Aluminimum in New Zealand Part 1 & 2


Scuba Diving on the Great Escape Southern California Live-Aboard Dive Boat

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Posted by ptf on October 23, 2001 at 07:11:38:

Some stuff that I pulled up for my local shop in aug99.
there are 3 editorials to look into and one comment by
Luxfer. I would suggest that you look at the Luxfer
via the link as they have a cool pic of a tank that
had a slight failure and tore off the leg of the filler!

It ain't just in Florida Ken!
patrick

http://www.divenewzealand.com/53tank1.html
http://www.divenewzealand.com/53tank2.html

http://www.divenewzealand.com/53tank1.html
Are Aluminium Cylinders Safe?
Interview with Guy Kidd, The Dive Centre, Auckland
By Dave Moran

Guy, how long have you been involved in the dive industry, and how long have you been
testing dive cylinders?
I’ve been earning my living through diving for close to 40 years now. We started testing cylinders right
from the word go, before there were any rules and regulations, just for our own peace of mind because
we were the fellows that had to fill them. When I was in the Navy we tested them at the light machine
shop. They had a pump that could hydraulically pump cylinders in those days. We ended up getting an
engineer by the name of Jack Hanson, who was entrepreneurial in the mid ‘60s – who built a hand pump
that we purchased which enabled us to pump tanks hydraulically. In those days they were steel tanks with
a working pressure of 2250psi. We would pump them to 1.5 times their working pressure, in other words
3375psi, and measure the stretch. We used to do that once every five years. Eventually this became the
recognised standard and the Department of Labour got in on the act and formalised it all. Since those
days we’ve more or less followed Australia, whatever has been good enough for the Aussies the NZ
Department of Labour just copycatted. That’s why we’ve ended up with a strong formula for testing
cylinders.

Has there been some concern in recent years about some of the problems you’ve seen in the
cylinders that you’re testing?
Very much so, to the point where I even faxed OSH (Occupational Safety and Health) safety inspectors
quite recently, asking for a meeting because I’m very, very seriously worried that somebody is going to
become a statistic. My reasons for this are that the cylinders in question, the Luxfer E6498, SP6498 and
DOT3AL all have the same metal, and we believe all had the same manufacturing process. Now, these
tanks are developing structural failures well inside the test regime that this country has put in place, ie
one year for visual and two years for hydro. We have now proven that these cylinders can be perfectly
acceptable to the trained eye during a visual, or the visual that goes with a hydro, and you must
remember that we are visualising before and after a hydro in case the test pressure is making the
cylinders crack. They are passing happily, and then inside three or four months they’re failing. We really,
really started getting pedantic with these tests after Brian Schmidt lost his leg in Tairua. If there was any
doubt whatsoever whether a cylinder was suspected to have a crack, other qualified staff would reinspect
it, acid etch the neck region again if necessary, and if there was still any doubt we would condemn the
cylinder. Then within three months we have had the same cylinder that has passed happily develop
horizontally opposed cracks to the point where they become porous and we know that if the pressure had
been kept pumped into them, they would have let go. They would have turned into a bomb. Now, that’s
happened twice in my own filling bay.

So these tanks are being filled and all of a sudden you’re hearing air escaping from the tanks.
Correct. Not only us, but we’re starting to get reports in from other people. For example one of the dive
operators in Rarotonga recently said that because he filled in air (he’s not wet filling), he heard this hiss
and bent over to try and find out where it was coming from, and ascertained that it had horizontally
opposed cracks in the neck of the cylinder, and he took off!

Now we wet fill, but when you start filling an aluminium tank it’s buoyant and it tends to float in the water.
The first time it happened here I was filling a tank, talking to the owner of the cylinder, it got up to about
2800psi or 180 bar and I heard this rapidly increasing hiss. So thinking it was the blow-off disk vibrating
loose or something, I just pushed the tank an extra inch under water to ascertain where the leak was
coming from, and it was coming from two horizontally opposed cracks either side of the valve. That was
at 2800psi. Now luckily our system has a rotational valve, one way to fill, the opposite to bleed off the air
in the filling hose. And of course if the tank valve is still open you bleed the air out of the cylinders, so I just
spun that valve, told the fellow he should do something about sex and transport in a big hurry, and cleared
the building. We stood outside and listened to it vent until it was empty.

