindrical vessels, the western of these being the instrument air receiver and the other being the utility air receiver. Associated with the instrument air receiver was an instrument air dryer which was located on the west face of the Module and associated with the other receiver was a compressor which was located to the north of the receivers. In photograph 12/8G can be seen one of the instrument air receivers, the instrument air dryer and the potable water storage tank.

The percentage volume occupied by piping within Module C was approximately 15%. The module was more congested than Module B. Generally, access to the Module could be obtained from the west through two doors fitted for that purpose and forming part of the air filtration units. It was also possible to duck under the hoods to the north and south of the reciprocating compressors A and C. In the western half of the module on the north side there was an open stairwell which connected the Module to the 68-foot level. One of the walkways in the module was to the north of the reciprocating compressors. As in Module B there was grating about 18 inches to 2 feet above the floor and the walkways themselves were made of grating. There was grating between the centrifugal compressors. There were also piping penetrations in the module which were fitted with collars and such penetrations had gaps ranging from between one quarter inch to three quarters of an inch. There were some pipe penetrations associated with the relief lines that went from the 68-foot level to PSVs 504 and 505 and returned to the condensate suction drum 2- C-202 at the 68-foot level. The exact arrangements for the protection or sealing of these particular pipe penetrations was not investigated in detail although there was a certain amount of thermal sealing in the area of the reciprocating compressors to prevent the rise of heat from the John Brown exhausts and also a measure of insulation of the module ceiling.

2.65 Module D

This module is located at the north end of the platform. At the eastern end of the module were the John Brown Turbines A and these were substantial pieces of equipment. They generated electricity at 13800 volts. They were located in cabinets about twelve feet high and most of the east end of Module D was occupied by these. Otherwise the north-eastern side of Module D and the west and east ends were open. The exhausts and inlets of the John Brown generators can be seen in the photograph 12/8B of process. Adjacent to the C/D firewall at the eastern end of the module was the fuel gas heater. Next to the west within an enclosed area there was a diesel driven firewater pump and adjacent to it was an electric-driven firewater pump also called a utility water pump all adjacent to the C/D firewall. They drew water from below the sea level. The two pumps were housed within a fireproof enclosure and access to them was gained by entering the module on the north face, and going down some steps to the right of the John Brown generators. There was also within the enclosure a diesel oil tank to provide fuel for the diesel driven firewater pump and a further such tank as situated outside the enclosure. Outside the enclosure and to the west but again adjacent to the C/D firewall were two additional pumps to provide firewater and utility water for the platform.

Within the western half of Module D was a separate steel structure known as the Control Building and this was on two levels. It was bolted to the ceiling of the module. The outer skin of this building was lightweight steel three-sixteenth of an inch thick. Thus the Control Room itself was protected by a moderately strong independent skin. The lower level is shown in the schematic 12/75 of process. Access to that level could be gained through double doors and an airlock either from the west or east of the Control Building. It housed the Emergency Electrical Room at the south west corner and this contained the emergency electrical switch board. This provided power to emergency related equipment like the fire and gas detection systems, certain motorised valve operators, certain emergency electrical equipment and certain lighting. In the north west corner there was the Heating, Ventilation, and Air Conditioning (HVAC) room. Also in the east of the Control Building was a room containing electrical switchgear and known as the Electrical Room No. 2. This contained the 4.16 Kv bus bar which provided power to a number of electrical motors including the motor of the condensate injection pump. Also in No. 2 room was the 440 volt normal supply switchboard. This switchboard served the auxiliary supplies, the heating, control ventilation and lighting systems. Again in the lower level of the module but outside the structure of the Control Building there was a partly-enclosed area to the West and this area incorporated the workshop known as the Maintenance or Mechanical Workshop. The part of the wall of the Control Building which formed the west wall of the Emergency Electrical Room was a common wall with the Maintenance Workshop at this level as can be seen in Schematic 12/75 of process. Access to the workshop was from a sliding door on the west face and this can be seen in the photograph 12/8F of process. The south wall of this workshop was adjacent to the C/D firewall. Directly to the north of the Maintenance Workshop was an office/tea-room which had formerly been a tool store. Normal access to this area was from the Maintenance Workshop through a doorway which had a sliding door. The west wall of the office/tea-room was an emergency door which was normally closed and generally not used. There was a gap between the Maintenance workshop and the C/D firewall.

