I am considering putting a business case together to replace the use of acetylene to a safer method - Safer that is, in fire situations. To be fair the risks have been controlled to a high level, but management are anxious to avoid the potential shutdown of operations that may result from an overheated acetylene cylinder. (To both their and neighbouring premises) I have discovered that acetylene achieves approx 3200C, whilst MAPP achieves 2927C So does the circa 273C difference between acetylene & MAPP actually make much of a difference in terms of welding, braising or cutting? What could be welded with higher temperatures associated with acetylene, that could not be welded with MAPP? Has anyone any experience of replacing acetylene in the workplace and if so what difficulties did you face?

Captin S has hit the nail on the head You should determin why &/or if Acetylene cylinders are getting overheated as in my experience this has never happened when cylinders are used properly even when used in desert & similar hot conditions and in hazardous areas / situations

We replaced all accetalyene cyliders with propane ones due to time for recovery from propane is only two hours cooling where as its 24h for accetalyene, this was due to a fire with welding gear some time ago, have had no issues from welders as its cheaper safer does take a little longer but for special welds we use migs

i guess the only way to find out is to get the alternatives in to try them. have you had a word with the welders on site to establish what welding or cutting is carried out. Phil

Thanks to all so far. I will certainly be chasing the leads re MIG for welding and propane for cutting. A bit of background. The business case I am putting together relates to a small maintenance workshop in central London within a highly populated area surrounded by large buildings at close quarters (and very busy streets). The workshop use acetylene for a range of repairs aimed at keeping a manufacturing process operational. Quite often there is no notice of acetylene use, as a breakdown occurs and a repair is required asap. As a result, the gas cannot be stored offsite as it would seriously delay the repair. As the FSO makes it a requirement to consider the safety of all relevant persons - in the case of acetylene, this would mean anyone within a 200m radius of the cylinder. Consider that 200 metre radius (a fire service exclusion zone introduced at acetylene fires) this is an area equivalent to 1.25 KM2 of central London - which may be closed for up to 24hrs!!) - you can only imagine the chaos and compensation claims that may result. Plus the RP doesn't want any such disruption to his building. As a result, I am researching replacing acetylene altogether with a safer process, thereby reducing the risk. However the workshop manager (an old dinosaur, "Bloody health & safety" etc) says he can't do without the gas and the RP doesn't know where to turn. So where can I go for impartial engineering advice? I am reluctant at contacting BOC or Air Products as they've an interest in selling their gas. As far as the fire service are concerned, they'd rather see all acetylene gas cylinders replaced, but cannot offer any technical advice to support this corporate aspiration. Thanks once again

Just a small correction Messy - the exclusion zone based on a 200m radius would be 0.125 km2 not 1.25 km2. Still very inconvenient! (200m is 0.2km)

More than inconvenient, it hurts when it goes bang (thermal radiation and overpressure considerations taken into account) Always interested in how many people that reply to these type of questions have any degree of operational experience?? Nordic countries predertermioned response is to initiate imediate ignition via the use of rifle and incendriary (tracer) round. Negates prolonged exclusion zone requirement

Just my personal take on this having been involved in the Maintenance Repair & Overhaul industry from light through to heavy industrial operations in various roles for over 20 years, internal & external across many disciplines. Never found Propane any good for repair welding. Very good for heating with O2 mix. OK, ish for Oxy-Propane cutting, can't use same cutting nozzles as Acetylene though. Remember it would not be just the gas cylinders to change, but the regulators, hoses, flashback arrestors, the torches should be OK, but as I have said the nozzles are different for cutting. MIG does not take over for all odd job welds, for a start in the repair industry, the cleaning affect of the oxy-acet flame is a benefit, this cleaning may need to be done "mechanically" to use MIG, skill levels are comparable for operation. You will bring another hazard to the mix though with MIG in that you bring along electrikery! TIG can be used for much welding where oxy-acet is often used. e.g. thin sheet, MIG will do this, but you always have metal deposited with MIG, you have the choice with TIG & OA. Again with TIG, you have cleaning issues, and the skill level is generally higher. With MIG & TIG you still have compressed gas, not necessarily fully inert, CO2 is often used with MIG for low carbon steels it gives a different weld bead structure to Argon & Argon mixes. For TIG you pretty much have to use Argon or Argon mix. I notice in your post you mention MAPP, this is a mixed gas commonly used for heating and brazing. I have actually never used this, only Acet & Propane. I am not sure on the feasibility of MAPP/O2 mix. There are particular chemical actions that go on in an Oxy-Acet flame that are good for welding low carbon steels. I am not sure of the chemical products of MAPP/O2 and the affect that these would have on the metallurgy of the weldments. You would need to ensure that this was not compromised as it could result in the weld not performing to its required structural integrity. So you could end up reducing the possible risk from the Acetylene, and replacing it with a real failure mode in contaminated weldments? We don’t know enough about the materials being worked and the requirements of the repairs. MIG & TIG are no good for heating, flame cleaning, soft soldering, silver soldering, brazing or braze welding, where as Oxy/Fuel gas processes can undertake all of these, with the caveat above on the “weld” chemistry. Don’t forget Manual Metal Arc welding, with stick electrodes is also useful for repair work. IIRC from my C&G’s I had to be able to draw the inside of an Acet cylinder from memory! It goes something like this. The acetylene is dissolved in acetone, and the cylinder is filled with kapok. There is a small space at the cylinder neck where the gas is formed at low pressures, around 1 bar. The reason being that acetylene is unstable at pressure much above this. This is why you must stand an acet cyl for hours after transporting it in the horizontal plane to allow the contents to “settle” correctly preventing the drawing off of acetone thus causing other issues. The cylinders are very robust mind. Our BOC delivery driver when we were apprentices (it was our job to drag the cyls around) used to drop them straight off the back of the wagon vertically onto the tarmac. I saw this dozens of times, never a failure. He used to do this with all the cyls not just the DA. (Dissolved Acetylene). Once we stopped flinching he went back to using the little crane on the wagon! I think back and perhaps it was just a training thing to show us that the cyls were not glass, but he also taught us to handle them correctly but not to be frightened of them. Remember going to a pressurised gas such as MAPP & Propane brings in the element of storage of high pressure flammable gas. You could try the British Compressed Gas Association also for advice. BCGA – they are on the web. You may also have to retrain the users for different techniques for other gasses, and processes. BTW I think that the other posts are all very valid. TWI is also a good shout, no contacts there I’m afraid, never saw the benefit in joining, & the contacts I did have are no longer involved with TWI. HTH Paul

Great stuff and thanks to all, especially Paul for the detailed & most useful post