What is a visual inspection and why
should I have one?
During a visual inspection a scuba
cylinder is inspected on the inside and outside to standards set
by the Compressed Gas Association (CGA) as well as standards set
by The Professional Cylinder Inspectors (PCI formally PSI). The
cylinders are inspected for bulges, dents, rust , other corrosion
and other forms of damage that can weaken the scuba cylinder and
make it unsafe to be used. The threads and neck of the cylinder
are also inspected for corrosion and cracks to insure that the cylinder
is safe to fill.
In addition aluminum cylinders made by Luxfer and Walter Kidde prior
to 1990 are required to have an additional test known as a Visual
Eddy test, these cylinders were made of a different grade of aluminum
that the newer cylinders and are susceptible to Sustained Load Cracks.
A scuba cylinder that has neck cracks may fail violently when being
filled and kill the fill station operator. A cylinder that has had
a Visual Eddy test done during it Hydrostatic test will have VE
stamped next to the hydrostatic test stamp.
Scuba cylinders are made out of either aluminum or steel, the valves
are made out of chrome plated brass. Whenever you have two dissimilar
metals in a saltwater environment electrolysis can occur and the
two metals will try and become chemically welded together. At that
point the valve will not come out when it needs to without damaging
the cylinder. For this reason it is a good idea to remove the valve
at least one a year and replace the o-rings and relubricate the
threads. The burst disk should be replaced at least every five years,
generally at the time of the Hydrostatic test.
Most dive operations will not
fill a scuba cylinder that does not have a current visual inspection.
Great, what else can go wrong
with my cylinder?
|SCUBA cylinders as
well as other cylinders (Oxygen, Fire Extinguishers and some SCBAs)
generally will last a life time as long as they are taken care of.
With the exception of the older 6351 aluminum cylinders which may
have a birth defect, most other cylinders do not die a natural death.....
they generally die from negligent homicide....they are murdered. As
long as a scuba cylinder is never emptied while diving water can not
enter the cylinder and cause corrosion, however many people do use
up all of their air, empty the cylinder and allow water into a cylinder.
Water can also be introduced to a cylinder by poor compressor maintaince.
This can cause steel cylinders to rust and die an early death. Water
in an Aluminum cylinder can cause pitting and other forms of corrosion
that eat away the threads, this also leads to an early death.
A cylinder that has rust or other corrosion in it may have to be "Tumbled"
or "Whipped". Tumbling a cylinder involves putting an abrasive
medium (such as ceramic chips) into the cylinder and having it rotate
for a number of hours to help remove the corrosion so that it can
be inspected properly. Whipping a cylinder while it sounds worse is
a less sever cleaning method and us used on cylinders that only minor
corrosion. A special abrasive nylon whip is attached to a drill and
the inside of the cylinder is cleaned of any minor corrosion.
Many people never or rarely rinse their scuba cylinders. This allows
saltwater to sit at the top of the cylinder between the valve and
cylinder and cause corrosion and cause the cylinder to die an early
Periodic valve maintaince is a must. The valve should be removed once
a year for scuba, the o-rings should be replaced and it it should
be relubricated and reinstalled, burst disks should be replaced at
the time of the Hydrostatic test. The valve seat will have to be replaced
occasionally to insure proper operation.
Proper cleaning and maintaince will help a cylinder last a long, long
My oldest scuba cylinder is a steel cylinder manufactured in 1953,
I have seen an oxygen cylinder that has markings that indicate that
it was manufactured in 1922.
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