THD SERIES S11-S27 HEAVY DUTY ACTUATORS
Installation & Maintenance Manual
2
September 25, 2015
www.atcontrols.com
documents\products\IOM\IOM8036
CW PORT
CCW PORT
Figure 1
6. Spring Return Operation
Applying air pressure to the CCW Port drives the piston
toward the adapter as the spring is compressed. This rotates
the yoke counterclockwise when viewed from the accessory
side of the actuator. When pressure is relieved at the CCW
Port the spring drives the piston towards the end cap which
turns the yoke clockwise. This is shown in figure 2. To
reverse the failure mode the spring and pressure cylinder are
swapped end for end.
CW PORT
CCW PORT
Figure 2
7. Travel Adjustment
The Triac THD actuators have + or - 8 degree adjustment of
the end of travel stops in both the open and close directions.
CAUTION: DO NOT ATTEMPT TO ADJUST STOP
BOLT WITH AIR PRESSURE OR SPRING FORCE
APPLIED TO THE STOP BOLT. ALWAYS JOG
ACTUATOR AWAY FROM STOP BOLT BEFORE
ADJUSTING.
On models S11 thru S13 the stop bolts are in the center body
of the actuator. Figure 3 shows the stop bolt locations for the
S11 thru S13. On models S16 thru S27 the stop bolts are
located in the end caps / end plates. The stop bolt on the end
cap is for Closed (clockwise rotation) and the stop bolt on the
spring cylinder / end plate is the Open (counterclockwise)
rotation. Loosen and remove the stop bolt cap first. The air
supply must be removed before the stop bolt can be turned.
Next loosen the hex nut and then position the stop bolt in or
out to the correct position. Use care not to damage the o-ring
seal. Retighten lock nut and replace stop bolt cap
.
COUNTER-CLOCKWISE
STOP BOLT
CLOCKWISE
STOP BOLT
Figure 3
!!!WARNING!!!
FOR YOUR SAFETY,
IT IS IMPORTANT THAT BEFORE
REMOVING ANY COMPONENTS OF THE ACTUATOR,
ENSURE THAT ALL PNEUMATIC AND ELECTRICAL
SUPPLIES ARE DISCONNECTED AND LOCKOUT AND
TAGOUT PROCEDURES ARE IMPLEMENTED.
8. Replacement of Cylinder Seals
When the cylinder seals must be replaced, because of
leakage or a preventive scheduled maintenance, the
following procedure must be followed. Note only the soft
parts indicated on pages 5 and 6 are included in a seal kit.
If additional parts are required they must be ordered
separately.
Due to the continuing improvement of the Heavy Duty
Actuators, seal kits provided by A-T Controls may contain
extra o-rings so that all revisions of the actuators are able to
be repaired. When disassembling the actuator, it is
recommended to match the old o-ring with the new o-ring
from the repair kit by comparing the o-ring diameter and
cross section.
1.
Disconnect electrical supplies and shut off pneumatic
supply, vent actuator and remove from valve or damper.
2.
For spring return actuators the spring tension must be
relieved before starting. Apply air pressure until the
piston moves off the stop bolt. Remove the stop bolt cap
(item 36) then loosen the hex nut (item 8) then back out
the stop bolt (item7) until the preload is relieved. Do not
remove the stop bolt with air pressure in the cylinder. For
