Diaphragm pump fails to draw up bottom oil
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A diaphragm pump was used to transfer diesel from tank A to tank B. As the level in tank A dropped from 500 millimeters to 200 millimeters while the level in tank B reached 15,260 millimeters, the diaphragm pump continued to operate; however, the level in tank B decreased instead of rising, and the level in tank A increased. The flow of material reversed. After stopping the pump for about half an hour and attempting to transfer the liquid again, the same problem occurred after 3–5 minutes of pumping. Switching to another pump did not resolve the issue either. The air supply pressure was 6 kilograms. Question: 1) Is it because the level of liquid B is too high, resulting in the outlet pressure of the diaphragm pump being lower than the self-pressure of B? 2) Is it because the liquid level in A is too low, allowing a large amount of gas to enter at the inlet, which prevents the pump from delivering fluid? 3) How can the material end up back in the lower tank? Doesn’t the diaphragm have a one-way valve? 4) Can a diaphragm pump use an outlet valve to regulate the outlet pressure like a centrifugal pump? How can export pressure be increased?
1. Leakage in the inlet and outlet valves; 2. The static pressure difference is greater than the pump’s pressure; 3. Check the pneumatic supply
The main check is the one-way valve at the inlet and outlet.
Even after replacing it with a new pump, the situation remains the same!
What is an appropriate air pressure source for diaphragm pumps?
1) Is it because the level of liquid B is too high, resulting in the outlet pressure of the diaphragm pump being lower than the self-pressure of B? 2) Is it because the liquid level in A is too low, allowing a large amount of gas to enter at the inlet, which prevents the pump from delivering fluid? 3) How can the material end up back in the lower tank? Doesn’t the diaphragm have a one-way valve? 4) Can a diaphragm pump use an outlet valve to regulate the outlet pressure like a centrifugal pump? How can export pressure be increased? 1. It is possible that the pressure of the gas source is insufficient to overcome the resistance in the pipes and thus to continue pushing the liquid forward in order to increase the outlet pressure. 2. This is also a possibility; it is necessary to check on-site whether there is a low level of liquid A, which could lead to air leakage. 3. Backflow of the material indicates that the check valve at the outlet is not properly sealed. 4. I believe that, as long as it remains within the limits that the pump casing can handle, increasing the gas pressure can help raise the outlet pressure
It’s possible that the pressure setting for the pump was too low; as the back pressure at the outlet increased, the pump was no longer able to deliver fluid. Backflow may be caused by a leak in the outlet check valve.
A diaphragm pump was used to transfer diesel from tank A to tank B. As the level in tank A dropped from 500 millimeters to 200 millimeters while the level in tank B reached 15,260 millimeters, the diaphragm pump continued to operate; however, the level in tank B decreased instead of rising, and the level in tank A increased. The flow of material reversed. After stopping the pump for about half an hour and attempting to transfer the liquid again, the same problem occurred after 3–5 minutes of pumping. Switching to another pump did not resolve the issue either. The air supply pressure was 6 kilograms. Question: 1) Is it because the level of liquid B is too high, resulting in the outlet pressure of the diaphragm pump being lower than the self-pressure of B? 2) Is it because the liquid level in A is too low, allowing a large amount of gas to enter at the inlet, which prevents the pump from delivering fluid? 3) How can the material end up back in the lower tank? Doesn’t the diaphragm have a one-way valve? 4) Can a diaphragm pump use an outlet valve to regulate the outlet pressure like a centrifugal pump? How can export pressure be increased? Answer: 1. First, let’s check what the pressure difference is between the two tanks at the outlet height of the diaphragm pump. According to ΔP=ρgΔh=0.84*9.8*（15.26-0.2）=0.124MPa. The pressure difference is quite low, only a little over 1 kilogram; the air supply pressure is 6 kilograms. This rules out the possibility that the pressure at the outlet of the diaphragm pump is lower than the self-pressure of B. 2. When installing ordinary storage tanks, it is necessary to take into account the possibility that the medium contained within may be contaminated. To prevent such contaminated material from entering the system, the outlet of the tank is usually designed to be at a certain height above the bottom of the tank; 200 mm is a typical value. Therefore, this is feasible, and you can check on-site what the height of the tank’s outlet is. As for how to drain the remaining 200 mm of liquid level, there is usually an oil discharge port on the tank, located slightly above the bottom of the tank, so as to allow this liquid to be drained. As for where the drained liquid goes, it depends on how you arrange the piping system. 3. The return of material may occur when the diaphragm pump is pumping air, as compressed air comes out of the outlet; it is also possible that the check valve is open, causing some liquid to flow back. In other words, gas flows through the upper part of the valve while liquid flows through the lower part, until the entire space is filled with liquid, which is why some liquid returns. 4. To increase the pressure of a pneumatic diaphragm pump, efforts must be made to improve the pressure of the air supply, but this must be done within the limits of the pressure tolerance of the diaphragm.