British Sugar Plc v Cegelec Ltd [2004] EWCA Civ 1450

"4. The exciter incorporated a rotor, which was attached to the shaft and rotated with it, and a stator which was fixed to the ground. There was a three phase winding on the exciter's rotor armature connected to a series of diodes mounted on a diode hub attached to the rotor armature; each diode was connected to a heat sink -- and there were six diodes and six heat sinks on the hub. The windings comprised a series of electrically insulated turns of copper conductors; at each end of a winding a series of copper conductors leaving one slot were bent around and routed back along another slot, and the areas at the end of a winding are referred to as 'end windings'. "5. The rotor rotates at a speed of 1500 revolutions per minute and such rotation tends to cause the end windings to splay outward or migrate. Therefore additional bracing or cording was added to the end windings to provide support and reduce potential movement."

"On 11th March 1996 the defendant's engineers carried out an electrical and mechanical inspection of the generator. What they discovered regarding the exciter assembly was set out in a report of that date ... Under the heading 'Exciter assembly' it is stated: 'A visual examination of the Exciter and PMG assemblies was carried out ...' 'The PMG was in excellent condition with no signs of overheating or movement. The Exciter Stator was inspected and found to be in good condition showing no signs of overheating or distress. There were blobs of varnish, still in a tacky condition in the bedplate under the Exciter stator. There was no indication where this may have come from. Following the inspection of the Exciter rotor, it was observed that part of the outboard winding adjacent to where the rotor connection leads joined to the winding has begun to migrate in a centrifugal manner causing a part of the outer covering and cording to contact the stator coil washers. This has resulted in two of the cords being completely worn through and two others partly worn through. At this time it was agreed by all parties to call in a CEGA design engineer, Mr S Ross. This resulted in the Exciter rotor being despatched for repair. After the Rotor was rewound the air gaps were checked ...'"

"14. In May 1996 the defendant submitted a report to the claimant (at page 919 of bundle 4); however, no explanation was given as to the cause of the migration and indeed in a draft disclosed for the purpose of these proceedings the author of the report stated that 'there was no indication as to the cause of the winding being larger than the air gap.'"

"19. On 30th September 1996 the defendant's service engineer, Mr Paul Savory [called by the appellant as a witness], in the presence of various of the claimant's staff, dismantled the exciter so that it could be taken back to the defendant's Bradford works for repair. All appreciated that the work had to be done very urgently, because the claimant's plant was shut down because of the generator failure. The dismantling involved the removal of the stator and its housing -- which required a crane -- and in photograph 494(1) in bundle 2 Mr Savory can be seen manually steadying the stator as it was moved away from the rotor, with another operative operating the crane's control. In evidence Mr Savory described how the crane's motor was (repeatedly) stopped and started and he said (as is no doubt obvious) that the stator movements would have been jerky had he not steadied it. We can see from the photographs (once the stator had been pulled away) that aluminium heat sink fins (which are brittle) had been broken off at some stage (two fins on one side and three on the other: see the photographs in bundle 4 at 867 and 870). At the time, no one would seem to have made any comment about this occurrence, and Mr Savory not only has no recollection of the damage but until he saw photographs disclosing the damage in December 2003, he would 'have sworn that there were no fins broken'. He is adamant firstly that he did not break them in the course of his work, and secondly that had he done so he would (at the time) have noted the event and been surprised. He does not believe that anything that he did could have accounted for the breakage, and cannot say how the damage was caused. Mr Graham Heatrick, the claimant's Operations Manager at Wissington, was intermittently present during the dismantling process; he does not recall there being any aluminium debris in the base of the exciter and there are photographs of the base taken during the dismantling in the defendant's supplemental disclosure bundle at tab 11, photograph 36, and in bundle 2 at tab 4; in none I find is there any aluminium debris visible -- although copper debris is evident. "20. What was immediately apparent after the stator was removed was: (i) substantial penetration damage to the end windings in the location shown on the photograph at bundle 3, 527, and (ii) some damage to the stator including damage to the two stator damper bars shown at 12 noon and 3.00 pm on photograph 495(1) in bundle 2. "21. The exciter was taken to the defendant's Bradford works for repair and on the night of 30th September and over the one or two days following there were discussions between Mr Heatrick and the claimant's Senior Engineer (Electrical), Mr Richard Morgan, representing the claimant, and Mr T Cooper, the defendant's Bradford Plant Manager, its Bradford foreman, and others; the claimant's case as to these discussions is set out in the Particulars of Claim and in witness statements, and Messrs Heatrick and Morgan gave evidence before me. The defendant has not chosen to call any party to these discussions. Both Mr Heatrick and Mr Morgan were impressive witnesses, whose evidence I accept. I find that in the course of the discussions: (i) it emerged that the rewind had not been done in accordance with the new design, but in accordance with the old. (ii) there was an acceptance on the part of the defendant's representatives (and in particular Mr Cooper) that the failure had resulted from a defect in the end windings -- the likelihood being that the use of the original design had caused the problem, Mr Cooper stating that this design involved excessive shaping with a mallet, which process the defendant's foreman said was extremely difficult since there was so much copper to fit into a small space. (iii) it was agreed that there had been a migration of the windings, and a repeat of the earlier 1996 occurrence -- but this time the problem was not caught at an early stage but resulted in a catastrophic failure. (iv) there was discussion about the missing heat sink fins (because these had to be repaired or replaced) -- but there was no suggestion that these had contributed to or caused the failure."

