My local Church is supplied with gas via what looks like a 2" steel pipe.
Obviously there is a manual shut off valve on the inlet pipe.
On the other side of the meter, there is also a manual shut off valve and
also an electronic emergency shut off valve.
I was doing some work in the boiler house recently and caught my arm on
electronic valve. It was so hot that it burnt my arm, no too badly but bad
Making enquiries with the Church Secretary, he told me that it had always
been hot and that he was told it was because of the solenoid running all the
that it was like this since installation some 16 years ago.
A..... Should the (Solenoid) valve ever get hot like this.
B..... What are the risks of an explosion because of it being so hot.
C..... I know on domestic systems that anything after the meter is the
responsibility of the Householder. Is it the same for a Church, which I
under commercial installations.
I can supply a photograph if needed.
Regarding B, I would think that a flame or spark would be needed to ignite
gas. I am curious whether the service engineer was aware of this valve being
so hot at any of the annual inspections/services, and who told the Church
Secretary that the valve has always been hot and the reason for this
(whether this person was competent regarding this installation). If the
valve is supposed to be so hot I wonder why a safety notice hasn't been put
in place to warn of the danger of burns or better still a protective barrier
fixed in place to prevent burns. Church premises are not exempt from health
and safety regulations and obligations.
The valve will close off the gas supply when the electrical circuit is
interrupted either by a thermal switch or manual emergency button.
Sometimes a series of such devices if in a large boilerhouse or
multiple boilers and interlocking with the fire alarm system is also
common. The valve will also close under power failure conditions and
may require manual resetting.
the solenoid will be warm and some people could consider it hot. If
you are seriously worried try phoning the valve manufacturers
technical department for advice.
If its been like it for 16 years the risk must be low.
Probably, although that depends upon exactly how hot it is. You can get
burns from anything above 43C, although an immediate burn from a passing
contact suggests it is rather higher.
In the absence of a leak, none. If there is a leak, there will still not
be an explosion unless the ratio of gas to air is in the right range
(c5%-15% gas IIRC). Even then, the maximum permitted surface temperature
of electrical equipment operating in a town gas and air mixture is 450C.
If it's a solenoid valve then it would obviously have to have current
passing all the time, with a normally closed type valve - if you did
it the other way it wouldn't fail safe in a power cut. I was using a
gas supply system which had a solenoid valve like this, and the coil
on that was so hot we questioned the installer about it, but he
assured us they were rated for that operating temperature. I don't
think it was hot enough actually to cause burning, though. I don't
think the risk of explosion from this cause is high, though - the
autoignition temperature (i.e. ignition without a spark or flame) is
580°C for methane, and your description doesn't suggest it was
anywhere near that hot.
I'd guess that the operation method will depend on what kind of fault
detection system you're using - the fusible link idea works fine to
cut off the supply in case of fire, but if you're trying to stop the
buildup of explosive mixtures from leaks or other causes that wouldn't
work. As an example, the system I mentioned was supplying a nitrogen/
hydrogen atmosphere into an oven, and the cutoff was controlled by the
ventilation system, so that if the extract from above the oven failed
the gas would be cut off. I remember cooking in a village hall kitchen
which had a gas safety system installed because they were worried
about buildup of explosive vapou - if any of the fans stopped it cut
off the gas; that also worked with a solenoid valve. It also had
massively overspecified fans - 2 extract fans and 2 input fans
blasting cold air across the kitchen - but that's another matter.
I'm no expert on gas valves but what feels very hot to touch is often
nowhere near as hot as you might think, particularly if the object is a
good heat conductor. A metal object at 50 deg C can feel very hot and
65 deg C can give you a nasty burn in a few seconds but would be nowhere
near hot enough to cause a gas explosion.
Ignoring the fire risk, which is probably quite low if it is working in
spec' I would wonder how much power / money has been used by this device
to heat the room over its lifetime? Doesn't sound very "green".
That one cigarette butt thrown out of the window at the traffic lights
is not significant. By the time everyone who stops there has dumped
It's the sum of the waste from everything that matters. You know, like
the waste from fitting solar panels on a roof in a cloudy climate.
They can get quite hot, but not usually that hot, there may be a problem
with it. It'd be worth checking the voltage rating to make sure that
it's not being overrun.
Zero. From my time in designing systems for the oil and gas industries,
Methane is a T1 gas, which means that equipment can have a surface
temperature up to 450°C above ambient temperature without any danger of
igniting the gas - and if it's that hot, I think you'd have noticed!
I've just checked and the auto-ignition temperature of Methane is
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