Why isn’t the raw material water pump delivering enough flow?
Thread Content
Everyone, I encountered such an issue: a few days ago, an acid water pump stopped working properly because the inlet filter was clogged, which resulted in low flow rate and low pressure at the pump’s outlet. After cleaning the filter, the pump was tried out again, but it showed symptoms similar to those of vacuum conditions. Upon inspecting the pump, it was found that the clearance between the shaft sleeves was 3 mm, and the ring surrounding the impeller was not severely worn. The entrance is also not blocked. After assembly and trial operation, the vacuuming symptom reappeared. Finally, the shaft coupling and impeller coupling returned to normal. I want to know the reason for that.
The gap at the mouth ring is now 3 mm (the normal standard is in the range of dozens of millimeters; this is a serious deviation from the standard). After starting the pump, the internal circulation increases, resulting in something similar to vacuum effect – that is, the backflow at the inlet of the impeller increases as fluid passes through the mouth ring. Due to the high differential pressure and flow rate, there is a sound caused by fluid erosion, similar to that of a vacuum condition; obviously, both the outlet pressure and flow rate decrease significantly... In the end, the retaining rings on the shaft and those on the impeller were replaced, and normal operation was restored. It indicates that wear of the mouth ring gap is the direct cause!
I’m not involved in equipment maintenance; I asked the repair technician and he said the gap is 3 meters – but I’m not sure whether that refers to micrometers or millimeters. Maybe I’m just an amateur in this area. But indeed, after we replaced the inter-stage shaft sleeves and the impeller ring, the problem was resolved.
The Ministry of Chemical Industry has standards in its maintenance procedures; you can look them up in the \"General Provisions\" section
The maintenance staff mentioned 3, which is usually 3mm. Saying 20 means 200μm.
The main reason is that the gap in the mouth ring has exceeded the acceptable limit by too much; this not only affects efficiency but also causes significant vibration and noise due to the backflow of high pressure to low pressure, a phenomenon similar to pumping action. The original poster can take a look at relevant information to understand what consequences can arise from an excessive gap in the mouth ring.