Air entrainment into compressor other than intake

[dannobee]

What you really need isn't a compressor, but a big gas booster. Even a very big (portable) scuba compressor won't pump more than about 10 cfm. Some of the Haskel boosters will pump 200-350 cfm, but you'll need a low pressure shop style compressor to drive the booster.

The compressor won't like breathing 100% helium for hours straight. It'll overheat (not the motor, but the pump/compressor) because of helium's thermal properties.

 

[rjack321]

What you really need isn't a compressor, but a big gas booster. Even a very big (portable) scuba compressor won't pump more than about 10 cfm. Some of the Haskel boosters will pump 200-350 cfm, but you'll need a low pressure shop style compressor to drive the booster.

I thought of this, but which ones will boost from ambient pressure?

 

[Zodiacdiverdave]

Thanks I have a better understanding of Scuba compressors. And It sounds like we may be able to do this. You guys know whats doable , What compressor would you recommend now that we dont need an enclosure to isolate the compressor.

BTW , I service and rebuild Industrial type piston comps as part of my duties at work. but, I've never messed with Dive or extremely High PSI 3 -5 stage. I know the ones I work on would suck real bad at this job being basically swiss cheese when helium is concerned , Open vents to the crank case , sealing around manifolds, head gaskets and such and that is what prompted the pressurized enclosure idea.. So thats why I ask questions. Sorry for seeming dumb to you. I'm sure dives are much better built, but dont know first hand HOW much better built. and if there was a way for air to migrate into the gas flow, or gas escaping from anything other than a failure. Thanks for putting up with my ignorance.

Dive compressors are piston type units that work the same way low pressure piston compressors do except they may have other features like high pressure oil pumps, and safety switchs to prevent overheating and oil pressure loss. The filter or purification system will keep your gas clean and dry and will not alter your gas mix.
The only area where you could have a risk of air entering your gas stream is at the intake of the compressor.
Some of the helium will get by your piston rings but will be sent back to your first stage inlet valve and sent through the compressor again. If there is too much get by for this to handle then you could have some problems develop in the compressor. I would recommend using chemlub 800 as an oil. It is a heavier oil then the standard 751 and may prevent some of the blow-by. I don't see pumping helium doing damage to the piston rings.
Most new 10 cfm compressor sold in the USA and Canada now use rings on the final stage which will also help reduce the blow-by. I would recommend not buying used units, for this you would want a tight compressor so you don't loose alot of helium from leaks and your cylinder walls and piston rings will be in good shape.
I would have a concern on the intake pressure at the 1st stage. most compressor companies recommend no more then 2-3 psi at the intake or you could damage the compressor.
Good luck.
ZDD

 

[e1cycle]

ZDD Thanks very much for the info. The inlet will be just atmospheric pressure. The envelope does not pressurize . The helium just filles the volume So all is good here. .
I'm not familure with boosters . But any way to evac the volume and retank quickly would be optimal . Any thoughts on brands?

 

[dannobee]

I thought of this, but which ones will boost from ambient pressure?

Any of them will, just don't ask them to boost from ambient to 3000 psi. One of the checks to perform after rebuilding a Haskel is to let it pump from ambient to a spec. The usual Haskels will pump to at least 250 psi from ambient.

Make two boosts if you have to (ambient to 200psi, then 200 psi to ~2000 psi)

It will still be a LOT faster than letting a small compressor run for hours.

 

[e1cycle]

What does that do to a system price to use 2 boosters?

 

[dannobee]

What does that do to a system price to use 2 boosters?

You wouldn't. You would use one booster, but boost twice. I.E. Take your He from ambient to 200 psi in one storage tank, then boost that tank into another tank to, say, 1000 psi (or some other pressure that's convenient), using the same booster. Your original tank is now empty to start the process over. Once all of the ambient He has been stored, boost the same way to whatever pressure you want.

Just don't try it with one of the little single stage gas boosters. You'll need something fast, like an AGD-15 or an 8AGD-14.

 

[Zodiacdiverdave]

Dannobee is correct, using a booster system would be more cost effective, I would recommend that a LP compressor or a gas amplifier be used to initiallly bring the pressure up to 500psi and then send it through a booster. I would contact Hydraulics international Hydraulics International, Inc. PUMP DIVISION, Liquid Pumps, Gas Boosters, Air Amplifiers and tell them what you intend to do and they will be able to recommend the best set up for you. These guys manufacture gas boosters that are equal to the haskel pump but at far less the cost. Your system will likely cost you around $10K but it is still going to be cheaper then a HP comressor.
ZDD

 

[e1cycle]

This sounds Interisting. How many tanks would it take to do this ? I'll have 22 HP cylindrers form the fill . How would I work that? Using those tanks in a LP to HP affair ?

 

[Zodiacdiverdave]

I think that if you used a LP compressor of around 24 cfm with a receiver tank and pressure switch to maintain the receiver pressure at 150psi the intake of that compressor could be used to evacuate the envelope. The discharge line from the receiver would connect to the inlet side of the booster. And then the outlet side of the booster would go to your HP cylinders. The boosters can be ordered with a pilot valve to regulate out-put pressure, kind of like a pressure switch.
You would have to monitor the pressure in the receiver to ensure that the booster does not exceed the capablities of the LP compressor. This set up would require a second LP compressor to opperate the booster. Your booster speed can be regulated by controlling the amount of air that is running the booster.
One other option you could look at is using a booster compressor. Bauer Compressor manufactures HP nitrogen generator. They use a LP compressor and membrane system to manufacture nitrogen. (This is the same type of membrane used in making Nitrox). Then the nitrogen is sent to a booster compressor which is a three stage compressor that has had the 1st stage cylinder and piston replaced with a second, 2nd stage cylinder and piston. The nitrogen is feed to the compressor at around 50-psi where it can be boosted up to 5000-psi.
Again this system may be more expensive to set up but if I were you I would contact Bauer in Norfolk and discuse your requirements with them. Get a quote from BAUER and from Hydraulics International and move forward from there.
One more thing you will need to keep in mind is that this system will generate a lot of heat so your facility will need to be able to deal with this.
Good luck, keep us posted about your progress.
ZDD