Following on from recent controversy on tank failures we interview prominent members of the dive industry, and manufacturers, for their thoughts.



Are Aluminium Cylinders Safe?


Interview with Kim Comben, Occupational Safety and Health


By Dave Moran

Kim, is OSH (Occupational Safety & Health Service) aware of the concerns amongst scuba filling stations regarding certain cylinders?Kim, is OSH (Occupational Safety & Health Service) aware of the concerns amongst scuba filling stations regarding certain cylinders?


Yes, OSH is aware of concerns from gas cylinder testing stations and filling stations in relation to certain cylinders, specifically aluminium alloy dive cylinders. Sometimes problems can be limited to serial numbers or batches, but in respect of the current concerns, it’s in relation to a specific specification, which are DOT, SP and E 6498 cylinders. These are made from an aluminium alloy 6351 material, and the problem that has been exhibited is a tendency for cracks to develop in the neck area which may lead to rupture.


Has OSH made recommendations to filling and testing stations to prevent personal and material injuries?


No, but we have requested information from the testing stations on the numbers of cylinders that they are failing, so we can build up a database. We have also assisted the industry where requested in respect of determining faults in the cylinders insofar as actually giving explicit directives. Noted deficiencies in the testing procedure of cylinders have been raised with NZU (New Zealand Underwater) and the CTLA (Cylinder Testing Laboratory Association). One of those deficiencies is the tendency, in some instances, of testing stations not cleaning the threaded area of the cylinder prior to a visual examination, thus making it difficult to detect possible cracks.


Has OSH considered issuing a procedure standard for filling and testing tanks, as there seems to be a wide variation in the way people test tanks?


There is already a standard in place for the testing of cylinders. The NZU have their own code of practice for testing, and also IANZ (International Accreditation NZ, previously Telarc) accredited testing stations follow the guidelines for testing gas cylinders in accordance with (Australian Standard) AS2337 specification.


Does OSH have a procedure in place where they check on filling stations to ensure that they are using the correct methods to test cylinders?


At the moment, no. However, in respect of the current concern regarding aluminium alloy cylinders and what we are learning, I think it is something we must focus on in the future in terms of educating people filling cylinders, given that in many cases we will never see all the people that fill cylinders due to private compressors etc that are being used. But this point has been highlighted as a result of events in the last few months.


Has OSH considered issuing a standard or setting a standard for issuing licences to a person to be qualified to test and fill cylinders?


Currently testing stations are required to have an approved signatory that oversees the work of their station staff. We have noted that some test station staff are not at the desired skill level that we would deem appropriate for the task. There are new regulations in the pipeline in respect of gas cylinder testing stations, and one will probably be to ensure that the staff who actually carry out the test are fully trained and competent, rather than being watched over by somebody who is. In respect of the filling of gas cylinders, there are procedures on filling. We currently do not licence persons filling dive cylinders as we do for flammable gases, but we would expect those persons that are filling to be aware of procedures for filling and following the manufacturer’s recommendations, and in addition to that ensuring they are charging the cylinders in accordance with the requirements of the Dangerous Goods Class 2 Gases Regulation 1980. From time to time we act on complaints from customers, test stations or from the agencies that accredit the test stations, namely NZU or IANZ, to carry out the policeman-type function in investigations.


Can you comment on why there is a difference in the period of hydro testing? In New Zealand and Australia it’s every two years, while in the USA it’s every five years.


We actually follow the original Australian requirements for gas cylinder testing. When our regulations were written, steel dive cylinders were annually visualed and hydroed. Aluminium cylinders were visualed annually and hydroed every two years. As time went on we got requests from the industry in respect of steel cylinders, in that they would like a relaxation on the hydro test requirements. So we brought steel cylinders in line with aluminium cylinders. In recent times, as a result of issues surrounding cracks in cylinders, it’s my understanding that the Australians have now reverted back to an annual hydro and visual on all dive cylinders. In the USA the current requirement is five years. I believe that the DOT may be looking at extending it out to ten years; however, there is a strong industry-led campaign in the USA for dive cylinders to get looked at on an annual basis. But there’s no actual regulation insisting on an annual visual or hydro test in the States.


This seems a contradiction. Australia is looking at doing hydros every year, and the USA is going up to every ten years? That signals a very confused message!


