The Marine Safety Forum presents an incident where a crew member assisting with Breathing Apparatus (BA) sets accidentally released high-pressure air while opening a BA set valve, resulting in air entering his finger and causing swelling, to draw lessons learned.
The incident
During a vessel’s fire drill, the fire team was assisted with donning their Breathing Apparatus (BA) sets. The assisting crewmember opened the BA set valve, resulting in a release of high-pressure air that impregnated the assisting crew member’s finger. The injured finger showed immediate signs of swelling, and the medical support team advised medevac by helicopter. The crew member required surgical treatment to confirm the extent of the injury, ensure no debris was injected, and reduce the risk of infection and tissue damage.
Cause
The BA set involved was transferred ashore and tested. It was initially noted that the BA set, when landed ashore, still had a pressure reading of 270 bar of the original 300. The BA technicians noted that all connections were secure. To try to recreate the leak, they loosened the Cylinder Valve Handwheel (between the BA Set and the BA Cylinder Valve), and immediately there was a high-pressure air release from the Pilot Vent Hole on the Cylinder Valve. The Pilot Vent Hole is a safety feature in 300 bar-rated Cylinder Valves that has several purposes:
- It allows for pressure equalization between the BA and the bottle when the BA valve is initially opened.
- It reduces the risk of a high-pressure blowout by providing any excess pressure a means to vent.
- It serves as an indicator of the Cylinder Valve’s integrity (i.e., if the valve is closed, any air escape can be detected).
- It aids the initial reduction from high-pressure cylinder to equipment.
The Pilot Vent Hole is located on the Cylinder Valve so that any high-pressure release is in an upward direction and away from the BA Cylinder Valve Open/Close area, where the person operating the Cylinder Valve hand would be. During testing, it was noted that when the Cylinder Valve Handwheel was tightened to “hand-tight” (no tools should be used), as per manufacturer’s instructions, there was no escape of air from the Pilot Vent Hole. This only occurred when the Cylinder Handwheel was slackened slightly. The Cylinder Valve was then fully dismantled to check for any faults, and no faults were identified.
It was confirmed that the escape of air was initially felt by the BA wearer on the “back of his legs” and lasted only around one second. The downward escape of air felt on the BA wearer’s legs could only have been from the Cylinder Valve Handwheel connection not being secure. The injured crewmember could not recall the action due to the timescale and shock, although he was the only one who could have stopped the leak by tightening the Cylinder Valve Handwheel, inadvertently placing his impregnated finger over the Pilot Vent Hole.
When the Cylinder Valve Handwheel was tightened, there was a momentary release of pressure from the Pilot Vent Hole until the valve had full connection to the BA set and the BA bottle pressures were equalized.
Lessons learned
- When replacing a BA bottle on a BA set, always ensure that the Cylinder Valve Handwheel connection is tightened as per manufacturer’s instructions (hand-tight, no tools should be used).
- After changing the BA bottle, pressurize the system and listen for any leaks. Apply soapy water to the connection points and check for any bubbles indicating a leak. Tighten connections if necessary, but close the main valve first.
- Ensure the pressure gauge reflects the correct pressure.
- Conduct a breathing check by inhaling through the mask to ensure air is flowing correctly.
- Verify the low-pressure alarm is functioning properly by momentarily turning off the air supply. When conducting planned maintenance checks, the above should also be adhered to and checked.
- When donning BA, follow the manufacturer’s instructions, and if any leaks are observed, the main cylinder valve must be closed prior to tightening. Following the above checks when changing a BA bottle and conducting planned maintenance should ensure that the integrity of BA connections is confirmed prior to use in drills or emergencies.
