LATEST IMPORTANT SCUBA SAFETY NOTIFICATIONS

Latest 'HOT' Topics...

• International Product Recall Notifications

• Formal Requirement to Gauge 3/4 NPSM (Used in DOT-3AL3000 Cylinders et al)

• Luxfer Gas Cylinders continues to require the use of eddy-current testing devices

• Luxfer Policy statement concerning replacement of U.S. scuba cylinders made from 6351 aluminum alloy

• British HSE Cylinder Markings Notifications

Product Recall Data - Courtesy of  The Divers Alert Network

- ROMI Recalls Scuba Regulators Due to Drowning Hazard
   - Oceanic Announces Regulator First Stage Recall/Retrofit
   - Aqua Lung Issues Important Safety Notice
   - M&J Engineering Recalls Swivels for Scuba Diving Masks
   - Innovative Scuba Concepts Recalls Diving Regulator Components Due to Drowning Hazard
   - Apeks Issues Important Regulator Safety Notice
   - Kirby Morgan Issues Safety Notice
   - Pelagic Recalls Digital Dive Computers Due to Decompression Hazard
   - AERIS Announces Voluntary Recall of EPIC Wrist Watch Dive Computers
   - Oceanic Worldwide Recalls ATOM 2.0 Wrist Watch Dive Computers
   - Suunto Recalls D6 and D9 Dive Instruments
   - Scubapro® Recalls MK 20 Scuba Regulators for Service
   - Suunto Dive Computers Recalled Due to Decompression Hazard
     - Oceanic Recalls Digital Dive Computer Due To Decompression Hazard
   - Suunto D9 and D6 Diving Instruments Software Bug
   - Scubapro X650 Diving Regulators Recalled for Drowning Hazard
   - Kirby Morgan Systems Issues Urgent Safety Notice
   - Recall of Circle Seal Controls, Inc., One-Way Valve
   - CPSC, CSK Auto Announce Recall of Aqua Water Scooters
   - CPSC, Cressi-Sub Announce Recall of Scuba Buoyancy Compensators
   - CPSC, Head USA Inc. Announce Recall of Scuba Diving Computers
   - Ocean Management Systems Scuba Manifold Recall
   - Oceanic Reliant BC Inflator Mechanisms
   - Halcyon Stainless Steel Power Inflator Recall
   - Powerline Airway Ribbed Hose Replacement
   - ABS Octopus Exhaust Grid Replacement
   - Upgrade for Sea&Sea DX-3100 Aquapix Camera
   - Sherwood, Genesis BCDs Being Recalled
   - Classic Medical Has Recalled Oxygen
   - SunRay Mod Light Recall
   - Voluntary Recall: Smart PRO & Smart COM Dive Computers
   - Coppertone Kid's Insect Repellent Sunscreen Recalled
   - Zeagle Regulator High Pressure Seat Recall
   - UPDATE: Oceanic First Stage Regulators Voluntary Recall
   - PADI Issues Recall for Recreational Dive Planners
   - UWATEC AG 1995 Dive Computers Recalled
   - Oceanic USA Recalls CDX First Stage Regulators
   - Abysmal Diving Safety Notice on Cylinder Valves
   - Johnson Outdoors Recalls Dive Computer Consoles
   - Sherwood Scuba Recalls Maximus Regulators
   - Body Glove Wetsuits Recalls Flotation Devices
   - Quality Care Products Recalls Meclizine Tablets for Motion Sickness
   - FDA Recalling Compressed Oxygen Cylinders From Iowa Business
   - Custom Buoyancy Overpressure Valves on BC Systems

British HSE Cylinder Markings Notifications

• Labeling Notifcation Dec 2005

• Diving Cylinder Labels Clarification Dec 2005

February 4, 2004

Luxfer Gas Cylinders continues to require the use of eddy-current testing devices (such as Visual Plus and Visual Eddy) to detect sustained-load cracks (SLC) in Luxfer aluminum scuba cylinders manufactured from 6351 alloy. Luxfer also recommends the use of eddy-current testing on other types of Luxfer cylinders made from 6351 alloy. http://www.luxfercylinders.com

