MDE Manifold

[nickb]

Originally Posted by NeilB

No it don't....well it does but only once the valve is open. When it is closed there is no pressure between the slug and the spindle.

I have on many occasion removed the spindle and nut to clean the o ring or spindle shaft. Nothing bad has ever happened. In fact you know there is no pressure there becuase once you have moved the nut a quarter turn you can undo it by hand.

OK, if the valve is closed then you'll be relying on the very fine brass thread to hold the slug in place.

If you know this already Neil, why are you asking if it's OK? Frankly I think it's fucking stupid in the extreme coming on here suggesting that something like this is OK, but if you know better, suit yourself. You'll be saving a couple of quid's worth of gas after all

BTW, why is the manifold isolation valve any different?

[NeilB]

Originally Posted by Bottle Maker

I have looked at two valves both MDE one on a 300cylinder one on my 232 7s there is know way they willcome apart under pressure without releasing the contents.

Graham.

That is why I asked the question about MDE manifolds. On a normal valve you can take them apart (except for the slug) without draining the tank first.

It would appear MDE are different.

[NeilB]

Originally Posted by nickb

OK, if the valve is closed then you'll be relying on the very fine brass thread to hold the slug in place.

On an Apex we used to rely on fine plastic threads holding them in place....it worked. The spindle is free to move in and out anyway when the valve is shut on most valves. Take a handle off a valve and see for yourself. Every one I have seen except the MDE has some movement.

Originally Posted by nickb

If you know this already Neil, why are you asking if it's OK? Frankly I think it's fucking stupid in the extreme coming on here suggesting that something like this is OK, but if you know better, suit yourself. You'll be saving a couple of quid's worth of gas after all

I put a spanner on it and it didn't feel right so I came and asked the question - that is how we learn. Now I found out that MDE are not like any other valve I have dismantled, and in 25 years there have been many!

Originally Posted by nickb

BTW, why is the manifold isolation valve any different?

Because that valve is not stopping gas coming out of a cylinder it is stopping gas travelling down a tube from one cylinder to the other. Pressure is on both sides while the cylinders contain gas.

ps. it's not the saving of the gas that is the problem. As I said earlier I will leave it until after the Friday dive. It was just from previous experience a strip and clean of the valve could be done in 10 mins with the gas still in the cylinder. Now it sems MDE valves are different. We live and learn.....some without the swearing

[nickb]

Originally Posted by NeilB

On an Apex we used to rely on fine plastic threads holding them in place....it worked.

That doesn't constitute evidence that it's a safe practice. It's testament only to your luck.

Originally Posted by NeilB

The spindle is free to move in and out anyway when the valve is shut on most valves. Take a handle off a valve and see for yourself. Every one I have seen except the MDE has some movement.

That's 'cos they're better engineered than most others, they work in a similar fashion. The spindle is not free to move in and out, it just has some axial (longitudinal) play. The end cap prevents the spindle from coming out, otherwise the knob would fall off.

Originally Posted by NeilB

Because that valve is not stopping gas coming out of a cylinder it is stopping gas travelling down a tube from one cylinder to the other. Pressure is on both sides while the cylinders contain gas.

The valve still works in a similar manner to the cylinder valves. When it's shut, the gas is held behind the slug.

TBH all this sounds like just doing half a job anyhow. In my experience the slug thread needs cleaning and lubing in order for the valve to turn more freely. Just ask Mal Bridgeman, he does every month or so

[access]

I still don't see how you can service a valve with pressure in it as the slug should be cleaned and greased ?
But then again I have never serviced a valve still fitted to a tank as I would split it and change all the Orings
in the valve and manifold. I have used the same set of MDE valves for about 15 years and they don't get stiff
very often. Any MDE valves that I have worked on have had a plastic slug.
For the sake of a bit of time I would empty the twins, pull the slug out and DIR

[nickb]

Originally Posted by access

.....and DIR

And we were doing so well....

[access]

And we were doing so well.... 

I just couldn't resist

[bjg5858]

MDE twinset valves are different you can not take the spindle out on its own you have to take the high pressure seat out as well... so yes they will need to be empty

All mde valves have brass slugs (high pressure seat)