The Simple Pressure Vessels (Safety) Regulations 2016

Steel vessels

5.  Non-alloy quality steels must meet the following requirements—

(a) they must be non-effervescent and supplied after normalisation treatment, or in an equivalent state;

(b) the content per product of carbon must be less than 0.25% and that of sulphur and phosphorous must each be less than 0.05%

(c) they must have the following mechanical properties per product—

(i) the maximum tensile strength _{Rm, max} must be less than 580 N/mm^2;

(ii) the elongation after fracture must be:

if test pieces are taken parallel to the direction of rolling:

thickness ≥ 3 mm:	A	≥ 22%,
thickness < 3 mm:	A 80 mm	≥ 17%,

or, if test pieces are taken perpendicular to the direction of rolling:

thickness ≥ 3 mm:	A	≥ 20%,
thickness < 3 mm:	A80 mm	≥15%,

(iii) the average bending rupture energy (KCV) for three longitudinal test pieces at minimum working temperature must not be less than 35 J/cm². Not more than one of the three figures may be less than 35 J/cm², with a minimum of 25 J/cm². In the case of steels intended to be used in the manufacture of vessels the minimum working temperature of which is lower than - 10°C and the wall thickness of which exceeds 5 mm, this property must be checked.