US Ali Cylinders

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Aluminium cylinders (no, not aluminum) are rated in the UK by their volume - that is how big is the hole in the middle in litres and a maximum fill pressure. In the USA they are rated by how much total gas they hold with an accurate fill in cubic feet. This just does not translate by a simple formula.

What is worse is that there isn't an agreed equivalence as the fill pressure dances about. The table below is a cut and stick from two Luxfer tables so we get matching values in both sets of units. The first column is pretty much what they are called. There are also funny rules for overfilling but I'm not going down that path.

Also this is from the current Luxfer sales list so there will be other sizes out there.

Luxfer part number	Fill pressure in PSI	Fill pressure in Bar	'Capacity' in cu ft	'Capacity' in Litres	Weight in lbs	weight in kgs	Internal volume in cu in	Internal volume in litres
S006	3000	207	6.1	172.8	2.5	1.2	54	0.9
S13S	3000	207	13.2	373.8	6	2.7	116	1.9
S014	2015	139	13.7	388	4.9	2.2	172	2.8
S019	3000	207	19.9	563.6	8.2	3.7	175	2.9
S030	3000	207	30	849.6	11.6	5.3	263	4.3
S040	3000	207	40	1132.8	15.3	6.9	350	5.7
S050	3000	207	48.4	1370.7	21.2	9.6	424	6.9
S063	3000	207	63	1784.2	26.7	12.1	552	9
S072	3000	207	69.6	1971.1	28.5	12.9	610	10
S080	3000	207	77.4	2192	31.4	14.2	678	11.1
S80N	3300	228	77.4	2172	35.4	16.1	630	10.3
S100	3300	228	98.8	2798	41	18.6	804	13.2
S106W	4350	300	105.2	2976.4	33.8	15.3	678	11.1

Useful numbers for working out the weights of things:

Density of steel 7.85gm/cc (Kg/L) so steel loses 13% of its down thrust in water
Density of Aluminium 2.70gm/cc (Kg/L) so ali loses 37% of its down thrust in water

Weight of stage/pony reg set (Apex DS4/AX40/SPG/hoses) in air 1.44Kgs
Weight of above in the fresh water butt 0.88Kgs

Weight of a rather old cylinder pillar valve 0.61Kgs

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