"22. The defendant, by its defence of this claim, disputes all of the above matters, and yet has not chosen to call anyone (other than Mr Savory) who was involved in the 1996 works, nor Mr Richard Emery, who was the author of a memorandum dated 4th March 2003 (to which I shall refer presently) and who was heavily involved in the design of exciters for the defendant and was well acquainted with the 1993 design revision (and is employed by the defendant now). It may, of course, be the case that the defendant's representatives were wrong in the views that they expressed, but when weighing all the evidence it seems to me that I am entitled to have regard to what the defendant's employees thought and said at the time."

"23. At the beginning of October 1996 the defendant carried out the repairs to the exciter (including rewinding) in accordance with the later design, and the generator has worked without problem since then. These works were carried out without charge to the claimant. The defendant suggested (in a letter dated 3rd November 1997) that the work was done in the interests of goodwill and without acceptance of responsibility; however, the fact that no charge was made is consistent with the defendant's stated position at the time of the discussions I have referred to above."

"4.4 I consider that, on balance of probabilities, the integrity of the electrical insulation failed because the rotor winding migrated towards the stator, with which it came into contact, damaging insulation on the rotor winding and thereby causing it to fail."

"9.5 Failures of the diode cooling fins most likely occurred when the exciter was being dismantled rather than when the generator was in operation. Therefore, fin failures were not responsible for the failure of the exciter."

"9.6 On balance of probabilities, failure of the exciter on 29th September 2003 was due to an electrical fault."

"Against: no record of remains of such an object in the sump."

"Against: I would have expected the damage to the stator to be more extensive and uniform."

'There is disagreement as to the possibility that the heatsink cooling fins might have fractured during operation. There is no mechanism that IW is aware of that could explain the spontaneous mechanical failure of one, let alone five, diode cooling fins during operation of the generator after such a period of continuous operation. IW and PJ note that no debris from the damaged fins was reported when the exciter cowling was removed, despite five fins being found missing at a later stage. SW is of the opinion that abnormally high speeds will have been reached during the first generator trip, and that this, possibly combined with the violent axial movement of the generator shaft, might have caused the fractures.'

'... there will ... have been at least one transient pulse of torque during the "turbine manual trip", and that when transmitted through the gearbox this could have produced an axial movement through the shaft.'

