Paragraph 3 Filling systems for fixed gas containers
A connection for filling a fixed gas container shall be on the outside of the vehicle.
There shall be fitted to a fixed gas container either—
a manually operated shut-off valve and an excess flow valve, or
a manually operated shut-off valve and a single check valve, or
a double-check valve,
and all parts of those valves in contact with gas shall be made entirely of suitable metal except that they may contain non-metal washers and seals provided that such washers and seals are supported and constrained by metal components.
Where a pipe is attached to a gas container for the purpose of filling the gas container there shall be fitted to the end of the pipe furthest from the gas container a check valve or a double-check valve.
There shall be fitted over a gas filling point on a vehicle a cap which shall—
prevent leakage of gas from the gas filling point,
be secured to the vehicle by a chain or some other suitable means,
be made of suitable material, and
be fastened to the gas filling point by either a screw thread or other suitable means.