It is not uncommon to see waste of raw materials and energy, even fire, explosion, poisoning and environmental pollution caused by pump leakage in production. Mechanical seal is the most commonly used seal form of chemical pump. How to select the type and material of mechanical seal, use it correctly and maintain it reasonably is the key to improve the operation cycle of chemical pump, reduce leakage, prevent pollution and improve economic benefits.

　　The pump is delivered from the factory. The structural type of mechanical seal has been established. However, in chemical production, since the medium conveyed by the pump is different, it is required to select mechanical seals with different materials to meet the needs of sealing. The selection of materials for mechanical seals is complicated, and the emphasis is on the selection of friction pair materials. If the source and processing of materials can be solved, materials with better performance shall be used as far as possible. The moving ring is made of 9Cr18, 1Cr13 surfacing cobalt chromium tungsten, cast iron, tungsten carbide, ceramics, high silicon cast iron and other materials. The stationary ring is made of tungsten carbide, resin impregnated graphite, bronze and phenolic resin. The metal ceramic is filled with PTFE and other materials, and the auxiliary sealing ring is made of nitrile rubber, neoprene, silicone rubber, PTFE, fluororubber and other materials.

　　Several mistakes in the maintenance of mechanical seals for chemical pumps:

　　1. The greater the spring compression, the better the sealing effect. Excessive spring compression may cause rapid wear and instant burning of friction pairs; Excessive compression of the spring loses the ability to adjust the end face of the moving ring, resulting in seal failure.

　　2. The tighter the dynamic ring seal ring, the better. It is harmful and unhelpful if the sealing ring of the moving ring is too tight. First, it aggravates the wear between the seal ring and the shaft sleeve, causing early leakage; Second, the resistance to axial adjustment and movement of the moving ring is increased, which can not be adjusted timely when the working conditions change frequently; Third, the spring is easily damaged due to excessive fatigue; The fourth is to make the dynamic ring seal ring deform and affect the sealing effect.

　　3. The tighter the stationary ring seal ring, the better. The stationary ring seal ring is basically in a static state. The relatively tight seal ring is excessively deformed, affecting the sealing effect; The stationary ring is mainly made of graphite, which is generally brittle and easily broken under excessive stress; It is difficult to install and disassemble, and the static ring is easily damaged.