Common causes of failure to prevent and remedy Leakage of the valve body and bonnet Cast iron casting quality is not high, the valve body and valve body with trachoma, loose tissue, slag and other defects 2 day cold cracking; 3 welding Bad, there is slag inclusions, welding, stress cracks and other defects 4 cast iron valve is damaged by heavy objects 1 to improve casting quality, strictly in accordance with the provisions of the pre-installation strength test; 2 for temperatures below 0 ° and 0 ° Of the valve should be insulated or mixed hot, stop using the valve should be ruled out water 3. The welding of the valve body and the valve cover should be carried out according to the relevant welding procedures, and after welding should be carried out testing and strength testing ; 4 valve on the prohibition of pushing heavy objects, does not allow the use of hand hammer impact cast iron and non-metallic valves, large-diameter valve installation should be at the bracket filler leaks (valve leakage, filler accounted for the largest proportion) 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 stem gap is too small or too large, resulting in stem wear, filler damage 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 tighten the 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 sealing surface leakage 1, sealing surface grinding uneven, can not form a dense 3, the valve stem bending or improper assembly, so that the closure of the skew or not in every; 4, the quality of the sealing surface material used improperly or not according to Working conditions conditions choose valve 1, according to the conditions of the correct choice of material and type of top gasket; 2, carefully adjusted, smooth operation; 3 should be evenly and symmetrically threaded bolts, torque wrenches should be used if necessary, preload should be consistent with Requirements, not too big 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 gaskets; 5, static sealing 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 gaskets should pay attention to clean, sealing surface application of kerosene, gaskets should not be landing seal at the junction Leakage 1, the ring is not rolling 2, the sealing ring and the body welding, welding quality is poor; 3, the sealing ring thread, screws, pressure ring loosening; 5, the sealing ring is corroded 1, Should be marked adhesive and then fixed rolling; 2, the seal should be re-soldered welding welding regain the specifications. 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. For large corrosion damage to the larger components can be welded, adhesive and other methods to repair; 4, the sealing ring corrosion, grinding, bonding and other methods can be repaired, can not be repaired when the seal should be replaced off the closure of a leak 1 , The operation is not good, so that the closure of a 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, the choice of connector material is wrong, can not withstand the media corrosion and mechanical wear 1, the correct operation, close the valve can not force too much, 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 closure and valve stem connection should be firm, ; 3, the closing piece and the stem connection fasteners should withstand the erosion of the medium, and have a certain degree of mechanical strength and wear resistance
Non-Toxic PVC Ca/Zn Heat Stabilizer
Calcium and zinc stabilizers are mainly white in appearance in powder, flakes and paste form. Powdered calcium-zinc stabilizer is used as the most widely used non-toxic PVC stabilizer, commonly used in food packaging, medical devices, wire and cable materials, etc.. At present, there are already PVC calcium-zinc stabilizers that can be used for rigid pipes in China.
Powdered calcium-zinc stabilizers are not as thermally stable as lead salts, and have certain lubricity, poor transparency, and easy to spray frost. In order to improve its stability and transparency, often add hindered phenol, polyol, phosphite and β-diketone and other antioxidants to improve.
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