The West Winford Incident (16 page)

“Bloody hell, it's cracked to buggery, I can't believe it.” Gritty and Dave almost danced around the lab. They decided to continue loading this specimen to failure, upon which it was clear to see, on the otherwise bright fracture surfaces, a crescent shaped area of discolouration. This was the area of the stress corrosion crack and was almost identical to the appearance of the fracture surface on the failed Winford disc. The procedure was repeated on the second specimen with a similar result. Following this, Dave asked Gritty to carefully remove one of the other specimens, which had not been exposed to the NDT dye-penetrant fluid. He was delighted to find this also cracked. The other specimens were left undisturbed so that they could be used for demonstration purposes for anyone doubting their claims.

Dave was shaking as he took in the serious implications of this discovery. He was delighted, as he believed that he had produced the most unexpected result in the field of stress corrosion for years. Stress corrosion cracking in high purity steam! No one would believe it, but he had the proof. He had his specimens and he had Bunsen's steam analysis. The steam quality had remained high throughout. He didn't know what to do. He called Mike Pearson and Bunsen, both of whom had been so helpful to him. Ian had already arrived having been attracted by the noise of the two of them.

A couple of hours later Dave was still in a daze of pleasure. He was brought back to earth quite suddenly, as he realised that his personal joy at the findings would not be shared by the Authority or other utilities operating turbines of the Winford type. These results would send shock waves through many organisations. All turbines of this type were at risk of sudden catastrophic failure. Many had been in operation for much longer than Number 2 turbine at Winford. It was only the fact that the Winford discs had been unusually brittle that caused failure with such small cracks present. Other LP turbine discs still in service would, almost certainly, contain cracks and possibly some deep ones. There had already been one fatality resulting from the Winford failure. Next time, things could be much worse. Though there were usually few people around turbines under normal operation, more were present when measurements were being taken, or during turbine run ups, shut downs and overspeed testing.

Time was getting on and Dave was anxious to make a start on writing his report. He had the odd irrational fear that if he didn't claim the credit for this unexpected discovery, someone else would beat him to it – probably tomorrow. There was no point phoning Sue to tell her the news and say that he might be late home, as he knew that, as it was Friday, she would be at her blessed Peter's group indexing.

He settled to his work. Ian helped initially by taking a selection of photographs of the specimens and their cracks. They had photographs of the specimens before testing and the Station Chemist at Winford had taken a nice shot of the test rig in operation. Gritty cut a couple of sections through one of the specimens and prepared them for examination under an optical microscope. These showed other cracks, typical of stress corrosion, which he photographed. Soon Dave had all the illustrations that he needed and his colleagues went off on their weekend.

He stayed on and wrote his draft report, outlining the object of the experiment, and the on-site equipment details, together with the specimen design and purpose. He added the steam analysis record, quoting maximum and minimum values for impurities, which were miniscule. Then, finally, the results and a brief discussion, with such great pleasure, followed by his conclusions and recommendations. It was just past midnight. He spent the weekend putting the final polish to his report, which he would get typed first thing on Monday.

Sue was delighted with the Potten family bible which, via the Loomes family, came down to the Turners. It was heirlooms such as this that family historians loved to possess – a tangible link with their past. It had been her great grandmother Caroline's, whichever one of the two candidates she turned out to be. Caroline would have been seventeen years old when she wrote her name inside the cover in 1863. Amongst other things, she had listed the name of her husband and their children. The bible had been passed down to Sue's grandmother, Caroline Jane, who had carried on the tradition, recording her marriage and children's birth, including Sue's father. This was wonderful. She could now add more detail on her Turner ‘family tree'.

Sue was overcome by her great grandmother's foresight and she determined, despite her difficulty with the Potten line, that this was one ancestor whom she felt an obligation to pursue, and she would. That being accepted, Sue decided that she should narrow down her research, for the present, to two families – the Boughtons and the Pottens – as these appeared to be the most fruitful.

Her thoughts turned to the forthcoming summer holidays. She knew that Barry and Velma were planning to go to Hunstanton. She wondered if they would mind having Jo and Katy along for part of their stay. There was no doubt that the cousins would welcome their company. This would give her and Dave the chance to spend time together. Impulsively she phoned Velma and found that she was happy to help out, positively enthusiastic about the whole idea. Velma and Sue's sister had intuited, from their weekly phone calls, that relations between Sue and Dave were shaky at present. So Velma's enthusiasm was, in part, a kindness to her sister-in-law as much as a favour for the girls.

Dave's euphoric mood lasted for days and he gladly endorsed Sue's suggestion. He thought that he could take a few days off work, following the forthcoming sub-committee meeting. This would allow time for all his colleagues to digest his fantastic results, especially those smoothies at the Slough labs, he thought with relish.

“These are great results David.”

