Principles of operation for the Model 5200P air pressure regulator:
Turning the adjusting screw changes the force exerted by the range
spring on the diaphragm assembly. In equilibrium of set air pressure,
the force exerted by the range spring is balanced by the force form the
output air pressure acting underneath the diaphragm assembly. An
unbalanced state between the output pressure and the set pressure
causes a corresponding reaction in the diaphragm and supply valve
assemblies. If the output in the air pressure regulator rises above the
set pressure, an upward force is exerted on the diaphragm assembly
causing the relief seat to lift and open. Excess pressure in the air
pressure regulator is vented to atmosphere until equilibrium is
reached. If the output pressure drops below the set pressure the
unbalance force of the range spring causes a downward force on the
diaphragm as sem bly. The supply valve then opens until the pressure
builds up once more to the equilibrium condition. Under forward flow
conditions, the range spring force is balanced by the diaphragm
pressure force, with the supply valve open just enough to maintain the
required equilibrium pressure. When high flow occurs, a specially
designed aspirator helps maintain downstream pressure and compensates
for droop.

air pressure regulator