1. Leakage of valve body and bonnet: the reason:
1. The casting quality of cast iron parts is not high, and there are defects such as sand holes, loose structures and slag inclusions on the valve body and the valve cover body.
2. Day freezing crack;
3. Poor soldering, there are defects such as slag inclusion, unweld, stress cracking;
4. The cast iron valve is damaged after being hit by heavy objects.
Maintenance method:
1. Improve casting quality and conduct strength test in strict accordance with regulations before installation;
2. For valves with temperatures below 0° and below 0°, heat or heat should be applied. Valves that are stopped should be excluded from stagnant water.
3. The welds of the valve body and bonnet 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 and put heavy objects on the valve. It is not allowed to hit the cast iron and non-metal valves with the hammer. The installation of the large diameter valve should have the bracket.
Second, the leakage of the filler (the outer leakage of the valve, the proportion of the filler is the largest)
the reason:
1. The filler is not selected correctly, it is not resistant to the corrosion of the medium, and is not resistant to the use of high pressure or vacuum, high temperature or low temperature of the valve;
2. The filler is not installed correctly, and there are defects such as small generation, poor spiral coiled joints, tightness and looseness;
3. Filler exceeds service life, has aged, loses elasticity
4. The valve stem has low precision and defects such as bending, corrosion and wear.
5. The number of packing rings is insufficient, and the gland is not pressed;
6. Damage to the gland, bolts, and other components so that the gland cannot be pressed;
7. Improper operation, excessive force, etc.;
8. The gland is skewed, and the gap between the gland and the valve stem is too small or too large, causing the stem to wear and the packing to be damaged.
Maintenance method:
1. The material and type of the filler shall be selected according to the working conditions;
2. According to the relevant provisions of the correct installation of packing, the packing should be placed in a ring-by-turn compression, the joint should be 30 ° C or 45 ° C;
3. Fillers that are too long, aging, and damaged should be replaced in time;
4. After the valve stem is bent and worn, it should be straightened and repaired. If the damage is serious, it should be replaced in time;
5. The packing shall be installed according to the specified number of turns, the gland shall be tightly and symmetrically tightened, and the press sleeve shall have a pre-tightening clearance of more than 5 mm;
6. Damaged glands, bolts and other components should be repaired or replaced in time;
7. The operating procedures shall be observed, and the normal force shall be operated at a constant speed in addition to the impact hand wheel;
8. The gland bolt should be tightened evenly and symmetrically. The gap between the gland and the stem should be too small. The gap should be increased properly. The gap between the gland and the stem should be too large and should be replaced.
Second, the leakage of the filler (the outer leakage of the valve, the proportion of the filler is the largest)
the reason:
1. The filler is not selected correctly, it is not resistant to the corrosion of the medium, and is not resistant to the use of high pressure or vacuum, high temperature or low temperature of the valve;
2. The filler is not installed correctly, and there are defects such as small generation, poor spiral coiled joints, tightness and looseness;
3. Filler exceeds service life, has aged, loses elasticity
4. The valve stem has low precision and defects such as bending, corrosion and wear.
5. The number of packing rings is insufficient, and the gland is not pressed;
6. Damage to the gland, bolts, and other components so that the gland cannot be pressed;
7. Improper operation, excessive force, etc.;
8. The gland is skewed, and the gap between the gland and the valve stem is too small or too large, causing the stem to wear and the packing to be damaged.
Maintenance method:
1. The material and type of the filler shall be selected according to the working conditions;
2. According to the relevant provisions of the correct installation of packing, the packing should be placed in a ring-by-turn compression, the joint should be 30 ° C or 45 ° C;
3. Fillers that are too long, aging, and damaged should be replaced in time;
4. After the valve stem is bent and worn, it should be straightened and repaired. If the damage is serious, it should be replaced in time;
5. The packing shall be installed according to the specified number of turns, the gland shall be tightly and symmetrically tightened, and the press sleeve shall have a pre-tightening clearance of more than 5 mm;
6. Damaged glands, bolts and other components should be repaired or replaced in time;
7. The operating procedures shall be observed, and the normal force shall be operated at a constant speed in addition to the impact hand wheel;
8. The gland bolt should be tightened evenly and symmetrically. The gap between the gland and the stem should be too small. The gap should be increased properly. The gap between the gland and the stem should be too large and should be replaced.
Fourth, the leak at the joint of the seal
the reason:
1, the sealing ring is not pressed
2. The sealing ring is welded to the body, and the quality of the surfacing is poor;
3. The sealing ring is connected with thread, screw and pressure ring;
4. The sealing ring is connected and corroded.
Maintenance method:
1. Leakage at the sealing pressure should be filled with adhesive and then fixed;
2. The sealing ring should be repaired by the welding specification. The original surfacing and processing shall be removed when the surfacing is unable to repair the welding;
3. Remove the screws and pressure ring to clean, replace the damaged parts, grind the sealing and sealing joints, and reassemble. For parts with large corrosion damage, they can be repaired by welding or bonding;
4. The sealing surface of the sealing ring is corroded and can be repaired by grinding or bonding. If it cannot be repaired, the sealing ring should be replaced.
5. The closing piece falls off and leaks:
the reason:
1. Poor operation, causing the closing piece to be stuck or exceeding the top dead center, and the joint is damaged and broken;
2, the closing parts are not firmly connected, loose and fall off;
3, the selection of the connector material is wrong, can not withstand the corrosion of the media and mechanical wear.
Maintenance method:
1. Correct operation, the valve can not be used too much force, the opening valve can not exceed the top dead center, after the valve is fully open, the hand wheel should be reversed a little;
2. The connection between the closing piece and the valve stem should be firm, and the threaded joint should have a stop piece;
3. The fasteners used to connect the closing member to the valve stem should withstand the corrosion of the medium and have certain mechanical strength and wear resistance.