6.2.5.3

metal cylinders, tubes, pressure drums and bundles of cylinders

at the test pressure, the stress in the metal at the most severely stressed point of the pressure

receptacle shall not exceed 77% of the guaranteed minimum yield stress (re).

"yield stress" means the stress at which a permanent elongation of 2 per thousand (i.e. 0.2%) or, for

austenitic steels, 1% of the gauge length on the test-piece, has been produced.

note: in the case of sheet-metal the axis of the tensile test-piece shall be at right angles to the

direction of rolling. the permanent elongation at fracture, shall be measured on a test-piece of

circular cross-section in which the gauge length "l" is equal to five times the diameter "d" (l = 5d); if

test pieces of rectangular cross-section are used, the gauge length "l" shall be calculated by the

formula:

where f0 indicates the initial cross-sectional area of the test-piece.

pressure receptacles and their closures shall be made of suitable materials which shall be resistant to

brittle fracture and to stress corrosion cracking between –20 °c and +50 °c.

welds shall be skilfully made and shall afford the fullest safety.