Can the inlet valve of the positive displacement pump be closed?
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Both gear pumps and reciprocating pumps are positive displacement pumps. As we all know, the outlet valve must be opened when starting the pump; but is it necessary to open the inlet valve as well? Could an accident occur if it isn’t opened? I have a gear pump in my workshop; sometimes, for convenience, I close the inlet without turning off the pump, and no problems have occurred so far. I’m not sure though if there will be issues over time. Please give me some advice.
It is best not to run the pump for long periods of time, as this wastes energy and causes wear on the pump itself.
Prolonged exposure must be like creating a vacuum; it’s definitely not good
For example, a reciprocating compressor is also a positive-displacement compressor, and the inlet valve also needs to be slightly opened before it is started up. This is because it ensures that a certain amount of medium is drawn in, preventing the compressor from experiencing excessive suction force. If the inlet valve does not open, it will result in excessive suction force, excessive load on the compressor, and motor overcurrent. The device is overheating. Because the compressor has self-protection; it can shut down automatically if the current becomes too high. But for a small pump, where would such a self-protection system come from? Therefore, if the inlet valve remains closed for an extended period, it can eventually cause the motor to burn out or lead to increased wear in various parts of the pump due to heat, resulting in damage.
Thank you for the advice from above. Just to clarify, small pumps also have self-protection systems. Additionally, it remains to be determined whether keeping the inlet valve closed for an extended period will cause the motor to overload; this can be checked by measuring the current with a clamp meter. Also, it would be more persuasive if you could explain theoretically whether there is any basis for concerns such as rotor overheating.
I think it doesn’t matter much whether the current increases or not, as the material itself has a certain degree of lubricity; closing the inlet will cause wear
I support all those who post; it’s great to discuss with each other
If the inlet of the gear pump is closed, and no material enters between the two gears, the wear is likely to be extremely severe. :lol
The key issue is gear wear due to idling, but running it for a short period of time is acceptable. In some manufacturing processes, it is necessary to let it run without any load as well, but only for a brief time
That is operation under no load; without a medium, wear inevitably increases. Pay attention to sealing.
Doing this will certainly cause damage to the pump. The pump moves back and forth, performing work on the fluid. If the pump remains in a vacuum state, heat accumulates, which can accelerate the aging of the seals. In such a situation, the fluid inside the pump vaporizes or expands due to the inability to dissipate heat, thereby increasing the work required by the pump and raising its load.
For this positive-displacement pump, it is essential to open both the inlet valve and the outlet valve when starting the pump; otherwise, your motor could get damaged at any moment! If you don’t open the inlet valve, then won’t it be like a vacuum inside when liquid is being drawn in? You can imagine it using the principle of the Magdeburg hemispheres experiment – even eight horses couldn’t move them; so wouldn’t the motor also be very heavy? And it’s all pointless effort!