Portable Compressor Realities

[SurfLung]

Portable Compressor Realities
- When a gas engine powered portable compressor is running nearby, it's difficult to visit with your dive buddies between dives because you can't hear very well above the noise of the compressor. Duh. For 2-day dive trips, we have always brought enough tanks so we would not need re-fills. But on a recent couple of dive trips, I thought it would be fun to bring along my little Aerotecnica portable gas engine powered compressor. And sure enough it was difficult to hear each other speak when the compressor was running.

- I also learned some new things:
1. The compressor weighs as much as two tanks.
2. The compressor takes up as much space as two tanks.
- So, if you just brought along an extra two tanks, you'd have enough air for a 2-day dive trip and not have to listen to the compressor noise.

- Another revelation is this: Just because its gas powered and portable doesn't mean you HAVE to take it with you on trips. You can fill tanks at home just as you would with an electric powered compressor. In fact, the last time I was refilling a bunch of tanks, I ran BOTH compressors... My RIX on electricity at 2.5 cfm and my little AERO on avgas at 2.9 cfm. That's 5.4 cfm and some really fast tank filling!

- I think the cut-off is on dive trips where I might be diving 3 or more days... Which is probably not likely. But even then, I think I would bring 2 days worth of tanks. And then find someplace (like a roadside park or rest area) away from the dive site to just re-fill them all in one loud session.

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[ScubaLawyer]

We had a guy running his gas powered compressor out of the bed of his pick-up in a parking space above the beach a few weeks ago. The police in our town came by and asked him to shut it off due to noise complaints from nearby residents. Two hours later he was still filling tanks so he got a hefty ticket for violating the decibel level noise restriction ordinance. While many of us love the smell of a gas compressor early in the morning one does have to be conscious of ones surroundings. M

[SurfLung]

Geez... the bed of his truck must have made a good sounding board to amplify it. Rich and I were back up on the hill parking lot at Ore-Be-Gone with nothing but cars and I thought it was too loud. Down below along the beach, the a visiting dive shop started up their compressor among all of the swimmers and divers. I was surprised he got away with it but we figured if he can do it down there with the people, we can do it up with the cars.

[antique diver]

We carted this beast all over Florida and some Texas cave sites. The compressor in the big red housing is a 15 cfm Davey with 4 cylinder Wisconsin engine. It made some noise, but lower pitch and seemingly less irritating than the small units. Engine was muffled pretty well and we had minimal complaints, since you didn't have to get to far from it to converse, and we tried to get a reasonable distance from others. Of course it didn't run as long either.

Comp.trailer..jpg

Location is Phantom Cave in West Texas

[captain]

If you don't absolutely need to fill the tanks at the dive site just drive to a secluded place with the compressor and an ice chest of beer and have a tank filling party.

[tbone1004]

how much of the noise was motor vs compressor related?

If compressor, could you put a better intake filter on there to muffle it? I.e. oversized solberg on the intake?

If motor, does it make more sense if you need it regularly to use a small generator and your Rix?

[swimjim]

With a welder and a little imagination you could probably fab up a better (quieter) exhaust. The Swimjim approach is to pump at home and take all the tanks I need to the dive site. My 3/4 ton van is pretty handy for that.

[SurfLung]

It may surprise a some of you but, my electric powered RIX SA3 seems louder than my gas powered Aerotecnica MCH-6. They both are running at about 2300 rpm and filling tanks at 3.0 cfm or less. I haven't measured any actual decibels but my garage is about 100 feet from the road and when I turn either compressor on and walk out to the road, they seem to have about the same noise level.

That may seem odd for the RIX but then when you consider it is oil-less and the bottom of the cylinders are open rather than closed... I think the compressor itself is going to be louder than a similar capacity compressor with an enclosed oil lubrication system.

Thanks for the photo of your crew-served "Portable" compressor Bill! I heard about your career in equipping and training cave divers as well as building custom compressor systems... It's neat to see a photo of one of those compressor systems.

