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Results

We tested a number of turbines, typically those driving boiler-feed pumps or forced-draft fans. Of the first five steam turbines we trip-tested with the revised method, three more failed to trip. This confirmed the experience with the emergency generator turbines, and established the need to change our trip testing strategy.

Lessons

1. The need to avoid production losses can blind us from doing a very important duty of maintenance—to ensure TI and hence plant safety.

  • 2. We can improve TI and avoid losses if we can accept a slightly less-than- perfect solution.
  • 3. The alternative is to accept production losses so as to be able to assure we meet TI requirements fully.
  • 4. Trip testing is an important safety check, and must be performed diligently.
  • 5. There are ways to eliminate or limit the associated loss of production, so there is no justification to avoid testing of trip devices.

Principles

Reliability and safety are closely linked. Protective devices ensure safe operation of equipment and maintenance has a key role to play in ensuring that these devices work whenever they are required. We can ensure we have an acceptable level of technical integrity by testing trip devices at a suitable frequency.

References

. http://www.newscientist.com/article.ns?id=dn3140 i. http://news.bbc.co.uk/1Zhi/uk/4221465.stm ii http://www.theage.com.au/news/tips/crash- alert/2005/09/02/1125302695092.html

(Australia, through its Civil Aviation Safety Authority grounded part of Ansett's fleet in 2001 just before its demise, because of concerns about procedures in the maintenance department).

 
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