To the north side of the Maintenance Workshop was a stairway leading to the upper level of the Control Building. To the north of that stairway was the Instrument Workshop shown in photograph 12/8F of process. It was a portacabin which had been placed at the western end of Module D. Access was obtained through a sliding door on the south wall and this door was always open. There was also a separate internal hinged door before actual access into the work shop could be obtained. In an open area at the north west corner of the module was the diesel-powered Emergency Turbo-Generator which supplied emergency electrical power for critical items on the platform via the switchboard in the Emergency Electrical Room.

The upper level of the control building was called the mezzanine level. Access to the mezzanine level was via the stairway at the west face and this stairway can be seen in the Photograph 12/8F. At the top of the stairway to the north and left was the Safety Office and this was above the Instrument Workshop. Entry was through a door in its south wall. Safety personnel on the platform were based in the Safety Office. In this office completed and suspended permits to work were in certain circumstances filed. To the south and right of the stairway at the mezzanine level were the Electrical Maintenance shop, Electrical Store, and Instrumentation Store. These areas were directly above the Maintenance Workshop and their south wall was adjacent to the C/D firewall. At the top of the stairs to the mezzanine level moving eastwards there were double airlock doors.

To the right on entering the Control Room were the control panels for the John Brown Generators. Moving to the east there was a worktop and visual display unit (VDU). The VDU displayed inter alia information relating to the telemetry system. There was a rack on the worktop which contained the active permits to work according to their designated areas. Further to the east within the Control Room were a series of display panels as are shown in photograph 12/203. The panel to the left and nearest to the centre of the Control Room was the electrical mimic panel. This panel displayed the status of the distribution of electrical power throughout the platform. Next to that panel and to the south was the main process control or mimic panel. This panel displayed the status of process equipment and contained a number of lights indicating which major items of equipment were operating or shut down. To the south of the mimic panel were the fire and gas display panels. There was also an additional fire and gas display panel on the south wall of the Control Room. Moving east and behind the mimic panel and the main fire and gas display panels, there were inter alia panels relating to the fire and gas and telemetry systems. Adjacent to the east wall of the Control Room there were additional fire and gas panels. Slightly north of these additional fire and gas panels there was a table which was used for tea or coffee and by Phase 1 operators and the oil and water operators. The Control Room operator normally sat in the general area of the control desk and the mimic and main fire and gas display panels. The Lead Operator usually sat at the area designated "worktop" on the drawing 12/188 of process.

To the north of the Control Room area and within the Control Building there were areas known as the DC room and the Battery Room. The DC Room housed safety-related switchgear for the instrument systems. The Battery Room housed the battery packs which provided DC electrical supplies via the DC Room equipment. The eastmost part of the Control Building was sound-proofed and had its own heating and ventilation system. The Control Building had double doors to prevent the ingress of gas.

The fuel gas for the John Brown Generators originated from the centrifugal compressors and was processed in the fuel gas heaters in Module D. Thereafter it traversed Module C before reaching the generators.

2.7.1 Produced Water Package and Laboratories

On the east side of the 68-foot level on an extension, outwith the confines of the jacket legs, there was the produced water treatment plant comprising the plate skimmer and hydrocyclone units. The plate skimmer was below Module B. There was a windwall protruding out from the 68-foot level a few feet beyond the east ends of Module B and C. The hydrocyclone units were positioned beneath Module C. One way of obtaining access to this area of the 68-foot level was via a stairway from the base of the east crane pedestal outside the windwall. The water laboratory, fine filters, and oil laboratory were on the west face and at the south end of the platform.

2.7.2 The Dive Package

Also at the west side of the platform underneath Module B and part of Module C but extending westwards beyond these modules was the Dive Package area. This area can be seen in photographs 12/8D, 12/8E, and 12/8G of process. Moving from north to south the Dive Package extended from the blue container seen at low level in photograph 12/8 G to the divide between Modules A and B. The blue container was for wet suit storage. The adjacent yellow container was the switchgear room and dive machinery room. The Dive Package extended partly under Module C but the greater part of it was beneath Module B. It extended from Module C across the whole width of Module B and inboard for some 50-feet in an easterly direction under Module B.

