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Air Fills
The new standards make
recommendations. This is important
because it is not in itself illegal
for a dive shop to fill a cylinder
which does not have, say, a contents
label conforming to EN 1089 Pt 2.
Air
cylinders that are not used 'at
work' and are currently in test
according to BS5430 do not have to
adopt labeling or painting. This
will be left to the discretion of
the owner but you are recommended to
follow the requirements of the
Carriage of Dangerous Goods
Regulations.
It is
ultimately up to the filler to
decide whether a cylinder is safe to
fill or not. If they are not
completely satisfied this is the
case they have every right to refuse
to fill the cylinder.
Hydraulic Testing
The hydraulic test period has now
been changed from 4 to 5 years. This
has been done mainly to bring it
into line with standards for testing
other industrial compressed gas
cylinders. Similarly visual
inspection periods have changed from
2 years to 2½ years after a
hydraulic test.
The
new standard doesn't extend the test
expiry for cylinders with a current
test-due date. In other words,
cylinders tested before the new
standards came into force, and with
either no test-due sticker (see
below) or a 2-year sticker, will
still need their next test at the
expiry date of the old 2-year
interval test/inspection.
Don't
forget that as before, the hydraulic
test period is not affected by the
date of the visual inspection. For
example, say you don't use your
cylinder for a year or so then have
it visually inspected 3½ years after
it's hydraulic test. The cylinder
will only then be in test for a
further 18 months. This is because
you will need another hydraulic test
five years after the last,
regardless of the visual inspection
date.
In
this test the cylinder is filled
with water and then placed inside a
water-filled, high-pressure chamber.
The water pressure inside the
cylinder is then increased to five
thirds of it's maximum working
pressure. This is sufficient to
cause the cylinder to expand
slightly. This expansion causes the
water outside the tank to be
displaced and this is channeled into
marked collection tubes that allow
it to be measured. If the tank's
expansion is within acceptable
limits (< 5%), it successfully
passes the test. If not, the tank
may not be refilled.
After
pressure testing, tanks that pass
are cleaned and dried, then stamped
with the current month and year and
the tester's initials.
Visual Inspection
(every 2.5 years)
Essentially this test is a detailed
visual inspection, both internal and
external with the following failure
criteria:
-
Bulge - all fail
-
Dent - fail if any greater than
2 mm
-
Wear - reduction of wall
thickness greater than 25%
-
General Corrosion - reduction of
wall thickness greater than 20%
OR where original surface is not
visible
-
Area Corrosion - (i.e., where
corrosion is limited to less
than 20% of surface) a reduction
of wall thickness greater than
25%
-
Isolated pitting - Reduction of
wall thickness greater than 40%
-
Thread damage - all physical
damage or imperfections (recutting
of threads can be achieved up to
a maximum tolerance )
-
Weight Check - Weight of
cylinder ( minus valve ) less
than 95% of the tare weight
stamped on the cylinder
Any
cylinder that has been subject to
impact damage should be pressure
tested before use. If in the opinion
of the inspector, any of the above
criteria are borderline, then
hydraulic testing may also be
required.
Test procedures
All testing is undertaken by
qualified and experienced
technicians. The procedure is as
follows:
-
Removal of the tank boot, bands
and valve.
-
The exterior of the tank is then
inspected for impact damage and
corrosion.
-
The interior of the cylinder is
examined using a special
endoscope.
-
Dental mirrors may enable the
inspector to examine the area
around the inside of the tank
neck.
-
The valve is checked for smooth
operation and its threads
lubricated to help prevent
galvanic action between the
dissimilar metals of the tank
and valve.
-
Valves may also require periodic
overhauls, just like scuba
regulators.
-
If
no corrosion or damage is
detected, the cylinder is
reassembled and filled.
-
A
sticker is then placed on the
tank which identifies the
facility providing the
inspection and the month and
year in which the inspection was
done.
-
If
damage or corrosion is detected,
the technician will decide upon
an appropriate course of action.
-
Minor scale or the presence of
contaminants on the inside of an
aluminium cylinder can usually
be removed by rinsing with
distilled water and drying with
warm air.
-
Minor oxidation on the inside of
a steel cylinder may be best
left untreated due to the fact
that the process of removing it
might actually weaken the
cylinder more than the oxidation
itself.
-
Extensive oxidation or deep
pitting is treated by degrees of
sand blasting.
Test Certificate
Centres and shops should now ensure
that the paper test certificates
issued with a tested cylinder bear
the name of the cylinder's owner,
not just whoever dropped it off for
testing.
More Stringent
Testing
The new standards are more stringent
and require that all but the very
lightest of corrosion needs to be
cleaned. This means that your
maintenance costs will go up
although they will be slightly less
frequent. In addition, the criteria
for failing cylinders are now much
more strict. The new standard
accepts less damage, set (the degree
to which the cylinder permanently
stretches during a hydraulic test)
and corrosion on a cylinder before
it's scrapped.
Enriched Oxygen
Cylinders
You will find that shops and filling
stations probably still demand that
inspections and cleaning for Nitrox
cylinders remain at 12month
intervals.
Mini Cylinders
Cylinders of 0.5 litres or less are
NOT covered by the new standards.
These will still be tested to the
old standards (BS 5430 part 6) with
the test intervals of 2 and 4 years.
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FAQ's
