Waukesha Cherry-Burrell
Maintenance
April 2005
95-03077
Page 33
Switches
Switches sense the position of the actuator stem and
indicate three positions either correctly closed, correctly
open or fault (not correctly closed or open). The lower
switch is normally closed (N.C.) and senses when the stem
is lowered or fully extended from the actuator. The upper
switch is normally open (N.O.) and senses when the stem
is raised or fully retracted into the actuator. When the
valve is correctly closed, a closed circuit will pass
electrical current through the lower switch. When the
valve opens, the stem raises and the lower switch changes
to open circuit and the upper switch changes from open to
closed circuit. If the stem is raised only halfway, both
switches are open and a fault is indicated.
Micro Switch
•
mechanical switch using a lever arm and roller that is
compressed or released by stem movement.
•
AC/DC 24VDC or 100AC
•
position of actuator stem is felt by a roller
Proximity Switch
•
electronic version of micro switch
•
AC/DC
•
position of actuator stem is detected by a sensor
Switch Adjustment
1.
Raise stem to open valve, loosen setscrews holding
switch blocks (Figure 45, item A) with a 5/64" allen
wrench and slide switches to set distance between
switches and stem shaft at .040" (1 mm) (Figure 46). If
using a micro switch, place .020" feeler gauge between
roller and small diameter of stem. Adjust switch toward
stem until a “click” is heard.
2.
Tighten setscrews.
3.
With stem raised, adjust vertical height of upper
switch target to slightly below stem shoulder (Figure
45, item B), by raising or lowering the lower switch
carriage. Tighten locknuts securely.
4.
Lower stem to close valve and adjust target of lower
switch to slightly above stem shoulder (Figure 45).
Tighten locknuts securely.
CAUTION:
Do not over tighten as excessive
torque can twist switch adjustment posts.
NOTE:
In this manual,’stem-raised’ is understood to be
when the valve stem is fully retracted into the
actuator.’Stem-lowered’ is understood to be when the
valve stem is fully extended out from the actuator.
Figure 45 - Switch Height Adjustment Setscrews
Figure 46 Valve Open Adjustment
Figure 47 - Valve Closed Adjustment