I can’t understand why DOT is looking at possibly extending it from five to ten years. In terms of what’s happening in New Zealand, I remain comfortable with an annual visual, and a hydro every second year for both steel and aluminium cylinders.


There have been discussions as to whether these cylinder cracks are visible or not, in other words the crack is subsurface. Do you feel that the industry may need to look at more sophisticated testing gear like ultrasound, which would require a higher skill level?


From a regulator’s viewpoint, yes, we are looking at the installation of examination equipment that will be able to detect subsurface faults in cylinders. It may not necessarily mean that the actual person conducting the test has to be any better skilled than they currently are. In fact it could be quite the reverse, if a machine is used to find a fault and provide a readout. So maybe it would be a case of a person being skilled in operating the machine, rather than actually being skilled in finding faults. I have asked one of the manufacturers whether more sophisticated testing equipment is available for finding defects in cylinders. Naturally if one moves to more sophisticated equipment there is a greater capital outlay, which may ultimately lead to a rationalisation of testing stations in New Zealand.


Has OSH been in constant contact with the manufacturers of the faulty cylinders to make them fully aware of the concerns that OSH has regarding these cylinders?


We have been in contact. CIG as a manufacturer of cylindrs doesn’t exist anymore, but Luxfer bought the CIG plant, so whilst we speak to Luxfer, they tentatively represent the old CIG market. We’re speaking to Luxfer Australia and Luxfer USA. I’ve asked certain questions at the moment, and I’m looking at bringing the other manufacturers like Walter Kidde and Catalina into further discussions very shortly. I’ve suggested a number of agenda items for discussion, and Luxfer Australia. They are sending a copy of the agenda items to their sister company in the States. One of the individuals for Luxfer in the USA is the chairman of the ISO committee for the testing of gas cylinders, and I have included into the proposed agenda items like a finite life for cylinders.


I understand that on August 5-6 this year there’s going to be an industry meeting. Could you expand on that?


The industry meeting is the Cylinder Testing Laboratory’s Association annual general meeting, in which we have been invited to participate and contribute in respect of issues that have emerged in the last 12 months. It was my intention to invite Luxfer to speak at that meeting to give details of the findings from the Tairua accident, and the ongoing investigation into the cylinders. Unfortunately, Luxfer are unable to attend due to internal commitments on those dates, so it’s anticipated that later in the month there will be a number of industry workshops both for CTLA and NZU stations.


How seriously is OSH looking at recommending that scuba cylinders have o finite life of 20 years?


We are looking at possibly putting a finite life on dive cylinders. We had seen problems with the 6498. Some of the 3AL cylinders are now beginning to exhibit similar problems to the 6498, hence the reason why the department is now saying it may be more appropriate to put a finish date on the life of the cylinders. That’s one of the things we intend to discuss with the manufacturers. We are saying that when cylinders reach the 20 years of age mark, regardless of whether they have been in the rental market or recreational sector, they would be removed from service. The other thing that is beginning to emerge is that many new cylinder ( not dive cylinders) designs are in fact beginning to stipulate the cylinder is fit for service for a certain number of years, and after that it should be destroyed. New cylinders are entering the industrial scene that have a finite life of 20 years. I suspect it would only be a matter of time before such cylinders start to appear in the dive market.


Are testing stations procedures of a high standard?


It has come up, during the course of discussing faults of cylinders at cylinder testing stations, that the odd station has confessed that they weren’t perhaps as thorough as they could have been when examining cylinders. For example, they weren’t actually treating the threaded area with a cleaner prior to examination, and as a result there was a potential that they could have missed cracks. In addition to this, it’s also become apparent in respect of filling that some cylinders may have been overcharged above their working pressures. Again, this will contribute to the stresses placed on the container which can exacerbate the faults that are found therein. We see this as a matter of ongoing education for testing stations, that they must test and fill in accordance with prescribed procedures.

Has O

SH considered putting in place spot checks which will ensure that the test and filling procedures are up to standard?


We rely very much on the auditing functions carried out by International Accreditation New Zealand (IANZ) and the NZU. From time to time we do spot audits of testing stations to ensure that they are testing in accordance with prescribed standards or procedures. However, like most government departments these days, we are very resource-thin. It comes down to a matter of priorities in terms of what we’ve got the time to do, and what resources we have available. I think in respect of the filling of cylinders, it’s something we’ve got to look at more closely in the future. But again, whilst you can visit one day and check, what’s preventing someone overfilling the next day? It all comes down to education of the person on the job.

