What Kind of Manifold for Twins?

[ltstanfo]

All,

I've found a replacement for my old USD twin manifold (3/4 inch pre 1962)... thanks for the help on the previous thread.

Now I have another question...

Was / is there an isolation manifold made for 72's? My local dive shop is trying to be helpful but they apparently don't feel comfortable trying to put a 200 or 300 bar (OMS, Dive Rite, etc...) DIN manifold on a pair of 72s that I have located. Is there an issue with tank spacing, etc...? I have a new (replica) pair of SS 6.9 in bands for these tanks. Am I missing something? I am hoping to mount these tanks on a plate and use them for wreck diving.

All help is appreciated.

Thanks,
Ltstanfo

PS: My LDS also has recently come into possession of a pair of 1/2 inch neck steel 72 tanks. They have hydro'd them (and VIP) but I don't know if I want this pair or not. If anyone else is interested I'd be happy to pass along the info.

[SeaRat]

LTstanfo,

A couple of points. First, the original twin manifolds are not isolation manifolds. But you can get one simply by using two K-valves on each cylinder, and hooking it up using a "Twin Tank Bar Yolk," USD #0513. The USD 1969 catelog states that the Twin Tank Bar Yolk "Converts two standard single "J" or "K" valves and tanks together to form a twin unit," and it sold then for $23.50. I used it for years with my twin 42s, and it is an excellent way to mate two single 72s or 80s. You may think about that for those two 1/2 inch neck 72s you talk about. By the way, the 1/2 inch necks use a tapered thread with teflon tape to seal, and are every bit as good as the 3/4 inch manifolds of today with an O-ring, without the possibility of an O-ring failure. I used the twin tank bar yolk last fall on a dive with twin 72s, and my Trieste II regulator, and that combination worked extremely well. It does afford tank isolation too.

Or, you could use the two tanks as twins, but independent twins. Usually this is done with two single-hose regulators on the tanks, but I experimented with one having a double hose regulator. You would need either long hoses, a hose extension on the exhaust hose (which is what Cousteau did with his wreck dives using asymmetrical triples), or a double hose with much longer-than-normal hoses. I choose the later route, and used my DX Overpresure Breathing regulator on one tank and a single-hose regulator on the other.

Now, you asked about the "modern" manifolds too, and putting them onto the 72s. Well, the only problem would be the overpressure relief valve, which usually is a 3000 psi valve (200 bar, or approximately 2900 psi), or 4400 psi (300 bar, or 4351 psi) on these manifolds. If they make a replacement for the overpressure relief valve mechanism (usually a copper insert of a specific thinkness) on the manifold when the tanks themselves are rated for the 2250 (or 2475) psi tanks, then you could do it. The dive shop would charge you for this, or maybe you could order them with that pressure rating. I think OMS would have those, as they for a time were selling a 2400 psi steel tank. So this really should not be a problem, unless the dive shop is simply unwilling to accomodate the older 72 cubic foot tank.

John

[YankDownUnder]

Vintage steel 72 3/4 in. isolation manifold by Nemrod of Spain.

The purpose of the isolation manifold is to save the air in one tank, when air is discovered leaking from the other. That can come from either the tank O ring, or a regulator. Tank O rings rarely fail, although I had one leak and found my primary tank empty on an Azimuth rebreather and made the dive with the utility tank. Single hose regulators have many leak points because of thier many O rings, so the isolation manifold is a good idea. Most double hose regulators do not employ O rings and are thus safer. Remember, modern isolation manifolds only save one tank. However, Nemrod made a one piece twin tank manifold which allows the use of a double hose or single hose regulator between the tanks and has a pillar valve over the right tank for a back up single hose regulator. With this manifold, either can be turned off and the other will get air from both tanks. I used one cave diving in Florida in 1974, while I was at flight school. I bought another one on eBay recently and they do appear evey once in a while. The manifold has a J valve on the left side, and a valve handle on the right. The right side handle turns off the center regulator and the pillar valve has it's own on/off valve. As the manifold is made from a single piece of metal, there is very little flex in it and thus tank O rings are seldom a problem unless poorly torqued.

For the modern vintage equipment diver these manifolds are ideal. A double hose regulator of any type can be used in the center and the second regulator can be used to provide all the utility hoses, used today.

There is a Nemrod one piece manifold on eBay at the moment, but I think it will not accomodate two regulators. I cannot tell from the picture. It is the first I have seen with a 'one regulator only' capability. Using a temporary type manifold is not recommended if mandatory decompression is going to be a part of the dive and you cannot simply ascend with a leak. If you do decide to use one, insure that you have strong tank bands which will prevent flexing and also be sure that the tank valves are directly opposite. Early pig tail manifolds are suitable for 72s and the pig tail helps with the alignment problem. Good Luck.

[SeaRat]

yankdownunder said:

Vintage steel 72 3/4 in. isolation manifold by Nemrod of Spain.

