3. Leakage of sealing surface

The reason:

(1) Sealing surface grinding uneven, can not form a close line;

(2) The top center of the connection between the valve stem and the closing part is suspended, or worn;

(3) The valve stem is bent or improperly assembled,so that the closing parts are skewed or out of place;

(4) Improper selection of sealing surface material quality or valve selection according to working conditions.

Maintenance method:

(1) Select the material and type of gasket correctly according to the working conditions;

(2) Careful adjustment, smooth operation;

(3) The bolt should be uniformly and symmetrically screwed, and the torque wrench should be used if necessary. The pre-tightening force should meet the requirements and should not be too large or small. Flange and thread connection should have a certain pre-tightening gap;

(4) Gasket assembly should meet the correct,uniform force, gasket is not allowed to lap and use double gasket;

(5) The static sealing surface corrosion, damage processing, processing quality is not high, should be repaired, grinding, coloring inspection, so that the static sealing surface meet the relevant requirements;

(6)The installation of gasket should pay attention to clean, sealing surface should be kerosene clear, gasket should not fall.

4. Leakage at the sealing ring connection

The reason:

(1) The sealing ring is not tightly rolled

(2) Sealing ring and body welding, surfacing welding quality is poor;

(3) Sealing ring connection thread, screw, pressure ring loose;

(4) The sealing ring is connected and corroded.

Maintenance method:

(1) The leak at the sealing rolling should be filled with adhesive and then rolled and fixed;

(2) The sealing ring should be repaired according to the welding specification. If the surfacing place cannot be repaired, the original surfacing and processing should be removed;

(3) Remove the screw, clean the pressure ring, replace the damaged parts, grind the sealing and connecting seat close surface, and reassemble. The parts damaged by corrosion can be repaired by welding, bonding, etc.

(4) The sealing ring connection surface is corroded, which can be repaired by grinding, bonding, etc., and the sealing ring should be replaced when it cannot be repaired.

5.Leakage of valve body and valve cover:

The reason:

(1)Cast iron casting quality is not high, the valve body and valve cover body have sand holes, loose organization, slag inclusion and other defects;

(2) Freezing crack;

(3) Poor welding, there are slag inclusion, non-welding, stress cracks and other defects;

(4)The cast iron valve is damaged after being hit by heavy objects.

Maintenance method:

(1) Improve casting quality, and carry out strength test strictly according to regulations before installation;

(2) For valves with temperatures below 0° and 0°, heat preservation or mixing should be carried out, and water should be excluded from valves that are stopped in use;

(3) The weld of the valve body and the valve cover composed of welding should be carried out according to the relevant welding operation procedures, and the flaw detection and strength test should be carried out after welding;

(4) It is forbidden to push heavy objects on the valve, and it is not allowed to impact cast iron and non-metal valves with a hand hammer. 

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