Dangerous Goods by Road
connections to pressure-relief devices shall be of sufficient size to enable the required discharge to
pass unrestricted to the safety device. no stop-valve shall be installed between the shell and the
pressure-relief devices except where 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 in use. 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 or pipes from the pressure-relief device outlets, when used, shall deliver
the relieved vapour or liquid to the atmosphere in conditions of minimum back-pressure on the
relieving devices.