INSTALLATION AND SERVICE INSTRUCTION
Siemens
Energy & Automation
SD73
Rev 13
September 2008
Supersedes Rev 12
MODEL 73N BUILT-IN VALVE POSITIONER
The Model 73N is a Built-in Valve Positioner which is mounted directly on the topworks of a valve. It is capable of
utilizing the full force of its air supply to drive the piston or diaphragm, in a pneumatic actuator, to a position called
for by the control instrument. The positioner incorporates a single-axis force-balance principle of operation to insure
accurate and stable positioning of a control valve.
MODEL DESIGNATION
73N 12 F
Basic Model Number
Input Span – psig
Special Feaures
F — Fast response
R — Reverse acting
E — Tapped Exhaust
USM — U.S. Electrical Motors Type
Fast Response: The fast response positioner is used on actuators with large volume topworks requiring a fast
response action. Due to increased pilot plunger travel and larger ports in the fast response positioner, greater filling
and exhausting capacities result. This permits a quicker response to a change in control conditions, plus increased
speed of valve operation.
Tapped Exhaust: The Model 73N Positioner can be ordered with a tapped exhaust port. This feature permits piping
of the pilot exhaust to a safe atmosphere on applications where noxious gases are used as a control medium instead
of air.
USM: On actuators with small topworks and a low volume, a special hi-response positioner may be used. This
positioner is denoted by the letters USM in the model number. There is no bleed on this model due to the low
volume. A special valve plunger is used to ensure fast response for close control.
GENERAL SPECIFICATIONS
Instrument Input Pressure Range...................3-15, 3-9, 9-15, and 3-27 psig
Supply Pressure
Minimum................................................3 psi above required actuator pressure
Maximum ...............................................100 psi
Air Consumption ...........................................0.25 SCFM (in balance condition with 20 psi supply and 9 psi dead
ended output)
Valve Travel
Minimum................................................1/4"
Maximum ...............................................4"
Ambient Temperature Limits ........................-40°C to +82°C (-40°F to +180°F)
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