Bailout cylinder and pillar valve compatibility failure

A member has reported a near miss incident in which there were failures of pillar valves.  The incident occurred during visual inspection of bailout cylinders, when it was identified that six out of the twelve pillar valves tested, with GO/NO-GO thread gauges, failed the GO thread gauge test. 

Of the six cylinders that passed the original test, four cylinders were rechecked at the next six-monthly planned maintenance check, and two of the pillar valves failed the GO gauge thread test.  A possible cause of the later failure may have been wear and tear, continual emptying and recharging to 200 bar (at 200 bar there is almost 1 tonne of force on the pillar valve).

Our member has introduced a quality check of cylinder threads and pillar valves whereby GO/NO-GO thread gauges are used before accepting any new stock.  When recently purchasing new cylinders and additional pillar valves the pre-acceptance tests were performed.  It was identified that there was a surprisingly high failure rate when testing the new pillar valves.  Of six pillar valves purchased, four failed the GO thread gauge test.  It is to be noted that similar failure rate has also been the case with subsequent purchases of pillar valves.

Attached are photographs of both the six pillar valves which failed during the original test and two other, order replacement pillar valves which also failed the test.  Also attached are photos of a new pillar valve with packaging and demonstration photos of successful & unsuccessful GO thread gauge tests.

All tests were conducted by a technician who is qualified as an “ASSET” Part 1 & Part 2 Cylinder Inspector using recently calibrated GO/NO-GO thread gauges.

Our member’s recommendations and lessons learnt were:

• It is recommended that organisations using Bailout Cylinders:
  • establish a planned maintenance system procedure whereby on all 6 monthly internal visual inspections the cylinder and pillar valves threads are checked using the GO/NO-GO thread gauges
  • ensure that cylinders and pillar valves are checked when purchased and before putting into service to ensure correct fitting using calibrated GO/NO-GO thread gauge and by a trained technician
  • implement a method of marking the pillar valves so that a register can be created to record or link a particular pillar valve to a particular cylinder by serial number.

Members may wish to refer to the following incidents:

• Pillar valve failure
• Injuries due to failure of diver’s emergency gas cylinder
• Injuries due to failure of divers emergency gas cylinder – use of incompatible threads