Mailing List Archive Mailing List Archive
Just a few comments on the steel tank issue: Bill Wolk wrote: > > All -- > > Many thanks to everyone who responded to my message on why PST 104s are > the preferred tank for cave and tech diving. I got some terrific > responses and appreciate the time they took. For the list and anyone > who's interested, they're summarized below. Basically, the consensus is > that the PSTs have a reputation for being more durable *and* for caving > they start more negative and stay more negative so you stay off the > roof. Staying off the roof is more a function of the diver than of the tanks. unless of course the bouyancy changes drastically, from one minute to the next! > > Jon Breazile, breazile@ne*.co* wrote: > > >The 104s are great because they are heavy. The OMS 112s are almost > >the same. The more you can take off your weight belt, the better. > >The 104s also have a history of being very tough. Some people have > >had sets for 20 years with a lot of overfilling (3500 PSI) and they > >still pass hydro. > My understanding was that: as one became more comfortable in the water the amount of weight needed would drop due to better breathing patterns and control. I don't see how taking weight from you belt and putting it on your back (except for trim purposes) offers any advantage. Hydro tests measure the plasticity in the walls of the tank. The difference between most hp steel and lp steel tanks is primarily (only) in the size of the neck. LP tanks are rated as such to allow for standard (yolk) valves. HP tanks have a smaller neck; this results in less pressure on the threads holding the valve in place. Overfilling lp steel tanks fatigues the threads not walls. > Michael Picou, picou.michael@MA*.DC*.ST*.FL*.US* came through with specs > > >I have some info on the PST 104's that I found in Vol 15 No. 4 of > >Discover Diving Mag, I will assume its accurate: > > > >capacity 104 @2400 psi > >O.D. 8 in > >length 26.19 > >weight 46lb > >buoyancy -5.3full/ -2.5 empty > > > > The buoyancy is interesting in that for a set of 104 doubles the > >gain is > > 5.6 lbs. (full to empty), while the OMS would be around 15 lbs. > Removing 200 cubic feet of air (~15 pounds) from a set of doubles MUST result in the tanks being ~15 pounds more bouyant. Unless the tanks deform in the process any information to the contrary is probably a typo! Try +2.3 lbs when empty, it makes more sense. > > And....last but not least, Peter Gottlieb, TMBG@ix*.ne*.co* provided > the gossip and a guarantee <g> -- > > >2) A friend of mine dove a set of double 121's and found them > >excessively buoyant once they were about 1/2 capacity, with full cave > >gear (this would include a neoprene driest, though). A good example of improper weighting. This is not a result of the tank characteristics, but of the intelligence of the diver. Refer to the comment about staying off the roof.) In the end it goes back to the fact that the equipment doesn't make the diver (although we can all agree that it is important to look good), experience does. Shaun -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]