T&T: Old valves on Propane cylinders, why want the old one?

[bob england]

The main reason for opd valves was that the filling stations (ours included)
would fill the tank using the bleeder as the full indicator. They are required
by law to weigh the tank to acertain it's fill level. Some do and most don't,
especially if the state inspector is not around. The bleeder is assumed to
blow liquid at 80%, if it in fact has a drop tube. But, if they let it spew
for a few seconds it quickly approaches 100%. The problem being that if the
cylinder is filled at say, 45 degrees to 90% full, and then stored in an area
that say is 80 degrees, the pop off device will vent the excess pressure, from
fluid expansion, causing a serious fire hazard. Also, a properly filled
cylinder is unlikely to blevy even in a structure fire, but an overfilled one
certainly will. OPD's are much safer, but I still dislike them and disable
(remove) them from my cylinders. As a side note,on my new fiberglass
cylinders, I have a mark at 80%, (you can see the liquid level) so I never
overfill them. They were about 60 bucks each through our supplier, really
neat, and yes I removed the opd valves myself, but, I refill my own tanks and
have a class 1 licence to do so (I weigh them to). I've never had a problem
filling my own bottles at any retailer in the U.S. except that I usually have
to sit around with the guys (and gals) talking about the industry and the
differences here and there. I will say that for most folks the opd valve is a
good thing.