Now OSH came, said ‘Oh my God,’ and took it away. Six weeks later the exact same thing occurred on
another cylinder that was only three months into its test period. So that’s two in my establishment. Same
series, they’ve all been E series and the SP and AL. Even though Luxfer tell us that it is a user problem,
in other words the cylinder is being damaged by the owner, that is an absolutely incorrect statement. The
reason for this is that divers aren’t stupid. They realise it’s a high pressure vessel, they do transport them
carefully, they do tie them into their boats, they don’t have them thrashing around, and the other thing is
we’re not talking about user damage. We are talking, in my opinion, about a stress crack which has been
in the metal from day one. When the neck area was formed, something, maybe the temperature that they
were heated to, because they’re cold drawn and then the top of the barrel is heated to form the neck
area, maybe that heat was incorrect. That meant that as it was formed the metal actually had cracks, and
those cracks in the centre of the metal have been travelling. Some of them travel inwards and some have
travelled outwards. When they travel both ways you get a porous area. This is one of the reasons why I fill
in water. It’s no safer, because the water will just transfer the pressure as quickly if not quicker than air. It
just means that as you get your head blown off you get wet as well!

The cracks have been there and they are growing. But everyone says, ‘Oh yeah, but they only grow very
very slowly.’ My experiences and my gut feeling is that they are growing much quicker than people
realise. They are minute one moment, and then they are catastrophic the next.

A lot of divers, after their tanks are filled, put them in their garage. These filled tanks could sit
for a couple of months before their next dive. Is this part of the problem?
No, I don’t think it is a problem. The safety factor of these pressure vessels is huge. The half life and the
number of cycles they’re supposed to be able to handle defies all reasoning that they should be kept
empty until immediately before they’re used. I believe it is nothing to do with the pressure they are
designed to handle. I believe it has everything to do with the manufacturing process being incorrect for
the type of alloy that was used in the forming of the neck. Now, we’re not getting cracks in the base. They
get tested to 1.67 times their working pressure, that’s over 5000 psi, and no, it’s not leaving them filled. It
is a manufacturing problem, I am convinced. Regardless of what the manufacturers say about washing
them down, drying them down, where you store them, that’s not the issue. The issue is they’re letting go,
they’re failing. If it is a diver-produced problem, how come we have never had a failing of the English
Luxfer, the HOAL2 cylinder? We just have not had one, in over 28 years of testing on these premises, we
haven’t had one HOAL2 fail. How come they are all this particular group of one company’s cylinder?

So what would you like to see happen in the industry to safeguard against the possibility of a
disaster, someone losing their life?
Well, if you buy a car for $30,000 you get three years’ guarantee. Anything that happens after that time,
you pay for, not the manufacturing company. Luxfer’s system at the moment is if it gets a crack they’ll
replace it, which I believe is magnificent. I believe that an owner of a cylinder who has had possibly 20
years or more use out of the cylinder is totally delighted at the public relations of Luxfer in giving him a
new cylinder once the crack has been found. If they had a blanket condemnation and just pulled the plug
on these cylinders, and that was it, ie these tanks would not be allowed to be presented for testing or
filling, they were all trashed, then the diver, being who he is, would possibly be offended. A few would be
philosophical, but the majority of them in my opinion would be offended. I would like to see some sort of a
business deal done by Luxfer where the divers present the suspect cylinders and are given some sort of
a reduction on the price of a new cylinder.

So you’d like to see these cylinders completely removed from the market.
Oh yes, they must be. They will be, the day after they kill somebody. I am sure of that. But I would prefer
that the plug gets pulled prior to that happening, rather than as an after effect of a fatality. They say they
will give you a new cylinder, but they might have to give it to your widow. This is why I went public with
OSH and I believe the plug should be pulled on them.

http://www.divenewzealand.com/53tank2.html
Are Aluminium Cylinders Safe?
Interview with Brian Horton and Ian
McIntyre, Air Technology, Auckland
By Dave Moran

How long have you both been involved in the dive industry filling and
testing cylinders?
We’ve been involved for over 20 years in making and selling hydrostat test
equipment, and we’ve had our own test station for ten years.

Have you seen major faults starting to appear in tanks recently that you
didn’t see 20 years ago?
We’ve seen an increasing number of cracks appearing in the necks of aluminium
cylinders. We still see some problems with rusting of steel cylinders.

When you pick up these cracks, is it during the normal two-yearly visual
test?
We mainly pick them up on the visual inspection prior to the hydrostat test, or the
alternate year for the visual inspection.

Some people are saying that during the period between hydro testings
they’re finding cracks are appearing. Have you had that problem?
Yes, it’s a fairly common problem. There is a difference between Australia and
New Zealand in the test procedure: in Australia it is mandatory to do a visual
inspection after the hydrostatic test, while in New Zealand it is not mandatory, and
very few stations do it. If the hydrostatic test causes a crack it won’t be picked up
until the next visual inspection one year later. It’s very rare to find a cylinder that’s
leaking through a crack in the neck between the test periods.

