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Valve leakage analysis and solutions

What should I do when the valve in use leaks? What is the main reason? Below, the Asian Fluid Network Xiaobian will bring you up. 1. The closing piece falls off and leaks: Causes: 1. Poor operation, so that the closing piece is stuck or exceeds the top dead center, the joint is damaged and broken; 2. The closing piece is not firmly connected, loose and falling off; 3. The connecting piece 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, open the valve can not exceed the top dead center, after the valve is fully open, the hand wheel should be reversed a little; 2, the closing piece and the valve stem should be connected firmly, the threaded joint should have The retaining member; 3. The fastener for connecting the closing member to the valve stem should withstand the corrosion of the medium and have certain mechanical strength and wear resistance. Second, the leakage of the filler (the outer leakage of the valve, the proportion of the filler is the largest) Reasons: 1. The filler is not used correctly, is not resistant to the corrosion of the medium, is not resistant to high pressure or vacuum, high temperature or low temperature; The installation is not correct, there are defects such as small generation, poor spiral coiled joints, tight and loose; 3. The filler exceeds the service period, has aged, loses elasticity. 4. The valve stem has low precision, and has defects such as bending, corrosion and wear. The number of packing rings is insufficient, the gland is not pressed; 6. The gland, bolts, and other components are damaged, so that the gland cannot be pressed; 7. improper operation, excessive force, etc. 8. gland skew, gland and The gap between the stems 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 packing should be selected according to the working conditions; 2. Install the packing correctly according to the relevant regulations, the packing should be placed in a circle and compacted, and the joint should be 30 ° C or 45 ° C; Long, aging, damaged packing 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 should be installed according to the specified number of turns, and the gland should be symmetric and even. The grounding should be tight, and the pressure sleeve should have a pre-tightening clearance of more than 5mm; 6. The damaged gland, bolts and other components should be repaired or replaced in time; 7. The operating procedures should be observed, except for the impacting handwheel, at a constant speed. Strength operation; 8. The gland bolt should be tightened evenly and symmetrically. The clearance between the gland and the valve stem should be too small. The gap should be increased properly; the gap between the gland and the valve stem should be too large and should be replaced. Third, the leakage of the sealing surface: 1, the sealing surface is not smooth, can not form a close line; 2, the connection between the valve stem and the closing member is suspended, not correct or worn; 3, the valve stem is bent or improperly assembled, so that the valve stem is closed 4. The piece is skewed or not in the middle; 4. The quality of the sealing surface material is improperly selected or the valve maintenance method is not selected according to the working conditions: 1. The material and type of the inverted gasket are correctly selected according to the working conditions; 2. Carefully adjusted and smooth operation; 3. The bolt should be screwed evenly and symmetrically. If necessary, a torque wrench should be used. The pre-tightening force should meet the requirements and should not be too large or small. Flange and threaded joints should have a certain pre-tightening clearance; 4. The gasket assembly should be aligned in the middle, the force is even, the gasket is not allowed to overlap and use double gasket; 5. Static sealing surface corrosion, damage processing , processing quality is not high, should be repaired, polished, color inspection, so that the static sealing surface meets the relevant requirements; 6, should be cleaned when installing the gasket, the sealing surface should be kerosene clear, the gasket should not fall. Fourth, the leakage of the seal ring: 1, the sealing ring is not strict 2, the sealing ring and the body welding, poor quality of the surfacing; 3, the sealing ring connection thread, screw, compression ring loose; 4, the sealing ring is connected Corroded. Maintenance method: 1. Leakage at the sealing pressure should be injected with the adhesive and then fixed; 2. The sealing ring should be repaired according to the welding specification. When the surfacing is unable to repair the welding, the original surfacing and machining should be removed; 3. Remove the screws, press the ring to clean, replace the damaged parts, grind the sealing and sealing joints, and reassemble. For parts with large corrosion damage, it 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. V. Leakage of valve body and bonnet: Reasons: 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 bonnet body. 2. Days of freezing cracks; 3. Poor welding, existence Defects such as slag inclusion, unwelded, stress crack, etc. 4. The cast iron valve is damaged by heavy objects. Maintenance method: 1. Improve the casting quality, strictly carry out the strength test before installation; 2. For the temperature of 0 ° and 0 ° below the valve should be insulated or mixed with heat, the valve should be used to stop the accumulation of water 3. Welds of valve body and bonnet composed of welding shall be carried out in accordance with the relevant welding operation procedures. After welding, flaw detection and strength test shall be carried out. 4. Heavy objects are prohibited from being pushed on the valve, and it is not allowed to hit the cast iron and non-metal with a hammer. Valves, large diameter valves should be installed with brackets.

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