Valve daily maintenance methods: First, the valve body and bonnet leakage: Reason: 1. Cast iron casting quality is not high, the valve body and valve body blisters, loose tissue, slag and other defects 2. Days frozen Crack; 3. Poor welding, there is slag, welding, stress cracks and other defects; 4. Cast iron valve is damaged by heavy objects impact. Maintenance methods: 1. To improve the casting quality, strictly in accordance with the provisions of the pre-installation strength test; 2. On the temperature 0 ° and 0 ° below the valve, should be insulated or mixed hot, stop using the valve should exclude water 3. Weld composed of the valve body and valve cover should be carried out according to the relevant welding procedures, after welding should also be carried out testing and strength testing; 4. Do not push the valve on the heavy objects, not allowed to use hand hammer impact on cast iron and non-metallic Valves, large-diameter valve should be installed bracket. Second, the leak at the filler (valve leakage, filler accounted for the largest proportion) Reason: 1. Filler use wrong, not resistant to corrosion of the media, impatience valve high pressure or vacuum, high temperature or low temperature use; 2. Packing is not installed, there is a small generation, poor spiral wound joints, such as tight loose under the flaws; 3. Filler over the use of aging, loss of elasticity 4. Valve stem accuracy is not high, there are bending, corrosion, wear and other defects 5. Lack of packing, gland is not compressed; 6. Gland, bolt, and other parts damaged, so gland can not be pressed; 7. Improper operation, excessive force, etc. 8. Gland skew, gland and the gap between the valve stem is too small or too large, resulting in stem wear and tear, packing damage. Maintenance methods: 1. Should be selected according to conditions of packing materials and types of materials; 2. According to the relevant provisions of the correct installation of packing, packing should be pressed circle by ring, the joint should be 30 ℃ or 45 ℃; 3. Long service life, aging, damaged packing should be promptly replaced; 4. Stem bending, should be straightened after wear, repair, serious damage should be promptly replaced; 5. Filler should be installed according to the number of laps, glands should be evenly symmetrical tight, pressure sleeve should be more than 5mm preload gap; Damaged gland, bolts and other parts should be promptly repaired or replaced; 7. Should comply with operating procedures, in addition to the impact of the hand wheel, with normal speed operation; 8. Should be evenly symmetrical screwed gland bolts, gland and stem clearance is too small, it should be appropriate to increase the gap; gland and stem clearance is too large, should be replaced. Third, the sealing surface of the reasons for the leak: 1, the sealing surface grinding uneven, can not form a tight line; 2, the valve stem and the closure of the connection at the top of the center of the vacant, not correct or wear; 3, valve stem bending or improper assembly, Pieces of skew or not in every; 4, the quality of the sealing surface material improper selection or not according to the working conditions of the selection of valve maintenance methods: 1, according to the conditions of the correct choice of material and type of gasket; 2, carefully adjusted, smooth operation; 3, should be evenly and symmetrically threaded bolts, if necessary, should use torque wrenches, preload should meet the requirements, not too large or small. Flange and threaded connections should have some pre-tightening clearance; 4, Gasket assembly should meet in every, uniform force, the gasket is not allowed to overlap and the use of double shims; 5, static seal corrosion, damage to processing , Processing quality is not high, should be repaired, grinding, coloring inspection, so that the static sealing meet the relevant requirements; 6, the installation of gasket should pay attention to clean, sealing surface application of kerosene, gasket should not fall to the ground. Fourth, the seal ring at the Department of Leakage reasons: 1, ring rolling lax 2, the sealing ring and the body welding, welding quality is poor; 3, the sealing ring thread, screws, pressure ring loosening; Corroded. Maintenance methods: 1, seal leakage at the leak should be re-injection of adhesive and fixed; 2, the seal should be re-soldered welding welding regain the standard. Surfacing Department should not be repaired when the original welding and surfacing welding; 3, remove the screws, pressure ring cleaning, replacement of damaged parts, grinding seal and connection seat close to the surface, re-assembly. Large damage to the larger parts of corrosion, welding, bonding and other methods can be used to repair; 4, the sealing ring corrosion is connected, available grinding, bonding and other methods of repair, repair can not be replaced when the ring. Five, the closure off pieces produce leakage: Reason: 1, poor operation, so that the closing piece stuck or over the top dead center, the connection damage broken; 2, the closure of the connection is not strong, loose and fall off; 3, , Can not withstand the media corrosion and mechanical wear. Maintenance methods: 1, the correct operation, close the valve can not be too much force, open the valve can not exceed the top dead center, the valve is fully open, the hand wheel should be reversed a little; 2, the closing member and the stem should be connected firmly, threaded connections should be Stop parts; 3, the closing piece and the stem connection fasteners should withstand the erosion of the media, and have a certain degree of mechanical strength and wear resistance.