TANK BLANKETING VALVE OPERATION
Tank blanketing is the injection of a gas into the vapour space of a liquid storage tank.
When the tank pressure drops below a predetermined level, the tank blanketing valve opens and allows a flow of inert gas into the vapour space. The blanketing valve reseals when pressure in the tank has returned to an acceptable level.
This method can also be used as a primary vacuum relief for normal tank breathing as it is highly accurate and therefore avoids unwanted interaction with relief valves.
The blanket of gas above the stored liquid prevents atmospheric air entering the tank, this inert layer of gas, typically nitrogen, protects the product against contamination and also reduces tank corrosion.
Blanketing a tank reduces product combustibility by eliminating oxygen rich air within the confines as the blanketing gas contains no oxygen. This also alleviates the requirement for a flame arrester to be installed in a closed system.
Tank blanketing can be used in conjunction with pressure vacuum relief valves. Due to the breathing requirements of a tank, using a pipe away PV valve is a cost effective way to save wasting the nitrogen.