Valve Linkage Adjustments
Instructions 1020
Instructions apply to a wafer butterfly or adjustable port type valve linked to a modulating or 2-position control motor. Valve and motor combinations are assembled by North American with linkages set to give full valve travel with full motor travel. To change this, adjust effective motor arm radius and/or effective valve arm radius and/or connecting rod length.
The control valve linkage must always be adjusted for high fi re and low fire air pressure. A gauge or manometer must be used.
Procedure required for setup:
1. Install an air gauge in the line downstream of the control valve. Loosen the linkage locking screws and manually open the air valve to the high fire setting...such as 70% on the previous curve. 2. For most applications, set the motor arm at the 12 o'clock position. If it is necessary to characterize the valve flow to a controller output, the motor arm may need to be rotated slightly in either direction. The ex- act angle can only be determined through trial and error.
For Motors with 90 Degree Travel
Adjust linkage by trial and error until a setting is found that will give satisfactory high and low points. See the following instructions for more set up tips.
LINKAGE ADJUSTMENTS FOR BUTTERFLY VALVES
Butterfly valves are considered to be fully opened at 70%. Opening the valve beyond this point produces only a small increase in flow. Adjusting the motor/valve linkage for 100% opening results in poor temperature control, as the travel from 70% to 100% is effectively a "Dead Band". Flow through a butterfly valve is not linear to valve position, but reasonably effective characterization of the valve to the controller output may be achieved by adjusting the motor arm starting point, in relation to the valve arm. Motor arm angular travel should approximate the valve arm angular travel to avoid problems when adjusting the linkage. Therefore 90 degree travel motors are better suited for use with North American control valves than are 160 degree travel motors.
3. Adjust the rod swivels to about the midpoints of the slots in the motor arm and valve handle.
4. Use the controller or jumpers to drive the control mo- tor to its low fire position. The downstream pressure gauge should then read the desired low fire air pres- sure (usually 14"w.c. to 27.7"w.c.). 5. Use the controller or jumpers to drive the control mo- tor to the high fire position. If the valve dœs not open to the correct high fire point, determine whether you have too little travel, or have too much travel.
6. Loosen the Allen setscrew and locking nut on the swivel assembly at the valve arm.
100
SET HIGH FIRE HERE; NOT HERE
(a) If you need more travel to get a higher pressure reading, move the entire assembly toward the valve shaft (reduce the radius). (b) For less travel (lower high fire pressure), move the entire assembly away from the valve shaft (increasing the radius).
NO REAL CHANGE IN FLOW THRU THIS 30% OF VALVE TRAVEL
% FLOW
0
0
70
0
100
% VALVE OPENING
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