"36. The following are the reasons for my finding as to the migration of the end windings: (i) Once a fin or other foreign object is excluded as cause of the damage, then the expert evidence of Professor Williamson (the defendant's witness) is that migration was the most likely scenario. (ii) There was unexplained migration discovered in March 1996 sufficient to bring the windings in a localised area into contact with the stator. (There is no basis for suggesting that the fault progressively developed over the preceding 5 years -- it was unexplained and Professor Williamson stated in terms when he gave evidence that he had no idea over what period the damage seen in photograph 475(1) in bundle 2 developed.) The rewind was carried out to the original design (as to which more later) and I have no reason to doubt the statement of Mr Emery (the defendant's employee who may be presumed to have knowledge of the matters spoken of by him) that the VPI process 'made little change to the performance ... mechanically': see his e-mail dated 4th March 2003. In the circumstances, it seems to me entirely plausible that what had earlier occurred had simply recurred, but that this time it was not discovered until there had been a catastrophic failure, this being indeed the conclusion reached at the time by the defendant's personnel who were actually involved in the events. (iii) Dr Jowett furnished an explanation, consistent with the evidence before me, as to how the penetrating damage visible on photograph 527 in bundle 3 could have resulted from migration bringing the end windings in one location into contact with the damper windings which can be seen damaged on photograph 495(1) in bundle 2. That explanation is that at the point at which the damper bar was severed, the bar could have been flipped back and pushed into the very small gap between the end winding and the damper bar. He was of the opinion that the damper windings had caused the damage visible on photograph 527 in bundle 3. I found his evidence not only plausible but convincing, and I accept it. In his closing submissions, Mr Sampson, in arguing that Dr Jowett's theory is unlikely, ignores part of the evidence of Dr Jowett and indeed of Professor Williamson. * In paragraph 10, he quotes Professor Williamson as saying that he would have expected to see evidence of bulging around the circumference, but ignores his evidence that the section shown on the photograph has been destroyed (along with any evidence of bulging). Professor Williamson indeed stated that the fact that there was no sign of scuffing or migration did not negative the claimant's case and did not mean that migration was not the effective cause of the failure. Indeed, I note that Professor Williamson in paragraph 4 of his report, stated: 'Photograph 43, which shows a damaged damper winding that has been twisted and bent back on itself. This is consistent with it coming into violent contact with the rotor. The mechanical damage to this damper winding might also have arisen as a result of it bearing the brunt of the reaction force exerted on the stator when some extraneous object became lodged between it and the rotor. The relative locations of the damper winding and the rotor end-windings indicate that the most probable site of such an interaction would be the end-winding.'. * In paragraph 12(b) Mr Sampson argues that with the mechanism for damage propounded by Dr Jowett 'it is inconceivable that no other damage would have been visible on the circumference of the end windings' but that point was specifically addressed in cross-examination by Dr Jowett, who said that if only one part of the end winding stood proud -- as it might have done because the end windings have elements of irregularity and unevenness -- the damage need not only have been in one location. In the end, I find that it is more likely than not that the damage occurred in the manner postulated by Dr Jowett."

"In the event, however, I am satisfied that the process did not achieve its objective, and I agree with the submission of Mr Davies, counsel for the claimant, and find that in the absence of any explanation for the failure, it is right to infer that there was a defect in the process involving a failure to use reasonable skill and care in its application since, as I have said, it is agreed by the experts that the process, properly applied, should have significantly increased the mechanical strength of the end windings."

"The learned judge erred in finding that the heat sink fins became detached during dismantling the Exciter when there was no evidence that the same happened and in fact the evidence suggested very strongly that it would have been impossible for such damage to have occurred in that way."

"The learned judge erred in refusing the Defendant permission to rely upon the expert evidence of Mr Regan of the Defendant company to deal with the Defendant's theory for failure. He had however on the first day of the trial permitted the Claimant to adduce and rely upon expert evidence in the form of supplemental reports from the Claimant's expert witnesses as to that theory. The Defendant was thereby denied a fair trial."

"Since 1989 Alstom have produced 164 of this type and size of generator exciter. There are no known instances of winding migration other than this machine in March 1996. I believe that the only explanation for this is repetitive significant over speed where the speed of the exciter was greater than 1800 rpm. The defendants have no control over the speed of the machine."

"The Renk Tacke gearbox controls the shaft axial position from its wheel thrust bearings on the alternator side of the wheel. "

"Dr Wadsworth does not agree with this theory and makes the point that there is no evidence of impact damage from broken heat sink fins. There may well not be. It is possible that the interior of the cowling would not show signs of impact from a fin travelling at such a high speed and it is far more likely that fins would have hit the base plate. The sheet metal casing would absorb a large part of the energy by deflection. I have already stated that there are gaps in the stator into which or through which a damaged fin could have entered. The photographs do not show any loose broken fins but the photographs were not taken by the defendants and they were not present during the initial stages of removing the cover and disconnecting the up shaft leads."