Can you tell us the difference between the normal filling rate and the
hydrostatic filling rate? What extra pressure does the hydrostatic test put
on the cylinder to show up any weakness?
The recommended fill rate put out by Luxfer is between two and four megapascals
per minute. The hydrostat fill rate is ten times that rate.

That’s quite a severe test on a cylinder.
It’s very severe.

In your operation it’s crucial that you look at the cylinder after you’ve done
the hydro.
Yes, and Luxfer have put this out in one of their bulletins which all test stations in
New Zealand received.

Is there any particular cylinder that seems to be having more problems
than other cylinders?/b>
In New Zealand there’s really only the one brand of cylinder which has more
problems, which is Luxfer. The majority of cracking is in the
American-manufactured 80 cubic foot aluminium cylinders, and the Australian CIG
manufactured cylinder. We’ve noted that the American cylinders manufactured up
to about 1988 seemed to be cracking: E6498, SP6498 or DOT3AL. It’s been
extremely rare to get one cracked that’s been manufactured after 1988. We
haven’t noticed anything in later cylinders, but you must remember that there are
very few of those cylinders imported into New Zealand.

In your opinion, has there been a change in the manufacture of the
cylinder, or do you feel that it has something to do with the composition of
the aluminium being used?
I couldn’t say. We know that Luxfer changed their manufacturing procedure, and
they’ve changed their aluminium alloys.

With the inspection around the neck, I know that some people say that
when the extrusion is rounded off at the neck of the cylinder you can see
some folds. Are those folds quite common?
It’s very rare to see those folds in the American manufactured cylinders. The
Australian CIG manufactured cylinders had a lot of folds in the early years, but
most of those have now been taken out of the system and all the new cylinders are
very smooth.

What do you feel is the cause of cracking? Is it diver abuse, or do you feel
that it’s inherent in the cylinders themselves?
I’d like to comment on the ‘Safety First’ bulletin put out by Luxfer in Australia, in
which they imply that it is up to the owner to look after the cylinder and this can
prevent problems. In our opinion it would be totally the manufacturer’s problem that
cylinders are cracking.

In the 40 years that you’ve been diving, Brian, have you had any of your
own cylinders fail?
I had quite a few HOAL2 English Luxfer cylinders and American Luxfer cylinders.
All the American Luxfer cylinders that I owned have failed, and the HOAL2
cylinders, which were manufactured in 1976, are still fine.

I understand that when cylinders are designed they have an unlimited life
as far as filling is concerned to meet safety standards, but the cylinders
don’t seem to be getting anywhere near the life expectancy stated in the
manufacturing specifications.
All these cylinders that crack or fail are not up to the manufacturer’s specification.
It’s as simple as that.

Do you feel that the testing procedures done by some facilities are not up
to scratch?
Yes, we do. We believe that you must have good cleaning facilities, a visual
inspection facility with a turntable that’s set at the correct height so that you can
turn the cylinder around smoothly. A lot of the cracks cannot be detected unless
you have a large oval mirror and a suitable magnification device. You can’t buy it
as stock, it has to be made up, or an existing one modified. I went to a large
station recently where they rolled the cylinder between two treads of a staircase to
do the visual inspection. You cannot possibly do a good job that way.

When a tank arrives at Air Technology, what’s the procedure?
Paperwork’s filled in, valves are removed and it’s inspected. If it’s dirty, and a lot
of them are, it has to be cleaned with an acid called Version. This dirtiness comes
from the fact that over a period of time a small amount of salt water will go down
the valve and get into the cylinder through bad filling procedures. This salt water
will corrode the threads, so you cannot see if the cylinder is cracked. We clean it
for 24 hours in Version, then water, then isopropyl alcohol, and then inspect it
again. We then hydrostat test it, re-inspect it and then dry it. The valve is torqued
back in the cylinder, not put in and tightened up with a very large spanner like so
many stations do. 1.5% of all the aluminium cylinders we inspect are cracked.
During the last recall, at the end of the ‘80s, there was a total of 3,618 tanks
inspected. 3,013 passed, which was a 17% failure rate. Failures varied from 45%
in some stations to 0% in others, so we know the 45% stations obviously were
seeing cracks that weren’t there, and those that had a really low percentage were
not picking the cracks up. They are extremely difficult to pick up.

