Centrifugal pumps rely on fluid to keep cool and lubricated while operating. They also rely on the fact that discharged fluid has somewhere to go. But what if the process dictates it needs only a fraction of the pump’s minimum flow requirement? What if there’s a closed valve downstream? What happens when a pump’s basic hydraulic needs are no longer met?
This is where a minimum flow bypass line is best applied. A bypass line is most commonly used when there’s an issue meeting the minimum flow requirements, and/or for protection against deadheading the pump.
A minimum flow bypass, or recirculation, line can be configured many ways. It could be as simple as a continuous bypass, where the requirements are only piping and an orifice. A more complex line could be set up to use a series of valves.
Below is an illustration of a simple minimum flow bypass line.
MEETING MINIMUM FLOW CONDITIONS
Every pump has a minimum flow requirement. Operating pumps at below minimum flow can result in the following consequences:
- Pitted/worn impeller vanes
- Overheated casing/bearings
- Excessive noise or vibration
- Broken shafts
- Mechanical seal failures
- Poor performance efficiency
Adding a bypass line will allow the pump to sustain the minimum flow requirement, even when the process requires less flow.