Usage Info on Air Operated Diaphragm (AODD) Pumps

https://www.michael-smith-engineers.co.uk/resources/useful-info/air-operated-double-diaphragm-pumps

Maybe a longer stroke and larger inlet/outlet....

Thanks, S.E.

At this point size isn't critical to what I'm looking at, although it's probably not worthwhile for the small (less than 1" inlet/outlet) pumps. I think the availability is probably just driven by demand- I've never used larger than a 2" pump myself.

Interesting you mention the stroke length, I do know that some of the newer designs on the market have that for increased flow volumes but the diaphragms have to be designed almost as a bit of a bellows to accommodate it, and the PTFE diaphragm pumps sometimes have to have a reduced stroke.

Well what about using a closed air system, but instead of air using nitrogen....or perhaps another refrigerant gas that would have expansion and contraction characteristics that complimented the process...perhaps a blend..? R112 and nitrogen for instance...

Wow, 35% efficiency over the existing would be a game changer - and I wish you luck.

These are a very useful pump for all the reasons you state - intrinsically safe, self priming, dry running capability etc. They are also cheap to purchase and cheap and easy to install.

My only reservation with the present design (which may or may not be the case with your design) is that it should never be used in "closed" hydrocarbon systems. Pumping hydrocarbons (flammable liquids) is perfectly OK, but into a pressurised system there is the danger that if a diaphragm ruptures you push air into the hydrocarbon system - not a great idea.

They are also limited by the available air pressure.

Looking forward to seeing your patent.

That's theoretical efficiency, if I can get a prototype done we'll see!

Especially since it should be able to pump to a higher pressure as well, without being significantly more complex- in fact it'd still be simpler than some of the designs on the market. It's still basically an AODD from the liquid side, but the linkage allows it to respond to higher head pressures so I should be able to see over 150 psi output on 120 psi air- and more importantly for use with compressors that cycle, stalling close to 120 psi on 90 psi in.

It won't make a difference to the diaphragm rupture issues you mention, but there are containment type pumps available that would address that. They're designed for use with aggressive fluids but the principal will also work the other way- essentially there are two diaphragms in each chamber: the conventional system, a sealed space that is filled with an inert fluid and then the chemical contact diaphragm which is pumped by the inert fluid and does not have any shaft penetrations. That inert fluid space can also be monitored for leakage of process fluid or air. They are more expensive though, and a diaphragm change is a nightmare!

Guess maybe I should have asked about advice with patents too....

You see these types of pumps used on small engines as fuel pumps. They use the crankcase pressure pulses to move fuel to the carburetor

https://itstillruns.com/fuel-pulse-pump-works-5020282.html

The pumps are cheap and reliable, and have little parasitic power draw on the small engine.

Cheap is the driving force for widespread use.

These pumps are used heavily in the paper industry, and other industry where nasty mixes, like oil & water emulsions in metals. Paper is often viscous chemicals, 50% solids clay & CaCO3 suspensions, used especially where portability is a major asset.

Limit of air pressure can be a problem when pump head exceeds motive pressure. When we have an application for continuous use in the process, a much more expensive and more difficult to repair rotary pump is often applied, shaft seals are a big problem. In some places, the diaphragm pumps are used and rotated through the maintenance shop as being easy to fix & repair, rather than consideration of compressed air consumption, but good clean compressed air can be difficult to come by in many places, so I think you have a good market for those plants, more & more these days, conscious of their energy efficiency. If you publish the kWh to run two 3" or 4" pumps for a week or a month, even using a high efficiency recip air compressor, that will be a good motivator, also list the average SCFM which directly relates to their compressor capacity, that will close the loop on the marginal compressor people...

Thanks for that point. I wasn't familiar with this application but it sounds like the higher pressure capacity from existing line pressures may be almost as important here as any energy savings. I definitely know where you're coming from on the subject of inconsistent air supply! It would still have to be clean.

Interesting you mention 4" pumps- largest AODD's I'm familiar with are 3", only seen larger in the mudsucker type pumps. Do you know who makes these larger ones?

After looking at some of the beasts Wilden makes, I can't say I've seen 4" pumps applied in paper mills (3.5" solids), wow. I think we used 3" clay & calcium carbonate unloading from tank cars, high solids, the larger pipe diameter keeps the velocity down, but if you lose the dispersant, you end up with large logs of clay to dig out.

Laying out 3" hoses with Cam-Lok fittings is tough enough...

Probably the 4" units are used in municipal sludge movement, when a progressive cavity pump just won't do. I also see some diesel powered units, those must be the mudsucker pumps you mention

They are the standard in the beverage industry. When you see a soda fountain, there is a pump for each flavor. Literally thousands in use in restaurants every day.

They say if you want to get rich, make something that will save McDonalds a few cents. If you can cut their co2 use noticably, you may have a shot. JHF

This type of pump became more popular for industrial use in the mid to late 70's as a development on the single diaphragm pump. The improvement was to put another "diaphragm" on the unused end of the diaphragm shaft and not wasting the energy necessary to return the shaft to the start position. For each cycle of the shaft two diaphragm loads are pumped instead of only one.

Some of the advantages not already listed are they usually have only one moving part, the shaft. Diaphragms are available in a wide range of chemical compatibilities. Maximum pressure is easy to regulate (max air pressure being used to drive them), no bypass system necessary to control pressure or temperature when flow is low and if necessary they can be submerged if proper piping/hoses are used to feed and discharge the driving compressed air.

They are normally quit easy and quick to do minor or even major repairs to (at least the Wilden's are). Unbolt the rings that hold the chambers together, unscrew the drive plate which holds the diaphragm in place and the old diaphragm is off. Just do the reverse with the new diaphragm and your back in service. I had a mechanic who could do this with a 2 or 3" pump in less than 10 minutes, much shorter than his coffee break.

These pumps can be used to pump a wide variety of materials and viscosities. For liquids and pastes they will pump adhesives such as the "glue-all types" all the way up to thick wall paper pastes, spackling compound, sludge, and extremely high viscosity materials. They can also be used to pump powders if a slight amount of air or other gas such as nitrogen is used to "liquify" the powder as it is being fed into the pump.

I have used them to pump all of these materials and more. On one occasion one was used to remove a very thick mud and gravel mix from a construction excavation. The mud sucker couldn't do it so we tried this and it worked.

The only cautions, based on my experiences, are that many of the Wilden pumps from the factory would have a short diaphragm life. Once we replaced that diaphragm all was well. We finally just removed the factory installed diaphragms with others before putting them in service. If one is torn it is easy to detect by the uneven sound of the air exhaust. Use automobile anti-freeze (ethylene glycol) instead of oil to lubricate the in-line air valve reservoir. Compressed air cools as it expands and can freeze the valve in one position. No problem with the lubricating properties of the glycol.

I prefer the Wildens over other brands based on experience, ease in repairs if there any at all and the wide range of pumpable products. I don't recommend any that have more than a couple of moving parts such as the Sandpi???.

Good Luck, Old Salt