Tony had already scanned Dave's report on the on-site rig experiments. He was pleased as this would be a feather in the Department's cap. He would discuss it with Sweety. They considered the wider implications of the results. Tony was thinking of how best to present them to the general scientific community.

“Is this the first time that stress corrosion cracking of steel has been observed in high-purity water or steam?”

Dave replied that from his own knowledge, plus an extensive literature search, it was the first time in the case of medium strength, mild or low alloy steels. Tony, after pausing for a moment, demonstrated to Dave one of the qualities of a good section head.

“If your results are correct, how do you explain the pattern of cracking found in other turbine discs on the failed rotor? I understood from the conference, the Slough people were arguing that the most severe cracking occurred in the inlet region of the LP turbine, where there was the greatest concentration of steam impurities and it was this contamination which caused the cracking.” Dave was taken aback, not by the question itself but rather that Tony had been astute enough to ask it. Clearly he had been keeping up with all the developments and understood the detail of the investigation. Dave replied that the observed pattern of cracking could still be explained if no contamination had been present, by virtue of the temperature variation along the LP rotor. The main requirement was that moisture was present, which it was, albeit cycling between wet and dry, near the inlet. The operating temperature of the various discs depended upon their position on the rotor, the hottest being near the steam inlet. This was where the worst cracking would be predicted. As the steam cooled the extent of cracking would be less severe, with little or no cracking near the steam exit. So the pattern of cracking was as expected, even without steam contamination. Tony thought about what Dave had said and after a moment, he suggested that Dave should begin preparing a scientific paper as, he believed, it would take some time to get into print. He should contact the editor of, say,
Corrosion Review
to obtain their instructions to authors.

“This is just the kind of thing that the Strategic Supplies Authority needs to fend off their critics. Let's get our own trumpet blown as soon as possible. Well done David.”

Dave reverted to the train for the next sub-committee meeting. He had been unable to arrange another overnight stay. His work had begun to build up again and he had agreed with Sue to take at least a week's break, whilst the girls were away.

In addition to producing a draft paper, he had begun laboratory tests in an attempt to resolve the most difficult problem of all – just how cracks could initiate in high purity steam. He envisaged that a crack-like surface defect was a necessary precursor to the process. Resolving this was an essential part of his hypothesis. He hoped that Pauline would understand.

On his arrival at the meeting room, Joe congratulated Dave upon his draft report, which he had received the previous day. He was pleased to see that their separate results of crack growth rates, were in good agreement. Dave was full of pride as the others arrived. Henry thanked him for the report and was as charming as usual. Dorinda and James avoided the subject and their conversation centred on the positive feedback they had received from the conference. True to form, Henry had kind words for them too. They took their places around the table. Pauline arrived on cue. She smiled pleasantly around the group without any obvious distinction to any member. Dave marvelled at her. He still could not believe it. Pauline was back to her civil service best. If only the others knew. He immediately dismissed this thought as Henry opened the meeting.

James expanded upon the comments that the Central Research Labs had received following their conference. Amongst them were several from noted authorities on the subject of stress corrosion, who agreed with the conclusion that sodium hydroxide contamination was the cause of the cracking and that mechanical carryover of this from the boiler water during commissioning, probably at times of high boiler water levels, was responsible.

Henry then asked an impatient Dave to introduce his draft report. Dave, bolstered by his pleasure at all the excitement within his own department over the last few days, made a competent presentation of his outstanding results. He concluded by asking the committee to agree to his report being submitted to the main Technical Committee's press office, for approval and permission to publish. He sat back and rather childishly hoped that, in addition to impressing his colleagues, Pauline had also been pleased.

“May I?” asked Dorinda, glancing towards Henry. Having received the slightest of nods, she expressed her grave doubts about the results obtained from the Winford test rig. In her view there were several potential flaws in the experiment, including the possible contamination of the specimens. This could have arisen in workshops, at the power station itself or during inspections. There was also the question of steam quality. She accepted that the bulk turbine inlet steam had been monitored throughout the trials and no contamination had been found. However, she and her colleagues felt that Dave did not fully appreciate all the aspects of their hypothesis, which had been presented at the conference. Their ideas on sodium hydroxide build up, she reminded them, were based upon the introduction of miniscule amounts of sodium hydroxide. Such amounts would not cause any concern to Dave's chemistry colleague, but, by an alternate wetting and drying mechanism, this would gradually build up to significant levels and initiate a small crack. This process would be repeated as evidenced by the pattern of staining clearly found on the fracture surface. As Dave listened to Dorinda, his initial feeling of shock gradually gave way to anger, which he did his best to hide. He replied that he had confidence in the continuous steam quality measurements. He reminded the others that the technique used was much more sensitive than the normal methods used on modern power stations. If these were being questioned, what were the value of any measurements elsewhere?

