Main Stop Valve (MSV) of Mitsubishi Steam Turbine ( MHI TC2F-40.5)

engineers November 11, 2023

Main Stop Valve (MSV) of Mitsubishi Steam Turbine MHI TC2F-40.5

Mitsubishi Steam Turbine MHI TC2F-40.5 has 2 set of MSVs. The MSV is the Double Plug Type Valve operating in a horizontal position with the body formed as integral part of the steam chest. The complete MSV arrangement includes Servomotor, Springs and Housings, Links, Levers and Crosshead. The complete valve consists of single seated unbalanced valves (Pilot Valve and Main Valve) which are placed within the other. The steam pressure combines with the spring compression during the opening of the MSV and holds the both valves tightly on respective seats.

The pilot valve which rests inside the main valve and possess its own stroke. As the steam pressure increases, it pushes the pilot valve to leave the main valve seat. The pilot valve after its travel, intimates to another seat fabricated on the main valve bush which consequently makes the lift of the main valve. The main valve travels to contact its backseat which completes the stroke of the MSV.

Maintenance Checks of MSV:

Following Checks on MSV were performed during the Major Overhaul of MHI TC2F-40.5 at

1-     Main Servo Valve Motor Over Travel Check
2-     Spring Bed Clearance Check
3-     Head Bonnet Gasket Compression Check
4-     Main Valve Lift Check
5-     Pilot Valve Spring Compression Check
6-     Valve Bush Clearances
7-     Stem Run-out Check
8-     Link Lever Pin Clearances
9-     Pilot Stroke Check
10-   Valve Seating Contact Checks