Discussion on commisssioning

DR J.R. WILLIAMS, Atomic Power Construction Ltd:

I was interested in Mr Lawrence's proposal to increase system redundancy by providing (together with other changes) triplicated feed valve differ ential pressure transducers on each set of feed valves. However, has he considered whether such differential pressure measurement is needed at all? On Dungeness B, the main feed pump speed is controlled, not from measured feed valve differential pressure but from the feed valve position demand signal. This system maintains the most fully open feed valve on the four boilers at a nearly fully open position in the steady state over the whole 25-100% load range, and so avoids any unnecessary pressure drop across the feed valves.