Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 31-03-2015, 11:05   #61
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,021
Re: Smallest compressor for diving

Since this question comes up quite often I'll put in this plug for steel 95 cubic foot tanks. These run at a lower pressure (2450psi) and have higher volume. Thus they fill faster and take less top end pressure to finish off. They also allow divers to get rid of about 5 pounds (2 kg) of lead weights.

The dive shops use Al 80's because they are lighter to lug around and arguably last longer. Water in the tank isn't a disaster. And I think they are cheaper at initial purchase. All good things for the dive shop budget. But filling them is more expensive which customers pay for so that isn't a big concern of the dive shops.

If you want to have your own compressor you will quickly appreciate the benefits of steel 95 tanks. Just keep them dry inside and inspect twice annually or any time the pressure drops below 400psi.
__________________

__________________
transmitterdan is offline   Reply With Quote
Old 31-03-2015, 11:11   #62
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29° 49.16’ N 82° 25.82’ W
Boat: Pearson 422
Posts: 12,374
Re: Smallest compressor for diving

Quote:
Originally Posted by transmitterdan View Post
Since this question comes up quite often I'll put in this plug for steel 95 cubic foot tanks. These run at a lower pressure (2450psi) and have higher volume. Thus they fill faster and take less top end pressure to finish off. They also allow divers to get rid of about 5 pounds (2 kg) of lead weights.

The dive shops use Al 80's because they are lighter to lug around and arguably last longer. Water in the tank isn't a disaster. And I think they are cheaper at initial purchase. All good things for the dive shop budget. But filling them is more expensive which customers pay for so that isn't a big concern of the dive shops.

If you want to have your own compressor you will quickly appreciate the benefits of steel 95 tanks. Just keep them dry inside and inspect twice annually or any time the pressure drops below 400psi.
Low pressure steel tanks can be a good option but a couple of cautions.

Most important, make sure you will be able to be positively buoyant by ditching weight if you need to make an emergency accent to the surface.

Also the steel tanks are heavier and can be awkward climbing in and out of the boat, especially if the seas pick up a bit.
__________________

__________________
The water is always bluer on the other side of the ocean.
skipmac is online now   Reply With Quote
Old 31-03-2015, 14:26   #63
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,021
Re: Smallest compressor for diving

Quote:
Originally Posted by skipmac View Post
Low pressure steel tanks can be a good option but a couple of cautions.

Most important, make sure you will be able to be positively buoyant by ditching weight if you need to make an emergency accent to the surface.
May I gently disagree with this? The absolute last thing you should consider is an uncontrolled emergency buoyant ascent (short of drowning). I think most (all?) training agencies recommend this as the last thing on the list of ways to self rescue.

A good diver is always neutrally buoyant and never needs to ditch weights in an emergency. Once on the surface then ditching weights is a good way to make life on the surface easier. But without weights a diver will very likely not survive the ascent or will die on the surface from pulmonary barotrauma.

Even if you can't breathe from the regulator usually the BCD low pressure inflator will still work.
__________________
transmitterdan is offline   Reply With Quote
Old 31-03-2015, 15:10   #64
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29° 49.16’ N 82° 25.82’ W
Boat: Pearson 422
Posts: 12,374
Re: Smallest compressor for diving

Hi Dan,

Guess I should clarify and elaborate.


Quote:
Originally Posted by transmitterdan View Post
May I gently disagree with this? The absolute last thing you should consider is an uncontrolled emergency buoyant ascent (short of drowning).

I assumed anyone dive trained would know this without saying but guess it's always good to be very clear. Yes, short of drowning or other life threatening event, never do an uncontrolled ascent.

I think most (all?) training agencies recommend this as the last thing on the list of ways to self rescue.

Yes. It is pretty much the last thing on the list BUT it still needs to be a last ditch option. Something happens, something really terrible and you can't achieve positive buoyancy then that could be drowning.


A good diver is always neutrally buoyant and never needs to ditch weights in an emergency.

