High temperature gear pump mechanical seal due to corrosion failure: a) pitting corrosion surface, or even penetrate. b) As the tungsten carbide ring and stainless steel seat and other welding, easy to use in the production of stainless steel seat intergranular corrosion; c) welding metal bellows, springs and other stress and corrosion under the joint action of the common rupture. Mechanical seal failure due to high temperature effects: a) Hot cracking is the most common failure of high temperature gear pump such as residue pump, refueling pump, atmospheric and vacuum pump etc. Due to dry friction and cooling water on the sealing surface, Sudden interruption, impurities into the sealing surface, such as taking the time, will lead to radial cracks appear on the torus; b) Graphite carbonization is the use of carbon - graphite ring sealing failure of one of the main reasons. In use, if the graphite ring once exceeded the permissible temperature (usually -105 ~ 250 ℃), the surface of the resin will precipitate, friction near the surface of the resin will occur carbonization, when there is a binder, it will foam softening, So that the sealing surface leakage increases, the seal failure; c) Auxiliary seals (such as fluorine rubber, ethylene propylene rubber, all rubber) will exceed the allowable temperature, it will quickly aging, cracking, hardening of missiles now used Flexible graphite high temperature, corrosion resistance is better, but its poor resilience and easy to brittle cracking, easy to damage when installed. Seal failures due to wear of seal faces: a) Materials used for friction pairs have poor wear resistance, large coefficient of friction, and excessive end pressure (including spring pressure), which shortens the service life of the mechanical seal. Commonly used materials, according to the order of wear resistance: silicon carbide - carbon graphite, cemented carbide - carbon graphite, ceramic - carbon graphite, painted ceramic - carbon graphite, silicon nitride ceramic - carbon graphite, high-speed steel - Carbon graphite, hardfacing surfacing - Carbon graphite. b) For solid particles containing medium, the sealing surface into the solid particles is the main reason leading to seal failure Solid particles into the friction side of the surface from the role of abrasive, the seal severe wear and failure. Reasonable sealing surface clearance, as well as the degree of mechanical seal balance, as well as the sealing surface of the liquid film flash are the main open end to open the solid particles into the main reason. c) The degree of mechanical seal balance β also affects seal wear. Under normal circumstances, the balance of β = about 75% of the most appropriate. β due to the installation, operation or equipment itself caused by the error caused by mechanical seal leakage: 1, due to poor installation, resulting in mechanical seal leakage mainly in the following areas: 1) dynamic and static contact ring surface uneven, bruised during installation , Damaged; 2) moving, static ring seal size is wrong, damaged or uncompressed; 3) moving, stationary ring surface foreign body; 4) moving, stationary ring V-ring mounted in the reverse direction, Edge; 5) leakage at the sleeve, seals are not installed or pressing force is not enough; 6) uneven spring force, single spring is not vertical, multi-spring length varies; There is a corrosion point on the seal ring on the sleeve. 2, equipment in operation, the mechanical seal leaks are mainly due to: 1) gear pump impeller axial movement exceeds the standard, the shaft vibration occurs periodically and the process operation is not stable, the pressure inside the sealed chamber often changes will lead to seal Periodic leakage; 2) friction pair damage or deformation can not run together to cause leakage; 3) improper choice of sealing material, swelling bullet; 4) large spring steering is not good; 5) equipment operation vibration too much; 6) Static ring and the shaft between the formation of scale so that the spring can not compensate for the sealing surface wear and tear; 7) seal ring cracking and so on.