1. Leakage caused by falling off of closing parts:

Reasons:

1. Poor operation, 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 connecting parts of the wrong material, can not withstand the corrosion of the medium and mechanical wear.

Maintenance method:

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

2. The closing parts should be firmly connected with the valve stem, 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.

Two, packing leakage (leakage of the valve, packing accounted for the largest proportion)

Reasons:

1. Filler selection is not right, not resistant to the corrosion of the medium, not resistant to the use of high pressure or vacuum valve, high temperature or low temperature;

2. Packing installation is not correct, there is a small generation of large, spiral coil joint is bad, tight under the loose defects;

3. The filler exceeds the service life, has been aging, loss of elasticity

4. Valve stem precision is not high, bending, corrosion, wear and other defects

5. Insufficient number of packing rings, gland is not pressed;

6. Gland, bolt, and other parts are damaged, so that the gland cannot 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 valve stem wear and packing damage.

Maintenance method:

1. The material and type of packing should be selected according to the working condition;

2. According to the relevant provisions of the correct installation packing, disc root should be placed and pressed by ring, joint should be 30℃ or 45℃;

3. Long use period, aging, damaged packing should be replaced in time;

4. Valve stem should be straightened and repaired after bending and wearing, and should be replaced in time for serious damage;

5. The packing should be installed according to the specified number of turns, the gland should be symmetrical and evenly tightened, and the press sleeve should have a pre-tightening gap of more than 5mm;

6. Damaged gland, bolt and other parts should be repaired or replaced in time;

7. Operating procedures shall be observed, and normal force shall be operated at uniform speed except for percussive hand wheel;

8. The gland bolt should be tightened evenly and symmetrically. If the clearance between the gland and the valve stem is too small, the clearance should be increased appropriately; Excessive clearance between gland and stem should be replaced.
3. Leakage of sealing surface

Reasons:

1, sealing surface grinding uneven, can not form a close line;

2. The top of the connection between the valve stem and the closing part is suspended, not straight or worn;

3, valve stem bending or assembly is not correct, so that the closing parts skew or do not meet;

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 the top gasket;

2, careful adjustment, smooth operation;

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

4, gasket assembly should meet the alignment, 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. Attention should be paid to cleaning when installing gaskets. Kerosene should be used for sealing surface, and gaskets should not fall to the ground.

Four, the sealing ring joint leakage

Reasons:

1. The sealing ring is not strictly 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 corroded by connection.

Maintenance method:

1. The leakage at the sealing rolling place should be injected 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 and other methods.

4. The sealing ring connection surface is corroded, which can be repaired by grinding, bonding and other methods. The sealing ring should be replaced when it cannot be repaired.
Tianjin valve manufacturers explain the main causes of valve leakage and countermeasures
Source: Internet Published on: 2016-6-29 11:41

1. Leakage caused by falling off of closing parts:

Reasons:

1. Poor operation, 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 connecting parts of the wrong material, can not withstand the corrosion of the medium and mechanical wear.

Maintenance method:

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

2. The closing parts should be firmly connected with the valve stem, 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.

Two, packing leakage (leakage of the valve, packing accounted for the largest proportion)

Reasons:

1. Filler selection is not right, not resistant to the corrosion of the medium, not resistant to the use of high pressure or vacuum valve, high temperature or low temperature;

2. Packing installation is not correct, there is a small generation of large, spiral coil joint is bad, tight under the loose defects;

3. The filler exceeds the service life, has been aging, loss of elasticity

4. Valve stem precision is not high, bending, corrosion, wear and other defects

5. Insufficient number of packing rings, gland is not pressed;

6. Gland, bolt, and other parts are damaged, so that the gland cannot 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 valve stem wear and packing damage.

Maintenance method:

1. The material and type of packing should be selected according to the working condition;

2. According to the relevant provisions of the correct installation packing, disc root should be placed and pressed by ring, joint should be 30℃ or 45℃;

3. Long use period, aging, damaged packing should be replaced in time;

4. Valve stem should be straightened and repaired after bending and wearing, and should be replaced in time for serious damage;

5. The packing should be installed according to the specified number of turns, the gland should be symmetrical and evenly tightened, and the press sleeve should have a pre-tightening gap of more than 5mm;

6. Damaged gland, bolt and other parts should be repaired or replaced in time;

7. Operating procedures shall be observed, and normal force shall be operated at uniform speed except for percussive hand wheel;

8. The gland bolt should be tightened evenly and symmetrically. If the clearance between the gland and the valve stem is too small, the clearance should be increased appropriately; Excessive clearance between gland and stem should be replaced.

3. Leakage of sealing surface

Reasons:

1, sealing surface grinding uneven, can not form a close line;

2. The top of the connection between the valve stem and the closing part is suspended, not straight or worn;

3, valve stem bending or assembly is not correct, so that the closing parts skew or do not meet;

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 the top gasket;

2, careful adjustment, smooth operation;

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

4, gasket assembly should meet the alignment, 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. Attention should be paid to cleaning when installing gaskets. Kerosene should be used for sealing surface, and gaskets should not fall to the ground.

Four, the sealing ring joint leakage

Reasons:

1. The sealing ring is not strictly 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 corroded by connection.

Maintenance method:

1. The leakage at the sealing rolling place should be injected 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 and other methods.

4. The sealing ring connection surface is corroded, which can be repaired by grinding, bonding and other methods. The sealing ring should be replaced when it cannot be repaired.

Five, valve body and cover leakage:

Reasons:

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

2. Cryogenic 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 in accordance with regulations before installation;

2. For valves with temperature 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 shall be carried out in accordance with the relevant welding operation procedures, and the flaw detection and strength test shall 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-metallic valves with a hammer. The installation of large diameter valves should be supported.