Inboard of the container that housed the Switchgear Room and the Dive Machinery Room there were two decompression chambers. These are shown in photograph 12/8N of process. To the north of these chambers were the Dive Package Offices.

At a lower level some 10 or 15 feet below the dive complex there was a dive staging platform known as the Diver’s Launch and Recovery Platform. Photograph 12/80 of process shows the stairway that led downwards to the dive staging platform and the view from the top of the stairway to the dive staging platform is seen in photograph 12/8M of process. The structure at the bottom of the stairway was known as the Dive Wendy Hut. The dive staging platform provided an area from which divers would enter the water. It protruded somewhat from the face of the platform. The floor of the dive staging platform was constructed primarily of grating and rubber matting was normally laid over the grating in order to protect the divers’ feet. The dive staging platform was substantially underneath Module B and, in particular, underneath the part where the MOL descended through to the 68-foot level. The Tartan Riser also passed above the dive staging platform at a point just below the 68-foot level before turning to the north where it descended into the sea adjacent to leg B4.

2.7.3 Condensate Handling Facilities

The condensate handling facilities are an important feature of this case since the pursuers’ case involves them in their case as to how the accident happened. These facilities were directly below Module C and are shown in the schematic 13/49 and photographs 12/8Q and 12/8R. They included the JT valve and the JT flash drum, the condensate suction drum, the condensate booster pumps, the condensate injection pumps (and all their associated pipework) as well as the control instrumentation. The JT flash drum was on the east side of the 68-foot level. The JT valve was to the north east of the JT flash drum. There were two condensate booster pumps which were directly to the east of the JT flash drum. The condensate suction drum 2-C-202 was located in the roof space of the 68-foot level to the west of the JT flash drum. It had an internal diameter of 3 inches and its dimension from end to end was 13 feet.

The condensate injection pumps were generally located in the centre of the 68-foot level. There were two pumps A and B. Pump A was to the east and pump B was to the west. Each pump consisted of an electric motor, a torque converter (also known as the Voith coupling), a gearbox, crank casing and a pump chest or head. The motor of the each pump was to the north and the pump chest was to the south or east. The stairway connecting the 68-foot level to Module C was to the west and north of the condensate injection pump B. The distance from the bottom of this stairway to the pumps was about 20 feet. Each pump had suction and discharge pipework and on the pipework there were gas operated valves (GOVs) known respectively as the suction and discharge GOVs. The GOVs were situated to the south of pumps. They were operated by push/pull buttons local to them. The push/pull buttons were on stanchions some 2 feet or 3 feet further to the south of the GOVs. With regard to pump A the GOVs were respectively GOV 5005 on the suction side and GOV 5006 on the discharge side. The GOVs for pump B were GOV 5007 on the suction side and G0V 5008 on the discharge side. There were pulsation dampeners on the suction line of each pump and also on its discharge line. The pulsation dampeners were added to the pumps about a year after the commencement of the operations of the condensate injection pumps. There were four pulsation dampeners - two for each pump. Each pump had a relief line going to its PSV. Since this involved pipe penetration it offered a possible route for escaped oil or condensate to pass from module C to the lower floor. Even if the discharge GOV of the pump was closed gas would enter the PSV relief line. Thus in a depressurised pump if the suction valve was opened the pressure would reach the PSV.

Situated between the JT flash drum and pump A was the control panel JCP- 057. Amongst other things this panel displayed the status of the condensate booster pumps and the condensate injection pumps as well of the GOVs of those pumps. Each condensate injection pump had a local control panel located to the north and east of each pump. The panel JCP - 057 was some 4 or 5 feet from the local panel for Pump A. On the stanchion beside the local control panel for Pump B there was a level indicator for the JT flash drum.

Because of the amount of equipment the area near and including the Condensate Injection Pumps was fairly congested.

