Dual Tank Manifold Service Pressures

[Bronze06]

Hey again Folks,

I am putting together a twin 80 steel set and I was wondering which of the following manifolds would give me the best performance as well as the highest service pressure. Granted the Sherwood is a 3000psi service pressure manifold, but I am leaning to the Nemrod (Which looks much better now than when I got it off e- bay), or the Voit. The tanks are 3442 Faber 80s.

Does anyone know the service pressures for the Voit and the Nemrod S-300? I am attracted to the Nemrod due to its solid bar construction.

[captain]

Any of the manifolds are capable of 3500 psi with the correct burst disc. The main issue is the use of a yoke regulator connection at higher pressures.

[ScubaLawyer]

Any of the manifolds are capable of 3500 psi with the correct burst disc. The main issue is the use of a yoke regulator connection at higher pressures.

My understanding is that a 5250 psi burst disc is appropriate for 3442 tanks. I've always wondered about the safety of using a yoke at the higher pressures but don't most all HP DIN valves come with a yoke insert these days? Is it really an issue? Just curious. Mark

[rhwestfall]

yoke is fine for 3442....

the concern is the yoke "frame". Older ones are "questionable"..... modern yoke is fine.

[Bronze06]

Thanks for the input Folks. I've checked the burst disks on all three and they are all at around 5000psi. or the BAR equivalent. Hmm? Which one to use? Decisions, decisions....?
I agree that the yoke must be able to withstand higher pressure settings. As you all know, the original yokes from the 40s to the early 70s were designed for pressures of 2250-3000 depending on make, model and year of manufacture. As I and all of you can attest to seeing "yoke stretch" or "jump" when you hook up a vintage DAAM to 3000 psi. tank. Though I have read in this forum (I forget where) that it was common for the military to use 3000 psi on DH regs. in the late 50s to the mid 70s, I will not do so on my vintage babies.
The simple fix is to tailor the tank fill to meet the regulators operating specifications. That is why I want to double up with modern steel 80s. For example, if I have a vintage reg that can withstand a yoke pressure of 2600psi. and safely operate at tank pressure 2600 psi. I fill the HP 3442 doubles to that level and dive it. With double 80s, 2600 psi. will give me approximately 75% capacity, or 120 CF. You can dive for a good while on a 120 cubic feet of air. Full capacity is no problem of course with a Phoenix HPR, or a Kraken, or any reg that has a yoke strength of 3500 or higher.
I don't think it is wise to "push" the engineering specs on regulators that were built at the time I was born (54 years ago) beyond their original design limits at this point in time. Though vintage DH regs were engineered extremely well (over engineered really), to exceed their original operational paradigms (I feel) could invite catastrophic yoke failure, or invite possible regulator failure internally (regulator freeze or "lock up"), even if you have replaced seats and diaphragms with new ones. Metal fatigue and general wear do to age and inception should be taken into account for safety as well as to preserve the reg. for future generations of divers use.

[captain]

I can't recall ever hearing of a yoke failure due to pressure. The likely issue is an older, lighter yoke will stretch under perssuer and allow to O ring to blow out. Again I have never experienced it personally and reports of blown O rings can generally be attributed to improper regulator instalation on the valve or old/defective O ring.

[Bronze06]

Sounds like the Captain is on top of it as usual.
I have not ever seen yoke failure nor have I every personally experienced regulator lock-up nor do I know anyone personally that has. That being said I have read of this happening in periodicals and several Dive instructors have had to deal with lock up. The bottom line is of all this is conduct thorough maintenance, before, during and after operations and get your regs, and tank valves checked out by someone who knows what they are doing if you don't have the "regulator savvy".