Marking of pressure-relief devices

Pressure relief devices shall be clearly and permanently marked with the following:
(a) The manufacturer's name and relevant catalogue number;
(b) The set pressure and/or the set temperature;
(c) The date of the last test.
(d) The cross sectional flow areas of the spring loaded pressure-relief devices and frangible discs
in mm².

The rated flow capacity marked on spring loaded pressure relief devices for low pressure liquefied
gases shall be determined according to ISO 4126-1:2004 and ISO 4126-7:2004.

Connections to pressure-relief devices

Connections to pressure-relief devices shall be of sufficient size to enable the required discharge to
pass unrestricted to the pressure relief device. No stop-valve shall be installed between the element
and the pressure-relief devices, except when duplicate devices are provided for maintenance or other
reasons, and the stop-valves serving the devices actually in use are locked open, or the stop-valves are
interlocked so that at least one of the duplicate devices is always operable and capable of meeting the
requirements of There shall be no obstruction in an opening leading to or leaving from a vent
or pressure-relief device which might restrict or cut-off the flow from the element to that device. The
opening through all piping and fittings shall have at least the same flow area as the inlet of the
pressure relief device to which it is connected. The nominal size of the discharge piping shall be at
least as large as that of the pressure relief device outlet. Vents from the pressure-relief devices, when
used, shall deliver the relieved vapour or liquid to the atmosphere in conditions of minimum backpressure
on the relieving device.

Siting of pressure-relief devices

Each pressure relief device shall, under maximum filling conditions, be in communication with the
vapour space of the elements for the carriage of liquefied gases. The devices, when fitted, shall be so
arranged as to ensure that the escaping vapour is discharged upwards and unrestrictedly as to prevent
any impingement of escaping gas or liquid upon the MEGC, its elements or personnel. For flammable,
pyrophoric and oxidizing gases, the escaping gas shall be directed away from the element in such a
manner that it cannot impinge upon the other elements. Heat resistant protective devices which deflect
the flow of gas are permissible provided the required pressure relief device capacity is not reduced.

Arrangements shall be made to prevent access to the pressure-relief devices by unauthorized persons
and to protect the devices from damage caused by the MEGC overturning.

Gauging devices

When an MEGC is intended to be filled by mass, it shall be equipped with one or more gauging
devices. Level-gauges made of glass or other fragile material shall not be used.

MEGC supports, frameworks, lifting and tie-down attachments

MEGCs shall be designed and constructed with a support structure to provide a secure base during
carriage. The forces specified in and the safety factor specified in shall be
considered in this aspect of the design. Skids, frameworks, cradles or other similar structures are

The combined stresses caused by element mountings (e.g. cradles, frameworks, etc.) and MEGC
lifting and tie-down attachments shall not cause excessive stress in any element. Permanent lifting and
tie-down attachments shall be fitted to all MEGCs. In no case shall mountings or attachments be
welded onto the elements.

In the design of supports and frameworks, the effects of environmental corrosion shall be taken into

When MEGCs are not protected during carriage, according to, the elements and service
equipment shall be protected against damage resulting from lateral or longitudinal impact or
overturning. External fittings shall be protected so as to preclude the release of the elements' contents
upon impact or overturning of the MEGC on its fittings. Particular attention shall be paid to the
protection of the manifold. Examples of protection include:
(a) Protection against lateral impact which may consist of longitudinal bars;
(b) Protection against overturning which may consist of reinforcement rings or bars fixed across
the frame;
(c) Protection against rear impact which may consist of a bumper or frame;
(d) Protection of the elements and service equipment against damage from impact or overturning
by use of an ISO frame in accordance with the relevant provisions of ISO 1496-3:1995.
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