DW Mistral - Tank Pressure???

[Terry]

;D Alright; this question should stir the pot a bit, and bring about some differences of opinion! Just rececntly I saw a post (not sure which message board) in regards to the proper tank pressure that should be used for a DW Mistral; 2250 vs 3000 psi. I have in the last couple of months obtained and restored a DW Mistral (my first), and am wondering what tank pressures you Mistral owners are subjecting your Mistral's to. I use 3000 psi tanks for my Voit Navy, USD AquaMaster DA and also my Nemrod Snark III and would like to know if it's OK to use a 3000 psi tank with a Mistral. Terry Stevens

[Broxton Carol]

Hi Terry: The mistral was designed to breathe easily with lower tank pressures than todays 3000 psi figure. Most tanks were only filled to 2250 back when the mistral came around. The design puts that high pressure behind the seat and makes it harder to breathe at high pressures, but better than a royal at lower pressure. You can do what you want but why put all that pressure behind your hp seat, and maybe wear it out prematurely, or sink it, or you could use pressures it was designed for, and have it last another 40 years.

[Linda]

Here's a very old thread that discusses tank pressures (although not the DW Mistral in particular...)

I wonder if Tom ever did those deformation tests?

vintagescuba.proboards2.com/index.cgi?board=general&action=display&n=1&thread=28&page=1

[nemrod]

It may have been my post and in any case, go ahead and use it on 3,000 PSI. It will breath poorly, it will damage the seat. The Mistral is an entirely different animal from those other regulators you mentioned. It is a single stage and the HP seat is not intended for those pressures. Really, I hate putting more pressure on my Mistral than 2,200 PSI. The two stage DA, RAM and others handle the high pressure much better. In fact, the RAM using Conshelf seats can use any pressure you would feel appropriate for a Conshelf. Unless someone else can show different--my answer is no--you cannot, not if you want good performance and don't want to destroy the seat, which are very hard to find.

It is also commonly discussed the suitability of the standard yokes for 3,000 PSI. I have had good success with the standard long yokes and 3,000 PSI (DA and RAM).
Nemrod

[duckbill]

Again, can anyone tell me their opinions regarding 2475 psi (2250 plus the 10% overfill for which they were originally designed) in regard to seat damage?

I think the later Mistrals did come stock with long yokes around the mid-60s.

[Terry]

Thanks everyone for your input; I always appreciate and find it informative. As for the single and two stage factors regarding the regs mentioned I am well aware of those facts; but since there has been as much controversy regarding 2250 vs 3000 psi when using these vintage regs I am always curious as to who is using what procedures, and what results they are having. So with that concern in mind I value the info given by Chuck and Nemrod hoping to get many more years of performance out of this good ole two hoser. Thanks again! Terry Stevens
Now; let me go find my al. 3ooo and get that bad boy filled with it's 10% overfill and see how that Mistral performs

[nemrod]

I have one new seat for my MIstral. The seat that is in it now was installed in around 1968. It has relatively few dives after about 1972 when it went into the bottom of my diver gear locker and sat there for three decades and then some. Upon rescuing it and giving it a once over it came back to life and the "new" old seat is doing fine. I have used it with 2475 PSI. It breaths stiffly with this pressure. I got the new seat from Bryan. I have it as a spare.
I have used both of my heavy yoke RAMs on 3,500 PSI and they could care less. I would not put my DA on that pressure because --and I have no proof---I just think that the standard long yoke is at it's limit at 3,000 so why push my luck.
James

[SeaRat]

If you'll look at Linda's post, with the thread, you will find one of my posts at the end. I had a discussion with Bryan about the 3000 psi issue on ScubaBoard, I believe, as I have lost one of my seats to a 3000 psi tank. But Bryan pointed out that in the Aqualung Repair Manual, June 1, 1971, Part No. 7803-00, that this manual mentions on page 8 to:

Attach reguator to "Aqua-Lung" tank. Turn on valve. Put soap water over pin (9) (Ref photo). Check for bubbles at 2000 psi to 3000 psi. There should be none.

I tried it with my new seat, and it worked okay (but very stiff). My limit for the Mistral is the 2475 psi (10% overfill).

I mentioned the DA Aquamaster in that post Linda refers to too. The DA Aquamaster, with the standard yolk, was used for years by the US Navy on 3000 psi aluminum 90 double tanks without problems, and is pictured as that system in the 1971 US Navy Diving Manual. We were taught on that scuba system at the US Navy School for Underwater Swimmers in 1967. So I would have no problem using the DA Aquamaster at 3000 psi. I would not go above that, however, without a heavier yolk.

John

[Voice of Gomez]

With due respecto, we tried all that stuff on the tv show, and we had to admitto the designers were far ahead of our ignorant experimenting we peons attempted. They tried it all before we did. So quit screwing with the mechanisms. they were made to operate within the limits customary with the times. Like bolting on a jetex 2000 EX MAGNUM onto a cessna 140A. Just dosent work..... Too powerful. Get real. Watch next weeks exciting episode on channel 6, " The double hose lawyers versus the teenage scorpion people! Playing tomorrow on LUZ 105.9 brought to you by sugar jets, the cerial that makes you feel............ " Jet propelled"!

[Broxton Carol]

who is this GOMEZ guy anyway? Does he have a new movie out? If not, can I watch him in re runs?

[YankDownUnder]

I have a set of US Diver's triple 44 Broxtons, dated 4/54. (Eat your heart out, Chuck!) They have a working pressure of 2600 PSI. I tend to think the regulators made from that time on could handle that pressure or the tanks would not have been sold. My 'green label Broxton', made in '54 also, works just fine on it. The yoke is the weakest link, not the mechanism.

Later regulators seem to work on even higher pressures. I dived my Royal Aqua Master at 232 BAR (3410psi) on Sunday, and it works great. It has the stronger yoke, which is standard on those models. I have a banjo fitting with 'Gomez' stamped on it, and with a Suunto Vytec transmitter on the end. It looks very slick. The transmitter sits under the late model USD J- valve and is hardly noticable. There is a small adapter required and that provides the extra length required for my Faber 100 cu ft tank.

I would suggest that the type of yoke you use, be the limiting factor. Breaking a yoke with a valve turned full on, could be very dangerous. When I restored the triples a few months ago, I blew an early tunnel type burst disk. It flipped the tanks over in my Land Rover, so an open valve could do much more damage if the yoke failed. Use caution!