difference between a tank and vessel
A pressure vessel is a closed tank that is certified by the manufacturer (at the least) to hold up to a maximum pressure. the tank is container like pot etc with or without a lid where we can store any liquid and from that we can draw any quantity. But a pressure vessel is not like a tank.
The most basic difference between pressure vessels and storage tanks is the internal design pressure: 1  Pressure vessels above 15 psi. 2  Storage tanks below 15 psi.