Pressures of some 4400psi were safely encountered by the very latest in valve-testing equipment, at Drakelow, TXU Europe’s power station in Derbyshire, on a unique super-critical boiler. Trevitest on-line valve testing was carried out by Furmanite technicians on eight 4-inch torsion bar safety valves on the unit 12 boiler to meet interim testing requirements. The ability to test valves without the need to shutdown is a significant benefit, avoiding undue stresses on the machinery – much of which is over 30 years old – as well as significant costs.
Furmanite’s Ken Coulston, central support group manager, explains: “The system operates by means of a hydraulic power pack and load cell linked to a computer-based recorder, to apply a force to the valve spindle, overcoming the spring tension. The data obtained is then used to determine set pressure, spring adjustment, valve lift, and an indication of reseat pressure.”
Work was also carried out in unit 10, where a sub-critical boiler had just been overhauled and was on full outage. All 16 valves were tested whilst the boiler was in operation at 2800psi. Accurate assessment of the valves requires the boiler to be operating at within 20% of full working pressure. This necessitated a testing period of three weeks, of which eight days were spent on-site – corresponding to times when boilers were operating at or near full load.
