Help: The water pump won’t start?
Thread Content
This post was last edited by yxmqh on 2009-11-29 09:43. Four water pumps were connected in parallel, with two in operation and two as backups, and there were no issues until recently. Pumps No. 3 and No. 4 were those in use (their flow rate and head were slightly lower). After some pipeline maintenance a few days ago, Pump No. 3 stopped delivering water; whenever the inlet valve was opened to allow water to flow in, the pump’s reservoir would get emptied. I had no choice but to start pumps 1# and 4# (pumps 1# and 2# are slightly larger). Could someone who knows more about this explain what’s going on? If it’s because pump 3 is too small, then why was there no problem before, and why wasn’t pump 4 affected? Thank you
I tried this in a petrochemical plant before as well. It was later found that the leakage was caused by a problem with the imported pipeline.
I’ve checked; there’s no leakage. Is there any other reason?
Noting the poster’s comment: “A few days after the pipeline maintenance, Pump No. 3 stopped pumping water”? It is doubtful whether there are foreign objects in the pipeline!
Is the pump running in reverse? Do you have a filter? Also, check to see if the gasket is compressed off-center.
I’m not quite sure. “Four water pumps are connected in parallel, with 2 in use and 2 as backups, and there have been no problems until recently. Pumps #3 and #4 are those in use (their flow rate and head are slightly lower). After some maintenance work on the pipelines a few days ago, Pump #3 stopped delivering water; as soon as the inlet valve was opened to allow water to flow in, the pump’s reservoir became empty.” Does it mean that the reservoir becomes empty only after the inlet valve is opened and Pump #3 starts operating? Will it still get emptied before the pump starts? Are the inlet pipelines for the other pumps independent of each other, or are they shared? Is it negative pressure water intake? Is there a bottom valve? What is the medium? Could you provide more details?
Did LZ make it clear? If it’s clear, then it’s due to your operational mistakes.
1. There is a leak in the intake pipeline, allowing gas to enter and disrupt the vacuum； 2. Leakage from the mechanical seal or packing seal allows gas to enter, preventing a vacuum from being created ； 3. Internal leakage in the inlet valve of the associated pump, resulting in a loss of vacuum ； 4. Mechanical failure (possible).
Additional note from Floor 8: 5. An electrical fault caused by incorrect wiring led to the pump running in reverse.
Leaking packing at the inlet valve prevents a vacuum from being created; leakage in the pump’s mechanical seal or packing may also be the cause. If that doesn’t work, check whether there are any foreign objects blocking the pipes. This is for reference only
This situation often occurs when multiple pumps are used in parallel. We encounter it often too. For example, sometimes running 2 pumps doesn’t even yield as much water flow as running just 1 pump. Cause analysis: The problem lies in the inlet piping and the pump itself. 1. When not in use for an extended period, the bottom valve becomes clogged and rusted, preventing it from functioning. When it is open, the pump cannot be filled fully; when it is closed, the pump cannot draw in water. 2. Leakage at the import pipeline interface. 3. The pump seal is not tight; pay attention to details such as the vent hole and drain hole. 4. Valve problems, such as the valve stem coming loose, especially in gate valves. If the valve won’t open, water naturally won’t flow in.