Liquid Cryogenic Gas Tanks

Liquid nitrogen is used almost exclusively as a coolant in the lab. Liquid argon and oxygen are not used as coolants, but they may be used in the lab or in industry when large quantities of these gases are required. The liquid form of the gas occupies much less space than the equivalent quantity of compressed gas. In addition, less time is lost in changing the equivalent number of tanks that would otherwise be required. 

There are two major types of cryogenic tanks one used primarily for liquid dispensing (see Fig. 6.6 and Fig. 6.7) and another used primarily for gas dispensing (see Fig. 6.6 and Fig. 6.10). Both are similar in size, both have rings of sheet metal around their tops to protect their valves from impact, and both have float devices on the top that indicate approximate liquid volume. 

The Liquid Dispensing Tank. As opposed to high-pressure tanks filled with a highly compressed gas, cryogenic gas tanks hold the liquid form of a gas and are insulated to maintain the cryogenic temperatures necessary to maintain the gas in its liquid state. 

Tube to vent, pressure gauge, container bursting disk, and 

Although the liquid dispensing tank can provide gas, it is best suited for dispensing liquids. The tank develops a head pressure of 20 to 30 psig, which is sufficient to dispense the liquid gas (like a seltzer bottle) at a reasonable flow rate. If you remove the gas (as opposed to the liquid) at too fast a rate, the head pressure drops sufficiently that the amount of discharge equals the rate of gas creation, and the pressure drops to zero. 

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