Case Histories

PRODUCT: Aeroflow Control Valve

CUSTOMER: BP Chemicals, Grangemouth Power Station

PROBLEM AREA: De-superheater Spray Water Control

Issues:

The power station at BP has no LP turbine. The exhaust steam from the IP turbine is used as process steam for the plant. This steam has a high superheat value and must be de-superheated to varying degrees for various processes.

Unfortunately none of their process runs for 24 hours a day, 7 days a week and during times when individual processes were not running, the steam legs would fill with water due to leakage of the spray water control valves. This resulted in increased operator time, to drain lines, plus water hammer issues.

Solution:

Fit Leslie Aeroflow, ZERO leakage, control valves.

The engineers at BP did not believe the Leslie claim for zero leakage, however, as we offered them a trial valve, on a no cure no pay basis, they decided to try one and installed their first Class 1500, Aeroflow Spray Water Control Valve in 1997.

Such was their scepticism that the first valve was specified to be flanged Class 1500 RTJ, so they could remove it and test it on the bench. They removed the valve for inspection two or three times in the first 12 months. The final trial on the bench was 150 Bar upstream, looking for seat leaks into the outlet side of the valve. Not a drip was seen.

As of this report (7 June 2005) BP Grangemouth now have 36 Leslie Aeroflow valves of varying classes installed on the site. Not only do they have valves that do not pass, but the quality of temperature control exceeds all previous installations.

CUSTOMER: British Sugar, CHP Plant, Bury St. Edmonds

PROBLEM AREA: Boiler Feed Water Spill Back to Hotwell

Issues:

The inlet pressure for this application is 107 BAR, the outlet pressure nominal, line head pressure between valve and hotwell. The original valve supplied suffered severe cavitation, resulting in trim damage to such an extent that it was permanently by-passed. This was having an effect on plant efficiency and maintenance man hours.

Solution:

Fit a Leslie Aeroflow Control Valve. We recommended a Leslie Aeroflow control valve with 3 Stage, Anti-cavitation trim and a REXA electro/hydraulic actuator. This valve, with recommended spares package, was supplied and fitted in 2001.

To date no further spares have been ordered.

CUSTOMER: Scottish Power, Cockenzie Power Station

PROBLEM AREA: De-superheater Spray Water Control

Issues:

Cockenzie, like many other UK power stations, is an old station, designed and built as a base load power plant. Unfortunately, in today’s environment very few, if any, power stations are run as base load. The necessity for two-shifting is putting demands on many control valve applications for which the original valves were never designed. The spray water control valves at Cockenzie were a major issue. The quality of temperature control was poor, with significant excursions from set point being experienced during any load change. The maintenance levels were unacceptable with valves constantly being isolated, requiring repair, and the master spray valves being used in an attempt to control steam temperature.

Solution:

Fit Leslie Aeroflow Control Valves. With an inlet pressure of 170 Bar, a downstream pressure of 160 Bar and a temperature of 222^oC, 2 Off  1” Leslie Class 2500 Angle Pattern control valves, with reduced trims, were fitted during the summer of 2003. These valves were fitted with PMV D3 digital valve positioners. Such was the improvement in performance, from both quality of control and reduction in maintenance to nil, that a further 14 valves were ordered in December 2003 and have been fitted.

As a result of their experience with the valves at Cockenzie, Scottish Power have ordered a further 12 Off 2” Class 2500 Aeroflow control valves for their spray water application at their Longannet Power station.

They have also ordered a Gland Steam pressure control valve for Cockenzie Power Station, handling 1500 Kg/Hr of superheated steam @ 60 Bar and 500 Deg C. but with a Maximum pressure capability of 171 Bar. This is a 1” Class 2500 valve in Stainless Steel complete with a Leslie cylinder actuator, to open of air failure.