2.8.1 The Gas Conservation Module and Utility Module

This module comprised equipment aimed at improving the quality of the gas produced on the platform. The module can be seen above Module B in the photographs 12/8 H and I of process. It was also partly above Module C. The equipment included in particular molecular sieve dryers, a turbo expander, and a demethaniser . Located within this module was a sound proofed hut which was used by the Phase 2 operators. The Utility Module was directly above Module C. This contained a main 13.8kv switchboard and 4.16kv switchgear. The power supply for the condensate injection pump came from this switchgear.

2.8.2 Sub -module D

Above Module D in the 107-foot level was sub-module D and the western half of this was a self-contained building consisting principally of the Telecommunications Room and Occidental Production Stores. The eastern half of this sub-module was open to the north and east and housed the Occidental Maintenance Office, foam storage, pumps, and HAVC systems. At the east of the sub-module were the generator inlet ducts for the John Brown generators. The exhaust ducts were on the north face and the inlet ducts were on the east face. Immediately outboard of this area was the Occidental Maintenance Superintendent’s Office. This can be seen as the orange portacabin protruding from the north face in photograph 12/8E. Inboard of that office was the Occidental Maintenance Office.

2.8.3 The Drilling - Related Modules

Immediately opposite the GCM and on the west side of the 107-foot level was the Mud Module and the main items of equipment included two shakers situated in the south east corner of the module. The west wall of the Mud Module is seen in photograph 12/8G of process. To the north of the Mud Module was the Storage or Sacks Module and to the north of this was the Pods Module.

The skid deck was also on the 107-foot level directly above Module A. On the skid deck, running east to west were the main skid beams on which the drilling derrick was supported. This allowed the derrick to move and be centred above any of the 36 well slots. The top of the derrick was about 289 feet above sea level. Individual covers on the skid deck and above each of the well slots allowed for access to each well for drilling or well maintenance operations. There were two hatches for each well slot namely an outer and smaller inner hatch. The outer hatch had a dimension of about 10 feet by 7.5 feet. The inner hatch was located within the outer hatch and was about one third of the size of the outer hatch. Each type of hatch was made of a steel construction some 3/8 ths of an inch thick. The inner hatch was designed to be bolted to the outer hatch. Part of the skid deck with one of the skid beams and hatch covers for the well slots can be seen in photograph 41/11.

The pipedeck was located above the Mud and Gas Conservation Modules at the 133-foot level and can be seen in photograph 12/8D. Access could be obtained from the pipedeck to the drilling derrick via a pipebridge and V door. On the west side and to the north of the pipedeck was the Submersible Pump Electrical Module (SPEEM). This can be seen in the photographs 12/8D and 12/8G. The ERQ East consisted of four levels and is seen on photographs 12/8B and 12/8E of process. The helideck was on top of the ERQ at the 174-foot level. Level 1 housed a number of cabins, the offices for the OIM and Production Superintendent and a general office. The highest level housed the dining and kitchen area. This area also housed additional accommodation and recreational areas.

In accordance with practice within the industry the platform areas were classified into different zones depending on the likelihood of the development of a potential unsafe gas/air mixture. Zone 1 was where an explosive atmosphere was likely to occur in normal operations. Zone 2 was where an explosive atmosphere was not likely to occur in normal operations and if it did it would only exist for a short time. Safe and unclassified was an area where an explosive atmosphere was not expected to occur and was considered to be a safe area.

Module A was classified as Zone 2. Module B was classified both as Zone 1 and Zone 2. The area in that module classified as Zone 1 was the area associated with the production manifold where there were sample collections. Module C was classified as Zone 2 and Module D was unclassified. These classifications are shown diagrammatically in the Operations Manual 12/3 or process. In the main the 68-foot level was classified as Zone 2 but with areas to the north and east being unclassified. The design of equipment in a classified area had to meet certain safety standards. These were directed towards preventing ignition sources being caused during the normal operation of such equipment. In areas designated as Zone 2 gas detectors were likely to be in positions where gas was most likely to be detected.

