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 when 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 the requirements of 6.7.4.7 are always fulfilled. 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. pipework to vent the vapour or liquid from the outlet of 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.