Service equipment


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
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.


Additional provisions relating to aluminium-alloy pressure receptacles for compressed gases, liquefied gases, dissolved gases and non pressurized gases subject to special requirements (gas samples) as well as articles containing gas under pressure other than aerosol dispensers and small receptacles containing gas (gas cartridges)

The materials of aluminium-alloy pressure receptacles which are to be accepted shall satisfy the
following requirements:





Tensile strength,

Rm, in MPa (= N/mm2)

49 to 186

196 to 372

196 to 372

343 to 490

Yield stress, Re, in MPa (= N/mm2) (permanent

set  = 0,2%)

10 to 167

59 to 314

137 to 334

206 to 412

Permanent elongation at fracture (l = 5d), in %

12 to 40

12 to 30

12 to 30

11 to 16

Bend test (diameter of former d = n  e, where e is the thickness of the test piece)

n = 5 (Rm  98)

n = 6 (Rm > 98)

n = 6 (Rm  325)

n = 7 (Rm > 325)

n = 6 (Rm  325)

n = 7 (Rm > 325)

n = 7 (Rm  392)

n = 8 (Rm > 392)

Aluminium Association Series Number a

1 000

5 000

6 000

2 000

a See "Aluminium Standards and Data", Fifth edition, January 1976, published by the Aluminium Association,
750 Third Avenue, New York.
The actual properties will depend on the composition of the alloy concerned and on the final treatment
of the pressure receptacle, but whatever alloy is used the thickness of the pressure receptacle shall be
calculated by one of the following formulae:

e = minimum thickness of pressure receptacle wall, in mm
PMPa = test pressure, in MPa
Pbar = test pressure, in bar
D = nominal external diameter of the pressure receptacle, in mm and
Re = guaranteed minimum proof stress with 0.2% proof stress, in MPa (= N/mm2)
In addition, the value of the minimum guaranteed proof stress (Re) introduced into the formula is in
no case to be greater than 0.85 times the guaranteed minimum tensile strength (Rm), whatever the
type of alloy used.
NOTE 1: The above characteristics are based on previous experience with the following
materials used for pressure receptacles:
Column A: Aluminium, unalloyed, 99.5% pure;
Column B: Alloys of aluminium and magnesium;
Column C: Alloys of aluminium, silicon and magnesium, such as ISO/R209-Al-Si-Mg
(Aluminium Association 6351);
Column D: Alloys of aluminium, copper and magnesium.
NOTE 2: The permanent elongation at fracture is measured by means of test-pieces 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 section are used the gauge length shall be calculated by the formula:
where Fo is the initial cross-section area of the test-piece.
NOTE 3: (a) The bend test (see diagram) shall be carried out on specimens obtained by
cutting into two equal parts of width 3e, but in no case less than 25 mm, an
annular section of a cylinder. The specimens shall not be machined elsewhere
than on the edges;
(b) The bend test shall be carried out between a mandrel of diameter (d) and two
circular supports separated by a distance of (d + 3e). During the test the inner
faces shall be separated by a distance not greater than the diameter of the
(c) The specimen shall not exhibit cracks when it has been bent inwards around the
mandrel until the inner faces are separated by a distance not greater than the
diameter of the mandrel;
(d) The ratio (n) between the diameter of the mandrel and the thickness of the
specimen shall conform to the values given in the table.

A lower minimum elongation value is acceptable on condition that an additional test approved by the
competent authority of the country in which the pressure receptacles are made proves that safety of
carriage is ensured to the same extent as in the case of pressure receptacles constructed to comply with
the characteristics given in the table in (see also EN 1975:1999 + A1:2003).

The wall thickness of the pressure receptacles at the thinnest point shall be the following:
- Where the diameter of the pressure receptacle is less than 50 mm: not less than 1.5 mm;
- Where the diameter of the pressure receptacle is from 50 to 150 mm: not less than 2 mm; and
- Where the diameter of the pressure receptacle is more than 150 mm: not less than 3 mm.

The ends of the pressure receptacles shall have a semicircular, elliptical or "basket-handle" section;
they shall afford the same degree of safety as the body of the pressure receptacle.

Pressure receptacles in composite materials

For composite cylinders, tubes, pressure drums and bundles of cylinders which make use of
composite materials, the construction shall be such that a minimum burst ratio (burst pressure divided
by test pressure) is:
- 1.67 for hoop wrapped pressure receptacles;
- 2.00 for fully wrapped pressure receptacles.

Closed cryogenic receptacles

The following requirements apply to the construction of closed cryogenic receptacles for refrigerated
liquefied gases:

If non-metallic materials are used, they shall resist brittle fracture at the lowest working temperature
of the pressure receptacle and its fittings.

The pressure relief devices shall be so constructed as to work perfectly even at their lowest working
temperature. Their reliability of functioning at that temperature shall be established and checked by
testing each device or a sample of devices of the same type of construction.

The vents and pressure relief devices of pressure receptacles shall be so designed as to prevent the
liquid from splashing out.

General requirements for aerosol dispensers, small receptacles containing gas (gas cartridges) and fuel cell cartridges containing liquefied flammable gas

Design and construction

Aerosol dispensers (UN No.1950 aerosols) containing only a gas or a mixture of gases, and small
receptacles containing gas (gas cartridges) (UN No. 2037), shall be made of metal. This requirement
shall not apply to aerosols and small receptacles containing gas (gas cartridges) with a maximum
capacity of 100 ml for UN No. 1011 butane. Other aerosol dispensers (UN No.1950 aerosols) shall be
made of metal, synthetic material or glass. Receptacles made of metal and having an outside diameter
of not less than 40 mm shall have a concave bottom.
Previous Matter Next Matter - Copyright all rights reserved. © 2015-2018