What is the function of the bypass line for centrifugal pumps?
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This post was last edited by lijianhuai on 2011-8-20 21:36. As the title suggests, many centrifugal pumps are equipped with bypass lines; some call them minimum flow lines, while others refer to them as pressure balance lines. So I have the following questions: 1. If it’s a minimum flow line, then why choose a pump with such a high rated flow capacity? A lot of money? 2. If it’s a pressure balance line, then why choose a pump with such a high rated power? Once the pressure balance line is opened, a portion of the fluid at the pump outlet returns to the pump inlet, which indeed helps to maintain the inlet pressure and addresses the issue of liquid vaporization caused by low pressure at the pump inlet. However, this also results in a decrease in the pump’s head, meaning the pump performs a lot of unnecessary work – isn’t that a waste?
If production is not continuous, pumps on the pipeline need to be equipped with bypasses in order to adapt to different operating conditions or during start-up and shutdown; valves are available on these bypasses for adjustment.
Just imagine, if the control valve at the pump outlet suddenly closes completely, won’t there be no flow at the pump outlet?
The minimum flow line is intended to be activated when switching between pumps, in order to prevent the standby pump from being damaged due to pressure buildup; it should be turned off during normal operation. The selection of a pump is based on the quantity and physical properties of the material at that location; the minimum flow rate requirement is intended to prevent pressure buildup in the pump, and there is no inherent connection between the two. Additionally, does the bypass line of the pump refer to the line between the inlet and outlet or the line across the check valve? The cross-line at the inlet and outlet is designed to prevent freezing of the heavy oil pump during maintenance, and to avoid steam passing through the pump body for extended periods during purging. The check valve across the line is used to preheat the backup pump.
Reply to 1# yueling323: You can’t say “there’s plenty of money”! There are many special situations; for example, in the case of the boiler feed pump, the amount of water supplied is determined by the boiler’s water level. During the ignition process, the water flow may be less than the minimum required level, so it’s necessary to have a bypass route
Reply to 1# yueling323: Dear friend, are you referring to a small path that crosses the road at the pump’s outlet? If so, you can check whether there are valves installed on this small pipe At both ends of which component is this small pipeline installed? If it is what I said, then its function is as follows: 1. It ensures that the entire system is emptied on both sides of the check valve; since the check valve can only allow flow in one direction, upward, it is used to empty the system in the downward direction ； 2. In the event of a failure in filling the pump at the inlet side, it is possible to fill the pump in reverse through this pipeline.
Prevent low tank level, pump cavitation, and insufficient flow rate