Suit inflator bottle on twinset set up ?

[50BarBill]

Hello all, just set up my first twinset. And as usual you immediately look into other gear.
What’s everyone’s thoughts on running a drysuit inflation bottle when I typically dive air and soon more nitrox.
In my mind having a separate way to inflate my drysuit in the case of a complete manifold failure would be a good safety aspect, along with being able to gas plan more accurately by removing the usage of direct twinset suit inflation? Mostly online I’ve seen people use them prominently on CCR or at the least trimix diving to save on expensive gases.
Obviously I know I could do it, but the question is should I.
I’ll add a picture of my set up for those who enjoy photos.
Cheers.

 

[Nick_Radov]

Running a separate drysuit inflation bottle is more for insulation than gas cost. Helium is an excellent heat conductor so inflating with bottom gas is a bad idea whenever the water is cold enough to actually require a drysuit. With a separate bottle you can inflate with air — or maybe argon which feels warmer to me although experiments haven't shown much benefit.

For ocean diving it's best to use a small bottle mounted to the left side of the backplate because it tucks away there without creating any additional drag. For long cave dives that involve a lot of repeated ascents and descents you can use a larger inflation bottle mounted on the left side of your doubles. This isn't practical for ocean diving because it sticks out and gets in the way.

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[jborg]

… but if you’re not diving trimix there’s no real reason to have a separate suit inflation bottle.

 

[Wibble]

A suit inflate is necessary for use when the backgas contains (cold and very expensive) helium.

The DIR "standard" rig is the longhose and wing inflate off of the RHS 1st stage, with the necklaced backup reg and drysuit inflate off of the LHS. This is designed to give one source of buoyancy -- wing or drysuit -- if either valve has to be turned off.

Suit inflates for twinsets tend to be the small 0.85 litre steel or 1 litre aluminium cylinders. You can use larger, but space is a premium.

The BIG issue with tiny suit inflate cylinders... they run out of gas. Wonder how I know that... You'll inevitably discover this at depth and this will result in water getting into the suit inflate cylinder -- and it failing a test later, so expensive mistake.

Suit inflates are fiddly to use IMHO, but then again so are valve shutdowns on the twinset.


So, for me, it's a question of do you want one?
If yes, go ahead.
If not then there is much better things to spend your money on such as an ali40 deco cylinder which you can put another reg and hose on and fill with 50% for your journey into some deco

When/if you do start doing deeper diving, the contemporary route is through rebreathers. On those you tend to mount a 2 or 3 litre steel (or ali) suit inflate cylinder and you can use transmitters (or analogue gauges) to monitor the gas pressures.

A 21/35 fill on a twinset is 35% of ~5000 litres = 1750 litres of helium at circa 10p/litre = £175 just for the frigging helium!!! Contrast that with CCR (with an enormous initial cost) which will use, say, 150 litres of diluent, e.g. 52.5 litres = £5.25 for the helium (plus £10 of sorb, £2 of oxygen, £2 for the catheter, £1 for the two CO2 cartridges for the SMB, £75 for the boat, £+ travel, etc.)

 

[OTF]

I avoid using a suit inflation bottle when possible. As in, unless I'm diving a high helium mix in very cold water I don't use one. Sure it does sit out of the way when rigged properly, but tech diving already involves too much gear and I would rather shed it if not strictly necessary.

In terms of buoyancy redundancy, a standard doubles setup fills the drysuit off one post and wing off the other so you should always have inflation gas even if you shut down one post. You should also have a DSMB which can be used as another redundant buoyancy option (practice the technique of straddling it and filling/dumping small amounts of air for control). Not sure what "complete manifold failure" means.

When I do use a suit bottle, I rig it like this on the left side of my plate. Get a transfill whip to top it up.

 

[Badger7]

If you're eventually going to get into helium mixes and you want to sort out the gear required to run a separate inflation bottle now - sure go for it, mounted just like in the pic in the post above.

However, if you're just concerned about what might happen if you lose the post feeding your drysuit, or you're just looking to extend your back gas a little farther, maybe consider:

1) If you lose a post, thats pretty much it for that dive, unless you're like in a cave that requires to you descend before you can ascend, you're going to abort the dive and your general trajectory from that point forward is going to be up. You likely won't need to put any additional air in the suit if you have to abort the dive early due to a one of your first stages failing or the connected second stage freeflowing, you'll just be slowing dumping expanding gas from the suit on the way up.

2) You can always remove the quick disconnect hose from your wing power inflator and connect that to your drysuit instead, and then manually inflate your wing as needed. Check to see whether your hose lengths permits this and practice sometime.

