ALERT! Old Aluminum Scuba Cylinders at Risk of Explosion

 In Education

Being an integral part of the Scuba system, cylinders that holds high pressure breathing air is an essential piece of diving equipment, and without one, going underwater would be synonymous to skin diving or snorkeling.

Scuba cylinders are made of steel, but the most common type available in today’s market are made from at least 12mm-thick aluminum. They are made to create a sturdy built that can withstand and hold pressure over 3,000 psi (306 bars). The sturdy and strong built of scuba cylinders has often led to misconceptions that they will last forever, if not, for a long long time. This is where the problem comes in as scuba cylinders have a shelf life and can only be determined through cylinder visual inspection and hydrotesting.

Reported Incidents of Old Scuba Cylinders Exploding

If you look at the web for this kind of incident, search results will tell you that there are several around the world ranging from a simple sudden rupture of the burst disc releasing intense air pressure to total explosion of a cylinder.

We rather choose not to discuss the details of the aftermath of these incidents as there are fatalities involved and with due respect to the bereaved families. On the other hand, what we would like to discuss is the cause of these explosions and how we can prevent such event to happen in the future.

SLC: A Common Exploding Factor

Photo courtesy from Scuba Engineer

Let us take the case of 2 incidents that happened in New South Wales in Australia (one happened in 2009 and another in 2016) where a scuba cylinder exploded during the filling process. According to a Government Report made by SafeWork NSW and Queensland’s Workplace Health and Safety Office, it initially ruled out that the tanks on those incidents that are being filled suffered from Sustained Load Cracking or SLC.

Frequent use and filling of scuba tanks stresses out the aluminum material as high pressure breathing air is pumped in during airfill and slowly drains out when use. It usually starts as a small internal damage and progresses overtime where most of the noted damage is located somewhere in the neck and shoulder part of the cylinder. Once the aluminum material can no longer hold the filled pressure, it will burst out releasing intense pressure where most of the notable damage can be seen in the central body of the cylinder.

Cylinders at Risk: Be Aware what Model, Material and Year of Manufacturing are Highly Susceptible to Explode

Further investigation reveals that there are certain types of scuba cylinders (according to model, material and year of manufacturing) that are considered to have a high possibility of exploding. As far as Australia is concerned, the Government was prompted to issue an ALERT NOTICE to warn the public and inform all businesses involved in filling scuba tanks and classified these problematic tanks as “AT RISK CYLINDERS“.

Hereunder is a list of AT RISK CYLINDERS.

  • All cylinders that are made from Aluminum Alloy 6351
  • All cylinders that are 15 years or older

Most common cylinders that are made from Aluminum Alloy 6351 are:

  1. Luxfer aluminum alloy cylinders manufactured between 1972 and 1988
  2. Luxfer aluminum alloy cylinder specification DOT SP6498
  3. Luxfer aluminum alloy cylinder specification DOT E6498, E7042, E8107, E8364 and E8422
  4. CIG (Australia) aluminum alloy manufactured in or before 1990

Note: For you to determine the manufacturing date and cylinder specification, please check the engraved/stamped date of the cylinder that is usually located on the neck or shoulder portion.

Photo courtesy from ScubaBoard

On top of this, Worksafe New Zealand has withdrawn all the design approvals for SCUBA and SCBA cylinders that are made from the above-mentioned Aluminum Alloy 6351 effective October 31, 2017. This has been promulgated under Regulation 79 of the Hazardous Substance (Compressed Gases) Regulation of 2004 and recorded on the Registers of Gas Cylinders that is further supported and backed up by the Cylinder Testing Laboratory Association and the New Zealand Underwater Association.

Visual Inspection and Hydrotesting

Before we proceed and for clarification purposes, it does not mean that your scuba cylinder is safe to fill or use if it is newly manufactured or not specified in the above-mentioned “at risk cylinders” and that a visual inspection and hydrotesting is not anymore necessary. IT IS STILL NECESSARY. IN FACT, IT IS REQUIRED BY LAW.

While we are all taught during our Open Water Certification course that a tank visual inspection is necessary once a year and a hydrotest every 5 years, Australian laws are more stringent when it comes to regulation and safety. Australian law under Australian Standards No. AS2030.5 of 2009 requires all scuba cylinders to be visually inspected and hydrotested once a year at a certified testing station.

Before we end this article, please reflect on the quote and picture below then ponder afterwards if we are right or wrong:


Photo courtesy from

And lastly, the consequence if you don’t follow this annual safety measure is the possibility of facing enforcement action which comes with stiff fines and pecuniary penalties.

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