An engine room crew member was preparing to do some torch cutting. He opened the stop valve on the oxygen pipeline that precedes the pressure reducing valve on the gas bottle. As he opened the stop valve an explosion occurred. Thankfully there were no victims.
On investigation and consultation with the manufacturers the following points came to light:
- The explosion was probably due to adiabatic compression (gas hammer effect); that is, ignition without external heat input. This can occur when there is a sudden increase in the pressure of oxygen in the presence of an ignition agent such as metal particles, an organic substance, oil or grease;
- Compression heat is generated locally inside the piping system when the pressure increases quickly. This increased temperature can, in turn, cause auto ignition, depending on what products are in contact with the oxygen;
- The ignition agent (e.g. grease or impurities) could have been deposited during oxygen cylinder exchange or have been present within the piping system.
- When working on oxygen gas connections, pipelines and hoses, working gloves should be clean and tools free from oil, grease and dirt;
- Ensure that all pipelines, hoses and valves in the connections between the manifold and cylinders are clean and free of all impurities;
- High pressure oxygen cylinder valves which connect the cylinders to the manifold should be opened slowly to avoid undue generation of compression heat;
- Ensure that there are no leaks from the oxygen installation, which can lead to dangerous levels of oxygen enrichment – especially in poorly ventilated areas;
- Ensure crew that use compressed gases know the best practices.