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> Subject: Neck O-rings...
> A participant in an ongoing thread re redundancy mentioned, in passing,
> the possibility of failure of a cylinder's neck o-ring. I've never
> even heard of this happening. Has anyone experienced this? I confess that
> the thought of the 3000 psi on my back atempting to make an exit thru
> a hole that large is disquieting. Are they routinely changed when a tank is
> visually inspected?
>
> Dave (Great, a *new* paranoia) Ventre
> Quincy, MA
Failure of the neck o-ring commonly occurs if an incorrectly
sized o-ring is fitted after removal of the pillar valve for
visuals, etc. Ensuring that a correct o-ring is fitted is extremely
important (micromillimetres become important). Cylinders generally
blow their neck o- rings during the first fill. In most instances
only part of the o-ring is extruded, accompanied with a great rush of
air (and water if filling in a tub) - note however that the pillar
valve will remain "screwed in" (sigh!), assuming the pillar valve
thread matched the cylinder thread (more paranoia). As yet I have not
heard of a neck o- ring blowing DURING A DIVE - what a thought! Maybe
someone has? I do however believe there should be enough air
remaining in the air to do an emergency ascent, from say, 30 m - no
time for decom stops though :).
********************************************************************
Philip Coetzee * E-Mail: zlapsc@zo*.up*.ac*.za*
Department of Zoology * Phone: +27-41-5042138
University of Port Elizabeth * Fax: +27-41-532317
P O Box 1600 *
Port Elizabeth 6000 *
SOUTH AFRICA * /// /
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