Risk Of Explsion ?

[the_constructor]

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 enough.

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 time and that it was like this since installation some 16 years ago.

My questions:

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 presume comes under commercial installations.

I can supply a photograph if needed.

Kindest regards,

Jim

[cynic]

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.

[Nightjar]

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.

Sounds probable.

Colin Bignell

[docholliday]

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=B0C 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. Mike

[Gareth]

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.

[Bill]

In message , Gareth writes

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".

[cynic]

Compare with the cost in money or carbon of a new boilerhouse or even a new building your green argument falls flat on its face at the first hurdle

[Bill]

In message , cynic writes

Every little counts........................

[Nightjar]

The entire output of Britain is 2% of man-made CO2, which, in turn, is only just over 5% of global CO2. Do you really think that the consumption of one solenoid is actually significant?

Colin Bignell

[Steve Walker]

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 actually 595°C.

I should think so.

SteveW

[Andy Champ]

No. But.

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 something though...

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.

Andy

[Weatherlawyer]

Sounds like the overture for batman returns. Jus tapply a few drops of blood and very little =3D counts.