However, based upon extensive testing by both Luxfer and independent laboratories, Luxfer does not recommend using eddy-current devices to test cylinders manufactured from Luxfer’s proprietary 6061 alloy. The reasons are:

1. Cylinders made from Luxfer’s proprietary 6061 aluminum alloy are not susceptible to cracks, including SLC. This fact has been conclusively shown by the exemplary safety record of cylinders made from this alloy, which Luxfer introduced in 1988 when it discontinued use of 6351 alloy.
   
   

2. Eddy-current devices sometimes give “false positive” readings when used to test Luxfer’s 6061-alloy, and such readings can lead to erroneous cylinder condemnation. These erroneous readings fall into three main groups:
   
   

   1. When threads are cut in the necks of new 6061-alloy cylinders, superficial tooling marks (sometimes called “tooling stops”) sometimes occur at the points where the thread-cutting tool starts and stops. On occasion these harmless marks are mistaken for cracks during eddy-current inspections, especially by inexperienced or inadequately trained inspectors.
      
      

   2. As a normal result of the neck-forming process during manufacturing, a small number of 6061-alloy cylinders may exhibit extremely slight wall variations in the neck area. Consequently, when the neck is threaded, partial threads may occur in the lower cylinder neck. While these occasional partial threads are normal and not detrimental in any way to cylinder performance, they sometimes show up on eddy-current devices as signals that can be wrongly interpreted as cracks in the lower threads.
      
      

   3. The threads of Luxfer 6061 cylinders sometimes exhibit superficial, harmless micro structural features that cannot be seen with the naked eye or even with a magnifying mirror. However, these features sometimes appear as low-level signals on eddy-current readouts, and inexperienced or insufficiently trained eddy-current operators can erroneously interpret these normal surface variations as cracks.

None of these minor, normal manufacturing variations is a product defect, and none leads to crack formation.

Luxfer continues to recommend regular visual inspection for its 6061-alloy cylinders in accordance with its published inspection guidelines. New developments in eddy-current technology now under way may lead to devices that can successfully test Luxfer 6061-alloy cylinders without “false positive” readings. Luxfer will test such devices on a case-by-case basis and issue timely recommendations concerning their use.

Luxfer is sometimes called upon to give “second opinions” about Luxfer 6061-alloy cylinders that have been erroneously condemned by inspectors who use eddy-current devices despite Luxfer’s recommendation against this practice. While Luxfer is willing to inspect such cylinders, we will charge $50 for each inspection, and all shipping costs must be paid by the person requesting the inspection.

If you have questions about this Luxfer inspection policy, please contact Luxfer Customer Service toll-free at 800-764-0366.

February 4, 2004

Policy statement concerning replacement of U.S.
scuba cylinders made from 6351 aluminum alloy

In the United States throughout 2003, Luxfer Gas Cylinders conducted a trade-in program for older Luxfer scuba cylinders made from 6351 aluminum alloy from 1972 through June 1988. That trade-in program ended on December 31, 2003. In prior years, Luxfer conducted various other kinds of rebate and replacement programs. http://www.luxfercylinders.com/

All such replacement and trade-in programs have now ended, with one exception: Certain older Luxfer scuba cylinders sold by U.S. Divers were issued with a lifetime warranty. This lifetime warranty will continue to be honored for the life of each cylinder so warranted. However, since this warranty was non-transferable, it will be necessary for those wishing to make warranty claims to prove that they are original owners of any cylinders in question. There are several ways to prove original ownership, including warranty certificates, cash register receipts, and records maintained by merchants. Luxfer Customer Service will be glad to assist in establishing original ownership by those wishing to make legitimate warranty claims.

All other Luxfer scuba cylinders made from 6351 alloy are now out of warranty and no longer eligible for replacement, rebates or credits. To determine whether a cylinder is made from this alloy, consult the Luxfer website at www.luxfercylinders.com or call Luxfer Customer Service at 800-764-0366.

