Help with compressor calculations and selection

[Prashun Patel]

I need to purchase a quiet air compressor that can deliver "7-8 Bar, 5000NL/hour". Online calculators puts this at between 2.8 and 3.0 SCFM. Does that sound right?

This will be used to power a small pump to pressurize 55 gal drums for a siphon.

Any recommendations on a good, industrial, quiet compressor?

[Andy Giddings]

California Air Tools and Rolair are very quiet, Prashun. Numerous threads on these, there was one just last week. Not sure what an NL/Hour is but 2.8CFM is 4800Liters/Hour

[Prashun Patel]

Thanks, Andy. How did you compute that? NL is (I believe) Normal Liters.

[Andy Giddings]

I just used a conversion tool for CFM to Liters/Hour. SCFM is, I believe, Standard CFM which means CFM of gas at standard temp/atmospheric pressure https://en.wikipedia.org/wiki/Standard_cubic_feet_per_minute. As most of us aren't working at high altitude in freezing or hot conditions I guessed it should be close :-) I would assume Normal Liters means something similar

[Van Huskey]

3 cfm will be about 5100 liters per hour.

The CAT 1hp compressors will not give you the volume you need at 7-8 bar which is roughly 100-115 psi.

Especially when you said "industrial" I would be looking at an oiled two stage compressor instead of an oiless one. The CATs are quiet, very quiet and I love mine but I think you need to look bigger and more robust if the job actually requires that volume and pressure, that is quite a lot of pressure compared to what the smaller compressors are designed to provide on anything like a continuous basis, the volume isn't high at all though.

[Andy Giddings]

Missed that part on the pressure, Van. I know the 2HP CAT I have delivers 5.3CFM at 90psi but don't have a number for 115psi. That model is also quiet and portable

[Van Huskey]

Missed that part on the pressure, Van. I know the 2HP CAT I have delivers 5.3CFM at 90psi but don't have a number for 115psi. That model is also quiet and portable

My concern is all the CAT compressors I am aware of (they do have some larger ones I think) max out at 120-125 psi, I would not feel comfortable expecting them to deliver over 100psi for long periods of time, but that may just me. I have never had to have any volume of air at those pressures.

[Jerry Bruette]

Are you pressurizing the barrels with the air or are you pumping liquid in to get the pressure?

I don't think a standard 55 gal drum can handle much pressure without bulging or splitting a seam.

[Prashun Patel]

Jerry,
We are using the air to drive a siphon pump to cause the liquid to draw out of the drum. The compressor just needs to run long enough to start that siphon.

[Van Huskey]

The compressor just needs to run long enough to start that siphon.

In that case I bet one of the 1HP CAT compressors would do and they are VERY quiet. I have the 5510SE with a 5.5 gallon tank and I think it would work well. Only $150 on Amazon (and others) and you can get it for under $130 when Zoro has a 20 or 25% off coupon.

[Ronald Blue]

The siphon pumps we use require constant air flow. They create vacuum but only while the air is flowing. But then your application is probably different. When we do it our goal is to keep liquid from gravity flowing out through an open valve, fitting or other orifice while we effect a repair. The alternative would be draining the tank while the repair was made.

[Prashun Patel]

Thanks for all your help. I ended up getting the California Air Tools 20040dcad

CAT makes an "SP" line which is in a soundproof cabinet. It's amazingly quiet.

[Mike Heidrick]

Id buy a $99 wayne pump and be done. No slow siphon.

[Prashun Patel]

Mike, I think I've misrepresented the size and complexity of the system. A $99 Wayne pump wouldn't be appropriate. We're using an air-driven pump. The system is for business, and I'm requiring a little more reliability than a standard, household electric pump would deliver (with confidence ;))

[Adam Herman]

We have found the best way to get fluid out of a drum is to put about 5 psi in the small bung and a tube that reaches to the bottom and screws into the large bung. simple, requires very little equipment and will never burn up a pump. no moving parts. we have a pop off valve on the air side to protect against over pressure. this also works for many different viscosities of fluid.