SCUBA SCHOOL LTD DIVE CENTRE 25119

CYLINDER MATERIALS

Diving cylinders are made from either or . Even though both types are metal the two cylinders are manufactured differently, look slightly different, have different working and behave very differently in the water.

Steel cylinders are made by and spinning the cylinder from heated steel to a thickness of 4-5mm. This manufacturing technique means that the cylinder is finished with a rounded bottom that will require a rubber boot in order to stand upright. The cylinders are typically galvanised before a protective paint finish is applied to the outside of the cylinder to help prevent rust forming and damaging the steel. Steel cylinders are negatively buoyant (more so when the cylinder is full) and are the typical dive cylinder to be found in the UK. Cylinders are available in a range of sizes include 3, 5, 7, 12 and 15 litres and 232 or 300 specifications

Aluminium cylinders are made using an and forming process that uses a ram to effectively the aluminium into a mold and create the internal space in one movement. This manufacturing technique gives the cylinder a flat bottom and negates the need for a separate rubber boot. Aluminium is a softer metal and requires a thicker wall of approximately 11mm to withstand the internal . Aluminium cylinders are typically bulkier than steel when comparing internal volumes and have a significant fluctuation of between slightly negatively buoyant when full to positively buoyant when empty. Aluminium cylinders are usually used for as stage or cylinders. Cylinders are available in a mixed range of sizes including 1.5, 3, 5.74, 7 and 11.1 litres with varying working pressures of between 200 and 232 bar.

CYLINDER MARKINGS he markings found on cylinders can vary depending on the region they were made and their layout can differ from manufacturer to manufacturer.

Below are two examples of cylinder markings you might find in the UK and the meaning of each marking

FABER STEEL CYLINDER

 M25 x 2 – This is the size of the thread in the cylinder neck and identifies the valve type required to fit correctly.  EN144 – The European Norm specification the cylinder neck and thread were manufactured to.  BS5045/7/CM/S – The BS5045/7 refers to the British Standard specification for seamless steel gas containers between 0.5 and 15 litres  Faber – The manufacturer of the cylinder  12/2074/039 – This is the unique serial number for the cylinder. If required the manufacturing history of this cylinder can be recalled.  CE 0038 – This is the conformity mark for products placed on the market in the European Economic Area (EEA). By using marking a cylinder with CE the manufacturer declares that the product conforms with the essential requirements of the applicable EC directives.  UT 4.8mm – The minimum wall thickness  WT 14.2KG – The empty weight of the cylinder only and will not include the weight of a valve or boot  V12.2L – Minimum water capacity in litres  PS 232 BAR AT 15cC – This represents the working pressure of the cylinder at 15°C and should not be exceeded.  PT348 BAR – The Test Pressure that the cylinder should be pressurised to during a test.  TS-50+ 60°C – This is the additional service pressure (50 Bar) at 60°C  2012/08 – This is the initial test date of the cylinder, in this case August 2012. LUXFER ALUMINIUM CYLINDER

 M25 x 2 – This is the size of the thread in the cylinder neck and identifies the valve type required to fit correctly.  UK – Country of manufacture  LUXFER – The manufacturer of the cylinder  P3173V/LUXUK 1234A – This details the cylinder type and unique serial number. This number could be used to recall the manufacturing history if the cylinder.  AA6061 T6 – This details the alloy used to construct the cylinder  11.6MM – The minimum wall thickness  9.8KG – The empty weight of the cylinder only and will not include the weight of a valve or boot  7L – Minimum water capacity in litres  PW232 BAR – This is the working pressure of the cylinder and should not be exceeded.  PT348 BAR – The Test Pressure that the cylinder should be pressurised to during a test.  PS287 BAR AT 60°C – This is the maximum service pressure and the operating at the cylinder design was approved to.  CE – This is the conformity mark for products placed on the market in the European Economic Area (EEA). By using marking a cylinder with CE the manufacturer declares that the product conforms with the essential requirements of the applicable EC directives.  2012/2 – This is the initial test date of the cylinder, in this case February 2012. CYLINDER VALVES

Cylinder valves are usually made from chrome plated brass and are available in two connection types, DIN and A-Clamp.

DIN VALVES

DIN valves (Deutsches Institut fur Normung which is a German manufacturing standard) are available for either 232 or 300 bar cylinders. The 232 bar connectors are shorter than the 300 bar version and will not seal in a 300 bar valve. 300 bar connectors will fit in either 232 or 300 bar cylinder valves. There are two distinct benefits to the DIN connection:

1. The o-ring is fitted to the regulator thread rather than the cylinder valve face. This means that when the first stage it fitted the o-ring is trapped inside the valve, preventing the o-ring from being forced out under pressure and it also protected. 2. The whole connection is much more compact and secure. A-CLAMP VALVES

A-Clamp valves are still widely used in the UK but as DIN valves become more popular sales of A-Clamp regulators have fallen. A-Clamp connectors have a maximum pressure of 232 bar and are typically only used in (ie non-technical).

Most modern 232 bar cylinder valves are now convertible between A-Clamp and DIN using an insert that is supplied with new cylinders. The insert is left in for A-Clamp regulators and removed to allow a Din regulator to screw into the cylinder valve.

INSPECTIONS nder the European EN standards a must be tested every two and a half years from the cylinders initial test date that is stamped on the cylinder by the manufacturer. The cylinder alternates between two types of test, a visual and a . The first test will be a visual test followed by a hydrostatic…visual…hydrostatic, etc throughout its entire life. A visual test is essentially that, a detailed visual inspection of the entire cylinder and includes the following checks:

 Bulges  Dents  Wear  General  Area corrosion  Isolated pitting  Thread damage  Weight check

A hydrostatic test is performed every five years and includes a visual inspection as well as a water pressurisation test. During the hydrostatic test the cylinder is filled with water and then placed inside a high pressure chamber that is also filled with water. The cylinder is then pressurised to its test pressure which is high enough to slightly the expand the cylinder. The expansion displaces the surrounding water which is channelled into a measurement tube. If the cylinder expansion is with acceptable limits it successfully passes the test.

Cylinders that do not pass either of these tests are generally destroyed to prevent continued unsafe use. Some test centres will return the cylinder if requested but the cylinder will be rendered unusable before the cylinder is collected.

DO I NEED A CYLINDER BOOT?

In the real world yes you need a cylinder boot. A cylinder boot gives your otherwise wobbly cylinder something to stand in and keep it upright. It also gives it a layer of protection against bumps and bangs. A worthwhile investment.

CYLINDER CARE

Handling – Keep your cylinder safe, the more hits they take the shorter their lifespan.

Keeping Moisture Out – Essentially if moisture gets in you are much more likely to get cylinder corrosion. The easiest way to avoid this is to keep your cylinder pressurised. Keeping some pressure in the cylinder will help to avoid this. When filling ensure that the has at least two moisture filters. This should keep moisture to a minimum.

Tests – Once every 2 and a half years you need to have your cylinder tested, first a visual inspection, then a full hydrostatic test. Alternating every 2 and a half years. When tested they will receive a stamp with the test date on it. Without this test your cylinder cannot be filled. If you feel that your cylinder is looking a little ropey then have it tested, a defective or damaged cylinder is an extremely dangerous thing.

Scuba School Ltd Dive Centre 25119

Tel: 07773-966-835 Email: [email protected]