This policy statement is not a recommendation to discontinue use of older Luxfer scuba cylinders made from 6351 alloy, nor is it a product recall. As long as such cylinders are inspected in accordance with Luxfer requirements and can be requalified according to regulations established by the U.S. Department of Transportation, they can continue to be used indefinitely. For information about inspection requirements and other pertinent safety information, please visit the Luxfer website or call Luxfer Customer Service.

This policy statement supersedes all other policy statements and programs concerning Luxfer scuba cylinders. If you have questions about this Luxfer policy, please call Luxfer Customer Service toll-free at 800-764-0366.

July 15, 2002

Product Safety Notice:
Potential Scuba Valve Oxygen Incompatibility

Please note the following product safety notice issued by Abysmal Diving, a distributor of Luxfer scuba cylinders. Although the notice refers to Thermo scuba valves used with Luxfer cylinders, Luxfer Gas Cylinders wishes to emphasize that the notice is not a result of any action or omission on the part of Thermo Valve Corporation. http://www.luxfercylinders.com

July 15, 2002

TO: ABYSMAL DIVING CUSTOMERS:

Abysmal Diving Inc. of Lake Havasu City, Arizona has been notified that some scuba cylinder valves manufactured by Thermo Valve Corp. and sold by Abysmal Diving Inc. as prepared for oxygen/nitrox service between August 2000 and July 9, 2002, may not be compatible with 100% pure Oxygen (when introduced at 200 psi and above) or Oxygen Enriched Air Nitrox mixtures greater than 21% oxygen content.

If you currently introduce into your scuba cylinder 100% pure oxygen or oxygen enriched air gas mixtures with an oxygen content greater than 21% and you are using one of the valves listed below, you must immediately discontinue such practice due to a RISK OF SPONTANEOUS FIRE AND SERIOUS PERSONAL INJURY OR DEATH.

If you use your valves for AIR only then this Safety Notice does not apply to you.

Valves Subject to Safety Notice
Val-131 Thermo valve 3000 PSI: K 3/4 - 14 NGS thread
Val-132 Thermo valve 2400 PSI K 3/4 - 14 NGS thread
Val-133 Thermo valve 3300 PSI K 3/4 - 14 NGS thread
Val-300 Thermo valve 2400 PSI, 300bar DIN 3/4 - 14 NGS thread
Val-301 Thermo valve 3000 PSI, 300bar DIN 3/4 - 14 NGS thread
Val-302 Thermo valve 3300 PSI, 300bar DIN 3/4 - 14 NGS thread
Val-303 Thermo valve 3180 PSI, 300bar DIN 3/4 - 14 NGS thread
Val-157 Thermo 200 bar twin Isolation manifold DIN/INT 3/4 - 14 NGS thread
Val-357 Thermo 300 bar twin Isolation manifold DIN 3/4 - 14 NGS thread
Val-351 Thermo 200 bar DIN/INT right hand modular valve 3/4 - 14 NGS thread
Val-355 Thermo 200 bar H connector / Right hand
Val-352 Thermo 200 bar DIN/INT left hand modular valve 3/4 - 14 NGS thread
Val-356 Thermo 200 bar H connector/ Left hand
Val-358 Thermo manifold cross bar with shutoff isolation
Val-359 Thermo manifold cross bar without shutoff

*This Product Safety Notice is not a result of any action or omission on the part of Thermo Valve.

DANGER:
DO NOT USE THE ABOVE LISTED VALVES WITH 100% PURE OXYGEN OR OXYGEN ENRICHED AIR NITROX MIXTURES.

Abysmal Diving Inc. of Lake Havasu City, Arizona has been notified that some scuba cylinder valves manufactured by Thermo Valve Corp. and sold by Abysmal Diving Inc. as prepared for oxygen/nitrox service between August 2000 and July 9, 2002 may contain one or more soft good materials (O-ring, seat) that may not be compatible with 100% pure Oxygen (when introduced at 200psi and above) or Oxygen Enriched Air Nitrox mixtures greater than 21% oxygen content.

