Twin Set Manifolds

Dear All

I've seen 232 bar twin set valves and manifolds advertised, but never
300bar.

Do they exist and if so where can I get them ?
___________________________________

Also for a strange idea.
Why not have say a 10 litre tank twinned with a 3 litre pony via an
isolation manifold.
Is it just the balance problems (ie off center weight)? Or just too much
redundancy, or mounting problems, or problems with changing tanks for second
dive???

Please discuss

James M wrote:
> I've seen 232 bar twin set valves and manifolds advertised, but never 300bar.
> Do they exist and if so where can I get them ?

I'm not sure there are distinct manifolds but the valves are
made 232 or 300 by the threads.
http://www.nigelhewitt.co.uk/diving/din.html

> Also for a strange idea.
> Why not have say a 10 litre tank twinned with a 3 litre pony via an
> isolation manifold.
> Is it just the balance problems (ie off center weight)? Or just too
> much redundancy, or mounting problems, or problems with changing
> tanks for second dive???
> Please discuss

Don't like it. What does it protect against? The isolating
manifold is there so you run the system as one big tank until
you have a problem then you snap the valve shut and you have
two seperate systems so which ever one has a problem then worst
case you can get out on the other and under most circumstances
you should be able to recover access to the rest of the gas.

A 3L is a good bail out for a non-deco dive provided it is still
at fill pressure. If you have used it down to say 100bar as part
of a 12+3 it isn't going to get you out with out some creative
breathing.

nigelH

Thanks for the reply Nigel

OK, you keep the isolation manifold closed, so your main tank feeds your
primary air source, and the pony bottle feed your secondary.

You lose main air due to a tank or valve problem, so you grab your secondary
and there's a reg problem.

Open the manifold and the pony air is available to your primary reg.

If a buddy needs your secondary air, he starts on the pony bottle, you then
open the manifold and both breathe from the same tank. Then close the pony
valve and your bail outs still there for another dive, you just need to
change the main tank.

"Nigel Hewitt" <nigelh@REMOVETHISnigelhewitt.co.uk> wrote in message
news:bo6mav$3q3$1@sparta.btinternet.com...
> James M wrote:
> > I've seen 232 bar twin set valves and manifolds advertised, but never
300bar.
> > Do they exist and if so where can I get them ?
>
> I'm not sure there are distinct manifolds but the valves are
> made 232 or 300 by the threads.
> http://www.nigelhewitt.co.uk/diving/din.html
>
> > Also for a strange idea.
> > Why not have say a 10 litre tank twinned with a 3 litre pony via an
> > isolation manifold.
> > Is it just the balance problems (ie off center weight)? Or just too
> > much redundancy, or mounting problems, or problems with changing
> > tanks for second dive???
> > Please discuss
>
> Don't like it. What does it protect against? The isolating
> manifold is there so you run the system as one big tank until
> you have a problem then you snap the valve shut and you have
> two seperate systems so which ever one has a problem then worst
> case you can get out on the other and under most circumstances
> you should be able to recover access to the rest of the gas.
>
> A 3L is a good bail out for a non-deco dive provided it is still
> at fill pressure. If you have used it down to say 100bar as part
> of a 12+3 it isn't going to get you out with out some creative
> breathing.
>
> nigelH
>
>

> OK, you keep the isolation manifold closed, so your main tank feeds your
> primary air source, and the pony bottle feed your secondary.

You'd never bother with a manifolded pony. You have the pony, completely
isolated. You never use the pony unless you have a problem with your own
air. If your buddy loses air, they would use your octopus as normal -
better that they breathe from a big supply of air. You use your own pony if
you lose your own air for whatever reason. It isn't there to extend your
dive though.
If you're going to manifold something, you should really get matching
tanks - makes air management make much more sense, keeps you balanced, and
gets you more air.

> If a buddy needs your secondary air, he starts on the pony bottle, you
then
> open the manifold and both breathe from the same tank. Then close the pony
> valve and your bail outs still there for another dive, you just need to
> change the main tank.

Unless you do that at the beginning of your dive, the pony will lose air to
equalise the pressure with the main tank, so would need refilling. If you
ever have reason to use a pony, you really shouldn't be worrying about
paying a couple of quid to fill it again - most likely it just saved your
life!

