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Old 26-03-2017, 06:49   #31
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Re: Dive Scuba compressor

Would it be that difficult to put a 48v 3kw electric motor to run the compressor? It's just a belt that runs it from the motor...
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Old 26-03-2017, 12:32   #32
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Re: Dive Scuba compressor

...an AC soft starter maybe also is an option to run a scuba compressor from inverter?
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Old 26-03-2017, 13:33   #33
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Re: Dive Scuba compressor

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Originally Posted by Hobie_ind View Post
My tired 20 yr old Coltri was about 45-50 minutes to 3000 psi. It wouldn't get there when I bought the boat but a few hours lapping valves and it was substantially better. I'm sure it would have been even better with new valves, but I just never got around to ordering them.

I'd have preferred a Bauer (much more common for parts worldwide it seemed) if I was buying one, but the Coltri was fine and came with the boat.
This is another good point - their numbers (as are most manufacturer numbers) are based in "ideal conditions". Once that compressor has a few miles on it the 25 minute mark will drift and it will be consuming a lot more electricity to get to 200 bar / 3000 psi. Likely it wouldn't be noticed if it was being run by a petrol engine, but taking power from a battery bank would get pretty tedious pretty quickly.
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Old 29-03-2017, 23:29   #34
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Re: Dive Scuba compressor

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This is another good point - their numbers (as are most manufacturer numbers) are based in "ideal conditions". Once that compressor has a few miles on it the 25 minute mark will drift and it will be consuming a lot more electricity to get to 200 bar / 3000 psi. Likely it wouldn't be noticed if it was being run by a petrol engine, but taking power from a battery bank would get pretty tedious pretty quickly.
Well, not sure about that.
A 5hp petrol engine is equal to about 3800 watt, but the efficiency is just about 25-30%. An electric engine is at either 2200w or 3000 watt but its efficiency is about 40-50%. What I mean is, the petrol engine can't do any magic trick to get more energy than it can produce and itīs equal to the electric one. So if the petrol version would take longer time to fill the tank, so would the electric.

Just like everything else, a compressor needs to be looked after but it should work accordingly to the spec as long as there are not parts being worn out. So... it should not be any dramatically differences in time/energy
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Old 31-03-2017, 10:33   #35
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Re: Dive Scuba compressor

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Well, not sure about that.
A 5hp petrol engine is equal to about 3800 watt, but the efficiency is just about 25-30%. An electric engine is at either 2200w or 3000 watt but its efficiency is about 40-50%. What I mean is, the petrol engine can't do any magic trick to get more energy than it can produce and itīs equal to the electric one. So if the petrol version would take longer time to fill the tank, so would the electric.

Just like everything else, a compressor needs to be looked after but it should work accordingly to the spec as long as there are not parts being worn out. So... it should not be any dramatically differences in time/energy
Ah, I was referencing that the petrol compressor would just crank along until the tanks were full and the user probably wouldn't even pay attention. But running from batteries the user would have to monitor power consumption and recharge the batteries, making it a lot more work, when the intent with using electrical was likely to make life simpler.
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Old 07-04-2017, 07:31   #36
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Re: Dive Scuba compressor

Once spoke to a gent who was busy refilling tanks for a group of divers at the Blue Hole in New Mexico. He lamented on how long it took and how many tanks he would have to fill before paying for the setup. Also the cost of fuel and maintenance. He talked me out of getting my own refill apparatus.....though it is easy to be interested in the convenience.

What about the economics of having a lot of scuba tanks instead? At roughly $250+ per tank, one could buy a lot of tanks indeed. What about buying a lot of used tanks. What does re-certification of tanks normally cost these days? I have 8 tanks and a pony that need to be re-certified.