You must stop using the valve and manifold combinations listed above immediately if being used with 100% pure high pressure oxygen (200 psi or more) or oxygen enriched air mixtures greater than 21% oxygen content or if the valve or manifold is exposed to high pressure oxygen (200 psi or greater) during a partial pressure mixing process. You must immediately return the item (s) to Abysmal Diving Inc. where they will be serviced and returned to you at no charge.

If you now use or intend to use your valve and scuba tank for AIR use, only, and if you have no intention of introducing 100% pure Oxygen (when introduced at 200psi and above) or Oxygen Enriched Air Nitrox mixtures greater than 21% oxygen content through it, then this Product Safety Notice does not apply to you.

INSTRUCTIONS:

If your valves are subject to this Product Safety Notice, please e-mail, call or write Abysmal Diving Inc. immediately at:
2099 Acoma Boulevard West, Suite C, Lake Havasu City, Arizona, 86403 USA Phone: (928) 854-9470 Fax: (928) 854-9473,
and request an SMA # (Service Merchandise Authorization #). Then pack your valves in an appropriate container and return them to Abysmal Diving Inc. When your valves arrives they will undergo a complete teardown, inspection, cleaning and will be fitted with any required oxygen compatible materials and lubricants. Your serviced valves will then be shipped back to you free of charge.

As of July 20th, 2002 Abysmal Diving Inc. has received no reports of any valve failing or exhibiting any oxygen compatibility problems. However this Product Safety Notice has been issued and a free retrofit offer made, in an attempt to ensure our customers have all the components originally intended in these valves for oxygen/nitrox service. Abysmal Diving Inc. strives to produce the finest and safest diving equipment, and protect its customers from the unreasonable risk of injury.

Again, if you currently introduce 100% pure oxygen or oxygen enriched air gas mixtures with an oxygen content greater than 21% you must immediately discontinue use of the above listed valves until such time as they have been returned to Abysmal Diving Inc. for a complete inspection and any required retrofitting and preparation for oxygen service.
DO NOT CONTINUE TO USE THESE VALVES IN OXYGEN-RELATED SERVICE BECAUSE OF THE POSSIBILITY OF FIRE AND SERIOUS INJURY OR DEATH.

Any questions can be directed to Abysmal Diving Inc.

February 2000

CYLINDERS MANUFACTURED TO LASS 1 STANDARD

A recent query from an ASSET Member:

"Are cylinders bearing the letters LASS 1 on a brass neck ring suitable for diving?"

Answer:

Absolutely not!

The scope of the LASS 1 specification states that the standard is intended for containers to be used for breathing apparatus for rescue purposes (except underwater). Additionally these cylinders will have been fitted with a valve not intended for constant immersion in water. These are most commonly in use for firefighting BA and escape equipment.

In our opinion any person who knowingly sells such cylinders as suitable for diving would be in breach of the HEALTH & SAFETY AT WORK ACT and a person who knowingly fills such a cylinder for a diver would be in breach of Statutory Instrument S12092 1997.

January 2000

CYLINDER CRACKING - AN UPDATE

In a recent issue of DIVE readers were advised about concern regarding sustained stress cracking in older Aluminium cylinders.

Luxfer UK has recently confirmed their support for the "Global Replacement program" that has been in place in the USA since last year. Briefly, Luxfer cylinders must be inspected with equipment that can detect cracks not visible to the human eye at the time of inspection or testing. Cylinders 15 years or older must be inspected for cracks annually. Those in continues use should be checked every four months. These inspections are in addition to inspections and tests required by BS5430.

The test equipment known as Visual Plus requires specialist training in its use: The Association of Scuba Service Engineers and Technicians will be incorporating this training into its Cylinder Testers and organizing update seminars for IDEST Test Stations.

For further information contact ASSET 

For information about the Luxfer Global Inspection Policy, see www.luxfercylinders.com/

March 1998

Poor visual inspections are the problem not old scuba cylinders

"Nothing inherently wrong with 10, 20 or even 30 year old scuba cylinders," says industry expert, Bill High of Professional Scuba Inspectors, Inc.

