Centrifugal pump mechanical seals due to overheating caused by the failure, that is, thermal damage failure, we often see the thermal damage failure of the end face thermal deformation, thermal cracking, blister scar, charring, elastic element loss, rubber parts aging, permanent deformation, cracking and so on.
The thermal deformation of centrifugal pump seal end face has local thermal deformation and integral thermal deformation. Many small hot spots and isolated discoloration areas are sometimes found on the end face of the seal, which indicates that the seal has local deformation and distortion under the influence of high pressure and heat. Sometimes it is found that there are symmetrical discontinuous bright bands on the seal end face, which is mainly due to irregular cooling, causing local thermal deformation of the end face. Sometimes it will be found that the seal end face is seriously worn on the inside, and the larger the radius, the shallower the contact mark, until it is indistinguishable. The inside edge of the sealing ring may have chipping and bounding phenomenon. When the shaft is rotating, the seal continues to leak, while when the shaft is stationary, it does not leak. This is because when the seal is working, the outside cooling is sufficient, and the inside friction heating is serious, so that the inside thermal deformation is greater than the outside thermal deformation, forming the inner contact type (positive cone Angle) end face caused by thermal deformation.
The high temperature environment may reduce the elasticity of the elastic element, so that the sealing force of the seal end face is insufficient, resulting in serious leakage of the seal end face. The high temperature failure of metal bellows is a common and typical failure form of this kind of mechanical seal. The effective way to avoid this kind of failure is to select reasonable corrugated pipe material and carry out proper heat treatment. The high temperature of centrifugal pump medium is an important reason for the aging, cracking and permanent deformation of rubber seals. Rubber aging, the performance of rubber hardening, strength and elasticity reduction, serious cracking will occur, resulting in the loss of sealing performance. Overheating also causes the rubber components to decompose and even carbonize. In high temperature fluids, there is a danger that the rubber ring will continue to vulcanize, eventually causing it to lose elasticity and leak. The permanent deformation of rubber seals is usually more serious than that of other materials. The sealing ring is in high temperature for a long time, and will become the same shape as the groove, when the temperature remains unchanged, it can also play a sealing role; However, when the temperature is reduced, the sealing ring quickly shrinks, forming a leakage channel and resulting in leakage.
Therefore, we should pay attention to the use of various types of rubber temperature, and should avoid the use of centrifugal pumps at the limit temperature for a long time.