Reasons for the easy damage of pump mechanical seals

Reasons for the easy damage of pump mechanical seals

1. Mechanical seal damage caused by idling

The reason is that in the case of idling (i.e. no material in the pump), the sealing surface of the mechanical seal does not receive lubrication from the material, resulting in dry friction on the sealing surface, which leads to the sealing surface not being smooth and even enough, causing the sealing surface to fail. At the same time, due to the high-speed operation of the motor (2900 revolutions per minute), the dry friction of the mechanical seal causes the mechanical seal to quickly heat up, and the temperature quickly exceeds the temperature that the O-ring on the mechanical seal can withstand, causing some or all of the O-ring to burn out, resulting in the failure of the mechanical seal. Due to the damage of the O-ring, the static ring of the mechanical seal (fixed on the pump) becomes loose and falls off, while the pump shaft rotates at high speed, causing the static ring of the mechanical seal to break.

2. Improper operation by the operator resulted in damage to the mechanical seal. Firstly, start the pump and then open the inlet valve of the pump. This operation caused damage to the mechanical seal, similar to the damage caused by idling above. At the same time, due to the high temperature of the mechanical seal itself, when the material at the inlet of the pump passes over, the mechanical seal instantly cools down from a very high temperature. The large temperature difference caused the mechanical seal to break. B、 After the material in the material tank is finished, the pump continues to operate, causing the mechanical seal's sealing surface to not receive lubrication from the material, resulting in dry friction on the sealing surface, which leads to the sealing surface not being smooth and even enough, causing the sealing surface to fail. At the same time, due to the high-speed operation of the motor (2900 revolutions per minute), the dry friction of the mechanical seal causes the mechanical seal to quickly heat up, and the temperature quickly exceeds the temperature that the O-ring on the mechanical seal can withstand, causing partial or complete burnout of the O-ring and resulting in mechanical seal failure.

3. Improper installation during mechanical seal replacement can cause damage to the mechanical seal. There are two or four anti rotation grooves with openings on the static ring of the mechanical seal. When installing, the position of the anti rotation groove must be aligned with the position of the anti rotation pin and installed in place. If it is not installed in place, it will cause the static ring of the mechanical seal to crack directly under the drive of the motor when starting the pump. If the mechanical seal cracks while the pump is still running at high speed, it is easy to cause the broken seal to cut the pump shaft like a turning tool, resulting in damage to both the pump shaft and the machine seal.

4. The high-speed reversal of the pump caused damage to the mechanical seal. After wiring the motor, it was not confirmed that the pump was reversing. After starting the motor, the pump reversed. B、 The absence of a check valve at the pump outlet resulted in rapid backflow of material in the pump's outlet pipeline, causing the pump to reverse at high speed. After the pump undergoes high-speed reversal, the spring on the mechanical seal generates reverse impact force due to high-speed reversal, causing the mechanical seal to break. At the same time, high-speed reversal can also bring down the nut on the pump shaft, causing the pump impeller to loosen, and in severe cases, it may also damage the shaft end thread of the pump shaft.

5. Incorrect selection can easily damage the mechanical seal. For materials with higher temperatures, a single mechanical seal should be used. Under normal circumstances, when using a single mechanical seal, the temperature of the material should not exceed 80 degrees, because if the material temperature is too high and the mechanical seal cannot be effectively cooled, the service life of the mechanical seal will be greatly shortened. In addition, whether the material used by the pump matches the material of the mechanical seal can easily lead to problems. Therefore, when selecting a pump, it is important to clearly explain to sales personnel what material, temperature, and operating conditions are being used, so that they can correctly choose a mechanical seal that matches the material and operating conditions. The above are several common reasons why pump mechanical seals are prone to damage. Therefore, when selecting a pump, it is necessary to clearly explain what material, temperature, and working conditions are being used. When using the pump at the same time, it is strictly prohibited to idle, dry grind, or reverse at high speed with material! Our experience is that the idle dry friction time should not exceed 25 seconds. If it exceeds 25 seconds, the mechanical seal has already been damaged.