Gas booster in a (possible) hurry

[Wookie]

This one sold for $1,000 in May. Had 2 hours on it. Sierra Precision Booster Pump - GovDeals.com

 

[rddvet]

Frank, thanks for the help. I figured someone would know. I've never checked out that site. That's a good one to have. If you've got some other sneaky sites like that let me know.

Do you or anyone have any experience with american airworks kit? I'm moderately good with my hands, but no expert mechanic. I do repairs on my K14, for reference. I swore I saw a kit on their site last year, but then looked recently and missed it.

Thanks again,
Richard

 

[Wookie]

Frank, thanks for the help. I figured someone would know. I've never checked out that site. That's a good one to have. If you've got some other sneaky sites like that let me know.

Do you or anyone have any experience with american airworks kit? I'm moderately good with my hands, but no expert mechanic. I do repairs on my K14, for reference. I swore I saw a kit on their site last year, but then looked recently and missed it.

Thanks again,
Richard

I've rebuilt my masterline once, and have another kit. If you get the Airworks kit, I'd live to sit down and compare parts. There is a special tool, which stacks the rings like you were rebuilding a regulator. My suspicion is, but have no proof, is that the kits will be remarkably the same.

 

[kelemvor]

This one sold for $1,000 in May. Had 2 hours on it. Sierra Precision Booster Pump - GovDeals.com

Totally off topic, but that site is GREAT! Thanks for posting it, now I'm going to be out of cash for a good long while...

 

[Wookie]

I also shop at www.governmentliquidation.com. Bought one of the spec ops booster sets for less than it cost to ship. $250 I think. Huge Haskels, my 37 CFM compressor couldn't keep up.

 

[TrimixToo]

Everything You Wanted to Know About Haskel Boosters But Were Afraid to Ask can be found in this software:

http://www.americanairworks.com/haskel.zip

Drive gas requirements, capacity per minute, input and output pressures, and so on are all there in a reasonably handy format. The drive gas requirements and time to boost from low input pressures make any sort of dive team-level blending on site a very time-consuming exercise with a single-acting booster*. (Sleep will be a problem.) On the other hand, boosting from high input pressures is not too bad. A good cascade system of preblended gas in combination with another cascade for drive gas and a booster (or a compressor that can pump the mix!) would be a nice solution if you have a big enough dive trailer to swallow that sort of system whole.

* Those are expensive enough. I have an AG-30. I did the math on expedition blending for four and declined to bring it along. "Bring more doubles."

 

[tbone1004]

I'm really hoping that someone with a Rix Microboost can determine if they can actually go above 2000psi or if they are just set to that for cutoff because of O2.
@iain/hsm anything on that?

 

[iain/hsm]

I'm really hoping that someone with a Rix Microboost can determine if they can actually go above 2000psi or if they are just set to that for cutoff because of O2.
@iain/hsm anything on that?

2200 psi? LOL

 

[iain/hsm]

Just kidding.

There are a few considerations at play here I will try and cover some.

To kick off it was designed to operate 24/7 with a small oxygen generator that developed around 5 to 6 lpm flow at 5 to 25 psi pressure from the oxygen generator. Now that's not a lot to go with for starters.

Its duty cycle design was therefore 24 hours continuous running to fill a 50L cylinder medical oxygen at around 19 hours. The 2200 psi design pressure was taken by the pressure rating of the aluminium Luxfer medical cylinders.

Now the question is really two fold:
First can be made to go higher than 2200 psi......Technically yes

The motor will go much higher without any modification
The pressure relief valve can be re set to 2900 psi (200 bars) or changed for a Swagelok Nupro
The pressure switch also can be adjusted to 2900 psi
The interstage 2nd stage relief valve is set at 1200 psi and again could be adjusted if required.

So mechanically all the parts can be adjusted to increase the cut out set pressure.
But there are other factors at play.

1. The compression ratio on the 1st stage increases
2. The interstage temperature increases and its a self cooled design ie the block is the heat sink
3. The rod loading increases with the increase in pressure on the 2nd and 3rd stage

Now you could lower the compression ratio by increasing the inlet pressure but the 2Mu paper pleated intake filter element may need changing for a Swagelok. The Tygon intake tubing may need better end fittings, but by lowering the compression ratio the rod loading goes into orbit as the 1st stage diameter increases rod loading, in other words to solve one area you create another problem elsewhere.

Also the bearing lubrication may have to be increased presently its 8500 hours or once a year,
The bearing grease thickener mix may need adjusting ie new grease but additional lubrication frequency may resolve that, say to every six months.

Additional cooling could be added with say a computor type 120 x 120 mm fan

I would also propose to fit a RTD to monitor gas temperature at the 3rd stage wih a high temp cut out. We have a 5000 psi 1/8 NPT oxygen rated RTD for another compressor that would work. The head would have to be modified unless it was added to the discharge tube with a tee

Ring wear could increase due to increased 30% uplift in pressure and this could block the inlet/discharge valves again interstage micron filtration could be considered. But as the ring materiel compound works very well with oxygen, just not so good on dry nitrogen it would proberbly pass the particulate test.

Compression ratio, Heat generated, cooling, and rod loadings would be my engineering consideration.

The second part of the answer is should you.

Using an Ideal for a 3000 psi design project would be to increase the inlet pressure, lower the first stage piston diameter to suit a moderate compression ratio, increase the cooling with a fan and monitor gas temps with safety cut outs. But that would be a completly new design .

Maybe we should do a separate post at some point on the beast and explain in detail the design philosophy.

 

[tbone1004]

@iain/hsm fair enough. My invacare unit is very small and is similar designed but has a flow rate of about 2lpm so moves incredibly slowly. It does have no problem going up to 3000psi intermittently so I let it do go for it. What I do is leave it to 2000psi and have it fill my big T bottles, and transfill into my ccr/bailout bottles from there. If I need them over the 2000psi, then I hook it up for the last boost which doesn't take terribly long. I was hoping that the Microboost was more easily converted to 3000psi service and then I could use an adjustable pressure cut-off to do the same thing.
Especially important for helium PP blending moreso than O2 which I only like to pump up to 2500-2600psi