2.10.1 The Piper Network

The 30 inch diameter oil export riser and the 16 inch diameter Claymore gas riser were on the north face of the platform. The 18 inch diameter Tartan Gas Riser was in the vicinity of leg B4 on the west face. The 18 inch diameter MCP-O1 Gas riser was in the vicinity of leg A4 on the east face. The MOL travelled from the platform down to the seabed and along the seabed to Flotta, a distance of 128 miles. The Claymore platform was located some 22 miles west of the Piper Alpha platform. Oil was exported from the Claymore platform via a pipeline which tied into the MOL at Flotta. The tie-in point was about 22 miles from Piper Alpha and was known as the Tee.

The pipeline of which the Tartan Gas Riser formed part was a gas line about 12 miles long used for Tartan to export their gas via Piper towards MCP-O1. The MCP-O1 Gas Riser travelled from the platform to the sea-bed and thereafter to the MCP-O1 platform some 34 miles to the north of the Piper Alpha platform. Gas from the Tartan Riser was routed into the MCP-O1 riser on the Piper Alpha platform. There was also a 16 inch diameter pipe running along the sea-bed between the Piper Alpha and Claymore platforms with associated risers on each platform. This pipeline allowed the Piper Alpha to supply fuel gas to the Claymore platform. Furthermore there was a 24 inch diameter oil pipeline running from the Tartan platform to the Claymore platform. This facilitated oil export from the Tartan platform via the Claymore platform into the main oil line to Flotta. The network is set out in the schematics 12/24 and 12/122 of process.

2.10.2 The Flotta Oil Terminal

This terminal in the Orkney Islands was built after the discovery of the Piper Field in order to provide a base for receiving, storing, and exporting hydrocarbons discovered offshore. The plant at Flotta consisted mainly of two areas, the processing area and the storage and transport area. As at 1988 Flotta was receiving hydrocarbons from three platforms, namely Piper, Claymore and Tartan, all via the MOL. At the time of the accident in 1988 the terminal was owned and operated by OPCAL.

2.11. The Firewall Structure

The firewalls between the modules on the production level were fabricated and supplied by Durasteel. This was done for OPCAL on the instruction of their designers, Messrs Bechtel, and the walls were fabricated at the yard of Allen & Grieve of Edmonton. Some challenge was presented by the defenders to the pursuers’ evidence about the structure of the firewalls but I was satisfied by this evidence. The firewalls had been altered to a degree from the original drawings but the witnesses were able to describe such differences so far as it mattered. I doubt in any event if at the end of the day they make much difference. The witness Mr Pickett was employed by Durasteel from 1963 until 1991 and had reached the position of Office Manager. He confirmed that about 1973 Durasteel had supplied three firewalls to OPCAL. One had been a 6-hour firewall both insulated and on integrity. The other two were fire integrity partitions only and were of a 4-hour standard. The 6-hour firewall was constructed of three thickness of Durasteel 3DF2 material with two layers of insulation. The other firewalls were a single sheet of the Durasteel material. In terms of their contract Durasteel supplied the whole firewall system including the frames and every nut and bolt. Subsequently before the platform came into operation the firewalls were assembled and installed on it. The effect was that each of the modules was separated from adjacent modules by such a firewall. The firewall between Module A and Module B was known as the A/B firewall, that between Modules B and C as the B/C firewall, and that between Modules C and D the C/D firewall.

Evidence about the construction of the firewall was given on behalf of the pursuers by Mr Terry Rogers. This witness is now a self-employed project engineer and he has a HND qualification in mechanical engineering. Between 1973 and 1980 he had been employed by Bechtel Great Britain as a piping engineer. This is to a degree significant because the Bechtel Group had been employed by the consortium as designers of the platform. He went to the Piper Alpha platform in 1978 and was there during the phase1 and 2 installation programmes. After he left Bechtel in 1987 he remained in employment on the platform and at the time of the accident was the Project Services Superintendent for OPCAL. This meant that he was Superintendent for construction work. His work involved supervising projects which required pipe penetrations through the firewalls and this gave him a familiarity with their construction. He had not worked specifically on the C/D firewall but had observed its construction. There was a gap between the C/D firewall and the maintenance building and a person could squeeze into this, as he had done, and observe the firewall construction. He was responsible for the personnel whose job it was periodically to check the firewalls. I had no difficulty in accepting his evidence in relation to the construction of the firewalls.