James, continuing Dorinda's theme, pointed out that these improved techniques were not being used when the suspected period of contamination took place. Dave, determined not to give ground, countered by reminding his fellow members that he felt his confidence in the rig results was supported by the fact that his growth rates were very similar to those obtained by Joe in his laboratory rig, where contamination was unlikely. James accepted this, but it was the question of crack initiation that was the issue, not its growth. The vital step in the whole Winford failure came down to this: just how did the cracks start in high purity steam? He pressed Dave on this point. Could he explain how cracks initiated in disc steel operating in high purity wet steam? Dave had to admit that he hadn't really got very far with his ideas on that aspect, but he still believed that his results were as valid as their own hypothesis. He became angrier and ended his argument by suggesting that Dorinda and James were biased towards their own tenuous theory. They didn't want his results to be circulated as this would cast doubts upon theirs. Joe, who, together with Henry, had been a spectator during these exchanges, found it amusing to observe the two rival centres within the same organisation clashing publicly in this way. Henry was more preoccupied with the likelihood of having to make a decision of how to resolve the difficulties.

To give Dorinda her due, she did not appear to take offence at Dave's personal outburst. She merely reiterated that there was the possibility of contamination in Dave's test and this should be addressed before proceeding. She continued by noting that their own hypothesis did not have the problem of explaining how cracks initiated, as everyone knew that sodium hydroxide would do this. All they had to suggest was a viable method of how it got there and this, she contended, they had done. Dorinda concluded by reminding Dave what he was asking the sub-committee to do. The frightening implication of his results was that many operating turbines around the world, were in imminent danger of blowing up, during normal operation. If the sub-committee agreed to circulate his report, they would be seen to be endorsing this possibility and therefore she felt that her colleagues were not being unreasonable in asking Dave to obtain some confirmatory evidence, to support his initial findings.

Henry politely called a halt at that point, suggesting that further discussion could be continued outside the meeting and a decision with regard to publication could be made. He assumed that it would take Dave a while to prepare his report in publishable form. Despite Dave's annoyance, he had little option but to go along with Henry's suggestion. The ramifications of this debate occupied Dave's thoughts for the remainder of the meeting, to the extent that his intention to try to have a quiet, private word with Pauline was forgotten. On his trip home he became calmer and gave some thought to the new situation and how he should proceed.

Could his specimens have been contaminated, as had been suggested? He didn't think so. After machining, the specimens had been carefully degreased and kept in a desiccator until the loading process and this had also been done under laboratory conditions. Following exposure, he had handed them to the NDT people making a point of requesting that only the two specimens selected for examination be subject to the dye-penetrant solution, the others would be protected. So that left the steam itself. According to Bunsen, no measurable contamination had occurred and Dave respected his opinion. No, he was confident, the results were valid. However, the difficulty was in convincing others of that. He could repeat the experiment, but that may not be enough. He really needed a different approach. Such an alternative course of action occurred to him and he began to plan his next move. He would have to work quickly.

Firstly, assuming that the test rig results were valid and low strength steel could indeed succumb to stress corrosion cracking in high purity wet steam, there was no reason why it would not suffer the same fate in high purity hot water. It would be easy to carry out a standard laboratory stress corrosion test. He could use very high purity, laboratory grade, deoxygenated water, which would be free from contamination, and if the specimens were fully immersed, there would be no chance of concentration by evaporation occurring. That would be his next job.

Secondly, he would put extra resources into the work he'd just begun, looking into possible ways that a crack might be formed in turbine disc steel in high purity hot water.

*

“So we're at the bottom of your list of priorities as usual,” complained Sue when Dave announced that he wouldn't, after all, be able to take any time off. She had spent part of the day making the final arrangements. “Well sod you, the rest of us are bloody well going.” Sue was shaking with anger.

Dave, still smarting from his earlier setback, found it difficult not to enter into a full scale row and clear the air once and for all, but he realised that they would quickly lose their tempers, so he left the house and sought solace at The Marden Arms. He had a pint of 6X and reviewed his position. He had been under pressure since joining the SSA, one thing leading to another, with increasing urgency. He recalled recent events, with the preparations for the Winford trial. Firstly, the rush to obtain the necessary equipment and test pieces in time for the turbine outage, followed by the difficulties of getting everything set up on site. Added to this was Sue's constant nagging. He brooded and became increasingly morose; the cheerfulness of the pub was at odds with his mood. He left abruptly.

He drove aimlessly towards Marlborough and stopped at a small village pub. The smoke-filled bar was busy, mostly agricultural workers it seemed, but, being a stranger, Dave thought that he would be left alone with his thoughts. He ordered a pint and a whisky and found a vacant table in an alcove. He drank quickly and collected another pint. This did not improve his mood and he continued to feel sorry for himself. He had been so excited. All the hard work setting up the on-site tests, followed by the elation of the unexpected and significant results. The prospect of having a paper published, which would surprise many in the corrosion fraternity and have a major impact on power plant operators worldwide, had heightened his delight. All this was now being put under threat by those smug buggers at Slough.