Can’t pump water using a centrifugal pump?
Thread Content
A centrifugal pump is used to draw water from the canal, with the water intake located at the drop well. Due to the shallow well, the water intake cannot be completely submerged in water. When pumping water, all that could be heard was the pump in operation, with no water coming out. How to solve the problem at the water inlet, given that the well cannot be dug any deeper (due to other constraints)? The water entering contains air – how can this be avoided?
Add a foot valve (one-way valve) at the inlet, then fill the pump chamber with water and give it a try.
Fill the pump inlet with water, then block the pump outlet with your hand, start the pump, and once pressure is built up release your hand – the water will then be pumped out. The premise is that the pump head is not high, the outlet diameter is small, and the water does not contain corrosive substances. Safety first.
What is said on the second floor refers to one aspect; but if there is air in the liquid, it seems necessary to solve this problem by ensuring that the water inlet is completely submerged in water. Is it possible to start it intermittently?
If the water intake cannot be completely submerged in water, then you will never be able to draw water out.
This problem is really difficult to solve; even if air leaks in through the bottom valve, it’s still not possible to establish a water connection. Moreover, the installation of the bottom valve requires a certain distance, which effectively increases the inlet height of the pump, thereby increasing the chances of suction issues
Fill it completely with water before starting the pump. It’s important to submerge the water intake tube opening in the water; otherwise, even after air gets in, it won’t work. Use a tube with a small opening, or ensure that…
Add an inlet buffer tank and install a return line at the pump outlet; this way, the inlet flow can be controlled to prevent emptying.
In the situation described by the poster, with air continuously entering the suction port, a regular centrifugal pump cannot function... If the suction conditions cannot be changed, try using a vacuum pump instead
The pump must be filled first before it can operate
If the water intake cannot be submerged in water, a vacuum cannot be created and water cannot be pumped up. The same is true if there are leaks in the pipes. If the water intake can be lowered below the liquid surface, it is possible to consider installing a bottom valve at the bottom of the pipe; this will ensure that the inlet pipe and the pump chamber are filled with water, thereby allowing water to be pumped out. Another consideration is the pump’s suction lift; the installation height of the pump (the height of the pump impeller’s centerline) must be less than 10 – the pump’s actual net positive suction head – 0.5 meters!
Should this pump be filled with water before use? Also, its suction inlet must be below the water surface in order to draw water up. Furthermore, a filter should be installed at the inlet to prevent dirt from getting into the pump, as that would cause problems !
The key issue is that the water intake is something like a drop well (with a depth of less than half a meter), and the pump is installed at a low position; air gets into the pump’s piping
If you don’t allow too much contact with water and yet want to pump water out, that’s ridiculous! ? !
The problem stems from two aspects: 1. There is no water inside the pump. Since the centrifugal pump must have water covering the centerline of the impeller before it can be started, priming is required. To prevent the water inside the pump from draining completely after it stops operating, which would force re-priming during the next start-up, a check valve can be installed at the inlet or a self-priming pump can be used! 2. The inlet must not be submerged in water; it is possible to add a section of pipeline in front of the inlet so that the entrance of that pipeline is submerged in water. If the inlet is not submerged in water, vapor-liquid mixing will occur, causing the pump to be unable to draw in water; and even if it manages to draw in water, cavitation will still occur! If the conditions cannot be resolved, consider switching to a vacuum pump! Personal opinion :)
It is recommended to replace the submersible pump, as it is impractical to use a centrifugal pump to pump water up, especially since the water level is so low – even installing a foot valve won’t help.
If it is difficult to achieve continuous and stable operation of the centrifugal pump under the above conditions, a submersible pump or another type of pump can be used instead.
Use a pump with fluid exchange or some other type of pump.
A vacuum water intake tank is installed at the pump inlet; it only needs to be filled with water during the first start-up.