David

"James M" <jrm7262@hotmail.com> wrote in message
news:bo6nen$smc$1@hercules.btinternet.com...
> Thanks for the reply Nigel
>
> OK, you keep the isolation manifold closed, so your main tank feeds your
> primary air source, and the pony bottle feed your secondary.
>
> You lose main air due to a tank or valve problem, so you grab your
secondary
> and there's a reg problem.
>
> Open the manifold and the pony air is available to your primary reg.

err you primary reg is us as stated above

> If a buddy needs your secondary air, he starts on the pony bottle, you
then
> open the manifold and both breathe from the same tank. Then close the pony
> valve and your bail outs still there for another dive, you just need to
> change the main tank.
>
> "Nigel Hewitt" <nigelh@REMOVETHISnigelhewitt.co.uk> wrote in message
> news:bo6mav$3q3$1@sparta.btinternet.com...
> > James M wrote:
> > > I've seen 232 bar twin set valves and manifolds advertised, but never
> 300bar.
> > > Do they exist and if so where can I get them ?
> >
> > I'm not sure there are distinct manifolds but the valves are
> > made 232 or 300 by the threads.
> > http://www.nigelhewitt.co.uk/diving/din.html
> >
> > > Also for a strange idea.
> > > Why not have say a 10 litre tank twinned with a 3 litre pony via an
> > > isolation manifold.
> > > Is it just the balance problems (ie off center weight)? Or just too
> > > much redundancy, or mounting problems, or problems with changing
> > > tanks for second dive???
> > > Please discuss
> >
> > Don't like it. What does it protect against? The isolating
> > manifold is there so you run the system as one big tank until
> > you have a problem then you snap the valve shut and you have
> > two seperate systems so which ever one has a problem then worst
> > case you can get out on the other and under most circumstances
> > you should be able to recover access to the rest of the gas.
> >
> > A 3L is a good bail out for a non-deco dive provided it is still
> > at fill pressure. If you have used it down to say 100bar as part
> > of a 12+3 it isn't going to get you out with out some creative
> > breathing.
> >
> > nigelH
> >
> >
>
>

In article <bo6l3t$pb7$1@titan.btinternet.com>,
James M <jrm7262@hotmail.com> wrote:
>Dear All
>
>I've seen 232 bar twin set valves and manifolds advertised, but never
>300bar.
>
>Do they exist and if so where can I get them ?

300 bar twinsets exist. I have one!

A UK source is simplyscuba.co.uk. The tanks probably
need M25x2 threads; I haven't seen 300 bar 3/4" manifolds.
(this is the thread in the tank itself; where the valve
go in). I know good sources for 200, 232 and 300 for
M25x2 and 200 + 232 for 3/4".

The reason you wouldn't use a 300 bar twinset is that
it is exceedingly heavy and extremely negatively boyant.

I have a 2x6 300 re-built Poseidon; and this is about
the limit of how heavy a twinset I will tolerate.
I use it mostly for easy summer dives. It gets too
heavy under water for me to use in winter.

This set is around 5.5 kg heavier in water than a 2x8 200; and
around 4 kg heavier than a 2x12 (long) 232.

A 2x8 300 is even three kilograms heavier than this; and
2x10 300 are so negatively boyant that they are dangerous
to dive with. They are heavier than 2x15's on land; but have
10 liters less boyancy. You get the drift.

>___________________________________
>
>Also for a strange idea.
>Why not have say a 10 litre tank twinned with a 3 litre pony via an
>isolation manifold.
>Is it just the balance problems (ie off center weight)? Or just too much
>redundancy, or mounting problems, or problems with changing tanks for second
>dive???

It is a bad idea all around.

One of the main points of the operation of a twinset is the symmetry.
If one of the halves break down you can just isolate; and have half
your gas, with outlets for breathing and boyancy intact. You just
do this as a standard procedure. If there is a leak; isolate. Identify
where the leak is; if necessary by watching the pressure gauge. (if
it does not move the leak is on the right post).

Destroy this symmetry and you break the concept. Also, the way
the tanks are mounted together they have to be identical. The manifolds,
valves and bands are really quite fragile things, and have to be assembled
with the right tightening so you don't break anything. You keep the
manifolds slightly loose until the bands are tightened. The bands also
"float" freely around the tanks; and will not handle different types
of bottles. Even different bottles at the same nominal size can be
problematic; because the bands will bend and twist if given half a
chance. This puts stress in the manifold; which will break easily.

