Valve Stem Position Transmitter Cam Information; Valve Positioner Bypass Operation - Emerson Fisher 3582 Instruction Manual

Instruction Manual
June 2010
CAM
C
INSTRUMENT PRESSURE - FLOW
CHARACTERISTIC WITH EQUAL
PERCENTAGE VALVE PLUG AT
CONSTANT PRESSURE DROP
CK4835-A / DOC
Figure 13. Flow Characteristics with Different Cams and
Equal Percentage Valve Plug
CAM
B
CAM
C
CAM
A
CAM
B
INSTRUMENT PRESSURE - FLOW
CHARACTERISTIC WITH LINEAR
VALVE PLUG AT CONSTANT
PRESSURE DROP
CK4833-A / DOC
Figure 14. Flow Characteristics with Different Cams and
Linear Valve Plug
When cam A is the operating cam, there is a linear
relationship between an incremental instrument
pressure change and the resultant valve stem travel.
The flow characteristic is that of the control valve.
Installing either cam B or C as the operating cam
CAM
NORMALLY
A
CLOSED
VALVE
CAM
B
CAM
C
NORMALLY
CAM
OPEN
A
VALVE
CAM
B
PERCENT FLOW
NORMALLY
CLOSED
CAM
VALVE
C
CAM
A
NORMALLY
OPEN
VALVE
PERCENT FLOW
3582, 582i, and 3583
changes the relationship between the incremental
instrument pressure change and valve stem travel,
thereby modifying the valve flow characteristic.
Valve Stem Position Transmitter Cam
Information
If the small arrow on the valve stem
position transmitter cam points up
toward the nozzle, output pressure
increases with downward stem
movement. If the arrow points down,
output pressure decreases with
downward stem movement. If the
arrow is pointing in the wrong
direction, remove, reverse, and
re-install the cam. Refer to the
Changing Cam Position section of this
manual.
Refer to figure 20 for key number locations. Unhook
the spring (key 38), and remove the cam bolt and
locking nut (keys 6 and 45). Remove the cam (key 4)
and spring retainer bracket (key 43). To install the
cam, screw the locking nut all the way onto the cam
bolt. Attach the cam and spring retainer bracket with
the cam bolt. Tighten the bolt to secure the cam.
Then, tighten the locking nut against the spring
retainer bracket. Hook the spring into the spring
retainer bracket.
The linear cam is the only cam available for the 3583
valve stem position transmitter. There is always a
linear relationship between stem travel and the stem
position transmitter output.

Valve Positioner Bypass Operation

3582 and 3582D valve positioners, and 3582NS
positioners with bypass, are supplied with a bypass
assembly. A handle on the bypass assembly permits
selecting positioner or bypass operation. Refer to
figure 24 for key number locations.
CAUTION
Do not use bypass when the valve
positioner is reverse-acting or is in
split-range operation. In these cases,
Note
21