Controlling Gas via IP differentials

Tiptopperoo

Tiptopperoo

CCRx Supporter
Hi guys,

I'm just wondering if anyone has had success controlling which gas comes in via a manifold fed from two different tanks with two different IP's on the first stages. I know some of the rEvo guys have done it succesfully, but I'd be interested to hear other's experiences, specifically on how much of a difference in IP, and how sure you are on which gas you are receiving.

Now some people are going to be dead against this, and that's fine. This is not your thread.:disappoin

The reason I want this, is to be able to have an off board bailout tank, plugged in and turned on at the same time as using my on board diluent. I want the system to preferentially use my onboard gas until that cylinder is empty at which point it will start taking from the off board.

Cheers,
Dave
 
Works fine on my KISS but in the opposite configuration. Inboard is 6 Bar, Outboard is 9.

No manifold, outboard plugs straight into my Golem Dil MAV. Gives me selectable gas to the loop, wing and BOV. Just by turning the valve under my arm pit. The QD is also within reach and easy to disconnect the BO and and hand it off when getting back on the boat

6 bar also keeps the KISS ADV cracking pressure manageable. Wouldn't want to reverse it and have it higher than all my other 1st stages set a 9 bar.
 
I seem to remember Draeger came out with, I think it was called the SMT, which was a real oddball mechanical system and the on-board bailout was basically just a supply with a lower I.P. plumbed into the main feed.
When I first got my Azimuth and before giving it the KISS treatment, I experimented with having a leaner bottom mix with a higher I.P. on what was supposed to be the reserve cylinder.(just flip the reserve lever and you were on your bottom mix) it worked OK, but once you do that, you have to have monitoring and with that complexity it was only a small step to MCCR and considerably improved flexibility and reduced Faff.
 
I know the arguments for using differential IP. I just never understood why that would be preferred over a positive shutoff system using either a 3-way ball valve or inline shutoffs or turning off valves. Being positive which gas is being delivered is sort of important. IP creep shouldn't be deadly.


iPhone. iTypo. iApologize.
 
I initially ran my inspo like this so that it would use onboard dil and then immediately take offboard via quick connect to dil manifold without any switching when onboard ran out. Freaked me out a little during my training when my instructor used my bailout reg on my stage and emptied my onboard dil tank however (unwanted and unnoticed side effect of this set up)! Sometime soon afterwards I decided that relying on a 1 bar difference in IP pressure was perhaps not the best idea, especially since the remains of my 3 litre dil tank will be lucky to last very long at 70 meters during a real emergency when my head disappears up my other end and my SAC rate goes through the roof. I now run independent systems with BOV connected to offboard bailout and no open circuit access to on board dil. In this way, the system is safer as it is more reliable (in my opinion anyway). The only annoyance is that I cannot dive without an offboard tank as I have no access to gas for the BOV without one. I therefore carry a 3 litre side slung for even shallow shore diving.

As always, pay your money and take you choice but just remember to "keep it simple!"

Cheers
Gar
 
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