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5. Disassembly and Inspection of the Main Steam Valve

Main Steam Valve Overhaul

The overhaul of a steam turbine's main steam valve involves critical steps including disassembly, inspection, repair, reassembly, and testing to ensure reliable valve operation during unit startup, shutdown, and operation.

1. Pre-Overhaul Preparation: Prior to overhaul, ensure the equipment is safely isolated. This includes removing insulation, disconnecting oil lines and thermal control components, and sealing all openings to prevent foreign object ingress. Simultaneously, verify that EH oil quality meets specifications, steam quality is compliant, and complete static valve operation test records to establish baseline data for maintenance.

2. Critical Component Inspection and Repair:

1) Sealing Surfaces: The sealing line between the valve plug and body must exhibit full circumferential contact without grooves, pores, or scratches. Any defects require grinding repair.

2) Valve Stem and Packing: Inspect the surface finish of the valve stem. Adjust the packing gland clearance to ensure no sticking occurs. Replace all sealing gaskets before reassembly.

3) Actuator Components: The inner wall of the piston cylinder should be smooth. Record the free length of the spring and compare it with historical data. The piston rod and piston surfaces should be free of damage.

3. Assembly and Testing:

Replace sealing O-rings before reassembly; lubricate piston surfaces with silicone grease. Calibrate piston rod free stroke to ensure smooth, unobstructed operation. Post-repair testing includes valve tightness tests and OPC overspeed tests. Only proceed with operation after passing all tests.

5-1. Manual Main Steam Valve Control Panel Disassembly and Inspection