Our diaphragm pumps are constantly 1

[Jim Hughes]

Our diaphragm pumps are constantly freezing-up from refrigerant-dried (moisture-laden even with +40’F. to +50’F. PDP) compressed air as it enters pump & then expands to atmospheric pressure conditions at the muffler/exhaust which subsequently freezes up due to the significant temperature drop and expansion.

Does anyone know of a cost-effective heatless desiccant air dryer that can serve as a point-of-use air treatment right before the pump?

Trying to keep our diaphragm & air actuated pumps reliably protected from any future freeze-ups.

 

[TugboatEng]

I used to work on the the test stand of an AODD pump manufacturer. We had icing problems even while trying to run the pump curves. There was discussion of heating the air which I don't see as a valid method. They never did find a working solution.

My suggestion? Oversize the pumps.

 

[Compositepro]

Are you using an oiler in the air supply to the pump? Oil should prevent frost from jamming the valve. Frosting is common, but I have not observed the pumps freezing-up so they do not work.

You may need better driers. AODD pumps use a lot of air and drier performance deminishes as air flow increases

 

[TugboatEng]

NO! Do not run oilers on modern AODD pumps. The oil can damage the valves.

I want to reiterate. The pump curves for AODD pumps aren't realistic. Size your pump so you're operating on the left side of the curve and you will solve your icing problems.

 

[electricpete]

If heating or dehumidification of the incoming air is not practical, what's wrong with external heat applied somewhere near the diaphram chamber valves? (harmful to the diaphrams?)

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(2B)+(2B)' ?

 

[georgeverghese]

Heatless air driers are commonly called PSA driers ( pressure swing adsorption) - off the shelf units available from companies that package compressed air drying kits. Active agent in these driers is molecular sieves - no refrigeration or heating required. They are sensitive to lube oil in the feed - preferably use oil free air compressors, or less preferred solution with oil lubricated compressors is to install prefilters and oil adsorption filters ( combination of small filter plus full size carbon bed) to adsorb residual oil vapors exiting the compressors.
Else find some way of heating up this cold dry air upstream of users.

 

[hydtools]

Put an antifreeze lubricant in the oiler.

Ted

 

[TugboatEng]

I repeat. Do not use oilers on modern AODD pumps.

 

[hydtools]

How does oil damage the valves?

Ted

 

[TugboatEng]

From one manufacturer:

Virtually all AODD pumps today have some form of lubrication free shuttle valve. These range from some form of carbon/ceramic setup to nitrided shafts in PTFE seals.

I may be a bit confused by antifreeze lubricant. Glycol is an acceptable additive.

 

[TiCl4]

To somewhat support Tugboat's post (from another manufacturer we use):

Jim, one means of controlling this (other than a new dryer unit) would be to oversize the AODPs. What size are your pumps, and what is the frequency of pulsation (how many pulses per minute)? Larger, slower pumps will have fewer issues with icing than smaller pumps that sound like machine guns when running.

AODPs are not very expensive, normally. It's likely more cost effective to either upsize all of your AODPs OR to change your air dewpoint via dryer replacement than it would be to install a point-of-use dryer for each AODP. If you have a large number of AODPs, then a new air dryer may be the most economical. If you have just a few scattered ones and the rest of your process doesn't need drier air, then upsizing the AODPs won't be all that much.