Self-priming pump mechanical sealing part under positive and negative pressure working condition

Abstract

The invention provides a self-priming pump mechanical sealing part under the positive and negative pressure working condition. The self-priming pump mechanical sealing part includes a sealing gland and a shaft sleeve, a negative pressure cavity sealing part is arranged in an inner hole of the back part of the sealing gland, the sealing gland is provided with an independent hollow quenching cavity,the shaft sleeve is mounted on a pump shaft and passes through the inner hole of the sealing gland, a bellow mechanical sealing part sleeves the excircle of the shaft sleeve, a movable ring of the bellow mechanical sealing part and the shaft sleeve are fixedly installed, and a fixed ring of the bellow mechanical sealing part and a boss in the sealing gland are fixedly installed; and the shaft sleeve, the bellow mechanical sealing part, the negative pressure cavity sealing part and the sealing gland form a negative pressure cavity together, and a flushing hole communicating with the sealing cavity, a pumping hole communicating with the negative pressure cavity and a drain hole and a quenching hole communicating with the quenching cavity are formed in the sealing gland. Before a pump starts, a vacuum pumping device vacuumizes a pump cavity and the interior of the bellow mechanical sealing part through the pumping hole, the effect of vacuum pumping in the pump cavity on welding joints ofbellow corrugated plates is eliminated, and the bellow stress condition is improved.

Description

technical field [0001] The invention relates to the technical field of sealing, in particular to a positive and negative pressure working condition mechanical seal for a self-priming pump, which is suitable for sealing of high temperature and solvent medium. Background technique [0002] Because the welded metal bellows mechanical seal has good floating and random compensation, there is no need to install the dynamic auxiliary sealing ring of the general push ring type spring type mechanical seal, which can avoid the axial friction caused by the sliding of the dynamic auxiliary sealing ring on the shaft It can reduce the sealing compensation ability by reducing the resistance, and avoid the problem that the auxiliary sealing ring is not resistant to high temperature and solvents, so it has become a very common type of mechanical seal. The normal working state of the welded metal bellows mechanical seal is that the outside of the bellows is filled with medium, which is positi...

AI Technical Summary

Problems solved by technology

Therefore, the pressure in the pump cavity of the self-priming pump is in a positive and negative alternating state, especially when the pump fails, the pump is frequently started during maintenance, and the frequent positive and negative pressure changes in the pump cavity will cause the welded metal bellows installed in the sealed cavity to be damaged. The welding seam of the mechanical seal wave plate is broken, so self-priming pumps can only use spring-type mechanical seals, and when the spring-type mechanical seal is used at high temperature and the medium is a solvent, the auxiliary sealing ring is mostly polytetrafluoroethylene (PTFE) Manufactured, the maximum operating temperature is around 200°C, which cannot meet the sealing requirements of high-temperature pumps

Although flexible graphite is resistant to high temperature, it has low strength and is easy to break, so it cannot adapt to the working condition of the spring seal moving ring seal ring that needs to slide along the axial direction

Although the perfluoroether rubber ring can increase the limit temperature, it can only withstand 300°C and is expensive

The welded metal bellows mechanical seal commonly used in high temperature and solvent medium conditions cannot be used because it cannot adapt to the alternating positive and negative pressures when the self-priming pump is working.

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