[tbone1004]

that makes sense, the fan on the Rixes are also wicked loud compared to many since the pistons don't get any help from oil to cool off. The bigger intake filters may be worth looking at though as they can make a pretty big impact on noise.
One of the things that I have used to demo that concept is to take the "quiet tech" compressor that is used for my booster and spin off the tiny plastic inlet filter and have people hear how much louder it is. It goes from mildly annoying *think idling car*, to something more akin to an idling harley. It's truly amazing how much work that little thing does.

[antique diver]

If you don't absolutely need to fill the tanks at the dive site just drive to a secluded place with the compressor and an ice chest of beer and have a tank filling party.

That's exactly what we did after finishing up a day of diving!

[antique diver]

how much of the noise was motor vs compressor related?

If compressor, could you put a better intake filter on there to muffle it? I.e. oversized solberg on the intake?

If motor, does it make more sense if you need it regularly to use a small generator and your Rix?

Hard to tell which was louder. I equipped it with a large Solberg intake filter/silencer on a 20' that we could set up on a pole or hang from tree.

My Rix is 5 cfm, and also gas powered, compared to about 15 cfm on the Davey. The amount of breathing gas we were brewing and filling would have taken three times as long with the Rix. It would have taken too much beer to sit through the filling process with Rix.

[antique diver]

It may surprise a some of you but, my electric powered RIX SA3 seems louder than my gas powered Aerotecnica MCH-6. They both are running at about 2300 rpm and filling tanks at 3.0 cfm or less. I haven't measured any actual decibels but my garage is about 100 feet from the road and when I turn either compressor on and walk out to the road, they seem to have about the same noise level.

That may seem odd for the RIX but then when you consider it is oil-less and the bottom of the cylinders are open rather than closed... I think the compressor itself is going to be louder than a similar capacity compressor with an enclosed oil lubrication system.

Thanks for the photo of your crew-served "Portable" compressor Bill! I heard about your career in equipping and training cave divers as well as building custom compressor systems... It's neat to see a photo of one of those compressor systems.

Thanks Eben. That trailer was customized to hold three large O2 cylinders up front for our mix, with a flat cover over them for gear assembly. Plus the locking tool box on front. Enough room in the rear compartment for 4 sets of doubles standing on side walls plus stage and deco cylinders laying in center with dive gear on top of those.

I sold it a few years ago to Scuba Point. They kept offering me more and more for it until I finally couldn't resist. We weren't running any large groups by then, and my Rix does fine for a small group.

[rx7diver]

If your dive vehicle is stout enough (3/4 ton pickup or van?), why not simply take along a few cascade cylinders with which to fill your scuba cylinders for a multi-day trip? It doesn't take but a couple of 6,000 psig cascade cylinders to fill quite a few 1,800 psig or 2,250 psig "classic" scuba cylinders.

Moving the whip from cascade cylinder to cascade cylinder would be a royal pain, but arguably less of a pain than tending a little, whiny, portable compressor for several hours each day, I would think.

rx7diver

[captain]

First you need to buy the cherry picker to load and unload the 6000 psi cascade cylinders.

[rx7diver]

First you need to buy the cherry picker to load and unload the 6000 psi cascade cylinders.

A two-wheel hand truck or dolly (is that what they're called?) and a ramp could be used to move the cascade cylinders, one at a time, into the truck bed. Be sure to use the valve cover/cage, and be sure to chain the cylinders in place (to keep them from shifting around). Do you think DOT would have any problem with this? We'd need to check.

If the 6,000 psig cascade bottles prove too massive (I don't have any experience with them), then use 4,500 psig cascade bottles (I do have experience with these), instead, which weight ~150 lbs each and hold ~450 cu ft of air at their service pressure.

(The quick and dirty Excel example I shared here a few months ago can be tweaked to show just how many classic 72's can be filled from empty to full + 10% using only a few of these cascade cylinders.)

rx7diver