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Question
Posted : January 27, 2009
Dear Sir,
Could you help me with the specifications of the approved paint scheme for diving cylinders. Thank you

Cylinders of Divator (steel) and Oxygen bottles( Aluminium alloy)
Answer
Posted : January 27, 2009
Hi there,

I'm affraid that is a really interesting question with two answers...

[1] repair market

[2] manufacturing market

Lets deal with the issues that are common to both... the colour of the cylinder denotes its purpose. For scuba cylinders the legislation denotes under CE EN 1098-3 that nitrogen cylinders should be black necked and that oxygen should be white. For Air the standard is that these colours should be used on alternating quarters so you end up looking valve neck down with alternating black and white quarter segments that stop at the end of the neck curvature where the cylinder becomes a parallel 'tube'.

The body colour is highly confusing in terms of applicable standards and the diving industry has yet to rationalise the manufacture and colouration to a uniform agreement. Some companies use this as a marketing identifier, most go for an all white finish. Large storage and gas supply cylinders have different designations and should not be confused with these small end user storage cylinders.

The standards also confuse the other breathing gas mixtures such as Nitrox, Trimix, Heliox etc

Oxygen should be all white top and body.

Nitrox, trimix, heliox etc are confusingly generally market up according to CE EN 1098-3 with black and white quarters.

I would have rather the stupidity of the new valve thread M26 and the reasoning behind it had addressed the colouration of cylinders as this alone would have done more for safety world wide than any rather doubtful change of cylinder valve for those involving oxygen or oxygen enriched mixes etc

That aside the next common thing is the marking of the cylinder with the right label or sticker to denote the gas that will be in it - ask another Q and i'll give you all the standards on these.

The cylinder test stamps, serial and all other manufacturers markings must still be visable after painting otehrwise the cylinder can be refused to be filled - or your paint removed before it is filled or retested !

Now to answer the question... Most manufacturers specially treat the cylinder both with acid and hot oil to specially condition the cylinders through a number of processes to destress the metal from the drawing process. Next comes a primer usually Zinc Oxide and then a conformal dry power paint that is electrostatically applied and cool heat cured. Cool heat or Low temp to prevent the heat from changing the annealing done to the cylinder.

Be warned you may face criminal charges of manslaughter or murder if you get a cylinder dry powder coated in a normal high temp oven as it will explode when filled.

The repair market either uses the above low temp dry powder coating process at the really good end of the market, to using Hammerite and other primer based paints (zinc oxide based) and then radiator paint or cellulose based. be careful not to paint the threads nor cake the top valve neck face (i.e. the bit perpendicular to the thread).

If the cylinder is for surface use only then go with the cellulose paints on primer as these will give a good finish at reasonable cost....

Hope this helps,
cheers Andrew.
Answer provided by ADM Diving

Andrew Dawson-Maddocks
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