Paragraph 8 Valves and cocks
A valve or cock shall be fitted to a supply pipeline as near as practicable to a fixed gas container and such valve or cock shall by manual operation enable the supply of gas from the gas container to the gas system to be stopped, and subject to sub-paragraph (2), shall—
if fitted on the outside of the vehicle, be readily visible and accessible from the outside of the vehicle, or
if fitted inside the vehicle be readily accessible for operation and be so arranged as to prevent so far as is practicable the possibility of gas entering the engine, passenger or living compartments due to leaks, and the space containing the valve or cock shall be so ventilated and drained as to prevent the accumulation of gas in that space.
Where a fixed gas container supplies no gas system other than a gas propulsion system and the gas container is so located that it is not practicable to make the valve or cock referred to in sub-paragraph (1) readily accessible there shall be fitted an electrically-operated valve which shall either be incorporated in the valve or cock referred to in sub-paragraph (1) or be fitted immediately downstream from it and shall—
be constructed so as to open when the electric power is applied and to close when the electric power is cut off,
be so fitted as to shut off the supply of gas from the gas container to the gas system when the engine is not running, and
if fitted inside the vehicle be so arranged as to prevent as far as is practicable the possibility of gas entering the engine, passenger or living compartments due to leaks, and the space containing the valve shall be so ventilated and drained as to prevent the accumulation of gas in that space.
A notice clearly indicating the position, purpose and method of operating a valve or cock referred to in sub-paragraphs (1) and (2) shall be fixed—
in a conspicuous position on the outside of the vehicle, and
where the valve or cock is located inside the vehicle in a conspicuous position adjacent to the gas container.
In the case of a high pressure pipeline for the conveyance of gas from the gas container an excess flow valve shall be fitted as near as practicable to the gas container and such valve shall operate in the event of a fracture of the pipeline or other similar failure.
All parts of every valve or cock referred to in this sub-paragraph which are in contact with gas shall be made of suitable metal, save that they may contain non-metal washers and seals if such washers and seals are supported and constrained by metal components.