Insulation systems, used for the purpose of reducing the venting capacity, shall be approved by the
competent authority or its authorized body. In all cases, insulation systems approved for this purpose
(a) Remain effective at all temperatures up to 649 °C; and
(b) Be jacketed with a material having a melting point of 700 °C or greater.

Marking of pressure-relief devices

(d) The rated flow capacity of the device in standard cubic metres of air per second (m3/s); and
in mm².
When practicable, the following information shall also be shown:
(f) The manufacturer's name and relevant catalogue number of the device.


Connections to pressure-relief devices

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 a vent or
pressure-relief device which might restrict or cut-off the flow from the shell to that device. Vents from
the pressure-relief devices, when used, shall deliver the relieved vapour or liquid to the atmosphere in
conditions of minimum back-pressure on the relieving device.

Siting of pressure-relief devices

longitudinal and transverse centre of the shell as reasonably practicable. All pressure relief device
flammable non-refrigerated liquefied gases, the escaping vapour shall be directed away from the shell
in such a manner that it cannot impinge upon the shell. Protective devices which deflect the flow of
vapour are permissible provided the required 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 portable tank overturning.

Gauging devices

Unless a portable tank is intended to be filled by weight it shall be equipped with one or more gauging
devices. Glass level-gauges and gauges made of other fragile material, which are in direct
communication with the contents of the shell shall not be used.

Portable tank supports, frameworks, lifting and tie-down attachments

Portable tanks 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 portable tank mountings (e.g. cradles, frameworks, etc.) and portable
tank lifting and tie-down attachments shall not cause excessive stress in any portion of the shell.
Permanent lifting and tie-down attachments shall be fitted to all portable tanks. Preferably they shall
be fitted to the portable tank supports but may be secured to reinforcing plates located on the shell at
the points of support.

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