Neutral as close as possible but even with a single Al80 there is a several lb difference in buoyancy from full to empty. If I recall a Luxfer 80 full is -3, empty +2 or something like that. You have to weight for neutral with empty tanks so you will be a bit negative when you first go in the water.

Once on the surface then ditching weights is a good way to make life on the surface easier. But without weights a diver will very likely not survive the ascent or will die on the surface from pulmonary barotrauma.

Bent you can fix. You even have a reasonable chance to survive barotrauma or pneumothorax (which are unlikely if you remember to exhale on the way up). However, it's 100% you don't survive drowning.

Even if you can't breathe from the regulator usually the BCD low pressure inflator will still work.

Yes but how many amateur divers are going to think about that if they run out of air and panic.
So no argument from me at all on this point. A bail out to the surface is pretty much at the bottom of the options list when you have a problem. But it does need to be an option and you should always have some quickly ditchable weight for bailout or, as you mention, on the surface if you're lost from the mother ship and need to float or swim. Of course in that case your tanks and regs are also disposable.
__________________
The water is always bluer on the other side of the ocean.
skipmac is online now   Reply With Quote
Old 31-03-2015, 15:24   #65
Registered User

Join Date: Jul 2012
Location: New Zealand
Boat: Ganley Transition 41 (corten steel )
Posts: 64
Re: Smallest compressor for diving

Some compressors can be belted of the main engine, could be a slick set-up, charge the batteries and fill the tanks at the same time.
Planned to do just that on my CSY 33, but not enough room as the engine box was part of the galley. Too much work and too little room to extend it.


I have been wondering about this option with my Bauer Junior 11. It currently has a 6.5hp petrol engine. I was told that to run the dive compressor off the front of the Yanmar 75hp engine,the most load that is recommend to run a device off the front of the engine is 4hp. Would 4hp be enough to run the compressor ??

I also have plenty of room and options for mounting the compressor
Thanks Ray
__________________
ski69sail is offline   Reply With Quote
Old 31-03-2015, 15:54   #66
Senior Cruiser

Cruisers Forum Supporter

Join Date: Mar 2006
Location: Nevada City. CA
Boat: Sceptre 41
Posts: 3,745
Images: 9
Re: Smallest compressor for diving

Can you add a PTO Power take off to an engine? I have one on my tractor and wonder if I could do that to my boat engine it would be great as a switch for water maker, dive compressor, generator etc.
__________________
Fair Winds,

Charlie

Between us there was, as I have already said somewhere, the bond of the sea. Besides holding our hearts together through long periods of separation, it had the effect of making us tolerant of each other's yarns -- and even convictions. Heart of Darkness
Joseph Conrad
Charlie is online now   Reply With Quote
Old 31-03-2015, 16:21   #67
Moderator
 
a64pilot's Avatar

Cruisers Forum Supporter

Join Date: Oct 2013
Location: Albany Ga.
Boat: Island Packet 38
Posts: 17,045
Re: Smallest compressor for diving

Often PTO's are part of a transmission, so with the right transmission, yes.
PTO would be a nice thing to have.
__________________
a64pilot is offline   Reply With Quote
Old 02-04-2015, 16:15   #68
Senior Cruiser

Cruisers Forum Supporter

Join Date: Dec 2010
Location: Cruising Indian Ocean / Red Sea - home is Zimbabwe
Boat: V45
Posts: 1,282
Re: Smallest compressor for diving

