The reasons for sealing leakage of screw pump are various, mainly covering the following aspects:

Installation problem: Too tight or too loose installation may lead to wear of the dynamic and static ring plane of the machine seal, causing leakage. Too tight installation will burn the plane, making it lose elasticity; Too loose may leak due to spring failure or poor assembly.

Water quality problems: Water containing small particles and high carbonate content will wear the sealing plane, causing grooves, ring grooves and other phenomena, which will lead to leakage.

Water shortage operation: common in the bottom valve installation form, the negative pressure at the inlet leads to the existence of air in the inlet pipe and pump chamber, and the machine seal cannot be cooled due to high temperature caused by high-speed operation after startup, resulting in leakage.

Cavitation: mainly occurs in the hot water pump, the steam generated by the high water temperature enters the upper part of the pump chamber, which cannot be excluded, resulting in the failure of the dry grinding of the machine seal.

Improper assembly: the pump cover is not installed flat, resulting in the shaft and the pump cover is not vertical, the dynamic and static plane can not match, resulting in unilateral wear and water seepage.

Evacuation or cavitation: this is one of the main reasons for sudden leakage in the normal operation of the screw pump, which will destroy the seal.

Media problems: the corrosive, cohesive, and gumming substances in the medium increase, frequent changes in ambient temperature and working conditions, and sudden power outage or failure to shut down will affect the normal operation of the screw pump, resulting in seal leakage.

The solutions include: adjusting the installation height, improving the water pressure or the quality of the medium, draining the air in the channel and pump chamber, checking the installation of the pump cover, replacing the mechanical seal, conducting field visits and technical exchanges during the selection, selecting the appropriate sealing material, checking the state of the spring and thrust ring, adjusting or replacing the spring, and replacing the parts that are resistant to corrosion and high temperature.

Key words: screw pump, seal leakage cause, seal leakage solution