Following an incident in which two people were injured when a gas cylinder valve ejected during analysis of a diving cylinder, the Health and Safety Executive (HSE) have issued precautionary advice to anyone involved in such tasks, in order to reduce the risk of further accidents.
A Draeger rebreather, four litre, steel cylinder, which had been charged with Nitrox analysis was being carried out in a dive shop, when the incident occurred.
Fitted to the cylinder, was a charging adaptor, supplied by the customer. The cylinder had no "boot", which would have allowed the cylinder to stand erect, thus the person about to carry out the analysis having to hold the cylinder upright in one hand.
To allow the necessary low flow of gas release for the analysis, the cylinder valve, as it was being opened, created an unexpected increase in gas flow, which in turn caused a violent rotation of the cylinder.
The unexpected rotation of the cylinder injured the hand of the person holding it, resulting in the release of the cylinder from his grasp and causing the cylinder to spin out of control into the shop.
One customer in the shop tried to stop the cylinder from hitting his son by stopping it with his foot and in the process of doing so was also injured.
The valve, still fitted with the charging adaptor, was then ejected from the cylinder, causing the cylinder to continue uncontrollably out of the shop travelling a further 20 meters before coming to rest outside the shop premises.
The valve, dislodged from the cylinder, travelled out of control for approximately 3 meters inside the shop.
Analysis by scientific and engineering specialists has failed to provide a conclusive result as to why there was an increase in gas flow, or what caused the ejection of the cylinder valve.
The HSE, in order to reduce the risk of similar accidents occurring, have issued precautionary advice to anyone involved in gas cylinder analysis as follows:
-
When a charging adaptor is fitted to the cylinder, there is a possibility that if struck it will affect the torque applied between the cylinder and cylinder valve. To reduce the probability of this happening charging adaptors should only be fitted immediately before charging and removed immediately afterwards.
-
Charging adaptors which are used with pure oxygen or oxygen enriched (oxygen greater than 21 per cent) gases should be suitable for use with oxygen. In order to maintain their 'fit for oxygen' status when not in use they should be stored to maintain that status - for example, placed in a clean transparent bag, which can be sealed closed and then placed in a second similar bag.
-
When carrying out any checks that require the cylinder valve to be opened the cylinder should be secured in a manner that allows both hands of the checker to be free. One hand to operate the valve and the other to hold any test equipment and does not allow the cylinder to fall over or be dropped.
The HSE have many leaflets and guidance sheets on diving cylinders etc available from their website, all of which can be accessed by clicking the following:
Article by Alexandra Johnston
