Since we're in a lull in the action, I've had some concerns about
some things I've lately seen in print on boilers, specifically testing
pressures, and my concern is that very misleading messages are being sent
by this and those who don't know better will take this to be good practice,
or worse yet "required" practice, and begin spreading misinformation,
possibly causing someone else who doesn't know better and follows the
misinformation to damage an otherwise perfectly good boiler.
What has caused my concern is the recent article in SitG wherein
it is stated that Torry Krutzke's Pikes Peak Loco K-loco retrofit boilers
are hydro-tested to 220psi, with fittings in place no less, and along the
same lines that Accucraft supposedly tests Ruby boilers to 160psi. It
almost seems to me that in Ga1 live steam these days there are a few
things, and a few people, who subscribe to the "If a little is good then a
lot more is a lot better" school of thought. This is unecessary, and
mis-guided.
This should not be taken as a criticism of Pikes Peak or
Accucraft, they are entitled to test to whatever pressures they see fit,
and they may very well have good reason for doing what they do, although I
can't think of a single one. The reason for my comments is to counteract
any tendency there might be in the wake of this for people in Ga1 live
steam to begin saying that hydro-testing to a high multiple (250% to 400%)
of WP (working pressure) is now in some way a requirement or a good thing.
It is not and should not be.
The universally accepted, and in some cases regulated, test
pressures for miniature copper boilers are 2 X WP (200%) for the initial
(new) test and 1.5 X WP (150%) for all subsequent tests. Thus for a boiler
intended to operate at a nominal 40psi, the new (1st time) test pressure
should be done at 80psi and subsequent tests should be done to 60psi.
These are neither minimum nor maximum pressures but are "target" pressures,
but in any case there is no compelling reason to take test pressure
substantially beyond this, certainly not to 300% or 400%.
The other thing that I see, in ALL gauges of live steam, is the
practice of hydro testing a boiler with the fittings in place. A hydro
test is not intended to test fittings nor are fittings intended to
withstand hydro-test pressures. One does a hydro test to determine the
soundness of the boiler structural envelope and one weep or leak at a
fitting renders any hydro test of the shell inconclusive, at least for the
purpose of a hydro test in the first place. I know that this won't prevent
people from hydro-testing with the fittings in place, because I know how
much extra work is involved in stripping a boiler down and plugging the
holes with solid threaded plugs for a test, but the record should show, and
the general Ga1 population should know, what the correct procedure is in
case they decide to use it.
Regards,
Harry Wade
Nashville Tennessee