As a semi-solar pro, I might assert that battery energy consumption would make battery usage for filling tanks a pretty tough thing to do. Unless one carried a 1500 pound forklift battery of course. Even the comparatively little air compressors that refill large 4WD tires to 35 psi can wear out a regular sized battery.
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Old 07-04-2017, 07:43   #37
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Re: Dive Scuba compressor

I won't comment on filling Scuba tanks off of your battery bank, cause it's I think silly.
Even if you could, you now have a dead bank, how are you going to recharge it? Nobody has enough Solar to run their boat and refill Scuba tanks

However going price for used aluminum 80's that have a fresh Hydro is about $100 a tank. Aluminum 80's are plentiful and cheap used.
Personally I won't dive with an aluminum tank, but that has a lot to do with physical conditioning, they are way big and heavy and require you to carry a lot of lead. Reason is they displace so much more water than a high pressure steel tank.
I just had four tanks Hydro'd and with the hydro and refill, and having the tanks VIP'd, which is ridiculous as they are just out of Hydro, ran I think about $50 a tank.
Normally I buy the VIP sticker from Ebay and do my own Hydro, I'm more qualified than the average tank jockey at the Scuba shop.
I started that after some idiot at the local Scuba shop put silicone grease on the valve O rings of my O2 clean tanks, meaning that I then got to have the valves disassembled and cleaned / rebuilt and the tanks tumbled.
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Old 07-04-2017, 08:10   #38
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Re: Dive Scuba compressor

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I won't comment on filling Scuba tanks off of your battery bank, cause it's I think silly.
Even if you could, you now have a dead bank, how are you going to recharge it? Nobody has enough Solar to run their boat and refill Scuba tanks

However going price for used aluminum 80's that have a fresh Hydro is about $100 a tank. Aluminum 80's are plentiful and cheap used.
Personally I won't dive with an aluminum tank, but that has a lot to do with physical conditioning, they are way big and heavy and require you to carry a lot of lead. Reason is they displace so much more water than a high pressure steel tank.
I just had four tanks Hydro'd and with the hydro and refill, and having the tanks VIP'd, which is ridiculous as they are just out of Hydro, ran I think about $50 a tank.
Normally I buy the VIP sticker from Ebay and do my own Hydro, I'm more qualified than the average tank jockey at the Scuba shop.
I started that after some idiot at the local Scuba shop put silicone grease on the valve O rings of my O2 clean tanks, meaning that I then got to have the valves disassembled and cleaned / rebuilt and the tanks tumbled.
A lot of people know that steel is better is many ways, with size, weight, and easier buoyancy compensation being factors. When I first took up scuba, steel was being phased out and I never seen steel tanks for sale. At the same time, dive shop operators were talking about much better steel tanks were. Is that progress?

I seem to recall people using scuba tanks for a long time indeed. So long as the tanks have not suffered the abuse of being used in a commercial operation. According to this advice on new valves, steel tanks also enjoy much greater longevity. 4. Do not install the valve to aluminum alloy cylinders aged of more than 10 years or steel cylinders aged of more than 15 years.

I guess my question is, what causes properly stored tanks to self-destruct? Corrosion is a possibility for improperly stored tanks in certain locations prone to high humidity and/or salt spray.


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Old 07-04-2017, 09:05   #39
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Re: Dive Scuba compressor

A good steel tank and I assume a good aluminum tank will last until corrosion gets them, the fatigue life for steel is pretty much infinite, and that is what Hydro's are for.
There are still good steel 72's out there, I have one I use for a deco bottle cave diving.
I think it dates back to at least the 60's, maybe earlier.
72's are LP steel and fell out of fashion years ago, and there are simply better tanks now, many had plastic liners and the plastic is falling apart, you can get it out with tumbling, but the tank just isn't worth it .
There was for a few years many aluminum tanks made from an alloy that I believe fatigues early, and that has made many shops have a policy of not filling older aluminum tanks.
http://www.ebay.com/gds/Danger-Warni...5952088/g.html
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Old 07-04-2017, 09:28   #40
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Re: Dive Scuba compressor

If you have a infitinitely large boat, you can carry an infinitely large number of tanks. But one tank per crew plus a compressor takes up a lot less space. I guess its a different story if you're going to dock near a dive shop every night.

