Cryogenic gas, as used in this handbook, is defined as any gas in a liquid state at
or below 20F. This chapter describes the bulk storage of cryogenic liquids used
for laboratory and light industrial purposes and the piping of cryogenic liquids from
storage tanks. There are two applications of cryogenic storage. The first is for a
facility that uses a large volume of gas and needs storage on site for practical and
economical reasons. The second is for cold liquids required for research, cooling,
and other purposes.
Cryogenic storage systems for gases in health care facilities and distribution of
gases created from cryogenic storage are discussed in Chap. 14, Compressed Gas
The major components of a cryogenic storage system include the bulk storage tank
containing gas in liquid form, a vaporizer (if a gas is desired), and the piping
network conveying either gas or liquid to the point of use. The vaporizer is directly
connected to the storage tank and is used to convert the liquid gas into its gaseous
state (see Fig. 8.1).
CODES AND STANDARDS
The following are codes used for the design and fabrication of cryogenic systems:
1. Underwriters Laboratories, UL-644
2. ASME Code for Unfired Pressure Vessels
3. NFPA 50, 50A, and SOB
4. NFPA 99 Health Care Facilities (often used as a standard for laboratory piping)
5. ASTM G-88
6. ASME/ASTM B3 1.3 Code for Pressure Piping
FIGURE 8.1 Ambient air vaporizers.
Gas is often stored as a cryogenic liquid when the anticipated volume of gas usage
is large enough to make cryogenic storage economical and practical. The reason
for this is volume. The cold liquid occupies considerably less volume than a com-
parable quantity of compressed gas. The gases most commonly stored as cryogenics
are nitrogen, argon, and oxygen. Also available but less common are carbon di-
oxide, hydrogen, and helium. The storage tanks can be generally categorized as
either large bulk tanks or smaller dewers.