RIVERSIDE, CA, MARCH 4, 1998 - In response to the flood of calls from concerned scuba tank owners following the rupture of another manufacturer's scuba cylinder in a South Florida dive store, Luxfer Gas Cylinders, the world's leading producer of scuba cylinders, issued the following statement today:

"Many owners of scuba tanks would like information regarding the safety of their scuba tanks. As the "Safety First" company, we want to assure all of you that all our high-pressure gas cylinders are safe for use whatever the date of manufacture. But if you are concerned, we strongly recommend you contact a dive store that has a professionally trained visual inspector and have your cylinder visually inspected. In the highly unlikely event there is any problem, even minor, with your cylinder, a competent visual inspection will find it. We recommend scuba technicians who have been certified by PSI, Inc. to carry out visual inspections.

We hope we have addressed your concerns. If you need additional information on tank care, please visit our website at www.luxfercylinders.com where you will find our new guide to cylinder maintenance, called AIRCARE, under the SCUBA Products Care & Maintenance section."

Bill High, founder and director of Professional Scuba Inspectors, Inc. and recognized as the leading industry expert on the visual inspection of scuba cylinders, commented today on the suggested guidelines for the inspection of scuba cylinders proposed by the Greater Fort Lauderdale Dive Association.

"The solutions proposed by the Greater Fort Lauderdale Dive Association do not actually address the problem," said Bill High. "The real problem is untrained visual inspectors who keep damaged cylinders in service. The solution is to require, as the U.S. law does (49CFR172.700), that everyone who handles a cylinder knows what he/she is doing.

"There is nothing inherently wrong with 10, 20 or even 30 year old cylinders," High added. "Certainly, some cylinders should be technically inspected more often than once a year. But, it is not old cylinders that is the problem, it's damaged ones. Florida has had more cylinder explosions than any other part of the world, both steel and aluminum. Why? Because many scuba technicians won't take training. There are also problems created by the warm environment and overfilling is a problem as well. Even the bath tubs used for that unnecessary water bath fill are a concern," High said.

High further suggested to members of the Greater Fort Lauderdale Dive Association that they participate in a PSI-led training session on professional visual inspections, which he offered to conduct personally, and assist in making a statewide set of fill station operator safety standards.

Luxfer Gas Cylinders manufactures more than 2.5 million high-pressure aluminum and composite gas cylinders annually for most major gas markets throughout the world. With plants in Australia and Europe, Luxfer has its U.S. corporate headquarters in Riverside, CA and manufacturing plants in Graham, NC and Riverside, CA.

Note to Editors: Bill High is available for interview. If you wish to speak to him you can contact him at 425/486-2252 or at www.psicylinders.com

October 28, 1999

Aluminium Tanks - What Every Diver Should Know
An interview with Bill High, President of PSI Inc.

by Dave Moran. Courtesy of www.luxfercylinders.com/

October 28, 1999

DM: How long has PSI been involved with cylinder testing and investigations?

BH: I formed PSI, Inc. (initially called Professional Scuba Inspectors) in 1982, following three years of research. I had completed four years as NAUI's president and was looking for another way to serve the diving community. Our first seminar was conducted in January 1983. We have trained over 10,000 inspectors for military, government, hydrostatic retesting, dive and fire industries in North America, and at numerous international locations. We have 65 instructors in ten countries conducting nearly 200 seminars each year.

What are the main reasons for an aluminium cylinder being condemned and withdrawn from service?

Aluminium cylinders have received a great deal of attention in the USA since an explosion in Riviera Beach, Florida in February 1998. This was widely discussed on the Internet. Before that event, the occasional explosion of either steel or aluminium cylinders was largely ignored by the dive industry. Internal and external corrosion are the main causes of steel cylinders failing inspection or test. Aluminium cylinders fail less often, but when they do the cause is either excessive corrosion, often in the thread area or beneath the boot, or from a crack discovered during a visual inspection.

