Reasons for the pump not being able to deliver fluid
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The actual pressure of the propane sphere tank in our polypropylene plant is 0.75 Mpa, while the designed pressure at the pump discharge outlet is 0.8 Mpa. Now, it often happens that the pump cannot deliver enough flow. By following the pipeline, it was found that there were diameter changes; the outer diameters of the pipes coming out from the bottom of the spherical tank were sequentially φ57 – φ89 – φ133 – output pump – φ114. The model of the output pump is: RWE82-417J4BM-0608UI-K. I wonder if the inability to pump enough fluid is directly related to the change in pipe diameter? It is still due to the issue with the pump’s net positive suction head. This post was last edited by songzi527 on 2009-4-7 15:22]
The design of the pump suction pipeline generally does not allow for a decrease in diameter as it moves forward; rather, the pipeline connecting to the pump’s inlet should be the thinnest, with the diameter increasing as it goes toward the tank. What the original poster is describing is that the bottom of the tank is narrowest and then gets wider; it’s like an osprey having its neck tied up by a fisherman, so only small fish can get in while larger fish stay outside. :lol
Based on what the poster has described, it seems to be a pipeline issue – the outlet of the spherical tank is too narrow, while the pump is too large, which causes the pump to run out of suction and thus fails to deliver fluid. This can be calculated.
The inlet of the pump should gradually widen as it moves outward, so that it can draw fluid more effectively; if it’s the other way around, there won’t be enough force for pumping.
Strictly speaking, the connections at the inlet and outlet of the pump narrow down.
φ57——φ89——φ133——output pump——φ114. It is obvious that φ57 is the bottleneck; as a result, a relatively high negative pressure is generated in the range of φ89–φ133 during operation, which leads to insufficient liquid supply to the pump. No matter how powerful the pump is, there isn’t enough water in the pipeline to allow the pump to function effectively.
The diameter of the pump’s inlet pipe should generally not be smaller than that of its outlet pipe; the values φ57 – φ89 – φ133 – for output pumps – φ114 indicate that the former values are too small.
In the case of a mechanical diaphragm metering pump, it may be that the pump’s seals are not tight enough (the valve ball, valve seat, and valve sleeve), which can result in insufficient vacuum and thus an inability to draw in liquid.
The outer diameters of the pipes coming out from the bottom of the spherical tank are sequentially φ57 – φ89 – φ133 – output pump – φ114; the pressure at the pump inlet gradually decreases, usually as the diameter of the pump inlet pipe gets smaller!
Is the production volume low, or is it absolutely zero? If the pump experiences cavitation or vacuuming, it may be related to the piping.
This can be calculated; it should be a problem with the pipeline.
Based on the conditions you’ve provided, it’s definitely caused by the reduction in diameter of the inlet pipeline. During design, in order to prevent negative pressure at the pump inlet or insufficient flow rate, the inlet pipeline of a pump is usually made slightly thicker than the outlet pipeline. In your case, the thinnest part of the inlet pipeline is 50, while that of the outlet pipeline is 100; this certainly results in poor flow rates. No matter how many parts the entrance consists of, the key is to look at the smallest part.
From the tank outlet to the pump’s suction pipe inlet, as the outer diameter increases, the pressure at the pump’s suction inlet gradually decreases. When this suction pressure reaches the inside of the pump, the low internal pressure causes cavitation, resulting in the pump being unable to deliver fluid
It’s a pipeline issue; during maintenance, swap out the pipeline
There must be a problem with the pipeline; in particular, the section from which fluid is drawn out needs to be replaced. I also noticed that most of our pumps have a small inlet but a large outlet