LP Inflator Hose - Right Post - Why?

[pcowboy6196]

Originally posted by DIR-Atlanta
I think what you really need to do is take a good hard look at what problem you are trying to "solve" with the H valve setup. Are you worried about insufficient gas for the dive? Added redundancy in case of emergency? Something else? Tell us what your exact concerns are and we can probably provide a more targetted response or suggestion to address that issue.

Isn't is recommended to dive either an H or a Y valve? I thought that it was to have redundant regulator in the case of a failure. I agree about the H valve with their being no way to isolate the failing reg in the case of a free flow. But I thought that using 2 1st stages was better than 1.

-Wes

 

[DIR-Atlanta]

Isn't is recommended to dive either an H or a Y valve? I thought that it was to have redundant regulator in the case of a failure.

It all depends on the requirements of the dive. I do plenty of shallow openwater reef diving with just a single reg setup. In most cases, a dual orifice valve is neither required nor recommended for that type of diving. If I'm in an overhead environment however (either physical or deco), then I prefer to use a redundant regulator setup. And it should be noted that there are numerous ways to provide redundancy, of which diving with a backup regulator is but one.

I agree about the H valve with their being no way to isolate the failing reg in the case of a free flow. But I thought that using 2 1st stages was better than 1.

Actually, a free-flowing second stage is one type of problem that an H or Y valve is specifically intended to address. However, that is not the failure mode that I was describing. I was specifically referring to a loss of gas that was the result of a failure in one of the mechanical connections in the valve itself (neck O-ring, barrel O-ring, or burst disc). With an H valve, any one of these is a non-recoverable failure - you will lose all your gas. With a manifold, you can isolate the side that has failed, thereby saving some of your gas for the return trip.

The point that I was trying to make is that if you are going to go with a redundant setup, then you should use something that is truly redundant. A manifold satisfies this requirement, while an H valve does not.

And as to the question of two first stages being "better" than one, see above - it all depends on the requirements of the dive.

 

[Soggy]

I am sorry but this doesn't make sense to me. Wouldn't one always analyze their gas before diving it? also wouldn't one know if they were or not blending tanks together with the manifold on or off? and would one also have the same gas in both back tanks and verify isolation maniford is open and that the gas is the correct mixture before diving it? Using what you said would make sense to me if the person in question doesn't believe in doing their pre-dive checks and gas analyzing. Please correct me if I missed something.

Wes

It is true that a lot of mistakes have to happen for a closed manifold to make it to the dive, but it has happened, most recently last year down in Florida at the Eagle's Nest where a woman breathed nearly 100% helium at depth. The gas was accidentally 'blended' with the manifold closed. Unfortunately, the only way to detect this problem afterwards is by analyzing both posts. If both tanks have equal pressure, it will take weeks for the gasses to blend after the isolator is opened. This has been tested empirically by Uncle Ricky.

So, yes, it can happen especially if you are not the one blending your own gas.

 

[Snowbear]

Thanks for the explaination - I missed some of this in the DIR Fundies book of mine. I will try to find it and reread it.

A more current as well as more detailed resource for the DIR gear configuration than the DIRf book is Dan MacKay's "Dress for Success."

 

[Scared Silly]

Cobb's Law applies here - "If you think you need a pony bottle, then what you really need is doubles." I suspect that a set of double 80s would be much easier for your wife to manage than a huge steel tank, and she could carry more gas to boot.

[snip]

I think what you really need to do is take a good hard look at what problem you are trying to "solve" with the H valve setup. Are you worried about insufficient gas for the dive? Added redundancy in case of emergency? Something else? Tell us what your exact concerns are and we can probably provide a more targetted response or suggestion to address that issue.

Before our trip to Chuuk my wife tried some doubles, a set of steel 95s. She had a hard time with them as it was a lot of mass for her. She never felt comfortable with them. I suspect that she would be fine in set of Al 80s. Which now that we are back we plan to put together such a rig. But before the trip we just did not have enough time to get a set for her to play with in our local dive pond. As such, I was trying to go with the next best thing while diving in Truk Lagoon. In this case the choice was either an Al 80 with a K valve or a Steel 112 with either a K or H valve.

So the goal was to provide enough gas for deeper dives and added redunancy. She felt very comfortable in the water with the 112. Especially, because she did not need any additional weight.