Yes, OSH is aware of concerns from gas cylinder testing stations and filling stations in relation to certain cylinders, specifically aluminium alloy dive cylinders. Sometimes problems can be limited to serial numbers or batches, but in respect of the current concerns, it’s in relation to a specific specification, which are DOT, SP and E 6498 cylinders. These are made from an aluminium alloy 6351 material, and the problem that has been exhibited is a tendency for cracks to develop in the neck area which may lead to rupture.


Has OSH made recommendations to filling and testing stations to prevent personal and material injuries?


No, but we have requested information from the testing stations on the numbers of cylinders that they are failing, so we can build up a database. We have also assisted the industry where requested in respect of determining faults in the cylinders insofar as actually giving explicit directives. Noted deficiencies in the testing procedure of cylinders have been raised with NZU (New Zealand Underwater) and the CTLA (Cylinder Testing Laboratory Association). One of those deficiencies is the tendency, in some instances, of testing stations not cleaning the threaded area of the cylinder prior to a visual examination, thus making it difficult to detect possible cracks.


Has OSH considered issuing a procedure standard for filling and testing tanks, as there seems to be a wide variation in the way people test tanks?


There is already a standard in place for the testing of cylinders. The NZU have their own code of practice for testing, and also IANZ (International Accreditation NZ, previously Telarc) accredited testing stations follow the guidelines for testing gas cylinders in accordance with (Australian Standard) AS2337 specification.


Does OSH have a procedure in place where they check on filling stations to ensure that they are using the correct methods to test cylinders?


At the moment, no. However, in respect of the current concern regarding aluminium alloy cylinders and what we are learning, I think it is something we must focus on in the future in terms of educating people filling cylinders, given that in many cases we will never see all the people that fill cylinders due to private compressors etc that are being used. But this point has been highlighted as a result of events in the last few months.


Has OSH considered issuing a standard or setting a standard for issuing licences to a person to be qualified to test and fill cylinders?


Currently testing stations are required to have an approved signatory that oversees the work of their station staff. We have noted that some test station staff are not at the desired skill level that we would deem appropriate for the task. There are new regulations in the pipeline in respect of gas cylinder testing stations, and one will probably be to ensure that the staff who actually carry out the test are fully trained and competent, rather than being watched over by somebody who is. In respect of the filling of gas cylinders, there are procedures on filling. We currently do not licence persons filling dive cylinders as we do for flammable gases, but we would expect those persons that are filling to be aware of procedures for filling and following the manufacturer’s recommendations, and in addition to that ensuring they are charging the cylinders in accordance with the requirements of the Dangerous Goods Class 2 Gases Regulation 1980. From time to time we act on complaints from customers, test stations or from the agencies that accredit the test stations, namely NZU or IANZ, to carry out the policeman-type function in investigations.


Can you comment on why there is a difference in the period of hydro testing? In New Zealand and Australia it’s every two years, while in the USA it’s every five years.


We actually follow the original Australian requirements for gas cylinder testing. When our regulations were written, steel dive cylinders were annually visualed and hydroed. Aluminium cylinders were visualed annually and hydroed every two years. As time went on we got requests from the industry in respect of steel cylinders, in that they would like a relaxation on the hydro test requirements. So we brought steel cylinders in line with aluminium cylinders. In recent times, as a result of issues surrounding cracks in cylinders, it’s my understanding that the Australians have now reverted back to an annual hydro and visual on all dive cylinders. In the USA the current requirement is five years. I believe that the DOT may be looking at extending it out to ten years; however, there is a strong industry-led campaign in the USA for dive cylinders to get looked at on an annual basis. But there’s no actual regulation insisting on an annual visual or hydro test in the States.


This seems a contradiction. Australia is looking at doing hydros every year, and the USA is going up to every ten years? That signals a very confused message!


I can’t understand why DOT is looking at possibly extending it from five to ten years. In terms of what’s happening in New Zealand, I remain comfortable with an annual visual, and a hydro every second year for both steel and aluminium cylinders.


