912N Series Pressure Regulators0 pages

Bulletin 71.1:912N
April 2010
912N Series Pressure Regulators
Introduction
The 912N Series direct-operated, spring-loaded regulators
are used in a variety of service and industrial applications.
These regulators have limited-capacity internal relief across
the diaphragm (see Figure 2) to help minimize overpressure.
Any outlet pressure above the start-to-discharge point of
the non-adjustable relief valve spring moves the diaphragm
off the relief valve seat, allowing excess pressure to bleed
out through the screened spring case vent. Inlet pressure
capabilities are the same for all regulators described in this
bulletin. However, outlet pressure ranges vary according to
construction (see Table 1).
Features
  •  Accurate and Sensitive Control—Disk/lever assembly
  is attached to a roller-style pivot for smoother action.
  Handwheel construction is available for adjustment of
  the pressure setting.
  •  Versatility—These regulators are suitable for a
  variety of gaseous fluids, including natural gas,
  propane, and air. They are often used to supply
  loading pressure to other units.
P1024
Figure 1. 912N Series Regulator
regulator
spring
  •  Weather and Insect Protection—“Drip lip” vent
  helps resist blockage during icing conditions. When
  the regulator is installed with the vent pointing down,
  any ice that builds up forms a protective sheath
  that helps keep the opening unobstructed. The vent
  screen helps prevent foreign material from entering
  the spring case and clogging or otherwise hindering
  regulator operation.
Relief Valve
Spring
pusher post
assembly
Relief Valve
Seat
vent screen
diaphragm
  •  Easy Maintenance—Diaphragm and disk/lever
  assembly can be replaced without removing the
  regulator from the pipeline.
Principle of Operation
M1021
Valve disk
disk/lever
assembly
D100124X012
Body/Lower
Refer to Figure 2. When downstream demand decreases, INLET PRESSURE
Casing
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
the pressure under the diaphragm increases. This pressure
Inlet PRESSURE
INLETpressure
overcomes the regulator setting (which is set by a spring).
OUTLET PRESSURE
OUTLETpressure
Through the action of the pusher post assembly, the valve
ATMOSPHERIC pressure
ATMOSPHERIC PRESSURE
disk moves closer to the orifice and reduces gas flow. If
demand downstream increases, pressure under the diaphragm
Figure 2. 912N Series Operational Schematic
decreases. Spring force pushes the pusher post assembly
(Standard Spring Case Vent Shown)
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