Aluminium oxide blocks diver’s regulator

Date: 1/8/2001

A diver had to terminate his dive after experiencing difficulties breathing from his regulator. His scuba cylinder was found to have large quantities of what appears to be aluminium oxide powder, which had entered the regulator’s first stage, cutting down the air flow through the regulator.

The Department of Labour Occupational Safety and Health Service (OSH) has sent the cylinder to Luxfer USA for examination.

So what’s new about what is now being seen in some aluminium cylinders compared with what cylinder testing stations have seen on many occasions?

The concern is that it appears some cylinders are showing this condition sooner than what has normally been experienced during the life of a cylinder.

The cylinders that seem to be showing this condition are cylinders manufactured from 6061 alloy. This newer alloy was introduced to replace the 6351 alloy.

Moisture inside a cylinder is the main culprit that kicks off these oxidation/corrosion problems. If you add a little salt you’re accelerating the process.

Divers and filling stations are repeatedly advised about avoiding moisture entering a cylinder. You should never completely empty your scuba cylinder. This prevents the cylinders from taking on unwanted moisture if the valve is accidentally left open. When cylinders are filled it is very important that the valve is cracked open, allowing air to escape through the valve, removing any salt deposits or water that may be trapped in the valve. Filling stations must maintain their compressor filters in good order, thus ensuring that only dry air is filling the cylinders.

Fillers of cylinders, by law, can not fill a cylinder unless the cylinder has evidence of a visual inspection not more than a year old and a hydrostat test no more than two years old.

If you fill your own tanks from your own compressor or from your mate’s compressor, you are still required by law to have your tanks inspected and tested. The law places the responsibility of ensuring cylinders are in test on the filler.

As we go to press we have not been advised of the cause of what appears to be unacceptable oxidization within these cylinders. Scuba cylinder testing/filing stations have been alerted about these concerns and are to advise the scuba cylinder testing authorities, New Zealand Underwater and International Accreditation of New Zealand (IANZ) if they find a potential problem in a cylinder they are inspecting/testing.

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