Reasons for Valve Leakage and Solutions

1. Leakage Caused by the Falling Off of Closing Part
Reasons:

1. Poor operation causes the closing part to jam or exceed the top dead center, damaging or breaking the connection.
2. The closing part connection is not secure, leading to loosening and falling off.
3. The selected connection materials are unsuitable and cannot withstand the corrosion of the medium or mechanical wear.

Maintenance Methods:

1. Operate correctly: Do not apply excessive force when closing the valve, and do not exceed the top dead center when opening. After fully opening the valve, the handwheel should be slightly turned back.
2. Ensure the closing part is securely connected to the valve stem, and provide anti-loosening devices for threaded connections.
3. The fasteners used to connect the closing part and valve stem should resist corrosion by the medium and have adequate mechanical strength and wear resistance.

2. Leakage of Sealing Surface
Reasons:

1. The sealing surface is not ground evenly, preventing the formation of a sealing line.
2. The connection between the valve stem and closing part is misaligned, or there is wear at the connection.
3. The valve stem is bent or incorrectly assembled, causing the closing part to be skewed or misaligned.
4. The selected sealing surface material is not suitable for the working conditions.

Maintenance Methods:

1. Correctly select the gasket material and type based on the working conditions.
2. Adjust carefully and operate smoothly.
3. Tighten bolts evenly and symmetrically. When necessary, use a torque wrench to ensure pre-tightening force meets the required standards. Do not tighten bolts too much or too little. The flange and threaded connections should have proper preload gaps.
4. The gasket should be properly centered, with even pressure. Gaskets should not overlap or use double gaskets.
5. If the static sealing surface is corroded, damaged, or poorly processed, repair and grind it, performing a color inspection to ensure it meets the required standards.
6. Ensure cleanliness when installing the gasket. Use kerosene to clean the sealing surface, and ensure the gasket is not dropped on the ground.

3. Leakage at the Seal Ring Connection
Reasons:

1. The seal ring is not pressed firmly.
2. The seal ring is welded to the body, but the welding quality is poor.
3. The seal ring connection threads, screws, or pressure rings are loose.
4. The seal ring has been corroded.

Maintenance Methods:

1. If there is leakage at the pressed seal, apply adhesive and press the seal firmly again.
2. Re-weld the seal ring according to welding standards. If the weld cannot be repaired, remove the original weld and reprocess it.
3. Remove screws and pressure rings for cleaning, replace damaged parts, grind the seal and connection seat to ensure proper sealing, and reassemble. For severely corroded parts, repair using welding, bonding, or other methods.
4. If the sealing surface of the seal ring is corroded, use grinding or adhesive to repair it. If it cannot be repaired, replace the seal ring.

4. Leakage Between Valve Body and Valve Cover
Reasons:

1. The casting quality of the cast iron components is poor, and the valve body and cover have defects such as sand holes, loose structure, or slag inclusion.
2. The valve is frozen in cold weather, leading to cracks.
3. Poor welding, with defects such as slag inclusion, incomplete welding, or stress cracks.
4. The cast iron valve is damaged after being struck by heavy objects.

Maintenance Methods:

1. Improve the casting quality and conduct strength tests strictly according to regulations before installation.
2. For valves used in temperatures below 0°C, perform insulation or preheating. Valves that are out of service should be drained of any accumulated water.
3. Welded valve bodies and covers should be welded according to relevant welding standards, followed by inspection and strength testing.
4. Do not place heavy objects on the valve, and avoid striking cast iron and non-metallic valves with hammers. Large diameter valves should be supported during installation.

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