What problems can occur if the circulation volume of a counter-circulation type shielded pump is insufficient?
Thread Content
The problem we’re facing now is that the pump is unable to lift liquid after running for a few hours. After checking, it turns out that the pump’s NPSH meets the required standards and there is no vacuum condition. We suspect that the low flow rate might be causing poor bearing lubrication; however, we don’t have any experience in this area. I would like to ask if this could be the cause, and if so, how should it be resolved? Thank you
This situation generally doesn’t occur; the manufacturer should have calculated this amount properly, with orifice plates included
Is it that some opening isn’t sufficient? Please check and confirm again
This problem can occur even when the valves on the circulation pipeline are fully open. The flow rate during our operations is relatively low, being less than one-third of the pump’s rated flow rate
According to LZ, is it impossible to achieve liquid lift after a few hours? Has it been impossible from the very beginning, or only after a few hours? By how much is the actual lift lower than the lift specified in the design? Or is there no pressure at all? First of all, LZ’s operating flow rate is only 1/3 of the rated flow rate. The manufacturer surely provides corresponding data for this; it’s necessary to have such information. LZ can try consulting the manufacturer, as during factory testing, the manufacturer conducts performance tests to determine what the actual reverse circulation volume should be at the rated operating flow rate. If the volume is low, it might be because LZ’s reverse circulation pipeline is too small. Since the pump is of the reverse circulation type, some of the fluid should return to the gas phase area at the back of the motor. This fluid should be relatively easy to vaporize. Since the NPSHa has already been calculated and it’s sufficient… (Is that confirmed?) Then check whether the exhaust is incomplete.