RE: [PSUBS-MAILIST] Breathable air compressor

Having made a few hundred high pressure compressors I’ll put in my pennies worth. There are many hydraulic gas compressors and air/gas over oil compressors used as transfer pumps. Haskel for one.

What you are describing is best done with two cylinders pumping water from one to another but best to use your Hookah compressor to boost the inlet to 5 or 6 bar which will reduce the number of cycles by 5 or so times.

Standard cylinders are about 40-50 water litre capacity about 1.75 cu ft. so for 80 cu ft scuba tank you would need to cycle 80/1.75/5 = 9 times approx. Cost of 2 tanks, hookah, filters, hp water pump, electrics, time = same as a dive compressor which will be much smaller and transportable and you can use the extra time making your sub. Hugh

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of ojaivalleybeefarm @dslextreme.com
Sent: Friday, 18 March 2011 3:55 p.m.
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Breathable air compressor

It seems like one could use a gear pump to pump water into a high pressure cylinder, the water would compress the air in the cylinder. That way you would avoid any problems with oil particles. Just a thought.

Brian

On Thu, Mar 17, 2011 at 11:14 AM, Daniel D. Lance <lanceind@gmail.com> wrote:

Its easy to convert a regular low pressure air compressor for hookah purposes. If you have an oil lubricated type take it apart and thoroughly clean out all the old oil . Reassemble it and refill it with a monolec type oil made for breathing air compressors. You can buy this oil at a dive shop or at commercial diving supply. Remember to place some type of filter on the air flow out of the compressor to trap any oil mist or droplets that might come down the breathing air hose. You don't want oil in your lungs. It causes a very nasty type of pneumonia.
Of course there are lots of cheap oil less compressors available that would also work well for this purpose.
A high pressure compressor for filling scuba tanks is a completely different animal. Unless you have access to a well equipped machine shop making your own will be a challenge.
If you really need to fill your own scuba bottles and you are on a budget then I would recommend going to www.airspeedpress.com and order a copy of their book called " Improvised and Low Cost HP Gas Boosters".While I don't recommend that you build your own booster to pump oxygen all of the designs in the book will work well for air or inert gases for technical diving.
Dan Lance

On 3/17/2011 8:06 AM, Stewart Gardiner wrote:

Hi guys, I’m fairly interested in SCUBA… as well as being VERY interested in subs… ive got a fairly good understanding of air compressor types etc… but does anyone here have any knowledge on the principal workings of a hookah or scuba tank filling type compressor? Its just something that ive never quite understood, and ive seen scuba refill compressors cost upwards of $2500AUD.. so I thought why not make one! J

One of the pre-requisites is an oil-less lubrication system for the piston/vanes? Obviously oil vapour in the breathing air isn’t a good thing J

Anything else anyone can put forward to further my knowledge?

TIA Stew

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