====== TIG welder risk assessment ======

This follows the template from the [[http://www.hse.gov.uk/risk/index.htm|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 {{ :gn11.pdf |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 = 71.37m<sup>3</sup>

Cautious estimate that 20% of that volume is taken by cupboards/tools/stuff, so actual volume of air in the room: V<sub>r</sub> = 71.37 * 0.8 = 57.096m<sup>3</sup>

Volume of oxygen after gas release: V<sub>o</sub> = 0.21 * (V<sub>r</sub> - Volume of gas in cylinder) = 0.21 * (57.096m<sup>3</sup> - (20L * 200bar / 1000)) = 0.21 * (57.096m<sup>3</sup> - 4m<sup>3</sup>) = 11.15016m<sup>3</sup>

Resulting oxygen concentration: C<sub>ox</sub> = 100 * V<sub>o</sub> / V<sub>r</sub> = 100 * 11.15016 / 57.096 = 19.53%

This oxygen concentration is well above the 18% minimum recommended by the HSE.