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Mechanical seal assembly and cleaning, grinding is analyzed

by:Lepu Seal     2020-03-27
Mechanical seal assembly and cleaning, grinding analysis of mechanical seal is made up of two pieces of sealing element ( Static ring and ring) Perpendicular to the surface of the shaft, smooth and straight fit each other, and the relative rotation of sealing device. It depends on the pressure of sealing medium in rotary dynamic cyclization static ring contact surface ( End face) On the proper compression force, make the two ends together, maintain between end face a very thin layer of liquid membrane and reach the purpose of sealing. This layer of liquid membrane with fluid dynamic pressure and static pressure, lubrication and balance role. 1. Cleaning and examination of the mechanical seal 1) The working principle of mechanical seal for mechanical seal inside without any impurities. Thoroughly cleaning before assembling mechanical seal ring and static ring, shaft sleeve, etc. 2) Check whether there is a dynamic and static ring surface defects such as scratch, crack, these flaws will cause serious leakage of mechanical seal. Conditional can use a special tool to check the sealing face whether level off, sealing surface uneven, pressure water will enter the assembly of mechanical seal ring sealing surface activity, separate of dynamic and static ring, mechanical seal failure. When necessary, can make tooling hydrostatic test before assembly. 3) See if there are any impact of dynamic and static ring seat sealing defects. Such as dynamic and static ring seat with dynamic and static ring sealing ring surface is flawed. 4) Check whether compensation spring mechanical seal damage and deformation, if stubborn coefficient change. 5) Check the sealing sleeve defects such as the existence of burr, the trench. 6) Cleaning the check all gasket exists defects such as cracks, porosity, measurement of synthetic diameter is within tolerance. 7) Have also check screw pump mechanical seal of pump body of the spiral line whether there is a crack, break the blemish such as. 2. Mechanical seal assembly dimensional check 1) The size of the measurement of dynamic and static ring sealing surface. This data is used to verify the radial width of dynamic and static ring, elected in different friction material, hard material friction surface radial width should be bigger than soft 1 ~ 3 mm, otherwise easy to face the hard stuff into soft material of end face edges and corners. 2) Check of dynamic and static ring and the clearance between the shaft or the shaft sleeve, the inner diameter of the static ring 1-2 mm, usually larger than the diameter of axle for ring, in order to ensure floating, inner diameter larger than the diameter of axle 0. 5 ~ 1 mm, in order to compensate for shaft vibration and deflection, but the gap not too big, otherwise it will make the ring seal card into and cause the destruction of the mechanical seal function. 3) Check of mechanical seal force. We usually speak is mechanical seal force of end face specific pressure, face pressure to appropriate, too, will make the mechanical seal friction surface heating, accelerate the end wear, increase the rate of friction work; Is too small, easy to leak. End face specific pressure is set at the mechanical seal design, when we are in the assembly can only be defined by measuring mechanical seal force. Usually measurement method makes measurement installed static ring end face to the vertical distance to the gland end, measured again ring end face to the end of the capping vertical distance, difference of the two is the mechanical seal of the force. 4) Measure the length of the compensation spring is changing. Change spring performance will directly affect the mechanical seal face pressure. Usually spring in the long run length is shorten, the compensation spring on the ring of the mechanical seal will also, because of the centrifugal force and deformation. 5) Measure the length of the static ring anti-rotating pin and pin hole depth, prevent the pin is too long the static ring cannot be assembled in place. The problem will damage the mechanical seal. 3. Mechanical seal ring and static ring end face grinding 1) The ring to be removed, and the grinding, coarsely ground first, after lapping, conditional can be polished. 2) When coarse grinding, choose # 80 ~ 160 of abrasive particle size, and trace to processing first. Then available more than 160 # abrasive finishing grinding, make the finish to meet the design requirements. Cemented carbides or ceramic ring need to use after fine grinding polishing machine polishing. The magnitude of the polishing machine can choose M28 ~ M5 boron carbide. After polishing mirror. Ceramic ring M5 agate powder after fine grinding, are available with chromium oxide polishing. 3) Static ring of graphite filled ptfe, due to the material is soft, available lapping with water or kerosene, gasoline, does not need to add abrasives. But also the research in the running-in process, so the finish requirement is not too high. 4) Grinding method, a grinding machine can be in the grinding machine grinding, no grinding machine can use the manual of the eight on flat glass grinding method.
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