The purpose of the isolation manifold is to save the air in one tank, when air is discovered leaking from the other. That can come from either the tank O ring, or a regulator. Tank O rings rarely fail, although I had one leak and found my primary tank empty on an Azimuth rebreather and made the dive with the utility tank. Single hose regulators have many leak points because of thier many O rings, so the isolation manifold is a good idea. Most double hose regulators do not employ O rings and are thus safer. Remember, modern isolation manifolds only save one tank. However, Nemrod made a one piece twin tank manifold which allows the use of a double hose or single hose regulator between the tanks and has a pillar valve over the right tank for a back up single hose regulator. With this manifold, either can be turned off and the other will get air from both tanks. I used one cave diving in Florida in 1974, while I was at flight school. I bought another one on eBay recently and they do appear evey once in a while. The manifold has a J valve on the left side, and a valve handle on the right. The right side handle turns off the center regulator and the pillar valve has it's own on/off valve. As the manifold is made from a single piece of metal, there is very little flex in it and thus tank O rings are seldom a problem unless poorly torqued.

For the modern vintage equipment diver these manifolds are ideal. A double hose regulator of any type can be used in the center and the second regulator can be used to provide all the utility hoses, used today.

There is a Nemrod one piece manifold on eBay at the moment, but I think it will not accomodate two regulators. I cannot tell from the picture. It is the first I have seen with a 'one regulator only' capability. Using a temporary type manifold is not recommended if mandatory decompression is going to be a part of the dive and you cannot simply ascend with a leak. If you do decide to use one, insure that you have strong tank bands which will prevent flexing and also be sure that the tank valves are directly opposite. Early pig tail manifolds are suitable for 72s and the pig tail helps with the alignment problem. Good Luck.

Yankdownunder,

You have a very good solution, but there is a potential problem here. Sherwood sells a very similar valve (or actually used to sell one) with the two posts. But this Sherwood valve is not an isolation valve, in that both tank's air supplies are available to both posts, and turning off a post does not turn off either tank, just the regulator. So if you go this route, be sure that you use the Nemrod valve, and not the Sherwood valve, if you absolutely need the isolation. But remember that the Sherwood valve was used by many of the cave divers in the 1970s and 1980s when it was manufactured. I have two of the Sherwood valves, and love them for their ability to accomodate two regulators on the scuba. But one is not being used, as I need the USD valve to use the DA Aqua-Lung regulator; it's the only valve that will fit this regulator's yolk.
John

[duckbill]

Ltstanfo,
If you are not cave diving, then an isolation manifold really isn't necessary, IMO. Maybe you have another reason for wanting to use one?

I don't have DIN, but I think I remember that the issue is that DIN is typically used on HP cylinders, which could cause some confusion when you go to get your good 'ole LP 72's filled by a non-observant attendant. Just a thought.

[ltstanfo]

All,

Thanks for all the comments. I am not a cave diver (and never want to be) but I do enjoy wreck diving.

My "vintage" gear consists of 2 UDS1 systems and a late model Royal Aqua Master (round foil label). I have several 72s as well as HP80s and an HP130.

When diving in the gulf last year (FL and AL - I live in Huntsville AL) several of the dive boats told me that they were actively discouraging divers from using twins without isolation manifolds for liability reasons. Now how much truth there is in this I don't know but if I want to use their boats to dive the Oriskany, etc.. then I have to play by their rules. As a result I picked up some used HP80s and the (new) HP130 but I don't like having so many different size tanks around. I'll keep the HP130 for quarry diving but likely sell the HP80s pretty soon (they are a bit short for me... I am 6'3").

In any event, from my experience I have found the old 72 to be the most versatile tank and I like the ones I have so I am toying with making two (or more) sets of twins.

In any event, I will check ebay for a Nemrod isolation manifold.



Thanks,
Ltstanfo

PS: My LDS has no issues with "vintage gear" but since I am virtually the only guy in my area using such (and getting such serviced) they don't have alot of experience with this type of equipment anymore. The owner and the senior tech all used this kind of gear in the past but have upgraded to recent stuff.

[ltstanfo]

John,

Thanks for your comments but I think there may have been a misunderstanding somewhere. I know that the old USD manifolds are not isolation. I wanted an old type set of twins for use with my RAM when I quarry dive but want something a bit more "modern" for ocean diving / dive boat use.

Regards,
Ltstanfo

[ltstanfo]

I just saw this Sherwood manifold on ebay. Anyone have any idea if this is 72 compatible?

Thanks,
Ltstanfo

[shackle]

I have that manifold on a set of steel twin 50's. I use it to dive my single stage regulators on dive boats. I put the Mistral or Voit 50 fathom on the center valve and have a modern regulator w/ spg, BC on my right valve. No problems so far.