The firewalls were attached to the trusses which were part of the module structure. There were two trusses for each module. These trusses were numbered 1 to 8 from south to north. The A/B firewall was built on the north truss line for module A and was built to the south side of it. The consequence is that an explosion within the module would push the firewall into the trusses. The position in relation to the construction of the B/C firewall was the same. It was built on the south side of truss 4. The C/D truss had a different construction from the other two but was also built to the south side of the north truss of Module C. The firewalls extended from the deck plate (rather than walkway level) up to the underside of the main beam on top of the truss. The length of the truss would be the length of the module, namely about 153 feet, and their height was about 19 feet. The defenders claimed that it was not clear from the evidence just how strong the connections of the firewall were at the junctions between the firewall and the deck and the ceiling respectively. However they accepted that this was not an issue.

The witness, Mr Crouch, was employed by Allen & Greaves until they discontinued business in 1976. That firm carried out work for Durasteel and Mr Crouch had a supervisory position in it. The timescale he gives for the construction of the wall is broadly consistent with that of Mr Picket. The pursuers’ witness, Mr Cole, was the Works Director of Durasteel and he had joined them about 1987. He had no direct knowledge of the supply of the firewalls to OPCAL by Durasteel but knew from his knowledge of the history of his firm’s works systems and from their records that such walls had been supplied and the details of the walls which were likely to have been supplied. The construction systems employed by Durasteel do not seem to have varied over the years. Durasteel supplied OPCAL with detailed drawings at the time of the installation of the firewalls. Such drawings were retained by OPCAL and updated where necessary. He spoke to the fact that the productions 12/80, 12/83, and 12/85 of process were accurate representations of how the firewalls would have been constructed and the evidence when viewed as a whole leaves me in little doubt that this is so. Indeed these drawings purport to be Durasteel drawings and have a Durasteel stamp on them. Each bears a date round about 1975. Mr Rogers was able to say in evidence that the door in the actual B /C firewall had a Durasteel logo on it. The schematic 12/93 of process also shows an outline of the construction of the firewall A/B.

Mr Rogers indicated that the A/B and B/C firewalls were plated in with a material called Durasteel which is a sandwich of perforated steel with a non-inflammable material in between. These plates were about three-eighths of an inch thick in all. The steel sheets were each about half a millimetre thick. The composition of the core was cement mixed with asbestos. The weight of the Durasteel sheets was about 21 kg per square metre. The flexural strength of the Durasteel panel was 60 Newton’s per square millimetre. The plates were supported in an angle frame bolted together so as to form frames around each panel. The angle frames were steel. The top and lower panels in the wall measured 8 feet and a quarter inch in length and the intermediate was 4 feet and a quarter of an inch. Each panel had a width of 5 feet. At the west section of the A/B firewall the drawings show a section of wall with rather smaller panels but Mr Rogers could not remember this detail. The frames were made of mild steel angles measuring 2 inch by 2 inch by a quarter inch, mitred at the corner and butt welded to form a 90 degree angle. The grade of steel was 43A. The frames were bolted back to back using three-eighth of an inch Whitworth thread bolts. When the firewalls were delivered to OPCAL the bolt holes were pre-drilled. The frame bolts were spaced at 18 inch centres. There was a distance from the outer edge of the angle iron to the centre of the frame bolt hole of 30 millimetres and this is referred to as the structural backmark. The distance from the centre of the bolt hole to the toe is 20 millimetres. These measurements have some significance when the prying action of the angle iron when subjected to pressure is being considered. They come from Mr Cole and Mr Crouch who agree within general limits.

With regard to the clamping of the frames to the trusses of the A/B and B/C firewalls the frames were fixed to the trusses by an arrangement of cleats as shown in the drawings I have referred to above (and also the schematic 12/93). Six inch long L cleats were positioned and welded on to the frames. Three-eighth of an inch screw rods are then used to secure other cleats at the back of the trusses so as to hold the firewall tight against the trusses. The clamps appeared at the points where the trusses intersected the panels of the firewall. These points are shown on the drawings by way of asterisks. Clamps were attached to both the vertical and diagonal members of the trusses. At the top the connection was a weld to the main chord of the truss and then a bolted angle connection to the angle iron frame. This arrangement is illustrated in the drawing 12/80 of process. At the bottom the firewalls were secured by a weld to the deckplates. The panels themselves were attached to the frames by five-sixteenths of an inch diameter Whitworth bolts and at 12 inch centres.

