Dangers of reversing a pump
Thread Content
In production, sometimes the check valve at the pump outlet fails, causing the pump to stop operating suddenly. The fluid then flows in reverse, leading to the pump rotating in the opposite direction; this can result in the back cover of the impeller becoming loose and also cause seal leakage. Just a gentle question: how can the reversal of a pump’s rotation damage the seal? I don’t quite understand it. Those who know could please explain in detail? Thank you
When a mechanical pump runs in reverse, a sudden change in the pump’s rotation direction causes changes in the originally designed liquid flow path and pressure distribution. The mechanical seals or other types of sealing systems inside pumps are designed for flow and pressure in a specific direction. When reverse flow occurs, these sealing surfaces may not be able to adapt to the new pressure distribution and flow direction. This can lead to an increase in the gap between the sealing surfaces or poor seal contact, ultimately resulting in leaks. Additionally, reversal may also cause wear or loosening of sealing components, further exacerbating the deterioration of the sealing performance. .
As I understand it, first, reverse rotation of the pump causes increased vibration, which may damage the seal. Additionally, certain seals—such as the pumping rings used in some applications—have specific requirements regarding the direction of rotation; when rotated in reverse, they cannot deliver enough pressure to the barrier fluid. This can easily lead to wear and leakage between the stationary and rotating rings.
You probably didn’t see either the question or the answer clearly; what was mentioned is a seal leak. As I understand it, backflow of the medium can cause axial movement, which in turn leads to seal leakage; at this point, it cannot be said that the seal is damaged.
In addition to the analyses by the previous speakers, there are also situations where the instantaneous torque becomes excessively high after the reversal of the transmission structure, causing the ring pieces to be shattered. (Cranking is performed before forward operation, ensuring a smooth fit of the transmission mechanism and enabling torque delivery)
It depends on what type of seal it is. For example, dry gas seals must never be rotated in reverse; they have directional grooves on them, and reversing the rotation will damage them. In other cases, reversing the rotation of a seal has no adverse effects
Reversing is stress-free. 1. No pressure in the self-flushing fluid at high temperatures; 2. Incorrect spring orientation – vibration; 3. Incorrect rotation direction of the pumping ring – dry friction; 4. In cases of passive reversal (e.g., siphoning), there is water hammer impact and vibration due to failure of the balance drum (disk).