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RTrueman  
#1 Posted : 24 June 2013 13:35:09(UTC)
Rank: New forum user
RTrueman

I am proposing a possible ban of oxy acetylene on our sites (mainly by our sub-contractor trades), due to it's highly volatile nature, and also that oxy propane is more than adequate for burning / hot work activities. All hot works are covered by an issued permit, with required control measures. HSE guidelines state that it is dangerous stuff, but over you Mr Contractor to adequately Risk Assess and control. (please correct me if I'm wrong!) Could anyone provide some solid info / guidance / evidence to help justify this, or any industry standard / best practices that are currently in place.
firesafety101  
#2 Posted : 24 June 2013 13:53:15(UTC)
Rank: Super forum user
firesafety101

Personally I don't see why you think one is safer than the other? They both have their individual hazards but both need similar controls. If I was responsible for a construction site where hot work involving either substance I would instruct the user/s to make sure the cylinders are taken off site at the end of each day. They should take their precautions using their own equipment (blankets, extinguishers etc.) and request a fresh hot work permit each day prior to starting work. (Further requirements as well as per the HWP rules). The main difference I can see is if there is a fire and acetylene is on the premises the FRS will introduce a 200m (or larger) exclusion zone around the site so if there is a fire and the cylinders can be removed when the operatives evacuate, that is what should happen, get it written into the evacuation Plan.
bob youel  
#3 Posted : 24 June 2013 15:16:32(UTC)
Rank: Super forum user
bob youel

Oxy propane is more than adequate for burning / hot work activities? With all due respect I say that a person has to work with such things for a long time to know the differences between the 2 gases with regards to physically cutting, burning, sweating and welding etc. to know the difference as Oxy-A is much better in many areas and banning may not ensure quality, speed etc. Just a thought - by somebody who has spent many an hour using both gases for different reasons and I would note FS101's comments and contractor/user management is a big area to get right irrespective of the gas used NB: Oxy is more dangerous than both the two other gases named in many a situation
NLivesey  
#4 Posted : 24 June 2013 16:05:36(UTC)
Rank: Forum user
NLivesey

RT, for me there's a couple of key differences in the types of gas that may guyide your decision. The first one is that propane is heavier than air and as a result, if it leaks, will effectively 'pool' in depressions in the ground. Acetylene on the other hand is slightly lighter than air and will tend to disipate if it leaks. The second difference is (to my mind at least), as already stated, the exclusion zone placed around acetylene in the event of a fire (200m) and this may be the driver for your decision. I had to make a decision of a similar nature a couple of years ago relating to how we use and store acetylene on one of our inner city key sites. Whilst the safety risk may not be significantly different in real terms the guidance of a fire engineer led me to decide that we couldn't afford to store acetylene at a location that had several major roads and mainline railway within 200m of the site. Whilst the storage was compliant the knock on risk in the event a fire did occur was too high for my liking. As a result we switched to propane with an option to get small quantities of acetylene when necessary. The overall performance between propane and acetylene shouldn't be a great issue, with the right setup and the right 'welder' they'll do the job as effectively whichever type of gas is used.
biker1  
#5 Posted : 24 June 2013 16:17:15(UTC)
Rank: Super forum user
biker1

As has been said, both gas mixtures have their own potential dangers. Acetylene is a highly unstable gas, which is why it is not stored at high pressure in cylinders, which can in itself present a hazard when it is connected to high pressure Oxygen if the right equipment is not fitted (flame arrestor, non-return valve). A fire involving Propane cylinders can give rise to BLEVEs, of course, with cylinders being propelled through the air. So, dangers for both combinations, but I wouldn't rate one as more dangerous than the other, providing the correct equipment and procedures are in place. As has also been rightly stated, don't underestimate the dangers of Oxygen, which can turn a small fire into an inferno, and poses serious danger if oil is around. Ironically, Nitrogen is recognised as one of the most dangerous gases within the gas industry, which might seem curious given that it is a relatively inert gas, but because of this the asphyxiation hazard is often forgotten.
firesafety101  
#6 Posted : 24 June 2013 16:26:06(UTC)
Rank: Super forum user
firesafety101