And you speak of changing tanks; you do not change tanks that
involve disassembling a twinset. This is garage work, and you
probably want to have a O2 clean environment as well.

-- mrr

Morten Reistad wrote:
> 2x10 300 are so negatively boyant that they are dangerous
> to dive with. They are heavier than 2x15's on land; but have
> 10 liters less boyancy. You get the drift.

Beg to differ. When you include the lead I carry I'm 4Kgms
lighter climbing the ladder after the dive than a 12/232 user.

If I, a grandfather with dodgy shoulders, can manage 10/300s
these young fit blokes should have no worries. I admit that once
I hang two 7L steel stages off the rig I really appreciate a boat
with a lift.

nigelH
Happy 10/300 twins user.

"Morten Reistad" wrote

> >I've seen 232 bar twin set valves and manifolds advertised, but never
> >300bar.
> >
> >Do they exist and if so where can I get them ?
>
> 300 bar twinsets exist. I have one!

Interestingly, I'm about to sell my two tanks that have 300 bar DIN valves
in favor of a couple more with teh 232 bar valves. Both fill to essentially
the same pressure, but the 232 bar valves will accomodate an A clamp
regulator, which is what most of my regulators have.

In article <booo09$5lk$1@sparta.btinternet.com>,
Nigel Hewitt <nigelh@REMOVETHISnigelhewitt.net> wrote:
>Morten Reistad wrote:
>> 2x10 300 are so negatively boyant that they are dangerous
>> to dive with. They are heavier than 2x15's on land; but have
>> 10 liters less boyancy. You get the drift.
>
>Beg to differ. When you include the lead I carry I'm 4Kgms
>lighter climbing the ladder after the dive than a 12/232 user.
>
>If I, a grandfather with dodgy shoulders, can manage 10/300s
>these young fit blokes should have no worries. I admit that once
>I hang two 7L steel stages off the rig I really appreciate a boat
>with a lift.

You are still using lead with 2x10 300?

Just out of curiosity, what is your other setup? (suit, BCD/wings etc)

I know from experience that they are dangerously heavy in water;
only tried them once, and was dangerously overweighted on that dive.

So let us do some math :

A 10L300 is normally stamped with a mass of 18.3 to 18.5 kg; which gives
a weight of

Tanks (sorry, UK.rec.scuba; bottles) .. 37 kg
Manifolds 2.3 kg
Bands and bolts 0,7 kg
20 L 300 bar air; 20L x 272 x 1.22g/l / 1000 6.7 kg the air inside
Total mass 46.7 kg

Volume : 20 L + (40 kg / 7 kg/l ) = 25.7 l
Displacement in salt water 25.7 l x 1.035 = 26.6 kg
Displacement in air 25.7 l x 0.00122 = 30 grammes


Weight on land, full : 46.7 kg (empty 40 kg)
Weight in water, full : 20 kg (empty 13.3 kg)

Compared to double 15s, which are somewhat lighter; 17.5 kg per bottle;

Tanks (sorry, UK.rec.scuba; bottles) .. 35 kg
Manifolds 2.3 kg
Bands and bolts 0,7 kg
30 L 232 bar air; 30L x 219 x 1.22g/l / 1000 8.0 kg the air inside
Total mass 46.0 kg

Volume : 30 L + (38 kg / 7 kg/l ) = 35.5 l
Displacement in salt water 35.5 l x 1.035 = 36.7 kg
Displacement in air 35.5 l x 0.00122 = 43 grammes

Weight on land, full : 46 kg (empty 38 kg)
Weight in water, full : 9.3 kg (empty 1.3 kg)

I uphold my position that diving with double 10x300 is exposing
the diver from a significant, unnecessary extra risk due to
overweighting. This is a danger that can be avoided. Compare the
example of the 2x15 232 below; less than half as heavy full;
almost neutral empty. This is enought to make a difference between
making it and not the day your suit floods at depth.

This danger is even greater with steel stages; two of these
would add another 4 to 10 kilograms of weight.

This has nothing to do with the ability to walk around
with the set on land. 2x10 300 and 2x15 232 are almost
exactly as heavy.

-- mrr

Morten Reistad wrote:

> A 10L300 is normally stamped with a mass of 18.3 to 18.5 kg; which gives
> a weight of

Well at least one brand of 10L 300 bar has a mass of 14.4Kg.
I don't know how much Nigel's weigh but your assumptions
may not be valid.

- Keith