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Re: [PSUBS-MAILIST] Propane tanks

shipmates
 
    i just ran the numbers on a amse rate propane tank with the assumptions of radisu 36 inches, shell length  6 feet. without suppr0t ring shell failure at 50 psi, cap failure at 100psi. these numbers are generous and should be derated due to weld imperfections but at leasts a factor of .6
rick m
 
 
----- Original Message -----
Sent: Sunday, October 30, 2005 8:12 PM
Subject: Re: [PSUBS-MAILIST] Propane tanks

guys
 i know that propane tank seam to be an easy way to start. But the cost of the hull tube conponents are a small frastion of the total cost. and you still have to weld the rest of it together. buy decent end cap and shells. For the cost testing the tank material you can buy the hull.
 
rick m 
----- Original Message -----
Sent: Sunday, October 30, 2005 7:26 PM
Subject: Re: [PSUBS-MAILIST] Propane tanks

From a manufacturer: Tanks are rated at 250 psig from -20° F. to 125° F. All tanks may be evacuated to a full (14.7 psi) vacuum.
 
On Sun, 30 Oct 2005 18:57:00 -0600 Myles Hall <myles.h@sasktel.net> writes:
I'd be curious as to what depth guys are getting on a new 500 gal propane tank (without ribs).  10M ?, 25 M ??
 
Myles.
----- Original Message -----
Sent: Sunday, October 30, 2005 5:41 PM
Subject: Re: [PSUBS-MAILIST] Propane tanks

Hi Myles,
 
I've cut a couple, 250 gallon or so, I think were over 1/8th.
Newer and smaller tanks have thinner walls. Could be the steel is stronger, could be they are not as overbuilt as the old school stuff?
Anybody else have experience here?
 
-PK
 
On Sun, 30 Oct 2005 10:53:09 -0600 Myles Hall <myles.h@sasktel.net> writes:
Peter,
 
   Is that some sort of custom tank ?  It seems to me they aren't that thick.  Don't quote me, I've never cut into one but I thought they were closer to 1/8 "  I'm referring to your run of the mill residential tanks.
 
Myles.
----- Original Message -----
Sent: Saturday, October 29, 2005 10:37 PM
Subject: Re: [PSUBS-MAILIST] Propane tanks

My propane tank sub has been to 300 feet. One thousand gallons, 4 by 10 feet, 1/2 in thick cylinder with 5/8 inch end caps. No reinforcing rings.
Peter K.
 
On Sat, 29 Oct 2005 14:06:40 -0400 "Akins" <lakins1@tampabay.rr.com> writes:
Hi Myles.
 
I would definately consider one for an ambient, but no way for a 1 atm. There was some discussion here a long time ago about
 
how the tank's holding internal propane pressure did not necessarily cross over to keeping pressure out the same way. I can't recall
 
what was said though, but I remember it was discussed. Some guys have built them (1 atm) and I have seen some for sale made from propane
 
tanks. But I'd want a thicker hull for a 1 atm if it was me. I wouldn't trust a propane tank hull, even with reinforcement rings.
 
I mean, if you are going to build a 1 atm with all the trouble it takes....you might as well make it where it can go relatively deep and build it with a thick pressure hull
 
and get down 600 feet or more. Most of the good non picked over wrecks are deeper than scuba depths because the divers have already picked most of them over.
 
Most wrecks (okay not all) at scuba depths have already been found too and there isn't much to discover new unless you go beyond scuba depths.
 
But for an ambient? Like I said I think it would be great for that for all the reasons you listed. I think it would be very durable for an ambient and if
 
you are still contemplating building an ambient, that would be an inexpensive way to go.
 
Bill.
 
 
 
----- Original Message -----
From: Myles Hall
Sent: Saturday, October 29, 2005 8:39 AM
Subject: Re: [PSUBS-MAILIST] Propane tanks

Bill.
 
   Yes, agreed.  When I was looking into the feasibility of a propane tank pressure hull, I was certainly only thinking of a new one.  There is no way in hell I would put my torch to a used one.  The reason I was considering one as a possibility is because:
 
1)  I'm not looking to go very deep.
2)  They are, by their very nature, pressure vessels complete with hemi-spherical end caps.
3)  Cost.  Being mass produced, you would expect them to be relatively cheaper than a scratch build.
4)  Availability.
5)  Convenience of having a pressure hull with end caps already.
 
Having said all that, if I'm taking the time to cut, grind, and weld, I was just as soon scratch build a hull that is a little more durable.
 
I don't know, it was something I was pondering but I'm leaning towards a scratch build.
 
Myles.
----- Original Message -----
From: Akins
Sent: Saturday, October 29, 2005 2:29 AM
Subject: Re: [PSUBS-MAILIST] Propane tanks

Hi Myles.
 
There have been some subs made from propane tanks but most of the knowledgeable subbers shun them.
 
Because...
 
1. They can explode from residual propane when you grind cut or torch them.
 
2. They are of an unknown metalic strength.
 
3. They are usually too thin for deep dives.
 
4. The interior of an empty one may be corroded if the valve was left open and hence you have something useless when you cut it open.
 
There are some other reasons I have heard of too, but that's all that comes to mind right now.
 
If you do use a propane tank I have always heard to make sure you buy a brand new one that is shipped to you without any gas ever having
 
been put into it. Then it is safe to grind cut or torch.
 
I wouldn't use one for a pressure hull myself, but I think they might be good for an ambient.
 
Bill.
 
 
----- Original Message -----
From: Myles Hall
Sent: Friday, October 28, 2005 8:20 PM
Subject: Re: [PSUBS-MAILIST] remove me second kind request

Patrick,
 
   Speaking of propane tanks for pressure hulls, is there any merrit to that, convenience or expense wise, or is a guy just as smart to scratch build the hull ?
 
   Have you done any research on the propane tank thing ?
 
Myles.