Leakage refers to substances or fluids that should not flow out or leak out of the industry, and flow out or leak out of mechanical equipment, causing losses.
There are two main reasons for the leakage:
First, due to the result of mechanical processing, the surface of the mechanical product (like centrifugal pump) must have various defects and shape and dimensional deviations. Therefore, gaps are inevitably generated at the joint of the mechanical parts;
Second, there is a pressure difference on both sides of the seal, and the working medium will leak through the gap. Eliminating or reducing either factor can prevent or reduce leakage. In the case of general equipment, reducing or eliminating clearance is the primary way to prevent leakage.
For the sealing of the vacuum system, in addition to the leakage of the above-mentioned sealing medium directly through the sealing surface, the following two leakage forms are also considered:
1. Leakage: that is, under the action of pressure difference, the leakage of the sealed medium through the capillaries of the seal material is called leakage;
2. Diffusion: That is, under the action of the concentration difference, the substance transfer by the sealed medium through the sealing gap or the capillary of the sealing material is called diffusion. It is customary in the vacuum system to be called "deflation of sealing material". First, the seal absorbs the gas by adsorption, and the gas diffuses in the seal and precipitates from the other side of the seal. The amount of leakage and discharge of the vacuum seal is related to the sealing type, the sealing material, the sealing surface processing precision and the assembly quality. In chemical production, most of the materials used are flammable, explosive, toxic and harmful. Once leaks occur for some reason, the leaked materials will diffuse in the atmosphere under the action of concentration gradient and wind. The diffusion mode can be used to estimate the extent of the spilled material and the nature and extent of the hazard. If it is within a wide range of fire and explosion danger zones, the extent of the acute poisoning-killing zone is beyond the scope of the area where there is no obvious toxic effect. Estimation of the diffusion model provides a scientific reference for the identification of the degree of danger, the control of the fire source after the accident, the clear evacuation of personnel, and so on.
