Home Dive Training Tech Tips: Portable Air Compressors Part II

Tech Tips: Portable Air Compressors Part II

Big air compressor

By Alec Peirce

So here we are at the backdoor of Roger’s air fill station. He carries a lot more here than just his air fill: tanks, scuba gear, and his friends’ gear as well. It gives you an idea of the complexity. Here’s the problem: I mentioned earlier this is an ACFM compressor: you hook up your 80 cubic-foot tank and roughly 10 to 15 minutes later, one tank is full. That won’t work for us. We need four or five tanks filled at once. How do you do that? You obviously hook up more hoses.

This is the airline coming from the compressor that goes back into the back, and that airline connects to the tank fill – called a whip. Roger has several of these and can fill eight tanks at once. The difficulty with that is that eight-cubit feet per minute… now you have eight tanks, which is 640 cubic feet. It’s going to take a while to do that so to speed things up, what most dive stores and what Roger has done here, are 400-cubic-foot tanks. Roger has six of them. What’s the big deal?

He can run this compressor for a few hours while having supper and enjoying himself. When the divers come in from Silver Springs, they land their eight tanks up, Roger puts the eight fill whips on, opens the valves, and the air comes out of those tanks into them – those tanks are high pressure. It takes time to fill all the tanks, but the point is we’re not waiting for the compressor to fill them. It’s called a bank, and this is a cascade system. If you go into your dive store, and if it’s pretty large, ask the operator – tell him you watch Alec Peirce on Tech Tips and know all about compressors – and see if he doesn’t mind you taking a look at his cascade system. Some cascade systems are very large and at my store, Scuba 2000, we have 30 tanks – up to 4500 PSI and we’d often fill 100 tanks a day. Next time you argue about that five-dollar air fill, think about that: $15,000 invested to fill it.

This is Roger’s fantastic system, and the nicest thing about it is that it’s very sophisticated, very capable, and on wheels! It’s a portable system in use today that you might consider. We’re going to take a couple of minutes and look at a much smaller system: a system that maybe one or two or four divers might get together and purchase: something they can haul around in the trunk of their car.

Now this is a portable compressor. You see? This blue thing here, you pick it up, throw it into the trunk, and off to the dive site. Take a gas can; it’s got a gasoline motor on it so you don’t have to have an electrical hookup with a lot of wires and so on. If you need to fill a couple of tanks this will do the trick. Let me tell you a bit about it: the Max-Air® 35. It’s very popular, and if you Google portable compressors it’s bound to come up. There are several companies that make these, and this compressor was made in Italy by a company called Coltri. Max-Air® is one of the most popular and I’ve sold dozens of these to small groups of divers and individuals. The 35 means 3.5 cubic feet a minute, approximately. If you take a standard 80 cubic foot tank and use this to fill it, then it’s going to take the better half of an hour to fill it. But it’s portable: you’re out of the dive site, you sit down and have a pop and a sandwich, and you need a tank to go diving again. Fill one tank in half an hour and the other, and you’re ready to go diving today. It’s hard to beat. You don’t have to own a bunch of tanks or run to the dive store. If you’re in that situation where you dive a lot with one diver or a small group of divers, then this just might be the answer if you’re interested in having a small compressor.

It is gasoline and that creates a couple of concerns. The gasoline engine is just like your lawnmower so there’s an exhaust. It’s very important to have an air intake hose. Here Jerry has his intake hose and he keeps it up nice and high, so it sucks in the cleanest air possible. This compressor is light as well at 75 pounds. These compressors have filters on them, and Jerry changes them after so many hours: it has an hour meter so he knows how long it’s been running, and buys a new cartridge so he knows the air coming out is safe for divers to breathe. Jerry has gone an extra step with a device, a supplementary super filter that is renewable: put it on there and on the off chance anything bad goes through the compressor after [the first] filter, this filter should catch it. Really simple.

Cost? It’s roughly $1000 per CFM plus $1000. If you buy one of these, Max-Air® wants $3500 plus $1000. Occasionally they’ll be on sale or good used ones come up: a diver bought it and they’re too noisy or he didn’t use them too much. Sometimes you buy one for $1500 or $2000 but to buy a brand spanking new full warranty from the factory, you’re looking at $4000.

Nothing is perfect. What’s the other disadvantage? Noise, a lot of which is coming from the gasoline motor. You will not put this in your living room. You can put extra mufflers on but there’s the weight and added expense. A lot of divers will have the compressor tucked away into the woods while camping.

There you go, guys. A little information on portable air compressors: if you and your friends get together for your own tanks. Go to Max-Air® to check out the really portable, inexpensive smaller compressors and speak to a supplier for a bigger one.

Send me some comments! Maybe you have your own compressor system and I’d be happy to talk to you about it.

Alec Peirce – 2018

Alec Peirce has been diving for more than 60 years. He is the founder and former owner of Scuba 2000, Canada’a largest dive centre, opening in 1969. He a dive instructor, author, public speaker and former member of the PADI IRRA Advisory Council.

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