Build a silent compressor

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Hi, I am trying to build a silent compressor using a fridge pump and a 6ltr tank from a belt driven pump.

My problem is that the check valve wont open to fill the tank ? Is this purely down to the fridge pump not being big enough ? Is there a solution, other than getting a larger more powerful unit ? Thanks, Wayne.

Willy R. says “Hi Wayne. The purpose of the tank check valve is to keep the compressed air in the tank when the compressor is stopped, as the unloader valve is open when the compressor is off, and the air path from the pump head is open to atmosphere. If the check valve wasn’t there, then the tank would empty every time the compressor was stopped and the unloader valve opened. So, I suspect that the check valve you are using may be in backwards, and that would prevent the compressor pump from driving the air down into it. Don’t know much about fridge compressors, though I suspect they do not have an unloader valve, else the refrigerant would exhaust out of the coolant system every time the compressor stopped.”

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Wayne says ” Hi WillyR, Thanks for replying. That’s what I was thinking about fridges !! They don’t have one in the system normally, so can I modify the tank set up, so the unloader is not used, then do away with the check valve (or add an inline one to prevent back pressure) ? Do you think that would be OK ? I assume the unloader only works, when the compressor power is cut off by the pressure switch. The compressor turns off, closing the check valve and diverting unused air to atmosphere ? If I blocked the route to atmosphere with a blanker, would that a problem do you think ? Not sure how a fridge compressor works either.

I am a complete novice as you can tell !!! But I am an engineer so not a complete idiot !!! Just a slight one !!

Just reading what you said “The unloader valve is open when the compressor is off” which implies it should be closed when the compressor is on ? But mine appears to be open permanently ? However, like I said, it works fine with the belt pump.

I will see if I can contact someone who has built one, I think. Maybe I am missing something !!

Will R. says “Have a look at the unloader valve page to better understand what it does. Yes, and air compressor typically requires a working unloader in order to help in the motor restart on cut in. If the air trapped over the cylinder piston can’t get out, it adds load to the start attempt of the electric motor, and sometimes sufficient load that the motor cannot start”

Do that please and then tell us if that helped, okay?

By Ashley Pearce

As a passionate manufacturing and mechanical engineer, I've had my fair share of run ins with air compressors and compressed air systems. With over a decade of experience in the industry, I have both a fresh perspective and time-served hands and mind to help you with your compressor problems (along with our able community!)

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