MIL-HDBK-1027/1B
tank(s) in case of a pullaway or break of the unloading hose or
other equipment. Refer to NFPA 58. The emergency shutoff valve
should be installed in the fixed piping between the tank and a
substantial bulkhead with hose or swivel-type piping connections
on the opposite side of the bulkhead from the emergency shutoff
valve.
n) The bulkhead should be substantial and should be
of concrete. The piping should be fully anchored to the
bulkhead not just by inserting the pipe through a sleeve.
o) Provide emergency shutoff with three modes of
operation: manually; remote control; and thermally. A
preferable installation can be made which provides both thermal
and remote control. The installation entails the running of
plastic tubing to strategic points in or near the storage and
etc., so that the pressure holds the valve open. Then if there
is a fire, the plastic will melt, thus, enabling the valve to be
closed. Install the plastic tubing so that it will be activated
at all potential points of a flame. Install the tubing at a
point where the emergency valve will be activated if there is a
flame downstream beyond the bulkhead. For remote control, there
may be a snap action release valve at several strategic
locations in the tubing so that activation of valves releases
the pressure and closes the emergency shutoff valve. The
plastic tubing must be tied to the unloading hose so that a
pullaway of the hose will break the tubing. In this way, a
pullaway of the hose will activate the emergency shutoff valve
and close the discharge from the tank storage. The excess flow
valves in the transport piping should stop the flow from its
tank. If it is a pullaway break, the transport tank valves
should always have been closed before moving the vehicle.
p) After unloading the liquid from either a transport
truck or a tank car, bleed the liquid propane from the
connection after shutting off the valve at both the hose end and
at the unloading piping. Many accidents have occurred because
such bleeding has not been done. There should be a bleed
attachment built into the unloading equipment for this purpose.
If the attachment is not provided then bleeding can be done by
only partially disconnecting the hose, thus, creating some
additional hazards.
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