This follows the template from the HSE's risk management site
|What are the hazards?||Who might be harmed and how?||What are you already doing?||Do you need to do anything else to control this risk?||Action by who?||Action by when?||Done|
|Fire||Everyone||Users are responsible for clearing the area of flammable materials before any welding takes place||Install a metal welding table and shield walls/conduits as necessary. Install a suitable fire extinguisher in the welding area||Mike Walters||Before welder is used||Done 2017-12-12|
|Fumes||User and other persons in the room may breathe harmful fumes from the welding process||TIG welding has minimal fumes to begin with. Users are trained to prep and clean their workpieces, reducing fumes. A large extractor fan is installed beside the welding area and is capable of cycling the room air once every 70 seconds||No further action required|
|Gas bottle falling over||Any person nearby. If the valve were damaged, the cylinder could become a projectile||Only using cylinders that have been inspected for safety and come from a reputable supplier||Chain the gas bottle to the wall in an area out of the way||Mike Walters||Immediately after obtaining a gas bottle||Done 2017-10-25|
|Hot objects||User and other persons nearby may suffer burns from handling hot objects||Users are trained to use appropriate tools & PPE to handle hot objects. Users are trained to leave the area safe for other users.||Install signage in the welding area to remind people that there may be hot objects left there||TBD||Before welder is put into general use|
|Oxygen depletion from compressed gas release||Any person in the room may suffer from asphyxiation||Limiting the amount of gas kept in the room to ensure that oxygen levels remain safe, even after accidental release||No further action required|
|UV radiation||User and other persons nearby may suffer eye/skin damage||Users are trained to use appropriate PPE||Install a welding curtain to protect other persons in the room||Mike Walters||Before welder is put into general use||Done 2017-11-01|
To gauge the risk of oxygen depletion due to release of the compressed argon, I've followed the British Compressed Gases Association's guidance node 11 - Reduced oxygen atmospheres. In it, they lay out a calculation for resulting oxygen concentration after a gas release in section 3.2 and a worked example in Appendix 1.
The following is the calculation for G8 given a 20L argon cylinder:
Total room volume: 4.5m * 6.1m * 2.6m = 71.37m3
Cautious estimate that 20% of that volume is taken by cupboards/tools/stuff, so actual volume of air in the room: Vr = 71.37 * 0.8 = 57.096m3
Volume of oxygen after gas release: Vo = 0.21 * (Vr - Volume of gas in cylinder) = 0.21 * (57.096m3 - (20L * 200bar / 1000)) = 0.21 * (57.096m3 - 4m3) = 11.15016m3
Resulting oxygen concentration: Cox = 100 * Vo / Vr = 100 * 11.15016 / 57.096 = 19.53%
This oxygen concentration is well above the 18% minimum recommended by the HSE.