Reducing air pressure and volume WAY down

Hugely inefficient.

80 liters/minute is 2.8 CFM. That's roughly 1 HP at 90 psi. You will spend $1000/year on electric power times your duty cycle. If your shop compressor lasts that long.

It's foolish to compress air much above the application pressure.

OK, I'm fed up paying $400 for a linear air compressor that puts out

3.5psi at 80 liters per minute. This is the pump on my aerobic septic system; three in 4 years. That must be why they have a one year warranty.

Shop compressor is always on anyway. I know how to reduce the pressure with a regulator and then the volume with a valve. But how do I measure the volume? Needs to be pretty reliable. I don't want a yard covered with stinky meringue.

--Andy Asberry--

------Texas-----

Time to look for a better quality unit. I see there are a lot of vendors. Have you tried thses guys?

know nothing of them, except they seems to be one of the few made-in-USA

Karl

I would think that you would need to regulate one or the other, but not both. Consider an electrical power supply as an analogue: it's either constant voltage or constant current. It will be rated in volts and amps, but that doesn't mean both are regulated.

In your case, 3.5psi at 80 lpm probably means a pressure regulated

3.5psi supply *capable* of supplying 80 lpm, depending upon the load. As in the electrical analogue, the indication that you are not supplying the required volume would be a drop in pressure.

Continuing with the electrical analogue, you might also want to filter the output to reduce ripple. I.e., an auxiliary tank after the regulator.

All of the above is strictly opinion without any substantiating credentials,

Bob

As others have said, won't work.

What you need is a regenerative blower, made by Rotron and others. We got one for a cooling application at work. They deliver a huge amount of air at modest pressure. I think there is a model that can deliver 3.5 PSI, but that is at the upper end of the limit. The makers have pressure vs. volume charts so you can figure out how much air you at at any specific back pressure. Do you actually need 3.5 PSI? That is equivalent to about 7 foot depth of water.

Another possibility is to make something yourself, maybe from a discarded lawnmower engine or something. seal the valves and make a new head with check valves in it, or change the cam to use the existing valves (more work for sure). You probably don't have to spin it real fast to get your 80 LPM.

Jon

A regenerative blower (AKA ring compressor) is another possibility, but pay attention to energy efficiency and noise when making the comparison. Grainger carries Fuji brand, Gast also makes them.

Ned Simmons

Andy You just need to hook up a little engine that will run on methane. Run a pipe from the septic tank vent. You can figger out the details, I know ya can :)

Rex

Actually it is their HP 80 model. I bought one online for $329 w/free shipping. A rebuilt, when they have it, is $255.

--Andy Asberry--

------Texas-----

Good idea. If I only knew where to get a naked 60 gallon Black Max tank to store the excess.

--Andy Asberry--

------Texas-----

The pump is at ground level. It has to push air to the bottom of a buried tank with a water depth of 5 feet. After that the pipe is open and the air bubbles to the top.

It is not like the air has to do any work. The only resistance is the column of water in the pipe.

Here is the one I have.

A simplified drawing of the operation.

--Andy Asberry--

------Texas-----

If you do need to measure the flow, invert a water-filled container under water over a pipe from the pump. Time how long it takes for the bubbles to displace the water out of the container and bubbles to appear out the bottom of the container. The flow will likely be highly pressure (depth) sensitive, so a swimming pool might be helpful. :-)

Don Young

Well, that's 60" H2O gauge of pressure. I looked up the Gast regenerative blowers at

didn't find a good fit. The smallest one they had that would do 60" H2O was the R4P, which is a 1 Hp blower. I don't think you want a 1 Hp load on your electric meter all the time. Gast also makes linear compressors, maybe they have a better one. The regenerative units are built like a tank, and after 5 years or so the bearings will get rough. You just open it up and put in new bearings for $30 or so, and it will be ready for another 5 years. I'm sure Gast sells replacement parts for their linear compressors, too.

Jon

I thought aerobic digesters didn't produce methane, or not much. MEthane already mixed with it's oxygen sounds like real fun to try to pump or compress too.

jk