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Welding Safety for Fuel Storage Vessels & Confined Spaces
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Posted By Shariq Naseem
Hi!
I have been asked to come up with some guidance material for staff and contractors required to undertake welding in confined spaces or on vessels used for storing fuel. I'll appreciate any leads to where can I find the information.
Regards
Shariq
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Posted By Philip McAleenan Shariq, There is a UK/NI Approved Code of Practice for Confined Spaces which can be obtained form the Stationary Office (Arthur Street, Belfast). It costs about £7.50 stg. Also, the following paper that I co-authored on confined spaces may be useful for you. It can be downloaded (free) from http://www.web-safety.com/Papers/CSZero.PDF.In respect of any h azardous work operation you should ask, 1. What can cause harm? 2. What is being done to control it? 3. Is it enough? Thus with welding in confined spaces, some of your considerations will be centered on the composition of the atmosphere (both before and during the operation) that will cause it to be a danger to those who work in or nearby, e.g. what toxins, flammables, etc. may arise, is there a possibility of flooding, substantial rise in the ambient temperature, oxygen depletion? How will the operative maintain communication with the outside? How will you ensure a constant flow of fresh air to the space? What if an emergency arises, how will you effect a rescue? Are you workers trained and competent in all aspects of the operation, including working in confined spaces, in emergency evacuation, in use of RPE etc? Do standby workers know NOT to effect a rescue unless they are trained and authorised specifically to do so? If anything went wrong, how much time will you have before a rescue team (own company or fire service) arrives? These are just some of the considerations but by carrying out an effective hazard analysis and putting in place appropriate controls, you work operation should be able to proceed without incident. Regards, Philip
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Rank: Guest
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Posted By Jane Blunt
Dear Shariq
There is quite a lot of literature to help you. It would help first of all if you could identify your welding processes. The power source is either going to be electric - i.e. arc welding, or gas, i.e. probably oxyacetylene.
Having done that you should research the process a little further, as the potential to produce fume is very different for the various processes. The commonest welding process 'in the field', which has a person holding a short covered electrode (Manual metal arc) tends to produce the most fume. Fume control is much more of a challenge in a confined space.
You need to consider both the possibility of oxygen depletion, but also oxygen enrichment, if the process introduces oxygen into the space (either as a result of cutting operations, or along with acetylene).
If the process is electric, there may well be an increased risk of electrocution (see the case against Friskies Pet Food) if the walls of the vessels are conducting. In this case, you may need a welding power source with a limited open circuit voltage, and you may need to take special precautions to prevent electrocution.
If the process is oxyacetylene, the possibility of creating an explosive atmosphere should be considered as well. If your workmen are pre-heating using propane, you need to consider what may happen to unburnt gases. When preheating there is a substantial risk of producing oxides of nitrogen in high concentrations. (Fatal poisonings have been recorded - the symptoms are delayed until several hours later).
The vessel itself, if it has contained flammable mnaterial is also a source of danger. There are publications on how to remove flammable residues and vapours. You will probably need specialist help.
Some useful publications:
Search The HSE Bookfinder site,http://www.hsebooks.co.uk/homepage2.html using the key words 'welding' and gas freeing'.
Books I would recommend to you are:
Safe use of compressed gases in welding, flame cutting and allied processes HSG 139
Health and safety in arc welding HSG 204
Control of exposure to fume EH 55, and also EH 54 (but note that the exposure limits listed in these documents have been superseded)
CLeaning and gas freeing of tanks containing flammable residues, CS15
Hot work on small tanks and drums INDG314.
You may find other titles are also useful.
Jane
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