What does your organization consider to be the main cause of these problems?

Corrosion damage is usually the fault of the cylinder owner or the fill station. Water, especially salt water, causes metal to corrode. Water lies in contact with the cylinder for days beneath a boot. If air fill stations have poorly maintained filters and water separators, water will be pumped into the cylinder during fills. Sustained load cracking is a defect that appears in some cylinders made from 6351 alloy. In the USA, this alloy was used by Luxfer Gas Cylinders from 1971 through to 1987. All Walter Kidde scuba cylinders were also made from 6351.

Is it hydro testing or visual testing that shows if there is a problem with a cylinder?

Hydro testing does not appear to be the best means to detect a sustained load crack in at-risk cylinders. Most cracks in cylinders are found by visual inspectors. Considering both steel and aluminium, over 90% of the cylinders failed by a hydro retester are failed by visual inspection prior to a pressure test.

Do you have an idea of the percentage of cylinders which fail out of those tested?

If you mean hydrostatic tested cylinders which failed that pressure test, then the number is very small, since most cylinders are failed based upon damage observed by visual inspection. The following example from one of our PSI affiliate instructors who is also a federally licensed hydrostatic retester may help. His retest business is primarily limited to scuba cylinders. He tests about 2000 scuba cylinders each year - these cylinders are visually inspected annually and hydro tested with visual inspection every five years. Of those 2000, he condemns nearly 12% prior to the actual pressure test, due to damage observed that exceeds the allowable limits. Of those that pass the pre-test visual examination and are then pressure tested, he condemns only one or two aluminium cylinders and about ten steel cylinders. This example is consistent with enquiries we have made of other hydrostatic retesters on other occasions.

What can divers do to ensure their aluminium cylinders are safe?

The final responsibility for cylinder safety lies with the cylinder owner. They must realize that an 80 cubic foot capacity cylinder contains more than one million foot/lbs of potential energy, very likely equal to a hand grenade. Divers should clean their cylinders, dry them and store them away from excessive heat, always with some internal pressure. They can demand that the fill station have properly functioning filter/separator systems, fill the cylinder slowly, and not overfill it. Cylinders should be inspected frequently, both internally and externally, by a technician who actually knows what to look for in the way of damage. In North America we found that, regardless of how many years of experience an inspector may have handling cylinders, without formal training they cannot properly assess damage.

Do you have any recommendations for filling/test stations to ensure the safety of their staff and customers ?

I have written several articles and produced a booklet that details safe practices for fill station operations. There are many things fill stations can do. Unfortunately, many dive stores in North America fail to appreciate the power of compressed air. Since most cylinder explosions occur during the filling process, there needs to be a separation of the operator and the cylinder. Separation can be accomplished by either distance or a barrier. Only cylinders that have been inspected by a trained visual inspector and are within the retest period should be accepted for filling.

What staff training procedures are recommended in the USA to ensure that people testing and filling cylinders are competent?

In Canada and the USA there are federal requirements and licensing for hydrostatic retesters. The test procedures are established by law, and enforcement is administered by the Department of Transportation (DOT) or Transport Canada (TC). By law, the retester must take training every three years and be examined by federal enforcement personnel every five years to retain their license. Unfortunately, enforcement is incomplete and there are many hydro retesters who are inadequately trained and certify improperly evaluated cylinders. The retester must conduct a visual inspection as part of the hydro retest, but many don't know what that entails. The North American dive industry has established its own standard of an annual or more frequent visual inspection. This standard is rather well enforced by dive stores and other air fill stations. There is no legal mandate that the inspectors be trained. However, untrained inspectors have no legal defense if a cylinder they inspected fails explosively. Most dive industry entities - including PADI, NAUI, Luxfer, Catalina, Compair/Mako, most dive stores and several court jurisdictions - accept the PSI training protocol as the industry standard.

What is the number one thing that divers do to affect the structural strength of their steel or aluminium cylinders?