As a firefighter from 1968 to 1991 I attended many incidents involving cylinders, some of which resulted in the BLEVE mentioned by biker 1, that has jogged my memory. I also trained at the fire service college on a number of courses where we learned the hazards involved with compressed gas cylinders, and exercises with real compressed gas cylinder fires at which we were taught the correct procedures for firefighting such incidents. Funny to say the Propane cylinder fires were always worse and it it those that resulted in exploding cylinders although acetylene cannot be discounted as a very hazardous material and a cylinder rupture can result from excessing heating of either cylinder.
johnmurray  
#7 Posted : 24 June 2013 16:39:30(UTC)
Rank: Super forum user
johnmurray

Acetylene isn't stored as a pressurised gas. It is stored as a dissolved gas, dissolved in acetone, which is itself "stored" in a porous medium in the cylinder. The concave bottom of that cylinder has a hole plugged by a soft metal plug, just in case. I have seen many acetylene cylinders being mistreated by "tradesmen" (usually poorly trained idiots) and consider THAT the most dangerous part of using acetylene. If you drop an acetylene cylinder and it dents, you have the potential for major problems. Once the porous "sponge" inside is damaged an area of pressurised acetylene can form which is HIGHLY unstable. Using the cylinders in anything but an upright position is also a no, although many 'site users seem to think that using them lying flat on a 20-year-old pickup is an ok thing. Idiots. They'll kill you every time. I would never let anyone near any form of pressurised or flammable gas unless they had some form of training..... I have worked with Oxy-Acet in both a welding and flame cutting routine and have never had one heat up.
paul.skyrme  
#8 Posted : 24 June 2013 18:35:49(UTC)
Rank: Super forum user
paul.skyrme

A few things from an engineering process standpoint. There are a few things that can ONLY be done with OA, OP will just no cut it. The removal of the DA from site each night is a very good idea, HOWEVER, it MUST be transported in an open vehicle, & MUST be transported & stored upright, unless, after it has been laid down, it is left to stand for the time specified by the cylinder supplier before it is used, TBH, not practical. The other replies are all basically sound. First port of call is to look at the processes that are being undertaken, heating & cutting only, for general construction industry, OP, silver soldering & welding probably OA. Brazing or braze welding, could be a close call, and silver soldering is borderline really too, but my preference would be for OA. DA is just that dissolved in Acetone, the absorbent material used to be "Kapok" (spelling) IIRC, though it has been a long time. Not sure what it is now, there is a pdf on the Air Products website that explains a little more. TBH, both are quite safe in competent use. Check valves torch end, flashback arrestors at the reg, quality kit, in good condition, inspected & checked by competent people before each use, I don't mean every 5 minutes or every time it is lit, I mean every time it is set up and dismantled. Leak checked correctly on assembly before use. Competent users, same people as the inspectors, as they should be competent to do both else they are not competent to do either. Oil & grease free setup. Regulators serviced / checked in accordance with manufacturers instructions. Suitable precautions during use, including serious thought about the positioning of the cylinders. I torched a 1/2 tonne piece off a machine as an apprentice, in a large RORO skip, but the back door had not been secured by the driver, the piece of cast came straight out of the skip and severed both lines, torch went out virtually instantly. Cylinders were safely secured, the buggy was about 1/2T itself! Apart from the row, no real issues. The lump of cast was cold, no reason for it to ignite the gasses, and we were outside. I jumped down and closed off the cylinder valves just like I was taught. DA first as that is where the valve key was, just like I was taught! This was a while ago! Anyway I digress. Oxy can also be dangerous, a full Oxy cylinder on its side unsecured, if it should have the valve assembly knocked off will go off like a rocket. So on to my next point, cylinders secured in the upright position. I'm going on a bit now, time to stop! HTH. Paul
firesafety101  
#9 Posted : 24 June 2013 19:53:25(UTC)
Rank: Super forum user
firesafety101

