Pressure receptacles assembled in bundles shall be structurally supported and held together as a unit.
Pressure receptacles shall be secured in a manner that prevents movement in relation to the structural
assembly and movement that would result in the concentration of harmful local stresses. Manifold
assemblies (e.g. manifold, valves, and pressure gauges) shall be designed and constructed such that
they are protected from impact damage and forces normally encountered in carriage. Manifolds shall
have at least the same test pressure as the cylinders. For toxic liquefied gases, each pressure receptacle
shall have an isolation valve to ensure that each pressure receptacle can be filled separately and that
no interchange of pressure receptacle contents can occur during carriage.
NOTE: Toxic liquefied gases have the classification codes 2T, 2TF, 2TC, 2TO, 2TFC or 2TOC.

Contact between dissimilar metals which could result in damage by galvanic action shall be avoided.

Additional requirements for the construction of closed cryogenic receptacles for refrigerated liquefied
gases

The mechanical properties of the metal used shall be established for each pressure receptacle,
including the impact strength and the bending coefficient.
 
NOTE: With regard to the impact strength, sub-section 6.8.5.3 gives details of test requirements
which may be used.

The pressure receptacles shall be thermally insulated. The thermal insulation shall be protected against
impact by means of a jacket. If the space between the pressure receptacle and the jacket is evacuated
of air (vacuum-insulation), the jacket shall be designed to withstand without permanent deformation
an external pressure of at least 100 kPa (1 bar) calculated in accordance with a recognised technical
code or a calculated critical collapsing pressure of not less than 200 kPa (2 bar) gauge pressure. If the
jacket is so closed as to be gas-tight (e.g. in the case of vacuum-insulation), a device shall be provided
to prevent any dangerous pressure from developing in the insulating layer in the event of inadequate
gas-tightness of the pressure receptacle or its fittings. The device shall prevent moisture from
penetrating into the insulation.
 

Closed cryogenic receptacles intended for the carriage of refrigerated liquefied gases having a boiling
point below –182 °C at atmospheric pressure shall not include materials which may react with oxygen
or oxygen enriched atmospheres in a dangerous manner, when located in parts of the thermal
insulation where there is a risk of contact with oxygen or with oxygen enriched liquid.

Closed cryogenic receptacles shall be designed and constructed with suitable lifting and securing
arrangements.

Additional requirements for the construction of pressure receptacles for acetylene

Pressure receptacles for UN 1001 acetylene, dissolved, and UN 3374 acetylene, solvent free, shall 
be filled with a porous material, uniformly distributed, of a type that conforms to the 
requirements and testing specified by a standard or technical code recognised by the competent 
authority and which:
 
(a) Is compatible with the pressure receptacle  and  does  not  form  harmful  or  dangerous  
compounds either with the acetylene or with the solvent in the case of UN 1001; and
 
(b)         Is capable of preventing the spread of decomposition of the acetylene in the porous 
material.
In the case of UN 1001, the solvent shall be compatible with the pressure receptacle.
 

Materials

Construction materials of pressure receptacles and their closures which are in direct contact with
dangerous goods shall not be affected or weakened by the dangerous goods intended to be carried and
shall not cause a dangerous effect e.g. catalysing a reaction or reacting with the dangerous goods.

Pressure receptacles and their closures shall be made of the materials specified in the design and
construction technical standards and the applicable packing instruction for the substances intended for
carriage in the pressure receptacle. The materials shall be resistant to brittle fracture and to stress
corrosion cracking as indicated in the design and construction technical standards.

Service equipment

Valves, piping and other fittings subjected to pressure, excluding pressure relief devices, shall be
designed and constructed so that the burst pressure is at least 1.5 times the test pressure of the pressure
receptacle.

Service equipment shall be configured or designed to prevent damage that could result in the release
of the pressure receptacle contents during normal conditions of handling and carriage. Manifold
piping leading to shut-off valves shall be sufficiently flexible to protect the valves and the piping from
shearing or releasing the pressure receptacle contents. The filling and discharge valves and any
protective caps shall be capable of being secured against unintended opening. Valves shall be
protected as specified in 4.1.6.8.

Pressure receptacles which are not capable of being handled manually or rolled, shall be fitted with
devices (skids, rings, straps) ensuring that they can be safely handled by mechanical means and so
arranged as not to impair the strength of, nor cause undue stresses in, the pressure receptacle.
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