Cylinder owners are probably most guilty of not regularly removing and cleaning the cylinder beneath the boot; and, for salt water divers, not washing and drying the valve/cylinder interface.

What are your recommendations to divers for maintaining their cylinders?

Cylinder owners should insist that a trained visual inspector inspect both the interior and exterior of the cylinder at least annually. In North America we have to recommend that a visual inspector look into the cylinder after the hydro retest to ensure no water or other foreign material has been left inside. Store the cylinder in a dry, cool location with some pressure. Secure the cylinder during transport. Don't drop the cylinder or allow it to bang against hard objects. If corrosion is noted, clean it away, assess the damage against allowable limits and protect the area from future deterioration.

Does storing a full cylinder for long periods - several weeks or months - have a detrimental effect on its structural strength?

There are several considerations when making this decision. In a clean dry cylinder, clean dry air will store quite nicely for long periods, certainly a year or more. Poorly filtered air containing various hydrocarbons or other contaminants could deteriorate in quality over weeks or months. The cylinder itself is designed for a sustained pressure load during its entire life. If moisture is left in the cylinder, then the increased oxygen in a full cylinder will contribute to more rapid corrosion that in turn could weaken the cylinder dramatically over a matter of months.

More importantly, internal corrosion activity will reduce the oxygen content of the air. In the USA we have two examples of oxygen depletion in steel cylinders (corrosion is more rapid in steel). Following three months of storage, a corroded cylinder contained only 15% oxygen, a near-deadly deficiency. Analysis of a dead diver's air supply in a heavily corroded steel cylinder revealed a deadly 6% oxygen content. The University of Rhode Island's study of cylinder internal corrosion reveals that under equal conditions of moisture in cylinders, aluminium cylinders fare much better, so air stored in aluminium cylinders may retain its quality longer.

There is one additional consideration for aluminium cylinders. Because of its low tolerance for heat, and where there is potential for the aluminium cylinder to be involved in a fire, there is merit in storing the cylinder either full or nearly empty (about 20 psig). A 3000 psig aluminium cylinder containing less than about 1500 psig is at risk of exploding in a fire. The metal will lose its strength before the heat causes a rise in internal pressure sufficient to activate the pressure relief device (burst disc).

Do you have any comment on the effect of hydro testing on the material of aluminium cylinders?

I am not an expert in metallurgy, so can say very little about material integrity. However, there are specialists who believe that the hydro test procedure may not adequately test aluminium cylinders. The manufacturers cycle many test cylinders to hydro test pressure thousands of times with no apparent damage. I have not heard any expert suggest that the hydro test causes damage to the cylinder.

In New Zealand and Australia, cylinders are currently tested every two years, and this may change to every year. In the USA, it is currently every five years and may change to every ten years! What are your thoughts on the wide difference in the period over which cylinders must be hydro-tested?

The hydro test alone is not a very good assessment of a cylinder's condition. Cylinders with obvious cracks and pinholes have passed hydro retest. US rules for retest were written more than 50 years ago, when cylinders were used very differently to how they are used by divers today. Experience in the USA shows that a five year interval seems to work for most gas industry cylinders. I can't speak about the logic used by the rule makers in New Zealand and Australia. Whether the retest is one year, two years, or five years is irrelevant for scuba cylinders unless a technical visual inspection is part of the test. Remember, 90% of the cylinders failed by a retester fail the visual inspection, not the pressure test.

In a test conducted by the University of Rhode Island in 1971, a steel cylinder with a small amount of salt water inside was damaged in 100 days to a point of imminent explosion. If I were only given a choice of my cylinder being either hydro retested by one of our less diligent retesters or by a PSI trained visual inspector, I would take a frequent visual inspection and skip the hydro test. There is a proposal before DOT to eliminate hydro retest and replace it with an ultrasound examination at ten year intervals. The vast majority of gas industry users oppose this dramatic change. Ultrasound cannot test for heat damage, the impact of continual over pressurization, or a number of other forms of damage. Because of the outcry from the dive industry and others, DOT has delayed its decision on this matter. Scuba cylinders cannot possibly remain in service for ten years without a formal examination. Should this rule pass, the frequency of cylinder explosions will increase rapidly.

