Owner's manual

b. Linkage Iastallation for a Linear Flow Control
m. 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 rqdred at start of power
positioner movement, characterize lb&age system.
This is covered in step 1. below.
If this additional starting torque is not required,
a linear lib&age can be installed. The power
positioner cam must be shaped to characterize
power positioner. This is cover.4 in step 2.
NOTE
Linkage installation described in this section
of the manual is for direct acting power
positioners.
1. Characterized Linkage System.
(a) Make sm. a linear cam is installed to
get linear outputs from power
positioner.
POWER POSITIONER
DRIVE
LEVER
Fire 2-6. Vertical Arm Travel
(h) Figure out how far vertically the
operating lever travels using Figore 2-6
and the following equation:
Y-2& tsin ( w,+p,) /2 * 0) 1 a- rsin~,/2.01z
NOTE
The following known values are wed to
calculate tbe vertical distance travelled by
the drive lever; “Y”.
R, = Length of drive lever (from shaft
center to clevis pin center) measured
in inches.
0, = Total angular rotation of drive lever.
If power positioner is at full stroke,
this measurement is 809
p, = Angular measurement of drive lever
from vertical centerline with piston
fully extended.
To perform the following procedure, a
calculator with basic functions, plus the
following scientific functions, is
necessary:
-Sine Function (SIN)
-Square Function (x2)
Use the following procedure to
determine Y, the vertical distance
travelled by drive lever:
1 Add vahxe of e1 to value of fl,.
2 Divide answer from step 1 by
2.0.
1 Enter answer from step 2 and
press sine key (SJN).
4 FESS square key (x3.
2 Multiply answer from step 2 by
length of drive lever (R,).
6 Multiply answer from step 2
by 2.
1 Write down answer from step 6
and label it 6 for use later on.