detroit diver
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Sorry, that had to do with valve manipulation.
The great independents versus isolation manifold debate
- Thread starter wazza
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Sorry, that had to do with valve manipulation.
andibk
Contributor
Detroit Diver,
Yes I do practice OOG drills every dive, this is ususally the last skill I do on the dive.
By your name I would guess you are from Detroit. I have been living in Thailand for the last 9 years but used to live in Algonac about 40 miles from Detroit. I did quite a few dives up in the lakes there.
Bruce
Yes I do practice OOG drills every dive, this is ususally the last skill I do on the dive.
By your name I would guess you are from Detroit. I have been living in Thailand for the last 9 years but used to live in Algonac about 40 miles from Detroit. I did quite a few dives up in the lakes there.
Bruce
The world's best tec divers are not the ones letting someone else make their equipment decisions for them. Do you think George Irvine would let someone make his equipment choices for him? We don't need any sock-puppets here. We all know where DIR stands on the issue.
R..
detroit diver
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I'll bet you it's warmer where you are than it is here right now! The diving is supposed to be excellent in Thailand, I hear.
re: OOG drills- How do you stow the bungee hose after you do an OOG drill?
rottodiver
Guest
G'day to you all out there..... you have probably guessed by the heading but what is the general feeling on manifolds... This seems to be a question that no one can answer... Manifold or no manifold???
DIR Tec Diver
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DEFINITELY a manifold and an isolator manifold at that! Diving doubles without one or even without an isolator manifold opens up a huge box of problems. Here is a good exerpt from www.gue.com:
Manifolds
A manifold is a device that combines the supply of two, usually back-mounted, cylinders. The manifold allows one to breathe from two cylinders at the same time. Diving with independent cylinders requires great care and superior gas management capabilities to effectively monitor the total gas supply, which experience has shown many divers are not capable of. Currently popular manifolds allow the diver to place two first stage regulators on their twin tanks, providing access to both tanks from either regulator. In the event of a first stage failure, the diver may shut down one regulator without losing access to the either tank. Divers may also choose a manifold with an isolator valve between the tanks allowing a diver to interrupt the flow of air between the cylinders. In the rare event that either a burst disk or a tank's neck o-ring were to fail, one could interrupt the flow between cylinders protecting at least half the air supply. Because this type of failure is highly unlikely, the use of an isolator has sparked some debate. The use of an isolator does require divers to guard against accidentally diving with a closed valve and is another potential failure point. However, when used with care and properly managed it allows for another potentially valuable line of defense, making it very common in technical diving.
The center isolator does NOT give the diver the option of closing the center valve and diving with different mixes in the two cylinders, this being an extremely dangerous practice.
Additional Considerations:
Consider using manifolds that allow a diver to adjust the distance between tanks. Popular favorites include the ScubaPro, DiveRite, and Diver's Supply manifolds.
Most current production manifolds allow one to place an insert into the DIN orifice, providing for the use of a yoke regulator. Avoid diving this manifold with yoke regulators where possible as o-ring failure is far too common.
H-valves are a better option as compared to Y-valves, as they allow for the use of DIN, have easier-to-operate valves and may be upgraded to manifolds for later use.
The center section of a manifold should be of the barrel-style o-ring construction, not the face-seal type. The barrel-style system allows the manifold's center section to move in the event of it becoming loose without twisting and possibly extruding the o-ring, thus causing a gas leak.
Knobs
Rubber knobs tend to be the best choice for use on tank valves. They are durable, shock-absorbent, shatter-proof, and easy to turn. Their major weakness is that they can roll easily upon contact, allowing for accidental shutdown. Alert divers should find this point irrelevant and will always check their knobs following any contact with the overhead. Plastic knobs do turn less easily but some are relatively fragile and can shatter and fall off, leaving the diver unable to t;urn the vlave off or on. Metal knobs attempt to solve this and the accidental roll problem yet fall a little short because they can bend upon impact and be rendered useless.
