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tigwelder_riskassessment

TIG welder risk assessment

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

Oxygen depletion calculations

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.

tigwelder_riskassessment.txt · Last modified: 2017-12-13 16:11 by mike