To limit the probability that the valve will not operate properly when subjected to a vehicle or physical impact, which could lead to failure of the valve or associated piping, which could lead to the escape of liquid, which could lead to the ignition of vapour from a nearby ignition source, which could lead to harm to persons.
To limit the probability that the valve will not operate properly when subjected to a fire exposure, which could lead to failure of the valve or associated piping, which could lead to the escape of liquid, which could lead to the ignition of vapour from a nearby ignition source, which could lead to harm to persons.