"My argument rests on whether or not this event [a reference back to what had happened at 2.15] subjected the generator to a sudden change in acceleration or deceleration, which when transmitted through the gearbox would I believe produce a transient axial movement of the shaft."

"For reasons that I shall state, in my judgment, it is not in the interests of fulfilling the overriding objective that permission be granted to adduce the witness statement of Mr Regan."

"3. D irections were given as to the adducing of lay and expert evidence. The lay witness statements of both sides should have been exchanged on 27th June 2003 and a debarring order was made against the defendant on 15th July, giving a final extension to 23rd July, at which time some witness statements were served which, frankly, do not take the matter any further forward at all. There was at all times, I am satisfied, available to the defendant, had it wished to adduce this evidence, the factual evidence of Mr Roger Regan, who has at all material times since the proceedings have commenced, as far as I understand it, been engaged by the defendant in a senior management position, being the manager of central operations of the defendant. The defendant, notwithstanding that it had thought it appropriate to plead a positive case, and had what appears to be relevant evidence that Mr Regan could give, chose not to adduce that evidence. "4. Moreover, permission was then given later in the year to both sides by order dated 19th September to rely upon the expert evidence of two engineers. The defendant again, notwithstanding that its pleading was averring a positive case, chose not to rely upon Mr Regan (no doubt for its own good reasons) as an expert, even though he was in a position apparently to put forward a theory as to how this failure had occurred. "5. The expert evidence that was relied on by the defendant was that of Professor Williamson. Professor Williamson in his report did not reach any clear conclusion, or indeed any conclusion on the balance of probabilities. But at some stage between submitting his report and the joint experts' meeting, Professor Williamson felt able to state the conclusion that he has now reached on the balance of probabilities as appears in the joint experts' statement. "6. Even then, there was no wish and no application by the defendant to adduce late the expert or lay witness evidence of Mr Regan. Only on the first morning of the trial (3rd December) after the defendant had been faced with rebuttal evidence that came inevitably from the theory that had come at a very late stage from Professor Williamson, did the defendant seek an adjournment to obtain further evidence. That evidence has produced a supplemental report from Professor Williamson and there is of course no objection to that going in. But it has also produced a witness statement from Mr Regan that contains a mixture of fact and opinion. There is no good reason that the defendant has advanced before me why it did not produce either factual or expert evidence from Mr Regan at the appropriate time. "7. Leaving aside paragraph 6 (which does seem to me to flow directly from the evidence with which the defendant has been faced) the expert theory that is now put forward and advanced in Mr Regan's evidence was a theory that, in my judgment, if the defendants had wished to advance through his evidence, they should have done by adducing the evidence at the appropriate time. To my mind, the defendant's action in doing this at this late time inevitably will cause significant prejudice if I allow this evidence to go in. "8. So far as expert evidence is concerned, the defendant in effect will put the claimant in a position of having to face substantial evidence from an additional witness at this stage (such evidence being produced only for the first time today). So far as factual evidence is concerned, leaving aside paragraph 6, again assertions are made without any documents being produced. For example, in paragraph 16 of the witness statement, oral evidence is given without discovery, and without the claimant having had the opportunity to investigate matters. It seems to me, as I say, the interests of justice are not advanced by allowing such evidence to be admitted now and I refuse permission in the exercise of my discretion to adduce this evidence late."

"2. Although I did not say so in my short ex tempore judgment: a. I felt that if I allowed Mr Regan's evidence to be adduced, it was unlikely that the trial would be concluded in the allotted time, which would have necessitated a significant adjournment, which I felt was undesirable; and b. I also did not think that the Court would be likely to be assisted or the interests of justice served by allowing to be adduced the non-independent expert opinion of Mr Regan, particularly when the defendant was in a position to adduce independent expert evidence to similar effect from Professor Williamson (in his supplemental report), as was conceded by Mr Sampson. (on 3/12/03 it was assumed then by all three Professor Williamson had the expertise required to give the evidence contained in his report, the true position only emerging when he was called -- see para 33.3 of my Judgment)"