[ltstanfo]

shackle said:

I have that manifold on a set of steel twin 50's. I use it to dive my single stage regulators on dive boats. I put the Mistral or Voit 50 fathom on the center valve and have a modern regulator w/ spg, BC on my right valve. No problems so far.

Thanks for the info! That is exactly what I was hoping to hear!

Regards,
Ltstanfo

[wd8cdh]

Personally, I think that more problems have been caused by the isolation valve being off or on at the wrong time than there have been problems that could have been saved by an isolation valve. Therefore, I slightly prefer manifolds that don't have isolation valves.

Older manifolds like the Nimrod and Sherwood mentioned before are great on double 72's and have the correct spacing for vintage bands.

If you want new, Thermo makes a crossover manifold WITHOUT isolation that is the same spacing as the older manifolds for 72's. The center bar is part number 8004.
www.thermovalves.com/manifold_center_bar.htm

Dive right also makes a double manifold WITH isolation that is the same spacing as the older manifolds. It is "200 Bar 5.5" Tank Manifold #VA3003-200"

www.diverite.com/products/catalog/valves/va3003-200

Both of those manifolds have two regulator fittings but neither is in the center. I am trying to get a center secetion with a regulator fitting out of a company in Europe that will replace the isolator section of a double manifold.

[SeaRat]

I was a bit out of it yesterday, as this should have been put on a different thread. Linda, you might want to remove these last two entries by me.

John

[JES]

searat said:

I was a bit out of it yesterday, as this should have been put on a different thread. Linda, you might want to remove these last two entries by me.

John

SeaRat,

As the other Moderator for VSS, I have deleted these posts as you requested.

[SeaRat]

wd8cdh said:

Personally, I think that more problems have been caused by the isolation valve being off or on at the wrong time than there have been problems that could have been saved by an isolation valve. Therefore, I slightly prefer manifolds that don't have isolation valves.

Older manifolds like the Nimrod and Sherwood mentioned before are great on double 72's and have the correct spacing for vintage bands.

If you want new, Thermo makes a crossover manifold WITHOUT isolation that is the same spacing as the older manifolds for 72's. The center bar is part number 8004.
www.thermovalves.com/manifold_center_bar.htm

Dive right also makes a double manifold WITH isolation that is the same spacing as the older manifolds. It is "200 Bar 5.5" Tank Manifold #VA3003-200"

www.diverite.com/products/catalog/valves/va3003-200

Both of those manifolds have two regulator fittings but neither is in the center. I am trying to get a center secetion with a regulator fitting out of a company in Europe that will replace the isolator section of a double manifold.

Thanks Joe,

I've been thinking about the manifold thing, and am going to tell you about another potential for triples. I've said this before, but sometimes it gets lost in as the threads become things of the past.

It is possible to use these kinds of manifolds, with the regulator fittings on top of the cylinder, as a setup for triples. If you can get a set of doubles that is fit close together, then put another cylinder on the right side upside down. Use the center post of the triples (right side of the double manifold) to put the double hose regulator. On the upside-down cylinder, put a first stage of a single hose regulator, set at the exact interstage pressure as the double hose, and hook the LP port of this first stage into the LP port of the double hose regulator. I'm assuming either a Royal Aquamaster or Pheonix Royal Aquamaster with a set of LP ports is being used (or in my case, a Trieste II). The two regulators can be hooked together with two normal LP single hoses, and the demand valve housing off an MR-12 regulator This is the seat of the MR-12, which is reversible so that a female end from the LP hose can fit into both sides of the housing, and it swivels too. This would leave LP sites on the reserve cylinder (the upside down one), and an unused site on the left cylinder for a separate regulator if desired.

The redundancy of this triple-tank system would be fantastic, with triple, separated air supplies (duel most of the time, unless the isolation was used for the double manifold). It would also be in keeping with Cousteau & Gagnan's original patent concept for the Aqua Lung, with triple cylinders that did not depend upon gauges to tell you the state of the air supply.

Cousteau himself enjoyed the triple tank system a lot. This is shown by his continued use of it in the production of the movie, World Without Sun[/I]. He did not use them on-camera, but for his off-camera dives he did use the triples (see page 62 of the book of the same name). There is also one scene, which is quite difficult to tell because of the angle, which the triple tank system was still used in that movie. Cousteau is shown on page 201 of that book using the quads too.

So the transition away from the triple tank system for Cousteau was about 1963, when they went to the quads, then the integrated scuba systems using quads, and the rest of the crew using the La Spiro doubles. There was a series of dives later, on a deep shipwreck in the early 1970s where the Cousteau divers again used triple tank systems, this time in conjunction with a submersible decompression chamber, where they housed the units on the outside of the chamber.

John

[wd8cdh]

Hi John,

Also after the La Spiro doubles (~ 72cf 3000psi tanks) Cousteau went to high pressure quads in a silver shell, 5000psi titanium tanks or 4500psi wraped steel tanks.