There have been discussions as to whether these cylinder cracks are visible or not, in other words the crack is subsurface. Do you feel that the industry may need to look at more sophisticated testing gear like ultrasound, which would require a higher skill level?


From a regulator’s viewpoint, yes, we are looking at the installation of examination equipment that will be able to detect subsurface faults in cylinders. It may not necessarily mean that the actual person conducting the test has to be any better skilled than they currently are. In fact it could be quite the reverse, if a machine is used to find a fault and provide a readout. So maybe it would be a case of a person being skilled in operating the machine, rather than actually being skilled in finding faults. I have asked one of the manufacturers whether more sophisticated testing equipment is available for finding defects in cylinders. Naturally if one moves to more sophisticated equipment there is a greater capital outlay, which may ultimately lead to a rationalisation of testing stations in New Zealand.


Has OSH been in constant contact with the manufacturers of the faulty cylinders to make them fully aware of the concerns that OSH has regarding these cylinders?


We have been in contact. CIG as a manufacturer of cylindrs doesn’t exist anymore, but Luxfer bought the CIG plant, so whilst we speak to Luxfer, they tentatively represent the old CIG market. We’re speaking to Luxfer Australia and Luxfer USA. I’ve asked certain questions at the moment, and I’m looking at bringing the other manufacturers like Walter Kidde and Catalina into further discussions very shortly. I’ve suggested a number of agenda items for discussion, and Luxfer Australia. They are sending a copy of the agenda items to their sister company in the States. One of the individuals for Luxfer in the USA is the chairman of the ISO committee for the testing of gas cylinders, and I have included into the proposed agenda items like a finite life for cylinders.


I understand that on August 5-6 this year there’s going to be an industry meeting. Could you expand on that?


The industry meeting is the Cylinder Testing Laboratory’s Association annual general meeting, in which we have been invited to participate and contribute in respect of issues that have emerged in the last 12 months. It was my intention to invite Luxfer to speak at that meeting to give details of the findings from the Tairua accident, and the ongoing investigation into the cylinders. Unfortunately, Luxfer are unable to attend due to internal commitments on those dates, so it’s anticipated that later in the month there will be a number of industry workshops both for CTLA and NZU stations.


How seriously is OSH looking at recommending that scuba cylinders have o finite life of 20 years?


We are looking at possibly putting a finite life on dive cylinders. We had seen problems with the 6498. Some of the 3AL cylinders are now beginning to exhibit similar problems to the 6498, hence the reason why the department is now saying it may be more appropriate to put a finish date on the life of the cylinders. That’s one of the things we intend to discuss with the manufacturers. We are saying that when cylinders reach the 20 years of age mark, regardless of whether they have been in the rental market or recreational sector, they would be removed from service. The other thing that is beginning to emerge is that many new cylinder ( not dive cylinders) designs are in fact beginning to stipulate the cylinder is fit for service for a certain number of years, and after that it should be destroyed. New cylinders are entering the industrial scene that have a finite life of 20 years. I suspect it would only be a matter of time before such cylinders start to appear in the dive market.


Are testing stations procedures of a high standard?


It has come up, during the course of discussing faults of cylinders at cylinder testing stations, that the odd station has confessed that they weren’t perhaps as thorough as they could have been when examining cylinders. For example, they weren’t actually treating the threaded area with a cleaner prior to examination, and as a result there was a potential that they could have missed cracks. In addition to this, it’s also become apparent in respect of filling that some cylinders may have been overcharged above their working pressures. Again, this will contribute to the stresses placed on the container which can exacerbate the faults that are found therein. We see this as a matter of ongoing education for testing stations, that they must test and fill in accordance with prescribed procedures.


Has OSH considered putting in place spot checks which will ensure that the test and filling procedures are up to standard?


We rely very much on the auditing functions carried out by International Accreditation New Zealand (IANZ) and the NZU. From time to time we do spot audits of testing stations to ensure that they are testing in accordance with prescribed standards or procedures. However, like most government departments these days, we are very resource-thin. It comes down to a matter of priorities in terms of what we’ve got the time to do, and what resources we have available. I think in respect of the filling of cylinders, it’s something we’ve got to look at more closely in the future. But again, whilst you can visit one day and check, what’s preventing someone overfilling the next day? It all comes down to education of the person on the job.

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