Valve repairs improve station startup performance

Edited by the Engineeringtalk editorial team Jan 31, 2005

Furmanite has completed a significant valve repair contract as part of a shutdown programme at Scottish Power's Cockenzie power station, at short notice and within time and cost parameters.

Furmanite has successfully completed a significant valve repair contract as part of a shutdown programme at Scottish Power's Cockenzie power station, at short notice and within specified challenging time and cost parameters.

Furmanite was called in by Mitsui Babcock on the basis of its experience and credentials in valve maintenance and repair including holding a three year contract for five BNFL Magnox Generation nuclear power generating sites to work on the Unit 2 shutdown.

"Among the key criteria we had to meet to secure the contract was the ability to undertake the work required within a specified number of hours on site, and within specified costs for off-site work, after the customer had had a bad experience with a previous contractor", Furmanite Business Manager Ken Coulston explained.

"The fact that we were able to commit to meeting these requirements, and have demonstrated that we could do so successfully despite a number of unanticipated hurdles, has been critical to the success of the contract".

Some 60 boiler safety valves including standard and servo loaded torsion bar, main steam stop and bypass valves in sizes ranging from 0.75 to 8in, and pressures up to 190bar, were tagged, removed, inspected and overhauled.

This included stripping and cleaning, replacement of spare parts as required, remachining as necessary, and lapping of seats and discs, followed by assembly, set pressure and leak tightness testing, and calibration.

The valves were inspected by the customer at stripped down stage, and testing was also viewed by the customer.

The valves were then returned to site and reinstated.

Some 14 of the steam valves were welded-in and these were overhauled in-situ, including seat reprofiling and lapping, using portable machines.

With all the valves reinstated the boiler torsion bar safety valves were then tested (first cold with no line pressure and subsequently at normal operating pressures and temperatures) using Trevitest, Furmanite's online valve testing technology for safety and relief valves, which produces extremely accurate test results, normally within +/-1% of the set pressure, and provides a date-marked certified print-out of valve performance.

This achieved one of the key requirements for the project enabling these valves to be set up to their design parameters under operating conditions, thus ensuring that they were fit for purpose.

The work was successfully completed within the anticipated time frame and cost parameters, with Unit 2 returning to full operation at the end of the allocated ten week outage.

The shutdown was completed safely, an achievement to which Furmanite contributed.

Following the success of the project Furmanite was also given work on Unit 4 (now complete) and Unit 1, which is on-going.

Commenting on the project, Donald Ross, Mitsui Babcock Site Manager said: "We were delighted with Furmanite's ability to rise to the challenge and meet all our specified requirements, giving us the reassurance of a high level of service and expertise within pre-agreed parameters".

"The Furmanite team worked extremely well and very efficiently Scottish Power Project Manager Finlay Macleod added: "Our arrangements with Mitsui Babcock challenge them to seek cost savings whilst improving performance".

"They do this by closely integrating their subsuppliers into their organisation on site".

"In Furmanite they have found a willing and effective team player".

Coulston concluded: "We have the facilities, expertise, quality assurance and proven track record to provide a reliable valve maintenance and repair service that will ultimately help customers to reduce cost and increase efficiency, by ensuring that their valves are in top condition in turn offering improved safety and reliability, and reduced operating costs".

"We were pleased to be able to step in at short notice and provide this service to Scottish Power, demonstrating what we are able to achieve".

Cockenzie Power Station, a coal-fired generating station in East Lothian, has an installed capacity of 1200MW comprising four 300MW units.

Work has been carried out to improve Cockenzie's startup times - an achievement to which Furmanite has contributed - enabling the station to capitalise on generating opportunities in the competitive market.