According to statistics from my country's petrochemical industry, more than 80% of centrifugal pumps use mechanical seals. Due to the different working conditions, during the process of conveying materials, centrifugal pumps often leak materials at the mechanical seal, causing environmental pollution and waste of energy.

Mechanical seals are one of the main wearing parts of centrifugal pumps, so most pump failures are caused by seal failures. According to statistics, the failure of the mechanical seal causes the failure of the pump to account for more than 50% of the equipment failure rate. Therefore, it is necessary to analyze and improve the mechanical seal leakage of the centrifugal pump to reduce the failure rate of the pump.

1. The working principle of centrifugal pump and the function of mechanical sealing device

The centrifugal pump makes its impeller rotate at a high speed through the motor and coupling. The liquid between the blades is pushed by the blades. Under the action of centrifugal force, it is continuously thrown from the center to the surroundings. When the liquid in the pump is thrown from the center of the impeller Toward the edge, a low-pressure zone is formed in the center. Because the liquid pressure before entering the pump is stronger than the pressure at the suction port of the pump, under the action of the pressure difference, the liquid is continuously sucked into the pump through the suction pipe to supplement the discharged liquid. Position, as long as the impeller keeps rotating, the liquid will be sucked and discharged continuously.

When the pump shaft passes through the pump casing, when there is a gap between movement and static, the liquid in the pump will leak from the gap to the outside of the pump. If the suction end is vacuum, the outside air will leak into the pump, which will seriously affect the operation of the pump. In order to reduce leakage, shaft end sealing devices are generally installed at the static and dynamic gaps. The shaft sealing device is an important part of the centrifugal pump, and it is directly related to whether the centrifugal pump can work normally. Now shaft seal devices generally use mechanical seals.

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