BA Compressor Union Coupling Failure

Parting of an adaptor at 100-bar pressure, with potential for serious injury.

What did the reporter tell us?

The officer was charging the lifeboat compressed air bottle. During the charging, the union/adaptor between the breathing apparatus compressor and the air bottle disconnected and was blown away when the pressure of the bottle reached about 100 bar. The maximum designed pressure of the air bottle is 200 bars. Fortunately nobody was injured, but clearly there was a possibility of a serious injury occurring. The specification of the union/adapter used on board was different from the original. The union/adapter could not withstand the pressure because it could not be tightened sufficiently. The failure to use the correct adaptor was the result of improper management of parts.

The lessons to be learnt

Lessons Learnt – Confirm that all unions/adapters between BA compressors and air bottles (such as for lifeboats, SCBA, EEBD, etc.) are the correct design, as per the instruction manual on board. If the instruction manual is unclear, consult with your ship’s manager.

CHIRP Suggests

Proper parts and good maintenance is the first and most important control measure for the hose whip risk.  When deemed necessary, an example of an additional control measure is “a length of suitable cordage, tie wrapped around the hose and secured, so as to prevent whipping should it fail at any point”.

It is most likely the connection was not manufacturer supplied and the connection thread, whilst fitting, was not the approved part and the thread may have had some slight unseen tolerance that caused the connection to blow at high pressure. CHIRP highlights the need for caution with all high-pressure equipment; when they fail it can have fatal consequences.

It is essential that only the correct manufacturer’s approved components are used on both the compressor and the connection with the air bottle. Refer to: The UK MCA’s Code of Safe Working Practices for Merchant Seafarers (2015 edition) COSWP 18.25.1 and 18.25.2.