Paul, you've just developed and given us all a checklist for OA and OP use, many thanks. All worth remembering.
CarlT  
#10 Posted : 25 June 2013 12:25:35(UTC)
Rank: Forum user
CarlT

RTrueman, As an ex-engineer I have some considerable experience with welding and cutting using both oxy-acetylene and oxy-lpg so I know that sometimes lpg just isn't up to the task. In addition to the really sensible comments above, you may wish to look at the British Compressed Gasses Association (BCGA) website which has a lot of information on risks, handling and using various gasses. They also have some generic risk assessments for transportation, handling and use of oxy-acetylene which are free to download. Regards Carl
Psycho  
#11 Posted : 25 June 2013 12:45:07(UTC)
Rank: Forum user
Psycho

RTruman we have done exactly what you are proposing we have banned all acetylene from all sites if any contractor as much as comes on site with one in a van they will be removed from our list of approved contractors -- zero tolerance. reason being we are a hospital a possible scinario someone comes into our service yard to weld a skip , accidently sets fire to other items in the yard, we get a hot bottle scinario up to 200m exclusion zone, that means we would have to close down Theatres maternity ITU and A&E which all back onto the yard for 24 -36 hours, it aint going to happen so the product is not allowed, as for oxygen we have that all over including tap and bottle.
RTrueman  
#12 Posted : 25 June 2013 12:55:06(UTC)
Rank: New forum user
RTrueman

Thanks all for your comments - all very helpful and informative. We haven't made any final decision yet, but as an example to put things into context, I had an M&E electrician using an oxy acetylene set to warm a duct fitting "because it is faster than using the blowtorch!" I will take all of these positive comments on board when finalising our decision on the matter. Rog T
CarlT  
#13 Posted : 25 June 2013 13:22:26(UTC)
Rank: Forum user
CarlT

Psycho, you seem to have overlooked the part where we were told it is a construction site, a bit different to a hospital service yard wouldn't you say? As in all things a suitable and sufficient risk assessment sohuld be carried out prior to work starting. Carl
Manion16110  
#14 Posted : 25 June 2013 13:35:22(UTC)
Rank: Forum user
Manion16110

Hi i have a copule of documents / processes, part borrowed and available for all to use. Send an email to competentadvice@groveservices.co.uk - Jeff Manion. There is no commercial gain to send these. Jeff Manion
stevedm  
#15 Posted : 26 June 2013 10:56:12(UTC)
Rank: Super forum user
stevedm

Don't normally respond in this way so not meant to offend anyone... Not an unfair practice restricting/banning contractors then...? Shouldn't you be looking at the causes of the fires and concentrating on their prevention rather than banning something that would only be a risk if a fire started? Would you also ban air flights over a construction sites because if they were involved in a fire...? Yes acetylene has it's risks and in my time in BOC I have seen my fair share of the results and carried out training to assist the Fire service to deal with them...but actually promoting a total ban?... Reduction of the risk should always be looked at and if there is a safer way of doing it then fine...but if someone wishes to take that properly controlled risk are you guys actually going to ban them from working with you?
walker  
#16 Posted : 26 June 2013 11:24:52(UTC)
Rank: Super forum user
walker

stevedm wrote:
Not an unfair practice restricting/banning contractors then...?
If you request contractors to conform to a site rule that is there for good operational reasons and they disobey -what do you do? Construction sites are rarely in isolation - they need to take into account client's adjacent operations and neighbours too.
MEden380  
#17 Posted : 26 June 2013 12:33:31(UTC)
Rank: Super forum user
MEden380

I have to agree with Stevedm - Banning acetylene because of a perceived hazard that if a cylinder is involved in fire the fire service put up a 200 metre cordon is poor practice. As previous posts have stated acetylene is the only suitable gas in some circumstances. Try brazing refrigeration pipe with propane, it does not work properly. Most Oxy Acetylene sets use small bottles, using Oxy Propane usually involves using large cylinders - not an increased hazard?
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