The seal is to prevent the pump shaft and the casing leak and the establishment of the sealing device, seal are commonly used in packing seal, mechanical seal and dynamic seal. The reciprocating pump is usually packing seal. When the transmission is not allowed to leak the medium, the diaphragm type reciprocating pump can be used. Rotary pump (including vane pump, rotor pump etc.) of the main shaft seal packing seal, mechanical seal and dynamic seal.
1. Mechanical seal:
Mechanical seals (also known as end face seal) the sealing effect is good, the amount of leakage is small, long life, but the price is expensive, processing and installation of maintenance than the general requirements of high seal. The mechanical seal is suitable for transporting oil and chemical medium, and can be used for various kinds of medium with different viscosity, strong corrosion and granular medium. The American Petroleum Institute API610 (Eighth Edition) stipulates: in addition to the user specified, shall be equipped with container type mechanical seal.
2. Dynamic seal:
Dynamic seal can be divided into two types of back blade seal and sub impeller seal. The pump when the leaves back (or vice impeller) of the centrifugal effect to seal Department of the medium pressure drops to atmospheric pressure or negative pressure, the pump does not leak during operation. When the centrifugal force disappears, the back blade (or the auxiliary impeller) is sealed, and the sealing device is sealed by the stopping and sealing device. Dynamic sealing performance is reliable, cheap, convenient maintenance, suitable for conveying solid particles containing more media, such as slurry pump, slurry pump in phosphoric acid industry. The disadvantage is that the power loss is larger than the mechanical seal, and the life of the parking and sealing device is shorter. To ensure the parking sealing equipment life, reduce the amount of leakage of the pump, the dynamic seal of the pump, the pump inlet pressure should be limited, namely: Ps < 10MPd type of Ps - pump inlet pressure, MPa; Pd - pump outlet pressure, MPa.
3. Packing seal:
Packing seal is simple in structure, cheap in price and convenient in maintenance, but the leakage is large, and the loss of supply is large. Therefore, the packing seal is used for conveying the general medium, such as water, which is generally not suitable for oil and chemical medium, and can not be used in the precious, explosive and toxic medium. The packing seal is used in the parking and sealing device which is matched with the back blade (or the auxiliary impeller). Packing seal with ordinary and mechanical elastic two. With the general packing seal pump similar to ordinary type packing seal, seal requirements at the micro positive pressure, in order to avoid packing friction. Mechanical seal with elastic filler parking weight, make the pump packing at run time to loosen, stop packing.
