PST insert inner o-ring failure ?

[idive2]

I've heard mention of some o-ring failures on the insert that gets screwed
into the convertible valve on PST steel tanks. I removed mine and it seems to be a very good seat for the o-ring with a flat surface on the insert that looks like it would
seat very well against the valve. Before removing insert I went to see how snug it was
in a tightening direction and it was not even close to snug. Just wondering if perhaps
from the factory these inserts are not snugged up. I think I will check mine from
time to time. I'm sure if it got loose enough the seal would blow from the seat but
from the design it's hard to imagine a blown seal when the insert is snug unless of
course the o-ring is very degraded.

 

[spectrum]

I'm running 4 E7-80s and dive them as DIN valves. However since all of my local fill whips are yoke I always install my inserts for fillling. This way I know what's getting screwed into the threads my regulator shares.

When tightening I put the long leg of the allen wrench in the insert and only apply torqe by holding the stubby end. This just snugs the seal. I have noted that i I tighten them much more the insert begins to take the skew of the thread and getting the whips to seat and seal is harder. My point here is that I wouldn't want the inserts to really be tight, but they should be snug. They may ship bareley seated to prevent the o-ring from taking a set.

Pete

 

[idive2]

I'm probably a tad more snug than what I would be using the long end in
the insert and stubby end to tighten but not much. I think snugging using
the stubby end to turn sounds about right. Even though I don't remove the
insert for normal use I think I will remove the insert occasionally and check the
condition of the o-ring just as I would take an occasional glance at the outer
o-ring.

 

[spectrum]

Even though I don't remove the
insert for normal use I think I will remove the insert occasionally and check the
condition of the o-ring just as I would take an occasional glance at the outer
o-ring.

That's a real good idea. Remember that the DIN thread is exposed to the water any way you dive it. Water will run in to fill the voids in the thread path. If left undistrubed some crud could build up in there and give you problems some day.

Pete

 

[Hoosier]

Another factor of the failure is the pressure. If you are filling and using more than 3442 psi frequently, there is more chance to fail insert O-rings. There are some pictuers on my gallery.