Garland G Series Technical Reference Manual page 51

The Restricting Element moves in response to the
measuring element when the downstream pressure changes.
Usually, it is a disk or plug that controls the amount of flow
by varying the orifice opening.
The Atmospheric Vent allows the air above the diaphragm
to escape or enter as the diaphragm moves up or down.
Vent Limiting Orifice is used in appliance regulators. It
allows equal limits of inhalations and escape of air from the
upper diaphragm chamber. If the diaphragm ruptures, the
leakage is limited to less than 1 cubic foot per inch at 7" W.C.
gas pressure. The size of the orifice is 38.
Basics Of A Gas Pressure Regulator
Inlet
Part # GCTRM Rev 3 (12/10/09)
Atmospheric
Vent
Low Capacity Appliance Regulators carry both main burner
and pilot gas loads. They are usually marked with the symbol
"P". This means they are suitable for pilot load capability.
These are designed to produce a fine pressure control.
They work with small pilot flame flows that are mandatory
operating requirements for some appliances.
High Capacity Appliance Regulators are only used to
regulate the gas pressure to the main burner. The pilot flame
receives the 7" W.C. gas pressure delivered by the gas meter
or system regulator. The gas to the pilot flame is controlled
by a throttling valve (needle valve) sometimes called the
B-cock.
Loading Element
Adjustment (Screw)
Loading Element
(Spring)
Measuring Element
(Diaphragm)
Restricting Element
(Valve Disk and Seat)
Outlet
Page 51