Manifolds
A manifold is a device that combines the supply of two, usually back-mounted, cylinders. The manifold allows one to breathe from two cylinders at the same time. Diving with independent cylinders requires great care and superior gas management capabilities to effectively monitor the total gas supply, which experience has shown many divers are not capable of. Currently popular manifolds allow the diver to place two first stage regulators on their twin tanks, providing access to both tanks from either regulator. In the event of a first stage failure, the diver may shut down one regulator without losing access to the either tank. Divers may also choose a manifold with an isolator valve between the tanks allowing a diver to interrupt the flow of air between the cylinders. In the rare event that either a burst disk or a tank's neck o-ring were to fail, one could interrupt the flow between cylinders protecting at least half the air supply. Because this type of failure is highly unlikely, the use of an isolator has sparked some debate. The use of an isolator does require divers to guard against accidentally diving with a closed valve and is another potential failure point. However, when used with care and properly managed it allows for another potentially valuable line of defense, making it very common in technical diving.
The center isolator does NOT give the diver the option of closing the center valve and diving with different mixes in the two cylinders, this being an extremely dangerous practice.
Additional Considerations:
Consider using manifolds that allow a diver to adjust the distance between tanks. Popular favorites include the ScubaPro, DiveRite, and Diver's Supply manifolds.
Most current production manifolds allow one to place an insert into the DIN orifice, providing for the use of a yoke regulator. Avoid diving this manifold with yoke regulators where possible as o-ring failure is far too common.
H-valves are a better option as compared to Y-valves, as they allow for the use of DIN, have easier-to-operate valves and may be upgraded to manifolds for later use.
The center section of a manifold should be of the barrel-style o-ring construction, not the face-seal type. The barrel-style system allows the manifold's center section to move in the event of it becoming loose without twisting and possibly extruding the o-ring, thus causing a gas leak.
Knobs
Rubber knobs tend to be the best choice for use on tank valves. They are durable, shock-absorbent, shatter-proof, and easy to turn. Their major weakness is that they can roll easily upon contact, allowing for accidental shutdown. Alert divers should find this point irrelevant and will always check their knobs following any contact with the overhead. Plastic knobs do turn less easily but some are relatively fragile and can shatter and fall off, leaving the diver unable to t;urn the vlave off or on. Metal knobs attempt to solve this and the accidental roll problem yet fall a little short because they can bend upon impact and be rendered useless.
Scubaroo
Contributor
Independant tanks, on this board at least, are nowhere near as popular as manifolded doubles. You'll get mostly a US perspective on your answers here.
Cutting and pasting "answers" from other websites to ScubaBoard seems to be a growing trend - thank you DIR Tec Diver for crediting the reference.
Cutting and pasting "answers" from other websites to ScubaBoard seems to be a growing trend - thank you DIR Tec Diver for crediting the reference.
sheck33
Contributor
manifold with isolater valve.
manifold failures are so unlikely that there is no reason not to use them.
manifold failures are so unlikely that there is no reason not to use them.
Peo
Registered
One seldom heard but very important reason to not dive doubles is that it screws up your gas planning.
If you want to dive by the rule of thirds, you should turn the dive when the remains in the emptiest tank is down to two thirds of your total gas supply -- which is an impossibility if you're diving independents, since obviously no single tank can contain two thirds of the sum of the two tanks.
So... The other option would be to apply the rule of thirds to each cylinder. This will severly limit the length of your dive since you're now basically doing a single tank dive with a (large) pony.
The third option would be to breathe the tanks down to the point where each tank contains one third of the total gas supply -- leaving you with EXACTLY the gas supply to get out should you loose one first stage.
The conclusion: if you dive independent doubles, you screw up your gas management even if you breathe them according to the "best" protocol, and you'll end up having to carry a lot of extra gas to achieve the same thing that you would with a manifolded setup.
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