What do the components of a liquid O2 bulk storage tank include?

1. Inner and outer steel shells, separated by a vacuum
2. Safety system that vents O2 if warming occurs
3. Vaporizer system that converts liquid O2 to gas
4. Pressure-reducing valves to lower pressure to 50 psig
a. 1, 2, and 3 only
b. 2 and 4 only
c. 1, 2, 3, and 4
d. 3 and 4 only

ANS: C
These stand tanks are like giant thermos bottles, consisting of inner and outer steel shells sepa-rated by an insulated vacuum chamber (Figure 40-10). Because it eliminates heat conduction, the vacuum keeps the liquid O2 below its critical temperature without refrigeration. When it flows through vaporizer coils exposed to ambient temperature, the liquid O2 quickly converts back to a gas. With the O2 in its gaseous form, the pressure is decreased to the standard working pressure of 50 psi by a pressure-reducing valve. A safety vent allows vaporized liquid O2 to escape if warming causes cylinder pressure to increase above a set limit.