Do you think aluminium cylinders should have a finite life, then be removed from service?

I have followed closely the issue of sustained load cracking of aluminium cylinders since 1985. As yet, I have not found a correlation between age and the formation of a crack. We do see more cracked cylinders now than we saw ten years ago. That probably means that we now have more people looking, and we have better tools such as the Visual Plus apparatus to conduct the assessment. Some of the cracked cylinders were made in the 1980s, while many thousands from the 1970s remain in service.

Since the cracks propagate slowly over several years, technical visual inspection of the suspect area at least annually should identify defective cylinders. Our records show less than ten aluminium scuba cylinders exploded in North America and several international locations, including Australia, that were most likely caused by sustained load cracking. Statistically, that is a very small number (several million were made), although tragic for those persons injured.

We know some of those cracks should have been found by the visual inspectors who last looked at the cylinder. Unfortunately they were not properly trained. PSI does not have information that would cause us to urge a condemnation of scuba cylinders over a certain age. We believe that no cylinder owner should imagine that his cylinder must last forever. It could last a lifetime, or as little as a few months. It all depends on its treatment while in service. Scuba cylinders are very well made and pass through a variety of rigorous tests both by the manufacturer and by third party examiners. Almost without exception, those that have exploded would have been removed from service by trained inspectors well before the failure, if the opportunity to inspect them had been there. This suggests that the opportunity for technical visual inspections should exist and be available to all cylinder owners. The cylinder owners then must be willing to have their cylinders condemned when damage beyond allowable limits is found.

Note to Editors: Bill High is available for interview. If you wish to speak to him you can contact him at 425/486-2252 or at www.psicylinders.com

July 2004

Known Scuba cylinders made of from 6351 aluminum alloy

February 4, 2004

• Policy statement concerning replacement of U.S. 'DOT'
  scuba cylinders made from 6351-T6 aluminum alloy

All DOT-3AL tanks manufactured under one of the following exemptions or special permits: 6498, 7042, 8107, 8364, 8422
All composite cylinders manufactured under one of the following exemptions: 7235, 8023, 8115
All Walter Kidde DOT-3AL scuba tanks.
All Cliff Impact DOT-3AL scuba tanks made before July 1990.
All Luxfer 80.8 cu. ft. scuba tanks (S80.8) made before May 1987.
All Luxfer 72 and 100 cu. ft. scuba tanks (S72, S100) made before August 1987.
All Luxfer 80 cu. ft. scuba tanks (S80) made before January 1988.
All Luxfer 50 and 92 cu. ft. scuba tanks (S50, S92) made before April 1988.
All Luxfer 30 and 63 cu. ft scuba tanks (S30, S63) made before May 1988.
All Luxfer 40 cu. ft. scuba tanks (S40) made before June 1988.
All other scuba tanks made in the US before February 1990 (except Catalina).
All scuba tanks not made in the US.
Unless proven otherwise, all scuba tanks in the above list should be assumed as being made using the 6351-T6 alloy.

Note that many other types of cylinders (SCBA, Medical, Industrial, CO2, etc.) were also made from the 6351-T6 alloy. However, for brevity, only SCUBA type cylinders are listed above. See the DOT Safety Alert Bulletin for information on those.

Also, it should be noted that Catalina cylinders were NEVER made from the 6351-T6 alloy. They were made using alloy 6061-T6, which as of yet, has not been known to fail explosively. All of the manufacturers in the above list, except Walter Kidde, switched to the 6061-T6 alloy on the dates shown.

The DOT has not as of yet issued a recall of these tanks - only a safety alert. Essentially, if you own or use a scuba tank in the above list , you should consider it as being a time bomb waiting to explode. You should consider the tank unsafe until you learn for certain that it is made from the new alloy.

(This article extract courtesy of http://www.scubabomb.freeservers.com/index.htm )