Recently there has been publicity for electronic devices which can be
used to detect cracks. What’s your opinion of those?
It’s just another tool that can be useful, but if you’re going to have to clean the
threads to use the machine, then you may as well do a visual inspection.

With the risk of cylinders exploding during fills, have you taken any
precautions in-house to protect your staff and customers?
We’re fairly relaxed filling cylinders that we’ve tested, but we aren’t so happy filling
cylinders that other stations may have tested. We’ve put in a heavy duty water bath
and a reinforced concrete-filled block wall so that our staff are protected during the
filling procedure.

In the last 12 months how many cylinders have you filled, and how many
would you have condemned due to cracking?
We fill just under 12,000 cylinders a year. In the last 12 months we have
condemned about 22.

With these cylinders cracking, what would you like the industry and
manufacturers to put in place to help prevent a major accident?
One of the problems is that both Telarc and NZU stations are audited, but the
auditing really only tests the paperwork and the procedures. There’s no ongoing
education of station operators. If you wanted to open a testing station tomorrow,
you don’t have to have any qualifications to do that. You are required to have some
training, and there are some training procedures that have been set out by NZU;
however, the person teaching you doesn’t have to be trained. Any instructor can
teach you within several hours the theory behind testing tanks, and he gets that
knowledge out of a book.

So at the moment there’s no training programme that people can go along
to and have hands-on training?
Well, I can’t speak for the Telarc stations, but I know that the NZU auditor
considers that they are qualified to do the tank testing training. So NZU are
providing training. When we sell hydrostat test equipment we’ve always trained the
operator. We must have them for one day so that when they buy the equipment
we’re happy that they can use it.

Are divers have difficulty getting these suspect models tested and filled?
Yes. One of the big problems is when we test the cylinders and we’re happy that
they’ve got no cracks when they leave us. But if someone goes out of town for his
holidays, he can’t get the cylinder filled, because in some areas everyone says
they won’t fill those particular cylinders or test them. So the customer comes back
to Auckland and has a row with us because we’ve taken his money and done the
tests, but he still can’t get it filled anywhere except by some of the Auckland
stations. If there’s not going to be an overall policy, then in our opinion the
cylinders should be withdrawn from service. Who pays is entirely a commercial
decision, but as far as safety and the way the industry’s going, it will be far better if
the cylinders are pulled out of operation.

Do you feel that someone could end up getting killed?
Someone will get killed. I read somewhere that there have been five accidents in
Australia over the last few years, fortunately with no injuries. New Zealand has had
one in Wellington that blew a garage up, one in Maketu, one at Richmond Sports,
and one in Tairua. We’ve had four with one major injury, and three were in one
year.

From what I can see, there seems to be an upsurge in people using steel
cylinders again. Have you seen a similar problem with steel cylinders?
No. However, NZU have put out a code of practice that says you must crack the
valve prior to filling to displace any water that may be in the valve, and to check
that the air is not contaminated. This is still not being done, so we’re seeing a lot
of steel cylinders after one year of operation coming in with quite bad rusting. But
this is a procedural matter at the filling stations. If the cylinder is in a boat and salt
spray goes on the cylinder, you can get up to a teaspoon of salt water going into
the cylinder valve. So when the cylinder is filled the water gets pushed in. Even
though it is well known and a procedural matter, they still don’t do it. A lot of the
problems leveled back at the diver/owner are really the testing station’s and the
filling station’s fault.

What can divers do to maintain their tanks?
All you can do is wash it down after you’ve used it, make sure you don’t drop it or
bang the valve, and ensure that you do not breathe the tank completely empty.
There’s not much else you can do. New Zealand seems to have more problems
with the older Luxfer cylinders. Very few were imported into Australia, so the
problem is not so prominent there. America had a lot, but they only hydro every five
years. The difference in New Zealand is that we hydro every two years, and we
had a lot of these cylinders. This could be why we have so many cracked
cylinders.

So you’re suggesting that hydro testing every two years is detrimental to
the life of the tank?
It could be, but we haven’t got any data that says it is.

There have been suggestions that after ten years cylinders should be
condemned and the diver would have to purchase a new cylinder. What’s
your opinion of that idea?
I’m totally opposed to it. There’s many steel cylinders around that are over 40
years old and are still as good as gold, and there are thousands of HOAL2
UK-manufactured Luxfer cylinders that have never given any problems. In fact, we
have never heard of or seen a HOAL2 cylinder with a crack.

In other words, you would agree with the old saying ‘Buy an aluminium
cylinder and it should last your diving life.’
I would agree that it should last your diving life.




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