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regulator failure - a kiln close call

updated fri 21 apr 00


Bruce Girrell on tue 18 apr 00

Perhaps I did something stupid. It wouldn't have been the first time. Does
anyone have an idea as to what went wrong here?

Yesterday, I started firing some raku. The first batch was uneventful. I
shut off the burners and unloaded the kiln. But the tanks were already low
and with a cold, humid day, had already started to frost over. I put the
tanks into large buckets and filled the buckets with warm, but not hot
water, pouring the water over the tanks as I filled the buckets. The tanks
were still cool to the touch after I poured the water over them. Certainly
nothing like they would be after sitting all day in the summer sun.

I loaded the kiln with the next batch and opened the valve on one burner. A
huge ball of flame engulfed the entire kiln. There was so much gas being
released that the back pressure of the kiln kept most of the gas outside
causing the fireball. I shut off the valve and everything was over as fast
as it had happened.

I looked at the pressure gauge and it read zero. But it read zero because
the needle was pinned against the stop peg after making a full revolution.
Apparently full tank pressure was reaching the burners. I shut off the
tanks and bled down the pressure. There was enough propane in the burner
lines that they frosted from the blowdown. Once the pressure was bled off I
opened the tank valve again and immediately the gauge spun around and pinned
against the stop.

I was able to finish the firing by turning the gas off at the tanks at the
end of each cycle. As long as the burners were not turned off, the regulator
would keep the pressure at an appropriate value and could be adjusted. But
if I shut off the burners without shutting off the tanks first, the
regulator allowed pressure to build sky high.

Anyone care to offer ideas as to what went wrong and what I can do to
prevent it in the future?

Thanks all.

Bruce "a hair-blazing experience" Girrell

iandol on thu 20 apr 00

From: Bruce Girrell

Subject: Regulator failure - a kiln close call

It is possible that the regulator needs replacing. Several things can happen
inside a gauge. The Bourdon Tube=3B that is, the pressure sensitive element,=
have distorted. Or one of the seals may be perished.

Either way, a defective gauge is a liability an should be repaired by a
qualified gas mechanic, or as I said, replaced.

Accidents with gas can be catastrophic, even fatal. Gas equipment should be
inspected and serviced regularly.

Ivor Lewis. Who nearly blew the house because of a faulty gas cooker valve.