3) Unless you're constantly adding and dumping gas to your drysuit using it as bouyancy compensation versus your wing, I really don't think you're losing all that much gas to suit inflation. If a 6 cubic foot inflation bottle isn't completely tapped out at the end of the dive, you used less than that, and that less than 100psi worth of gas in a set of HP100 doubles. I blow through more than 100psi laughing about finding an iphone at the bottom of a quarry and stuffing it in my pocket hoping I can charge it up and find the owner later.

4) If the goal is some extra gas for a dive in case of whatever, you're far better off slinging an AL40 as a pony bottle and having 40 cubic feet of gas available to your or anyone else on your dive team rather than keeping that 6 cubic feet in your back gas since you inflated your suit off a inflation bottle. It isn't either/or, but at some point just how many bottles and regulators do you want to manage for an NDL dive plan?

 

[pisauron]

Hello all, just set up my first twinset. And as usual you immediately look into other gear.
What’s everyone’s thoughts on running a drysuit inflation bottle when I typically dive air and soon more nitrox.
In my mind having a separate way to inflate my drysuit in the case of a complete manifold failure would be a good safety aspect, along with being able to gas plan more accurately by removing the usage of direct twinset suit inflation? Mostly online I’ve seen people use them prominently on CCR or at the least trimix diving to save on expensive gases.
Obviously I know I could do it, but the question is should I.
I’ll add a picture of my set up for those who enjoy photos.
Cheers.

Can you inflate you BC orally in a "complete manifold failure"?

 

[Badger7]

Can you inflate you BC orally in a "complete manifold failure"?

If you have to shut off a valve post, you're just not feeding gas to the regulator on that side. You're still able to feed gas from both tanks to the other regulator on the other post. If you shut down your right post, you can now longer use your power inflator on your wing, but you can certainly orally inflate via the corrugated hose. If you shut down your left post, you can no longer add gas to your drysuit, but you certainly have options available such as switching the inflation hose from your power inflator to you drysuit, if that is even necessary or helpful (wouldnt really be necessary during a blue water ascent). If you have a failure on the valve itself and shut down the manifold connecting the two tanks, you're now down to the contents of the single tank feeding the working post, but your inflation options are identical, it just makes it that much more time sensitive to clear any overhead obligations and get you and your buddies to the surface on remaining gas.

You could do an entire dive without the low pressure hose even connected to the power inflator of your BC, just by pressing the button and blowing into the inflator manually. Thats how you managed bouyuancy compensation before my time when using a horse collar:

 

[MarkA]

A suit inflate is necessary for use when the backgas contains (cold and very expensive) helium.

The DIR "standard" rig is the longhose and wing inflate off of the RHS 1st stage, with the necklaced backup reg and drysuit inflate off of the LHS. This is designed to give one source of buoyancy -- wing or drysuit -- if either valve has to be turned off.

Suit inflates for twinsets tend to be the small 0.85 litre steel or 1 litre aluminium cylinders. You can use larger, but space is a premium.

The BIG issue with tiny suit inflate cylinders... they run out of gas. Wonder how I know that... You'll inevitably discover this at depth and this will result in water getting into the suit inflate cylinder -- and it failing a test later, so expensive mistake.

Suit inflates are fiddly to use IMHO, but then again so are valve shutdowns on the twinset.


So, for me, it's a question of do you want one?
If yes, go ahead.
If not then there is much better things to spend your money on such as an ali40 deco cylinder which you can put another reg and hose on and fill with 50% for your journey into some deco

When/if you do start doing deeper diving, the contemporary route is through rebreathers. On those you tend to mount a 2 or 3 litre steel (or ali) suit inflate cylinder and you can use transmitters (or analogue gauges) to monitor the gas pressures.

A 21/35 fill on a twinset is 35% of ~5000 litres = 1750 litres of helium at circa 10p/litre = £175 just for the frigging helium!!! Contrast that with CCR (with an enormous initial cost) which will use, say, 150 litres of diluent, e.g. 52.5 litres = £5.25 for the helium (plus £10 of sorb, £2 of oxygen, £2 for the catheter, £1 for the two CO2 cartridges for the SMB, £75 for the boat, £+ travel, etc.)

As Mr Wibble has alluded to. It is probably worth configuring the hoses first to closer match a DIR setup. I did something similar when going to independent twins, left going left, right going right. But now with isolation manifolds there are better choices. Don't know if you are BSAC? But even they say have a long hose. It also puts the drysuit hose on the left for if you decide on a drysuit cylinder.

 

[Tracy]

It is pointless if you are diving air or nitrox. It is more gear to buy, carry, and maintain that serves no purpose.
If you have a complete manifold failure, inflating your drysuit won't be a concern. Nothing will be a concern in a few moments.