Thai This on for Size

The Tai Oil power plant is supplying power to the Thai Oil refinery. This is a small cogeneration power plant with 50 MW capacity. The plant was commissioned in 1999-2000. Since the startup the plant has had many problems with the turbine bypass valve.

The system consists of a steam pressure reducing valve, desuperheater and spraywater valve. The system serves a dual function of turbine bypass and pressure reducing and desuperheating station. Generally the valve is used during startup of the unit and remains in closed condition during normal run. On turbine trip the valve goes full open. The valve is also used to control and maintain the boiler output pressure.

Major problems observed with the existing valves were:

• Unreliable operation
• Sticking of the valve when the valve starts opening
• Trim (plug and seat) erosion resulting in frequent maintenance involving spares and manpower

Operating a unit with an unreliable turbine bypass system is a very serious problem for the operating personnel as it puts the safety of the unit in jeopardy. Thai Oil was looking for a reliable, field proven solution to this problem. CCI offered the technical advantages of the DRAG® trim backed up by experience of the last four decades of many proven installations all over the world.

Published in SOLUTIONS Spring 2002