11.2 Pressure Controllers
11.2.1 Regulators
Gases used in industrial processing, such as oxygen, nitrogen, hydrogen, and
propane, are stored in high-pressure containers in liquid form. The high-pressure
gases from above the liquid are reduced in pressure and regulated with gas regulators
to a lower pounds per square inch before they can be distributed through
the facility. The gas lines may have additional regulators at the point of use.
A spring-controlled regulator is an internally controlled pressure regulator and
is shown in Fig. 11.1a. Initially, the spring holds the inlet valve open and gas
under pressure flows into the main cylinder at a rate higher than it can exit the
cylinder. As the pressure in the cylinder increases, a predetermined pressure is
reached where the spring loaded diaphragm starts to move up, causing the
valve to partially close, i.e., the pressure on the diaphragm controls the flow of
gas into the cylinder to maintain a constant pressure in the main cylinder and
at the output, regardless of the flow rate (ideally). The output pressure can be
adjusted by the spring screw adjustment.
A weight-controlled regulator is shown in Fig. 11.1b. The internally controlled
regulator has a weight-loaded diaphragm. The operation is the same as the
spring-loaded diaphragm except the spring is replaced with a weight. The pressure
can be adjusted by the position of a sliding weight on a cantilever arm.
A pressure-controlled diaphragm regulator is shown in Fig. 11.2a. The internally
controlled regulator has a pressure-loaded diaphragm. Pressure from a