Specifications

APPENDIX A. LINKAGE INSTALLATION FOR EITHER A
CHARACTERIZED FLOW CONTROL DEVICE, OR A LINEAR FLOW
CONTROL DEVICE.
Linkage installed for a characterized flow control device will
result in rapid flow changes near the closed position. A
linear flow control device will provide linear changes in flow
in relation to changes in control signal.
Characterized flow control device results from linear linkage
and linear power positioner. Linear flow control device
results from characterizing linkage or from characterizing
power positioner.
Linkage described is l-l/Z inch diameter pipe.
A-l. LINKAGE INSTALLATION FOR A
CHARACTERIZED FLOW CONTROL
DEVICE.
a. Measure length of driven lever (R,) on &vice to
be controlled (Figure A-l).
b. Attach the linkage clevis to the power
positioner’s drive lever so that distance R2 is
equal to R,.
c. Close damper of device being controlled to
minimum flow position.
d. Measure angle (l3,) of device’s driven lever from
vertical center line.
e. Install power positioner’s drive lever so its angle
(0,) is the same as the device’s driven lever @,).
f. Measure distance (@) between drive and driven
levers connection holes. Allowing for cl&s
length, cut pipe to tit this measurement. Install
clevises.
g. Install linkage pipe between drive and driven
levers. Check for freedom of movement by
operating power positioner’s handwheel. Make
minor adjustments to linkage length by turning
DRIVEN
LEVER
DAMPER
LINKAGE
CLEWS
DRIVE
LEVER
POSITIONER
Figure A-l. Linear Linkage Design
A-2. LINKAGE INSTALLATION FOR A LINEAR
FLOW CONTROL DEVICE. Linear flow control
devices require a characterized control system. This
can be accomplished by either characterizing linkage
or characterizing power positioner.
If greater torque is required at start of power
positioner movement, characterize the linkage system.
This is covered in step a. below.
If this additional starting torque. is not required, a
linear linkage can be installed. The power positioner
cam must be shaped to characterize power positioner.
linkage ClwiS titting in or out as necessary.
This is covered in step b.