Is the piping for the siphon tank installed in front of the centrifugal pump correct?
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Our facility’s sewage tank needs to discharge wastewater into the sewage treatment plant’s pipeline system, and the original pumps often break down. Later, the company’s technical department designed and installed a siphon tank, along with a new pump equipped with a mechanical seal; the operation of this pump is controlled by a level switch. However, the pump generates a lot of noise during operation, and it leaked once after running for a short period of time. Another situation is that when the pump stops operating, there is a slight hissing sound at the pump’s seal area. I have two questions for Haiyou here. One question is whether there is a problem with the piping arrangement of the siphon tank in front of this pump. Another question is why this pump generates significant noise during operation
This seems to have little to do with siphoning. It’s just a buffer tank used to facilitate startup. It also has to be adapted to the required suction pressure of the pump. It is called the suction height allowance. If you have nothing to do, you can do a rough calculation; use the data on the label provided on the pump body and measure with a ruler for reference.
With the use of a siphon tank, there are certain requirements regarding the piping. Generally, the volume of the siphon tank should be 3 to 5 times that of the suction pipeline in order to ensure proper operation of the pump; furthermore, the suction pipeline must not leak air. . . The pump you have makes a lot of noise when operating; check whether there is air leakage in the suction pipeline and whether the pump is installed at the correct height
At least a pressure gauge should be installed at the pump outlet. Leaking seals and noise during operation indicate the presence of gas inside the pump; pumping to empty the pump causes the seals to be damaged, leading to leaks. After the seals are damaged, the pump stops operating, and the water in the inlet pipe of the tank flows back into the sewage tank. As a result, gas is drawn in at the seal area instead of water flowing out. How do you fill the pump?
Based on the suction sound heard at the seal area after parking, it can be determined that there is a leakage in the mechanical seal; this can lead to gas entering the pump chamber during operation, resulting in abnormal noises； The water intake tank and the pump share a single support mechanism; insufficient strength of this mechanism can cause vibrations that result in noise ； If the lower part of the support structure is empty, even just a concrete layer can cause vibrations during operation. Judging from the picture, the volume of the water inlet tank seems fine; it is necessary to check whether the suction height poses a risk of cavitation ； The piping is definitely correct!
A small contact area between the pump base and the concrete can also cause vibration; it is recommended that the water intake tank not share a support structure with the pump (as this can lead to resonance and synchronous vibration)
If the pump inlet size is larger than DN100, an anti-entrainment baffle should be installed to reduce the tendency to cavitation!
Theoretically, the shorter the suction lift of a pump, the better. Doesn’t such an installation method increase the length of the pump’s suction pipeline? Moreover, after the pump is stopped, the water in the vertical pipe at the pump inlet will flow back to the tank, which may cause the pump to run out of fluid