Gas leak from valve handle when tank is low?

[jtsfour]

Yesterday I was experimenting with my LP85s to see how they reacted to being breathed really low.

I got them down to ~300PSI and ended the dive.

When I was shoulder carrying one of them I noticed a very small and intermittent hiss of gas from the valve handle area. The valve was closed but regulator had pressure. The gas came from the regulator side I believe. It was a very small amount of gas.

When experimenting I could recreate it by jerking or shaking the valve handle. This only happens on one of my tanks.

Is this a symptom of something failing in the valve handle? Or is this just from the O-rings having less pressure to seat them? I would think 300PSI would be enough to fully seat any O Rings….

These are Blue Steel DIN valves. With apeks diaphragm first stage.

I think I have the tools to disassemble the valve but have never done it before. Once I get the tank filled I will test and see if I can recreate the leak.

I also have a replacement I can put on but wanted some opinions from more knowledgeable people.

 

[broncobowsher]

Probably time for a valve rebuild or replace. The stem packing is what it sound like you are describing. It's not going to get better on its own. How soon until the tank is due for the next vis?

The regulator still having pressure against it even with the valve closed will still have pressure on the stem packing. Once you release the pressure on the regulator the pressure on the stem packing will be gone. Leak will stop.

 

[grf88]

Could be the stem o-ring failing to make a solid seal when under reduced pressure.

Edit Looks like it was answered while I was typing.

 

[johndiver999]

probably takes 2 minutes and a 10 cent oring to fix

 

[jtsfour]

Probably time for a valve rebuild or replace. The stem packing is what it sound like you are describing. It's not going to get better on its own. How soon until the tank is due for the next vis?

The regulator still having pressure against it even with the valve closed will still have pressure on the stem packing. Once you release the pressure on the regulator the pressure on the stem packing will be gone. Leak will stop.

Tank is not due until March.

Just went into my library of scuba manuals and found a thermo valve service manual. I've heard most valves are very similar or the same. Do you know if Thermo and Blue steel valves are similar enough to use a thermo manual for reference? Looking at parts available it seems they are of the same design.

 

[grf88]

The only differences that I am aware of is that some seal the stem with a combination of a teflon washer and o-ring and others use two teflon washers. If it is leaking it is more likely to be the former. The stem can be serviced without depressurizing the tank but care must be taken.

 

[jtsfour]

The only differences that I am aware of is that some seal the stem with a combination of a teflon washer and o-ring and others use two teflon washers. If it is leaking it is more likely to be the former. The stem can be serviced without depressurizing the tank but care must be taken.

Looking at service kits it looks like it is a teflon washer and an o-ring. I'll go ahead and empty the tanks and rebuild the valves myself. Is there any reason to replace the stem or valve seat? I'm assuming replacing crush washers and o-rings is plenty.

 

[Jack Hammer]

The valves are close enough in design to be able to rebuild one. Make sure to get the correct parts kit as the individual parts are not universal and some valves have more or less parts than others. It sounds like your valve seat may have excessive wear and your packing isn't sealing well. As long as you don't have corrosion and there is no damage both are easily remedied by a rebuild.

 

[Jack Hammer]

Looking at service kits it looks like it is a teflon washer and an o-ring. I'll go ahead and empty the tanks and rebuild the valves myself. Is there any reason to replace the stem or valve seat? I'm assuming replacing crush washers and o-rings is plenty.

Some have a copper crush washer, some don't. Replace stem if bent or has weird wear, otherwise just the included parts. Pay attention to what comes out as some kits have extra parts to apply to multiple models of valves. Also some worn parts may look very different from the replacement (o-ring on stem, packing).

 

[broncobowsher]

If the tank is already down to 300 PSI, just empty it.