Tank valve doesn't open when charged

[emoreira]

I'm having a problem that has been puzzled me for some time.
I charge the tanks in my scuba school. We have a Bauer Junior II.
Tanks are Luxfer AL80 with XS Scuba pro valves. The regulator that we use are Yoke, so the Compressor fill assembly has a DIN to Yoke adapter.
Some tanks, especially when they are almost empty and are put on charge, I open the transfer valve in the fill ass., and open the tank valve, but the valve does not actually open.
The valve opening mechanism is pretty simple, and turning the knob open, the valve seat is mounted in a screwed assembly should go open.

 

[redacted]

The seats are free floating and may not open with high pressure on the back side.

 

[emoreira]

The seats are free floating and may not open with high pressure on the back side.

It doesn't seem that the seat is separated from the screwed seat holder, I'll take a closer look. However, this pretty much explains what's going on.

 

[redacted]

It doesn't seem that the seat is separated from the screwed seat holder, I'll take a closer look. However, this pretty much explains what's going on.

Free floating is not really correct. The seat is thread and screws into the housing. But the stem and the seat simply engage in a slot so that slotted interface with the stem held in place by the gland nut. You first might want to make sure the gland nut is tight. Or it could just be time for a rebuild.

 

[sealark]

try opening the tank valve first then the air supplying valve.

 

[tursiops]

try opening the tank valve first then the air supplying valve.

Duh.

 

[emoreira]

try opening the tank valve first then the air supplying valve.

This is what I actually do. I've disassembled the whole valve but I cannot figure out what's going on.

 

[Got2Go]

This is what I actually do.

I open the transfer valve in the fill ass., and open the tank valve, but the valve does not actually open.

I think this is why he suggested you open the cylinder valve first, then the supply valve.

Does air come out of the cylinder valve when opened in free air?
If so, and you connect the fill whip, and then open the cylinder valve, the fill whip should charge up to cylinder pressure.

If you indeed open the cylinder valve first, and then supply valve, and no air flows into cylinder, make sure there is no check valve connected backwards on the fill whip line or Din/Yoke assembly.

 

[emoreira]

I think this is why he suggested you open the cylinder valve first, then the supply valve.

Does air come out of the cylinder valve when opened in free air?
If so, and you connect the fill whip, and then open the cylinder valve, the fill whip should charge up to cylinder pressure.

If you indeed open the cylinder valve first, and then supply valve, and no air flows into cylinder, make sure there is no check valve connected backwards on the fill whip line or Din/Yoke assembly.

This is what I actually do in this cylinder specifically. The normal procedure is to change the position of the transfer valve and then open the cylinder valve.
In this particular cylinder, if it has some air inside, the air goes out as expected when I open it's valve.
The fill whip has no check valve.

 

[Got2Go]

Air comes out of cylinder valve when not attached to anything and valve is open = Good.

Attach the fill whip to cylinder, open bleed screw, then open cylinder valve...
Does air come out through bleed screw?

Close bleed screw, and completely open cylinder valve until it will not turn anymore.
Now lightly crack open the supply valve to the fill whip so that very little air goes through the valve.
Does air go into the cylinder then?

The only thing I can think of is that the the seat insert has become separated from its threaded carrier, and pressure into the cylinder is forcing the delaminated seat to close into the orifice, sealing it and preventing any gas from passing through. (If air comes out of the fill whip when not attached to a cylinder, and air comes out of the cylinder when not attached to anything)