Valve leakage cause analysis and solution

1. the closure pieces fall off and leak

The reason:

(1) the operation is poor, so that the closing parts are stuck or exceed the upper dead point, and the connection is damaged and broken;

(2) the closing part is not firmly connected, loose and fall off;

(3) the selection of connection material is not correct, can not withstand the corrosion of the medium and mechanical wear.

Maintenance method:

(1) the correct operation, close the valve can not be too much force, open the valve can not exceed the upper dead point, the valve is fully opened, the handwheel should reverse a little;

(2) The connection between the closing part and the valve stem should be firm, and the thread connection should have a stop part;

(3) the fasteners used to connect the closing parts with the valve stem should withstand the corrosion of the medium, and have a certain mechanical strength and wear resistance.

2. Leakage at the packing place (leakage of the valve, the proportion of the packing place is the largest)

The reason:

(1) the filler selection is wrong, not resistant to the corrosion of the medium, not resistant to the use of high pressure or vacuum, high temperature or low temperature of the valve;

(2) the packing is not installed correctly, there are defects such as small generation, poor spiral coil joint, tight and loose;

(3) the filler exceeds the use period, has been aging, loss of elasticity;

(4) the valve stem precision is not high, bending, corrosion, wear and other defects;

(5) the number of packing rings is insufficient, the gland is not pressed tightly;

(6)the gland, bolts, and other parts are damaged, so that the cap can not be compressed;

(7) improper operation, excessive force, etc.;

(8) the gland is skewed, the gap between the gland and the valve stem is too small or too large, resulting in the valve stem wear, packing damage.

Maintenance method:

(1) the material and type of filler should be selected according to the working conditions;

(2) according to the relevant provisions of the correct installation of packing, the disc should be placed and pressed by the ring, the joint should be 30°C or 45°C;

(3) the use period is too long, aging, damaged filler should be replaced in time;

(4) the valve stem bending, wear should be straightened, repair, serious damage should be replaced in time;

(5) the packing should be installed according to the specified number of rings, the gland should be symmetrically and evenly tightened, and the press sleeve should have more than 5mm Tight clearance;

(6) Damaged caps, bolts and other parts should be repaired or replaced in time;

(7) should comply with the operating procedures, except for the impact of the hand wheel, with a uniform speed of normal force operation;

(8) The gland bolt should be tightened evenly and symmetrically. The gap between the gland and the valve stem is too small, and the gap should be appropriately increased; Gland and Valve stem clearance is too large, should be replaced.

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, not correct 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) according to the working conditions of the correct selection of the material and type of gasket;

(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) the temperature of the valve at 0° and below 0°, should be insulated or mixed with heat, stop the use of the valve should be removed water;

(3) The welds of the valve body and valve cover composed of welding should be carried out according to the relevant welding operation procedures, and the flaw detection and strength test should also 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. The installation of large-caliber valves should be supported.