Quote:
Originally Posted by Time2Go View Post
Long Time Advanced Open Water diver (PADI Certification)
and the idea of having a gas motor running the compressor
gives me the chills (all the spots that I have dived have used shore based
electric powerwith plenty of extra bottles on the boat)
You would need really good seperation and ventilation
as not to compress the exhaust of the gas engine into the tanks.
This set uo would definitly get my attention.
If you want to live long and dive be Paranoid
There is zero issue with using petrol or diesel powered compressors as long as you ensure separation of the intake and exhaust. On a boat if you are using an electric unit there is still a generator running somewhere..........hmmmmmm, doesn't that mean an exhaust somewhere? Pretty obvious I would have thought. I am a BSAC qualified instructor - it does not make me an expert on compressors - that comes with experience of filling bottles, following the manufacturers instructions and using certified spare parts especially the filters.
__________________
Bulawayo is offline   Reply With Quote
Old 07-04-2015, 03:17   #69
Marine Service Provider
 
rcontrera's Avatar

Join Date: Jan 2013
Location: Seattle area
Posts: 49
Re: Smallest compressor for diving

WOW ... this thread sure took a lot of tangents!

To get back on subject, small compressors capable of pumping scuba grade breathing air start in the $3000 price range and go up way past $12,000. To hook up safely to 230 VAC you should have at least a 7KW genset.

As has already been noted, if you don't have the power to run one of these, you should look at gasoline or diesel. Bauer Junior II gas - about $5100, Bauer Junior II Diesel - about $7900, Coltri MCH6 Gas - about $3300

One thing that HASN'T been mentioned is that painted compressor frames are notorious "rusters" so you may want to look at going with a stainless steel frame. The Bauer stainless steel "Yachting" model is only available in electric. Coltri stainless steel adds about $500

As for the other compressors mentioned, Utilus hasn't been made in quite a few years. The shoebox takes about 12 hours to fill a scuba tank and requires a low pressure compressor to feed it.

As for best bang for the buck, the Coltri MCH6 is it. However, as has already been mentioned, you HAVE to do your maintenance. If you don't change your oil regularly, you WILL have valve problems. If you are bad at service, then the Bauer is a little better for you.

HOOKA is NOT scuba diving so I won't go into those.

Hope that helps.
__________________
Ray Contreras
CompressorStuff

rcontrera is offline   Reply With Quote
Old 07-04-2015, 07:45   #70
Eternal Member
 
monte's Avatar

Cruisers Forum Supporter

Join Date: Jul 2011
Location: Australia
Boat: Lagoon 400
Posts: 3,650
Images: 1
Re: Smallest compressor for diving

I see the shoebox isn't to be used for scuba tanks btw. We also have amps to spare and no rush too fill tanks so a slow filling compressor that works off 12Vdc or 220Vac with a 1500W inverter would be the solution we are looking for. Probably less maintainance and no worrying about carrying extra fuel and quieter operation. Is there a reason this can't be built? I'm not familiar with the mechanics but I would have thought less output would mean less power needed. Or is it simply because the demand is t there for a manufacturer to market them.
__________________
monte is offline   Reply With Quote
Old 07-04-2015, 08:12   #71
Registered User
 
hoppy's Avatar

Join Date: Sep 2009
Location: Melbourne, Australia
Boat: Jeanneau Sun Odyssey 40
Posts: 2,842
Re: Smallest compressor for diving

Quote:
Originally Posted by monte View Post
I see the shoebox isn't to be used for scuba tanks btw. We also have amps to spare and no rush too fill tanks so a slow filling compressor that works off 12Vdc or 220Vac with a 1500W inverter would be the solution we are looking for. Probably less maintainance and no worrying about carrying extra fuel and quieter operation. Is there a reason this can't be built? I'm not familiar with the mechanics but I would have thought less output would mean less power needed. Or is it simply because the demand is t there for a manufacturer to market them.
It's a solution you will never find.

Time or air volume is not an issue with filling scuba tanks, it's the pressure needed. If you want to fill a tank to 200+bar, you need a compressor that can pump air at that pressure and to achieve high pressure, you need a lot of power.
__________________
S/Y Jessabbé http://www.jessabbe.com/
hoppy is offline   Reply With Quote
Old 07-04-2015, 14:14   #72
Marine Service Provider
 
rcontrera's Avatar

Join Date: Jan 2013
Location: Seattle area
Posts: 49
Re: Smallest compressor for diving

Quote:
Originally Posted by hoppy View Post
It's a solution you will never find.

