increase in cargo temperature due to higher ambient temperature or cargo
heating will result in cargo expansion and an increase in vapour pressure.
If the tank is overfilled, product could escape through the relief valve.
If the loading temperature is known and the highest temperature the cargo
will reach either naturally or by heating is also known, it is a simple
matter to calculate the maximum safe load necessary to avoid discharge
through the pressure relief valve.
To calculate the maximum safe load:
V = A x C
V = Volume of liquid to be loaded (gallons or litres)
C = Capacity of tank (gallons or litres)
A = Fill percentage required
E = Cubical expansion co-efficient of liquid
t = Rise in temperature of cargo during containment
This calculation neglects the volumetric expansion of the vessel due to the rise in temperature. For all normal purposes this calculation will be adequate. For certain dangerous liquids definitive filling limits are specified by regulation (refer to the IMDG code).