The defender’s witness, Mr Barron was 58 years old and he was a foreman painter with Wood Group. He had been on the Piper Alpha at the time of the accident. An objection was taken by the pursuers to his evidence because he was only called on day 171 of the Proof and the matters he spoke to were not put to the pursuers’ witnesses. The thrust of Mr Barron’ evidence was that in February 1988 he had cut Mandolite from the B/C firewall in order to expose pipes at the western end of the firewall. He claimed that the whole of the wall where he had been working has been covered in Mandolite and he had needle-gunned some of it to remove it. He stated that it was one or two inches thick. Mr Rogers had spoken to the fact that Mandolite had been used to seal pipe penetrations but it was never suggested to him that at any point the substance covered other parts of the firewall. Certainly it was put to Professor Reid that a two inch coat of Mandolite would have an effect on the mass of the wall but until that point in the evidence there had been no suggestion that there was such a coat to the various witnesses (such as Mr Wottge, Mr Wylie, or Mr Rogers) who might have been expected to have had a better knowledge of the position than Mr Barron. Professor Reid did say that a coat of Mandolite would affect mass and thus by implication velocity but he did not attempt to quantify this effect. The suggested occasion in February was the only occasion Mr Barron claimed to have worked at the firewall. He also agreed that it was generally used as a sealant. It should be noted that the Durasteel Plates had a honeycomb constructions. If Mandolite was spread over any substantial area of the wall it would have been at the west end only but I am not convinced that even at that part of the wall the panels were covered in Mandolite although a certain amount will have been applied in the area of pipe penetrations as a sealant. Mr Wottge given the fire rating of the wall as 4 to 4.5 hours whereas the witness Mr Picket had ventured that the fire rating supplied by Durasteel had been 2.5 hours. Defenders’ counsel had sought to take from this that Mandolite could increase the fire resistance of a wall and that it may have been for that reason that OPCAL had sprayed Mandolite on the wall. However the only evidence was that the Mandolite had been used at the west end of the wall and if one was seeking to increase the fire resistance of a partition wall it is difficult to see why one would want to apply Mandolite at one end only. There is I think a certain amount of doubt as to whether or not there was at least some Mandolite on the wall (as distinct from the pipe penetration points). However any such doubts could probably have been resolved if the matter had been put to the pursuers’ witnesses (and in particular Mr Rogers) and in the circumstances I think the pursuers must get the benefit of the situation. Moreover the pursuers’ structural engineers were not asked about any effect the Mandolite could have had on their calculations.

Mr Barron also said that he was familiar with the door at the west end of the B/C firewall and gave evidence that when he was working on the platform this door was always left slightly ajar. He confirmed that he had informed Lord Cullen’s inquiry that during the period of eight months before the accident he had used the door three times. Once again this matter was first raised by the defenders at a late stage of the proof and neither the pursuers’ experts nor the platform witnesses were asked about it. Mr Rogers had claimed that the door in question had a self-closing mechanism which was very effective and snapped the door shut. There of course is the possibility that as workmen painted or worked at pipe penetrations the door was jammed in an open position but this may well have been temporary.

As I have already indicated the C/D firewall differed from the others in that it had three layers of Durasteel which sandwiched two layers of mineral wool each about 2 inches thick. In this construction the plates were rather smaller. Details of the construction of this wall are set out in the drawing which is 12/85 of process. The panels were about three feet square and the wall was seven panels in height. The firewall was considerably thicker than the other two firewalls. The panels were applied to the south face of the angle irons and this was secured to the truss line. The skins of the wall were attached to each other by coach bolts, four to each three foot length and these also held the angle frames together. The frames were fixed to the trusses by fabricated straps attached to cleats. This is illustrated in the schematic 12/94 of process and in the drawing 12/85. Because of the difference in this module any overpressure from Module C would push the panels on to the angle frames whereas the panels in the B/C firewall would be pushed away from their trusses.

