Zero leakage seal is the permanent pursuit of chemical equipment, it is this requirement that has promoted the application of magnetic pump and shield pump. However, there is still a long way to go to achieve the goal of zero leakage, there are still many problems to deal with, such as the life of magnetic pump isolation sets and shielding pump sets, the pitting corrosion problems of the material, the need of anti-corrosion seal material, the reliability of static sealing problems and so on. Some basic facts about seal are briefly introduced as follows:
1.Sealing form. For static seals, there are sealing plate and sealing ring. The O-ring is the most common in sealing rings. For dynamic seal, packing seal is scarcely used in chemical pump and is given priority to mechanical seal. And mechanical seal have single face and double face, equilibrium and non-equilibrium model. Equilibrium model is suitable for the seal of high pressure medium (usually the pressure is more than 1.0 MPa). Double end face sealing machine is used for this kind of medium with the feature of high temperature, crystallization, viscosity, containing particles and toxic volatile. Double end face machine seal should be added spacer fluid to the sealed cavity, the pressure is generally 0.07 ~ 0.1 MPa higher than medium pressure.2. Sealing materials. The materials used in the static seal of chemical pump are generally made of fluorine rubber. Polytetrafluoro materials are only used under exceptional circumstances. The configuration of mechanical rotating and static ring seal materials is very important. It’s not saying that cemented carbide is the best. High price is on the one hand, both no hardness difference is not reasonable, so it's best to discriminate based on the characteristics of the medium.