Pump seal classification and seal failure analysis (1)
Jilin Yidao Technology Co., Ltd , https://www.cniopticsqm.com
Devices or measures that prevent the working medium from leaking out of the pump or prevent foreign matter or air from entering the interior of the pump are called seals and the medium to be sealed is usually liquid, gas or dust. Leakage caused by the main There are two aspects: First, there is a gap on the sealing surface. Second, the pressure difference exists on both sides of the seal site, eliminate or reduce any one factor can prevent or reduce leakage, to seal the purpose. Pump design pressure and the use of pressure is an objective existence can not be reduced, so the pump seal solution to eliminate or reduce the gap between the sealing surface. This gap includes the clearance between the sealing surfaces and the gap inside the sealing device. Pump sealing device is divided into two categories: one for the static seal, one for the dynamic seal. Static seal usually gasket seal, O-ring seal, thread seal and other types. Dynamic seals are mainly soft packing seal, seal oil seal, labyrinth seal, screw seal, power seal and mechanical seal. Gasket Gasket is a centrifugal pump seal the basic components, the use of a very wide range. Gasket selection mainly based on pump delivery medium, temperature, pressure and corrosion and other factors. When the temperature and pressure is not high, generally use non-metallic gaskets; medium pressure and high temperature, the choice of non-metallic and metal combination gasket. Non-metallic gaskets are most commonly used in pumps, and are typically paper, rubber, and polytetrafluoroethylene. When the temperature does not exceed 120 ℃, the pressure below 1.0Mpa, the general choice of green shell paper or molded paper gasket. If the transmission medium is oil, the temperature is -30 ~ 110 ℃, the general selection of good aging resistance of nitrile rubber. When the transmission medium at -50 ~ 200 ℃, the choice of fluorine rubber is more appropriate. Because it is in addition to oil heat, the mechanical strength is also its main feature. In the chemical pump, due to the corrosive media, so the general choice of PTFE as a gasket material. As the pump is used more and more widely in the field, the types of media transported more and more, so the choice of gasket material should consult the relevant information or through the experiment before making the right choice. Gasket failure mainly due to the following situations: 1, the role of pressure on the gasket is not enough. Due to the microscopic unevenness always present on the sealing surface, sometimes a number of annular grooves are machined in the sealing surface. If the sealing is to be ensured, sufficient pressure must be applied to the gasket so that it is elastically or plastically deformed Fill these gaps. Compression force of various gasket material is usually the size of the gasket manufacturer samples or product specifications are given, but also by experiment. Due to the assembly of the gasket can not reach the required pressure or due to the vibration during the operation of the compression bolts to loosen the compression force is reduced as well as the gasket material aging deformation loss of the original elasticity will make pad Leakage failure. 2, gasket internal structure or thickness of non-uniform, and the use of a crack or wrinkle of the cardboard, the gasket itself formed a gap, when the gasket on the force of the spacer to produce the elastic deformation is not sufficient Leakage is inevitable when filling these gaps. 3, the material of the gasket does not match with the transported medium. Due to the chemical nature of the chemical products transported by the pump and the change in certain properties of the fuel resulting from the addition of a small amount of additive to the fuel to increase the fuel burn value or to modify the product after combustion, It is not easy to select the material of the gasket that is suitable for the transportation of the medium. Therefore, the gasket is often eroded due to the incompatibility and the leakage occurs.