When I worked at a large government facility, (I use a lot of compressed gases for my work) I'd occasionally get a steel cylinder with hydro stamps going back to WWI ! (That's a "one"). Who knew they even did that back then? Most of those old ones were marked "US Navy."
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Old 07-04-2017, 12:14   #41
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Re: Dive Scuba compressor

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A good steel tank and I assume a good aluminum tank will last until corrosion gets them, the fatigue life for steel is pretty much infinite, and that is what Hydro's are for.
There are still good steel 72's out there, I have one I use for a deco bottle cave diving.
I think it dates back to at least the 60's, maybe earlier.
72's are LP steel and fell out of fashion years ago, and there are simply better tanks now, many had plastic liners and the plastic is falling apart, you can get it out with tumbling, but the tank just isn't worth it .
There was for a few years many aluminum tanks made from an alloy that I believe fatigues early, and that has made many shops have a policy of not filling older aluminum tanks.
Danger Warning: Buying Aluminium Scuba Tanks | eBay
It appears that Luxfer was the manufacturer who used the inferior grade of aluminum. So everybody got a black eye.

I store my aluminums at 1500 psi to lower the pressure.

Some locations have high corrosion due to humidity. Some have a lot of salt spray. Everyone is held to the same protocol. It is a dummies world is some respect....geared to an IQ of 75.

I have pretty good endurance. Triathlons etc. Trying to use dual aluminum 80's is a bit dicey though I have done it.

I will never forget doing a night dive in Horsetooth Reservoir around midnight, Ive done some curious stuff, was looking for sunken boats. My anchor got donated to Neptune while I was messing around in a watery mud that allowed the diver to sink up to their waist.

I got to my boat and found that it was rapidly approaching the rocky shoreline on the east side. I'll never know how I thrust both tanks into the boat with one arm. It was either that or lose my tanks or the boat....in my mind at that moment.

Sometimes we can do stuff simply because we have to...
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Old 07-04-2017, 15:16   #42
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Dive Scuba compressor

Left to right, steel 130, steel 100, steel 80 aluminum 80 and aluminum 62.
The steel 80 has a boot, it's actually a couple of inches shorter, but as you can see the steel is much smaller, and holds a little more air as an aluminum 80 is really I think a 78

When I look, there is an aluminum 80 behind the steel 130, about the same height, the steel is a little bigger around though but a whole lot more gas
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Old 07-04-2017, 18:03   #43
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Re: Dive Scuba compressor

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Left to right, steel 130, steel 100, steel 80 aluminum 80 and aluminum 62.
The steel 80 has a boot, it's actually a couple of inches shorter, but as you can see the steel is much smaller, and holds a little more air as an aluminum 80 is really I think a 78

When I look, there is an aluminum 80 behind the steel 130, about the same height, the steel is a little bigger around though but a whole lot more gas
Perhaps twice as much time on the bottom with the 130! Why do steel tanks seem to costs significantly more?

I have eight aluminum tanks that I would trade for five-six steel tanks.
Having said that, unless one is a cave diver, aluminum tanks do still get the job done.

I just don't understand the switch, for the most part, to aluminum. Aluminum is about all that I see.
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Old 08-04-2017, 07:39   #44
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Re: Dive Scuba compressor

Aluminum cost much less to manufacture, more profit. It is as simple as that, and they of course do get the job done.
They are however inferior tanks, ever seen an aluminum tank used in industrial applications like welding etc? I haven't either, but they do get the job done diving.
A lot of people do cave dive aluminum, especially like Mexico when you don't need a dry suit. With a dry suit and sidemount steels, I carry no lead, and don't know anyone who does, if they were aluminum tanks then likely I'd have to have 10 lbs of lead. We do use aluminum tanks for stage bottles though, my wing doesn't have enough lift for four steel tanks.
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Old 09-04-2017, 07:30   #45
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Re: Dive Scuba compressor

Aluminum costs less to manufacture? Making the tanks of aluminum must cost a lot less. Steel is normally a fraction of the cost of aluminum...that is why I am still a bit perplexed. Perhaps it is hard to work with the needed alloys in the steel tanks. The aluminum tanks must also use special alloys...

What I am saying is that steel is normally much less expensive than aluminum. Feel like we are missing something.

As far as scuba tank compressors on a boat, I see that as a rich persons toy. Unless one does a lot of diving in a location with no scuba facilities.

Now if one could find a compressor that filled to, say, 1500 psi for a far lower cost. A unit that turned itself off at a set limit as well. That would work fine for the shallow dives that one often does in the Caribbean and many other locations.

Sure we would rather have 3000 psi. Most of us won't afford a 3000 psi compressor.
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