How can you check if a flashback arrestor has blown?

[duck in a bucket]

I was wondreing if there was a way of testing to see if a flashback arrestor needs replacing without hearing the loud 'pop' noise?
A friend heard the pop after she'd turned off the equipment correctly (she wasn't even in the room) and she heard the pop. But I don't really understand how that would have happened without the torch being lit?
Any advice?
Thank you!

[stuwaudby]

Arrestors generally contain a mesh or matrix of stainless steel. The mesh allows gas to pass through but absorbs any heat from a flame, this then reduces the temperature of the flame below the gas's ignition point and stops it. There are other types but they would not be suitable for workshop or welding use.

A flame arrestor is there to prevent a flame travelling back up the gas pipe and into the gas bottle - where it would cause a very serious problem. For Oxygen or Air to get into your gas bottle then the bottle must first be totally depressurised i.e. empty. You must then leave your torch gas valve open and allow the air to diffuse back up the gas pipe. There must then be a combustible mixture all the way from your torch through the pipe and to your gas bottle (believe me this is unlikely). There must then be a source of ignition at your torch head.

If you are using bottled oxygen and the regulator fails and your torch is blocked then it is feasible that oxygen could be pushed back into the gas bottle.

Note that butane (blue calor) boils at -12 DegC. If the temperature drops below this then the pressure in the bottle will drop low enough for air to be sucked back.

If a flame had passed back up your gas pipe and reached your flame arrestor then the indication would be much more dramatic than a pop. There would be a very sudden and loud expulsion of combustion products from your torch, if your torch were closed then your pipes would probably split or blow a connection off.

Note that the cheap barrel flashback arrestors typically sold for beadmaking in the UK do not provide any protection from external sources of heat. Always turn your gas off at the bottle.


[url[http://en.wikipedia.org/wiki/Flashback_arrestor[/url]