Draft of proposed new specification for British Standard cylinders (Direct and In-direct)

					Minimum nominal thickness of copper							Preferred height of connection above datum
					Grade 1		Grade 2		Grade 3			Preferred height of connections above datum
					Test pressure 3.65 bar		Test pressure 2.20 bar		Test pressure 1.45 bar
					Max working head 25m		Max working head 15m		Max working head 10m
					Concave bottom	Rest of shell	Concave bottom	Rest of shell	Concave bottom	Rest of shell		2nd return	Prim return	2nd feed	Prim flow	G2 1/4 Boss	Internal	External
	mm	mm	L	m sq	mm	mm	mm	mm	mm	mm	mm	mm	mm	mm	mm	mm
0	300	1600	96	0.42	1.6	1.2	1.6	0.9	1.6	0.7	28	1250	100	100	540	150	G1	G1B
1	350	900	72	0.32	1.6	1.2	1.6	0.9	1.6	0.7	28	700	100	100	400	150	G1	G1B
2	400	900	96	0.42	1.8	1.2	1.6	0.9	1.6	0.7	28	700	100	100	400	150	G1	G1B
3	400	1050	114	0.50	1.8	1.2	1.6	0.9	1.6	0.7	28	800	100	100	470	150	G1	G1B
4	450	675	84	0.37	2.0	1.6	1.6	1.0	1.6	0.7	28	450	100	100	300	150	G1	G1B
5	450	750	95	0.48	2.0	1.6	1.6	1.0	1.6	0.7	28	550	100	100	340	150	G1	G1B
6	450	825	106	0.53	2.0	1.6	1.6	1.0	1.6	0.7	28	625	100	100	370	150	G1	G1B
7	450	900	117	0.61	2.0	1.6	1.6	1.0	1.6	0.7	28	700	100	100	400	150	G1	G1B
8	450	1050	140	0.70	2.0	1.6	1.6	1.0	1.6	0.7	28	800	100	100	470	150	G1 1/4	G1B
9	450	1200	162	0.88	2.0	1.6	1.6	1.0	1.6	0.7	28	950	100	100	540	150	G1 1/4	G1B
9e	450	1500	206	0.90	2.0	1.6	1.6	1.0	1.6	0.7	28	1200	100	100	620	150	G1 1/4	G1B
10	500	1200	190	1.05	2.5	1.8	1.8	1.2	1.6	0.9	35	950	150	150	540	200	G1 1/2	G1 1/4 B
11	500	1500	245	0.87	2.5	1.8	1.8	1.2	1.6	0.9	35	1200	150	150	670	200	G1 1/2	G1 1/4 B
12	600	1200	280	1.32	2.8	2.0	2.5	1.4	2.0	1.2	42	950	150	150	540	200	G2	G1 1/2 B
13	600	1500	360	1.68	2.8	2.0	2.5	1.4	2.0	1.2	42	1200	150	150	670	200	G2	G1 1/2 B
14	600	1800	440	2.04	2.8	2.0	2.5	1.4	2.0	1.2	42	1350	150	150	800	200	G2	G1 1/2 B