Which of the following components are common to a standard compressed gas cylinder manifold system?

1. Automatic switch-over control
2. Pressure-reducing valves
3. Primary and reserve bank
4. Alarm system
a. 1, 2, and 3 only
b. 2 and 4 only
c. 3 and 4 only
d. 1, 2, 3, and 4

ANS: D
The alternating supply or cylinder manifold system consists of large (normally H or K size) cyl-inders of compressed O2 banked together in series (Figure 40-7). This alternating supply system has two sides: a primary bank and a reserve bank. When the pressure in the primary bank de-creases to a set level, a control valve automatically switches over to the reserve bank. When this occurs, the primary bank is taken off-line, and the empty cylinders are replaced with full ones. The replenished primary bank becomes the reserve bank. Some large alternating supply systems are permanently fixed and are refilled on site by a supply truck. These cylinder manifold systems have pressure-reducing valves for regulation of delivered pressure and normally have low-pressure alarms. These alarms sound when reserve switch-over occurs, and they warn of im-pending depletion or malfunction.