Shaft seal is to prevent leakage at the pump shaft and the shell set up seal. Commonly used shaft seal type packing seal, mechanical seal and power seal. The reciprocating pump shaft seal is usually a packing seal. Diaphragm reciprocating pumps may be used when delivery is not permitted. Rotary pump (including vane pump, rotor pump, etc.) are the main shaft seal packing seal, mechanical seal and power seal. First, the packing seal packing seal structure is simple, cheap, easy maintenance. However, a large amount of leakage, power loss. Therefore, the packing seal is used to transport general medium, such as water; generally not suitable for petroleum and chemical medium, especially not in expensive, explosive and toxic medium. Second, the mechanical seal Mechanical seal (also known as the end seal) sealing effect is good, the leakage is small, long life, but the price is expensive, processing, installation and maintenance requirements than the average seal. Mechanical seal suitable for conveying petroleum and chemical media, can be used for a variety of different viscosity, strong corrosive and particle-containing media. American Petroleum Institute standard API610 (8th Edition) states: Except as provided by the user, it shall be equipped with a cartridge mechanical seal. Third, the dynamic seal Power seal can be divided into back-leaf seal and vice impeller seal two categories. The centrifugal force of the backrest blade (or vice-impeller) during the pump operation reduces the pressure of the medium at the shaft seal to atmospheric pressure or negative pressure so that the pump will not leak during use. Centrifugal force disappears when parked, and the sealing effect of the back blade (or vice-impeller) fails. In this case, the sealing mechanism of the parking seal functions as a seal. And back-leaf (or vice-impeller) supporting the parking sealing device is more use of packing seal. Packing sealed with ordinary and mechanical elastic two. Ordinary packing seal and general packing seal pump similar to the shaft seal to maintain a slight positive pressure, in order to avoid dry packing friction. Mechanical elastic packing seal with counterweight, so that the pump loose packing operation, parking packing compression. In order to ensure the life of the parking sealing device and reduce the leakage of the pump, the inlet pressure of the pump should be limited for the pump with dynamic seal, namely: Ps Ps - pump inlet pressure, Mpa; Pd - pump outlet pressure, Mpa. Sealing performance is reliable, cheap, easy maintenance, suitable for conveying medium containing more solid particles, such as phosphoric acid industry in the pulp pump, slurry pumps and so on. The disadvantage is that the power loss is greater than the mechanical seal and the life of the parking seal is shorter.
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