Bombs on the back deck

Shark Cage Diving

Shark Cage Diving

Shark Cage Diving

Shark Cage Diving

By Keith Cardwell

I’m no expert on bombs. The closest I’m aware of coming to one was about 30 years ago when we hauled up what looked like an unexploded aerial bomb on the back deck of the boat we’d chartered out to New Zealand’s Great Barrier Island. It was common knowledge then that unused Second World War bombs had been secured for private salvage use and the one we’d hauled up was one of a few we’d found and assumed to have been left behind as ‘surplus to requirements’ after blowing a wreck up.

Notice any similarities?

To start, we thought we were doing the right thing by removing them from where other divers could be harmed if they also came across them, started to fiddle and be dumber than we were. But it was mutually agreed within minutes (seconds?) of the first arrival on the back deck that we should leave them all where they were. We quickly sent it back from whence it came. After returning to Auckland we did what we should have done in the first place – advise the authorities and those trained to deal with this type of situation. And thus followed my first seaplane flight, courtesy of the Royal New Zealand Navy, but that’s another story!

When we had the bomb on our back deck I had similar feelings to those when I was staring at bubbles of air fizzing from the shoulder of a cylinder I’d started filling several years later. I think I was lucky with that one but it made me even more cautious when filling cylinders in the future. However, even when cautious, the smallest of accidents regarding compressed air can have devastating results. The picture below shows the results of one such accident that occurred to one of New Zealand’s most qualified and experienced diving personalities. And in the scale of things, this is trivial.

Much worse could occur if a more sudden release of air was experienced from full cylinder failure and it makes sense to me to be much more circumspect in the way we handle these otherwise hardy appearing items of our dive gear. In this regard, I’d like to quote the following paragraphs from a Safety Alert put out by Workplace Health and Safety Queensland, Australia. The full transcript can be obtained at

by clicking here

and I suggest that all divers get on-line and heed its warnings and safe operation recommendations.

Safety Alert

The purpose of this alert is to inform all businesses and people who fill aluminium alloy cylinders of the risks of death and injury from cylinder explosion.

A recent incident has occurred in NSW where a person filling an aluminium alloy cylinder suffered serious bodily injury, including amputation, after the SCUBA cylinder that he was filling exploded.

Exploded cylinder

Initial investigations by Workcover NSW have indicated that the cylinder was being filled correctly and that the cylinder had had visual, hydrostatic and appropriate non-destructive (eddy current) testing. The cylinder was manufactured in 1983/84.

The cylinder involved in the recent incident was an ‘at risk’ cylinder.

Workplace Health and Safety Queensland (WHSQ) advises a risk assessment should be undertaken prior to any decision to fill ‘at risk’ cylinders to eliminate or minimise the risk from explosion.


Ongoing catastrophic failures involving certain aluminium alloy cylinders worldwide has prompted Workplace Health and Safety Queensland (WHSQ) to alert persons associated with these cylinders of potential hazards involved in their use.

An alert was issued initially in 1993 and then in 1997 following explosive aluminium cylinder failures. These failures have continued to occur worldwide, sometimes with severe injuries and property damage resulting.

Luxfer, a major manufacturer, has recorded a further seven ruptures since 1997, two of which involved Australian made cylinders.

Research has revealed that problems exist with cylinders manufactured from certain compositions of aluminium alloy. These problems cause a small percentage of cylinders to be rejected during routine inspections.

Problem cylinders

SCUBA cylinders manufactured from aluminium alloy 6351 are presently the main basis for concern. WHSQ strongly advises that all SCUBA cylinders manufactured from this alloy, and other aluminium alloy cylinders 15 years or older, be non-destructively examined annually for cracks and flaws in the neck fold and thread areas by competent and suitably equipped persons.

At risk SCUBA cylinders manufactured from aluminium alloy 6351 include:

  • Luxfer aluminium alloy cylinders manufactured between 1972 and 1988 (check oldest hydrostatic test date stamped into cylinder)
  • Luxfer aluminium alloy cylinder specification DOT SP6498
  • Luxfer aluminium alloy cylinder specification DOT E6498, E7042, E8107, E8364, E8422
  • CIG (Australia) aluminium alloy manufactured in or before 1990 (check oldest hydrostatic test date stamped into cylinder)

Bombs waiting to go off. Maybe or maybe not. Are you willing to risk it?

I hope like the dive group staring at a bomb on our back deck from those many years ago – with the accompanying cold sweats and realisation of what horror could ensue, you will take a trip out to your garage, car boot, boat or wherever, have a quick look to see if you have what may be a bomb in waiting and get in touch with your closest cylinder testing station.

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