Time or air volume is not an issue with filling scuba tanks, it's the pressure needed. If you want to fill a tank to 200+bar, you need a compressor that can pump air at that pressure and to achieve high pressure, you need a lot of power.
You are dead on!

Hi pressures mean high stresses on parts and, more importantly, on whatever is going to turn it. There IS, however, a hand pump that works like a bicycle pump. It can pump up to scuba tank pressures and I have actually seen guys buy these for that purpose. Of course, you are going to end up with Popeye arms before you get the tank full!

__________________
Ray Contreras
CompressorStuff

rcontrera is offline   Reply With Quote
Old 08-04-2015, 06:56   #73
Eternal Member
 
monte's Avatar

Cruisers Forum Supporter

Join Date: Jul 2011
Location: Australia
Boat: Lagoon 400
Posts: 3,650
Images: 1
Re: Smallest compressor for diving

Sorry I'm still not getting it. Take the hand pump as an example. Ok it's hard to push! But given the correct gear ratio of an electric motor, it could be pushed slowly by a very small electric motor. Or imagine the shaft is 1/4 the diameter. Easier but slower. I do t know but I imagine a compressor works by forcing air into a chamber that allows the air to flow one way with some kind of non return valve, so isn't it just a case of decreasing the chamber size or the gearing to allow a smaller motor to do the work?
__________________
monte is offline   Reply With Quote
Old 08-04-2015, 07:58   #74
Senior Cruiser
 
skipmac's Avatar

Cruisers Forum Supporter

Join Date: Oct 2007
Location: 29° 49.16’ N 82° 25.82’ W
Boat: Pearson 422
Posts: 12,374
Re: Smallest compressor for diving

Quote:
Originally Posted by monte View Post
Sorry I'm still not getting it. Take the hand pump as an example. Ok it's hard to push! But given the correct gear ratio of an electric motor, it could be pushed slowly by a very small electric motor. Or imagine the shaft is 1/4 the diameter. Easier but slower. I do t know but I imagine a compressor works by forcing air into a chamber that allows the air to flow one way with some kind of non return valve, so isn't it just a case of decreasing the chamber size or the gearing to allow a smaller motor to do the work?
You are correct that you could use a small motor, as long as it will achieve the pressures needed, and take a long time to fill a tank. However at the end of the day you will still use the same total energy. A lot of work for a short time or a little bit of work for a long time still adds up to the same total energy requirements.
__________________
The water is always bluer on the other side of the ocean.
skipmac is online now   Reply With Quote
Old 08-04-2015, 08:17   #75
Eternal Member
 
monte's Avatar

Cruisers Forum Supporter

Join Date: Jul 2011
Location: Australia
Boat: Lagoon 400
Posts: 3,650
Images: 1
Re: Smallest compressor for diving

Thanks skip, but that's the point. We and a lot of other yachts have the power resource with solar, but not the generator or inverter capacity. I just checked the power required to fill a scuba tank and it's around 600Ah. Ok that's a lot! I guess if it was buildable I would want something that consumes 60A for 10 hrs and I could fill one tank over two sunny days. 4 days between dives...
The gas powered compressor is looking good!
Actually our solar will put out about 60A so it would be possible to fill in a day without really taxing the house bank too much. Definitely an option I'd consider if it was available...
__________________

__________________
monte is offline   Reply With Quote
Reply

Tags
compressor, diving

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bauer Junior 2 Diving Compressor for Sale newbiesailor Commercial Posts 0 10-02-2012 20:18
Bauer Junior 2 Diving Compressor for Sale newbiesailor Classifieds Archive 0 10-02-2012 20:18
Onboard Compressor for Painting, Diving, and Pneumatic Tools . . . ActiveCaptain Auxiliary Equipment & Dinghy 7 13-06-2011 16:49
L&W diving compressor pier Fishing, Recreation & Fun 0 21-11-2008 04:17



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 08:24.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.