2.12.1 The Power Supply

The main witness for the pursuers on the matter of the power supply was Mr Lloyd who presently is their Chief Electrical Engineer. He is a Chartered Electrical Engineer and a Member of the Institute of Electrical Engineers. He holds the Higher National Certificate in Electrical Engineering. He first joined OPCAL in 1976 as a Platform Electrical Technician and worked in that capacity on the Piper Alpha platform for about 4 years. At that time he worked regularly with all aspects of the electrical system. He was also familiar with the air supply system. He then became a Facilities Electrical Engineer with OPCAL onshore. During this period any alterations on Piper to the electrical system would pass through his hands. In 1985 he was promoted to the position of Senior Electrical Engineer. In respect of the technical matters about which he gave evidence he was clearly well informed.

The productions 12/73 and 12/74 which were taken from the Operations Manual, but were spoken to by the witnesses, set out in detail the normal and emergency electrical supplies. The top bus-bar shown there on the left was located in Module D at the Mezzanine level in Electrical Room No 2 and is 13.8 kV. The power passes down to a bus-bar of 4.16 kV also in Module D and this supplies the Condensate Injection Pump B. The first bus-bar next to the right is 13.8 kV and is located in the Utility Module. This transfers electricity to a 4.16 kV bus-bar also in the Utility Module and this in turn supplies Condensate Injection Pump A. The bus bar coming down beyond that was a 440 V normal services bus-bar. The main implication of this is that at the time of the accident any electrical de-isolation of pump A would have required to take place in the Utility Module.

The productions number 12/75 and 12/76 of process show the John Brown generators which were the principal power source on the platform and as I have said these were located at the east end of Module D. 12/76 shows the main 13.8 kV switch-board which was located within Electrical Room No 1 at the east end of the Mezzanine level in Module D. The 440V and the 4.16 kV supply controls are in Electrical Room No 2. The drawing number 12/72 of process shows the power supplies to the various auxiliary services. The relevant bus-bar was located in Electrical Room No 2. In respect of emergency distribution Mr Wottge explained that this came from a solar generator illustrated in the drawing 12/75. This generator supplied power to the emergency services switchgear in the Emergency Electrical Room in Module D. The emergency supply would come on automatically if power was lost from the John Brown generators. The drawing number 12/73 of process shows two diesel-fired generators principally designed to provide an emergency supply for drilling operations but also available as an emergency supply for emergency services. Finally for emergency purposes there was an Uninterruptable Power System charged from a Trickle Charger from the 440 Volt emergency services bus-bar. This was intended to supply emergency power to essential services such as essential instrumentation, the general alarm system and the public address system. Indeed there are three independent batteries covering the various critical services. The batteries were in the Battery Room as shown in drawing 12/76. There was also a back-up system to supply emergency lighting.

2.12.2 Control Panels

The local control panels for the condensate injection pumps are located as shown in the Schematic number 13/49 of process. The elements displayed on the panel are as shown in 15/21 of process. The panel contains alarm lights. These signal a range of difficulties that might arise such as those relating to pressures levels and temperatures. A light shown as number 1 remains on if the pump is running and if this goes off it of course signals that the pump has stopped.. There is a further lamp which signals that power is servicing the relevant pump. If the power lamp is on and the pump is not shown as running the reason for this is not indicated. There is also a local Instrument Panel (JCP-57) which provided local alarm indications of the process conditions. The Control Panel will signal if the Gas Operated Valves which relate to the suction and discharge sides of the Condensate Injection Pumps are open or closed. There is also a selector switch which governs the source from which the pumps are fed ( that is from the JT Flash Drum or the Condensate Suction Vessel). When the production system was running in Phase 1 the feed was always taken from the Flash Drum. The control panel had a bulb test button and an emergency shut-down button to shut down the condensate system. If the power supply to a pump was interrupted during isolation by being racked out there would still be a lamp to indicate the status of the GOVs. Racking-out is the procedure of isolating the electrical switchgear by withdrawing the compartment containing it. On the other hand the procedure of locking-off involves isolating the circuit by pulling the isolation switch. In both procedures the withdrawn compartment or switch as the case may be is locked in position