The Road Vehicles (Authorisation of Special Types) (General) Order 2003

Pressure relief devices

6.—(1) Every gas container must be provided with a suitable pressure relief device that complies with sub-paragraphs (3) to (7).

(2) Where a pressure regulator is fitted to a gas container, any pressure relief device attached to it must comply with sub-paragraphs (3) to (7).

(3) Any pressure relief device must be such that—

(a) there is an adequate discharge rate to ensure the safety of the system;

(b) any cooling effect of the gas during discharge will not affect the discharge rate;

(c) its relieving characteristics will not be impaired on exposure to fire;

(d) operation of the device will not inhibit the discharge rate from the device;

(e) its outlet size is not less than the size of inlet or outlet pipework of the gas container;

(f) it cannot be installed in the reverse flow direction;

(g) it is so protected as to ensure that its operation is unaffected by the collection of moisture and other foreign matter;

(h) if the device is adjustable, unauthorised interference with its settings is prevented; and

(i) it is marked clearly with the set pressure or temperature and with the flow direction.

(4) Any pressure relief device must be placed so that—

(a) as far as is practicable, the device and its outlets are protected from damage and blockage in the event of an accident;

(b) its discharge rate is not inhibited if an associated gas container is located within an enclosure; and

(c) it is away from any source of heat which could impair the designed operation of the device.

(5) The discharge from a pressure relief device must terminate outside the vehicle and be directed or deflected away from any opening into the engine, driver, passenger or living compartment, vehicle boot, or any space which is not so ventilated as to prevent the accumulation of gas.

(6) The discharge from a pressure relief device must not terminate near any source of heat or other potential source of ignition.

(7) A pressure release device on any gas container or regulator located within the driver, passenger or living compartment, vehicle boot, or in any space which is not so ventilated as to prevent the accumulation of gas must have its discharge vented separately and directly to the outside of the vehicle.