Nuclear tribology

Nuclear tribology

mentioned (quoted as being the greatest change in the last 30 years in condition monitoring), and some of the examples given of automation and custome...

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mentioned (quoted as being the greatest change in the last 30 years in condition monitoring), and some of the examples given of automation and customer satisfaction were outstanding. The turn round required meant that one oil laboratory had to deal with 65 000 analyses per annum, and there was no way this could be done without a high level of automation. Another laboratory, with an emphasis on the need to get the customer to take immediate action, even went as far as having final decision sheets with a colour code in the bottom right-hand corner of green, orange or red (and in case you were colour blind the colour dots were circles, squares and triangles !). 'Expert' systems were also publicized and given a definition which involved the human expert's knowledge and experience; they a.lso should be able to give their reasoning back to the operator should a query arise. The actual monitoring techniques were mainly either wear debris monitoring or vibration, although other steady-state parameters, and performance, were included. The well-established hardware was in evidence in both the exhibition and in the papers, with the shock pulse meter probably winning as regards the number of references. Ferrography, magnetic pick-ups and spectrometric analysis were also mentioned. However, the new techniques, such as wear rate and filter blockage were also in evidence; the latter being used to generate discussion on the distinct advantages of on-line monitoring as against off-line sampling and specifically able to cope with an aluminium piston failure. As is usual with this type of conference, there was a considerable amount of banter between the wear debris advocates and the vibration experts. Although there were papers where both were mentioned, it was usually in the sense that one was good and the other totally inadequate! There was also a slight sense of incredulity from time to time, such as

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when it was suggested that a vibration transducer (accelerometer) was able to specifically identify a minute spall on a bearing 8 m away when aroung 200 other bearings were running in the vicinity. (From the same exercise, debris monitoring was discounted due to commonality of the lubrication system for all the bearings!) The old question of whether the monitors were being monitored was not missed either, but at last, with computerization and

quite sensible techniques, it looked as if the answer had a possibility of being positive for a change. No doubt the organizers were pleased with the conference; after all, they had passed the break-even point but there was also a sense of approval from the delegates when it was announced that the 3rd International Conference could well be in two years time. T. M. Hunt

Nuclear Tribology 29 March 1988, Berkeley, UK This one-day meeting, held at the CEGB's Berkeley Nuclear Laboratories (BNL), was organized by the Institute of Physics Tribology Group and supported by the I Mech E and by the CEGB. Its objective was to bring together some of the many aspects of tribology which have required further investigation or development as a result of the advent of the nuclear power industry. The meeting was opened by Dr Les Mitchell (Head, C E G B Laboratories), who outlined CEGB research requirements and then noted the low profile which friction had been accorded in the day's programme. This, he suggested, showed a changing emphasis in that life-limiting phenomena such as wear had now taken priority over the earlier acute problems of persuading mechanisms to work in unlubricated, high-temperature environments. The next speaker and technical organizer for the meeting, Dr John Skinner (CEGB), spoke of the need to assess wear of vibrating structures. In particular he described the methods used to calculate wear of rattling or impacting components such as boiler tubes and then extended previous analyses to show how wear resulting from precessional movement might be calculated.

A presentation by Steve Radcliffe (CEGB) set the scene for a visit to the Tribology Laboratory during which visitors were shown apparatus designed to produce sliding, fretting or impacting wear under conditions of high temperature and environmental control. Also on view was one of Steve's specialities: surface profilometric facilities which in addition to normal surface texture assessment are capable of semiautomatically measuring wear volumes and providing threedimensional maps of the worn surface. Dr John Beard (National Centre for Tribology, Risley) opened the afternoon session with a talk on 'Effect of temperature and environment on wear'. In spite of the post-lunch spot, the only nods were those of agreement as Dr Beard first introduced data covering a wide range of conditions and then noted the ubiquitous nature of the near-surface, hard metallographic features composed of oxide and work-hardened metal which NCT have labelled 'calluses'. It was the origin and behaviour of these calluses which was fundamental to an understanding of high-temperature wear, he argued, and then detailed some of the factors which he believed to be relevant to their behaviour. Dr John Morri (CEGB) continued the

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programme with a description of the sensitivity of initial impact wear behaviour, especially of material transfer, to temperature gradients; the cause of this behaviour is currently not understood. The first truly 'nuclear' presentation was by Dr Paul Evans (Imperial College) who described the effect of 7 irradiation on tribological properties of PTFE and provided a convincing account of how the changing mechanical behaviour led to various responses under three quite different conditions, namely adhesive, abrasive and scuffing wear.

The polymeric interest was continued by Dr Sue Burnay (UKAEA, Harwell) who described her approach to the problem of estimating the ~ dose/temperature synergism of damage to elastomeric seals. She described how the damage rate activation energy is dependent on the dose rate and how it is possible to sum the material degradation over multiple temperature/dose conditions. The day's programme was completed by Dr Terry Chivers (CEGB) who described a contact mechanics analysis of fretting fatigue which rationalized the earlier, apparently conflicting, advice on palliatives. He

emphasized that fretting fatigue was a stress rather than a 'wear damage' related phenomenon; a view which provoked a lively, if inconclusive, discussion. In spite of the disparate nature of the programme content most attendees appeared to find something of relevance to themselves and many commented favourably on the loP Tribology Group philosophy of holding meetings at Laborat.e,ries around the country, allowing visitors to sample the flavour of the particular organization concerned. J. Skinner

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August 88 Vol 21 No 4