Main steam stop valve

October 2006 Valves, Actuators & Pump Control

The Spirax Mitech Compound valve consists of a 200 mm and an 80 mm angle valve joined together to supply steam to a power generation turbine. The large valve is fitted with a quick-opening trim, while the 80 mm valve is fitted with an equal percentage trim to allow a greater turndown.

When starting the turbine, the 80 mm valve is opened slowly in order to raise the turbine temperature. When the turbine has reached a high enough temperature, the 200 mm valve is then opened. This prevents damage to the turbine due to thermal shock.

The 80 mm valve is then used to control the turbine speed. The 80 mm valve is therefore actuated pneumatically, and fitted with a positioner, while the 200 mm valve is hydraulically actuated. The 200 mm valve is fitted with a drip tray to prevent leaking hydraulic fluid from dripping onto hot metal components and creating a fire hazard.

The 200 mm valve provides 85 t/hr maximum while the 80 mm valve provides a 20 t/hr maximum flow rate providing a total of 105 t/h maximum. The compound valve is suitable for use in temperatures up to 60°C and will operate with a 4,6 MPa inlet pressure.

For more information contact Richard Ransome, Spirax-Sarco, +27 (0) 11 929 6344, [email protected]

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Main steam stop valve

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