Leslie Controls DOT 3-WAY CONTROL VALVE - Manual (Page 8)

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4. TO CHANGE VALVE ACTION FROM
NORMALLY OPEN TO NORMALLY
CLOSED OR VICE-VERSA
To reverse the action of a single ported diaphragm control
valve it is only necessary to replace the actuator in use with
one having the opposite action. A single “D” in the control
valve class indicates actuator is “DIRECT ACTING” – Air
moves diaphragm downward. A double D (“DD”) indicates
actuator is “REVERSE ACTING” – Air moves diaphragm
upward.
PROCEDURE
To change actuator, loosen valve plug stem locknut under
travel indicator and turn valve plug stem all the way out of
the actuator stem. Remove capscrews securing actuator to
bonnet. Replace actuator with one having desired action.
Re-insert and tighten actuator spring preload and set valve
for rated travel.
CONTROL VALVE
REASSEMBLY AND
ADJUSTMENT
1. REASSEMBLY (SIZES 1” – 2”)
a. Install the bonnet into the cage and tighten the
two set screws.
b.
Insert the main valve up through cage and bonnet.
c. Insert the packing spring and packing washer unto
the bonnet.
d. Install new set of packing in the order in which
they are packed.
e. Install the packing follower, then install the
packing flange.
f. Insert cap screws through the packing flange and
hand tighten.
g. Lubricate “O” Rings and install on bonnet and
cage.
h. Insert the load ring into the bottom of the main
body. Be sure to replace in a concave manner.
(See diagram)
i. Insert main valve, cage and bonnet of the main
body. (Be careful not to damage the “O” rings.)
j. Position actuator on bonnet. Insert the capscrews
through the yoke and intro threads in the bonnet.
Tighten capscrews firmly.
k. Lift the valve plug stem and engage its threads
with those of the actuator stem. Screw into
actuator stem one to two diameters. Then adjust
the control valve for starting pressure preload,
rated travel and positive compression force.
2. HOW TO MAKE PRELOAD
ADJUSTMENT
a. Connect controlled air line to diaphragm case
connection at “A”.
b.
Supply 3 psig air pressure to actuator diaphragm.
c. Compress actuator spring until travel indicator
begins to move when air pressure is 3 to 4 psig.
NOTE: The valve travel should be checked under actual
operating conditions for rated travel. If the stem travel is
less than full, some additional spring compression will be
required.
d. To compress spring, screw-adjusting nut upward
on both reverse and direct acting actuators.
3. HOW TO ADJUST CONTROL VALVE
FOR RATED TRAVEL AND POSITIVE
COMPRESSION FORCE
In all cases full valve travel is mechanically predetermined
by the distance between seats valves must be adjusted to
make full contact with seat in either direction.
In direct acting actuators spring force brings vale plug in
contact with upper seat, air force with lower.
In reverse acting actuators air force brings valve plug in
contact with upper seat, spring force with lower.
In reverse acting actuators air force brings valve plug in
contact with upper seat, spring force with lower.