Workplace Health and Safety Queensland recently issued a safety alert highlighting the risks associated with the filling of scuba diving cylinders using a flexible fill hose following an incident in which a worker was seriously injured at a recreational dive business.
During the filling process, the ‘O’ ring in the scuba diving cylinder valve failed, causing a sudden release of gas. This caused the cylinder to fall over which in turn caused the end fitting of the fill hose to fail, and the fill hose then whipped and struck the worker filling the cylinder several times.
Scuba diving cylinders are filled with gas at pressure typically ranging from 200 to 250 atmospheres absolute (ATA). To fill a cylinder, a flexible high pressure hose and attendant fittings are used to decant gas from either bank storage or a compressor. Typically a worker connects and disconnects cylinders and remains at, or near the filling station while the cylinders are filling.
The flexible filling hoses may fail for a range of reasons including: inappropriate design or installation; inappropriate use (such as over-pressurisation) or physical damage (through corrosion, wear or misuse).
If the hose fails, the safety alert said it will typically whip in an uncontrolled manner until depressurised creating a serious risk of death or injury to people within the radius of the hose.
The safety alert recommended a number of action steps:
The person conducting a business or undertaking (PCBU) that fills SCUBA cylinders should review their filling operations to determine whether risks from the failure of the high pressure fill hose are controlled.
Scuba cylinders should be secured against falling during filling operations.
All components of the cylinder filling system should be specifically designed for the purpose intended and installed by a competent person.
The filling area should be isolated from workers and others not involved in the filling procedure.
Workers should wear appropriate personal protective equipment (consideration should be given to hearing protection, eye protection and foot protection).