Compressor loading, overheating, failing

by Kevin

Canister and Controller for air powered water pump

Canister and Controller for air powered water pump

Hi bill,

I manufacture air powered water pumps. They operate on the principle where air pressure is exerted in a canister full of water. The air pushes on the surface of the water. A delivery pipe extends almost to the bottom of the canister. The water is forced down and up the pipe.

When the canister is almost empty, an exhaust valve allows the remaining air to be vented to the atmosphere, allowing the cylinder to refill and the cycle is repeated.

I have a problem with one installation where the water is only being lifted 15 metres.

He only has single phase power and this limits the size of compressor he can use.

The result is that the compressor is overheating and blowing head gaskets.

The compressor manufacturer reckons that the problem is that as the air does the work of pushing the water, it is not being expelled into the atmosphere and this is creating excessive back pressure, creating the overheating problem.

Do you think this is correct? ( the higher the water is pumped, the longer the pump period has to be as it has to get the water moving from stationery each cycle).

Any advice you can provide would be appreciated.

Kevin, I'm puzzled that the air compressor does not appear to have a thermal safety switch, which would cut the motor power in the event of a too high temperature rise, and shut the motor down before damage could occur?

Am I correct in assuming that the water, once pumped down the line, exits somewhere, or is it going into a closed system.

When the water in the pump is blown out, what shuts off the supply of air to the pump, and does the compressor simply run without air outlet at that point? If so, then the compressor manufacturer might be right, although, I still wonder about the absence of the thermal safety.

If the air from the compressor is deadheading, and the compressor is still running, could you not put a diverter valve in before the pump that would allow the air from the running compressor to blow to atmosphere while the pump is filling, and then switch back to filling the pump when it has been filled with water?

Anyone else want to chime in on this neat application for compressed air?

Kevin, if you want to add more to this, or anyone else, please click on the comment button so your input stays with this post.



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Apr 13, 2014
air powered pump
by: Doug in

All else being equal, what is your normal height of water? More detail would help.

Whatever that is, with the AC power limit, I see two potential solutions:

First, use a smaller riser pipe, to reduce the load (weight) of the water in the riser.

Second, perhaps a multi-stage setup, with two or more canisters, to pump up sequentially.

Either way is going to reduce the flow, but something is better than nothing...

Apr 13, 2014
Not the Motor
by: Kevin

The problem is not with the motor but with the compressor pump. The motor doesn't trip.

The water is pumped into a tank. The deivery pipe is large enough to eliminate friction for the time it moves each pump cycle.

The air is controlled by two delay valves - one turns on the air to pump and the other turns it off to allow refilling of the canister.

The compressor runs just to maintain the 100psi in the system.

The only other factor that I did not mention is that the air supply to the control valves is via a 25mm pipe 500 metres long, which increases the size of the storage vessel.

Whatever weight is in the water, to my thinking, would be the same effect as pumping into the receiver tank.
Hmmm, I've never heard of a compressor pump that overheats when compressing air unless there is something wrong with it. Typically, as the load on the pump increases from backpressure from the tank, so too does the load on the motor, and it's the motor that usually suffers, not the compressor pump.

Are you saying that the compressor pump is pushing air into a pipe 25 mm (1") diameter by 500 meters (520 yards) long? Yes, that is equal to a good sized air tank in my mind.

So, if the compressor pump is pumping air into the line to the valves, and the pump is overheating, to my mind, you've got a compressor pump problem.


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Measure compressed air flow rate?

by Dave Hinder
(St. Catharines, Ontario, Canada)

Trying to determine consumption into various lines.
Are there any portable "quick-disconnect" type flow meters?


Hello Dave. Welcome to you and the other folks that visit from St. Catharines.

Any in-line flow meter can be set up as a quick connect.

You will want to install it where an existing air line enters a fitting. Perhaps on the valve power line etc.

Add an instant fitting to both sides of your flow meter. To the upstream fitting add a length of poly tube that's the same diameter as the existing line.

Then, when you disconnect the existing air line from the valve or other air using appliance, you simply insert the tube from the flow meter into that fitting, and insert the existing disconnected line into the downstream fitting on the flow meter.

With this rig you can insert the flow meter into the feed line anywhere you wish and monitor the flow to a specific use.

If it's a probe type compressed air flow meter, the test rig will include a Tee, a line running up out of the Tee into which the probe would be inserted, a length of tube from the upstream side of the Tee to plug into the air source fitting, and an instant fitting on the downstream side into which the line to the air using device can be inserted.

Where to get compressed air flow meters?

I know these guys have a pretty slick series:

Or, use your browser to search for "buy compressed air flow meter" and you will turn up lots.



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Jan 14, 2011
Measuring Compressed Air Flow Rate
by: Anonymous

Are there any ultrasonic or "non drilling" air flow measurement instruments on the market that you are aware of? I'm looking for a portable hand held measurement instrument to take from compressor to compressor to measure cfm in a large plant and haven't found any such tools that measure air, only fluid.

Bill says...

I know of no non-invasive flow meters for compressed air. It sounds like a need that the flow industry should be looking at. I invite anyone involved in that industry to post.



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