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Several types of mechanical seals

Update:29 Aug 2017
Summary:

   Ordinary bellows mechanical seal failure form The cu […]

   Ordinary bellows mechanical seal failure form The current use of the bellows mechanical seal and its auxiliary system caused by the main form of sealing failure are the following.
   1, bellows failure or fracture caused by sealing failure. Bellows in the use of the process, the stiffness of the fire pump mechanical seal or elasticity will gradually reduce the phenomenon of this elasticity is often called the loss of the bomb. Experiments and practical applications show that when the bellows loss of the amount of the design of the initial compression of 18% to 20%, the entire bellows mechanical seal will leak. Metal bellows machine sealed at a temperature below 200 ℃ when the phenomenon is not obvious, but at high temperatures (more than 300 ℃) use, driving the pump soon after the leak, the machine will be used to remove the mechanical seal The amount of metal bellows found in the height of the average installed before the reduction of 2 ~ 3mm. Corrugated tube loss is mainly due to permanent deformation or stress multi-stage pump mechanical seal relaxation, there is a situation is the working medium crystallization precipitation or solidification in the corrugated pipe gap, the bellows deformation capacity to reduce or loss of deformation capacity. Therefore, the high temperature and load is the main reason for the loss of bellows [1]. In addition, the high temperature and bellows compression or contact pressure is larger, the bellows will break; the higher the temperature, the greater the load, the higher the probability of occurrence of rupture of the bellows.
   2, the pair of friction on the graphite ring in the excessive wear caused by the seal failure. Typically, the failure of the machine seal removed inspection found that graphite seal ring wear serious. Through analysis and experiment, it is found that the end face of the metal bellows is affected by the effective diameter of the bellows, and the effective diameter changes with the change of the pressure. Due to excessive pressure, resulting in serious friction friction, graphite ring caused by excessive wear and tear.
   3, the pair of friction on the surface of the carbide ring hot cracking caused by the seal failure. It has been found that the cemented carbide rings of the sealing friction pairs appear to have many radial cracks, which are divergent from the center of the hard surface, which is a seal failure caused by thermal cracking. The main reason for the thermal cracking is the high local thermal stress. The difference of the linear expansion coefficient between the cemented carbide ring and the ring is different, and the type of the flushing liquid in the flushing system is sealed by the surfacing structure or the whole structure. The size of the flow and the size of the flow may be caused by the sealing surface of the hot crack.

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