BS
EN 1968 and 1802
In
March 2002, European standards for cylinder testing were changed. The familiar
BS 5430 part 1 and part 3 were withdrawn and replaced by new standards.
EN 1089
In
addition, a new standard was introduced, EN 1089 Gas Cylinder Identification.
This sets new standards for stamp marking, precautionary labels and colour
coding.
Labelling
and Marking
The Carriage of Dangerous Goods Regulations (1996) requires that cylinders
are either correctly labelled with their contents OR that they are painted
in the approved scheme. For compressed air and Nitrox this means black and
white quarters on the shoulder.
Test Periods
The hydrostatic test period has been changed from 4 years to 5 years. This
is to bring it into line with standards for testing other compressed gas
cylinders.
The hydrostatic test period IS NOT affected by the date of the visual inspection.
For example you don't use you cylinder for a year then have it visually
inspected 4 years after its hydraulic test. The cylinder will only then
be in test for a further 1 year.
Stamps and Markings
The test or inspection date stamp punched into the cylinder will from now
on show the year followed by the month.
In addition to stamping the cylinder with the test date, it will also be
MANDATORY to mark the cylinder with punch out stickers to make it easy to
see when the cylinder is next due for test.
Contents Labels
According to the new standard EN 1089 part 2, Cylinders must now also have
stickers showing their intended contents, e.g. Breathing Air, Nitrox or
Trimix
Colour Coding
All new diving cylinders will have the black and white quadrants on the
shoulder. Many recreational divers will of course have older cylinders without
this and may run into problems getting them filled.
Officially, professional divers “at work” must use the new standard,
The HSE state that the dive shop is a professional and operating as a “diver
at work” and therefore it is the prerogative of the shop to insist
on the correct labelling of cylinders.
In the event of a diving accident the HSE can come back to the shop and
investigate the circumstances surrounding the filling of the cylinder.
Air
Fills
The new standards make recommendations. It is not in itself illegal for
a dive shop to fill a cylinder which does not have, say, a contents label.
However, if anything at all were to go wrong as a result of the cylinder
having not in fact been safe or the contents mis-identified, then they may
well be legally liable for failing in their “Duty of Care” to
ensure that only safe cylinders are filled.
This may make them liable for prosecution.
It is therefore up to the filler to decide whether a cylinder is safe to fill or not. If they are not COMPLETELY satisfied they have every right to refuse to fill the cylinder.
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 greater than 2mm
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 (re-cutting of threads
can be achieved up to maximum tolerance)
Weight Check - Weight of cylinder (minus valve+boot) 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 Hydrostatic testing may also be required.
Hydrostatic
Test
The cylinder is filled with water and then placed inside a water filled, high
pressure chamber. The water pressure inside the cylinder is the increased
to five thirds of its maximum working pressure. This is sufficient to cause
the cylinder to expand slightly. This expansion causes the water outside the
cylinder to be displaced and this is channelled into marked collection tubes
that allow it to be measured. If the cylinders expansion is within acceptable
limits (<5%), it passes the test.
Test Procedures
> Removal of the cylinder boot, bands and valve
> The exterior of the cylinder 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
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 less frequent. In addition the criteria for failing
cylinders are now much more strict. The new standard accepts less damage,
set and corrosion on a cylinder before it is scrapped.
Enriched
Oxygen Cylinders
These still require inspection and cleaning every 12 months.