Emerson Hytork XL Series - General Notes when Fitting to Valves

November 2022
Installation, Operation and Maintenance Manual
MAC050515 EN Rev. 0
21Bottom Mounted Stop Block
Section 11: Bottom Mounted Stop Block
Body (a)
Quadrant (d)
Double Indents
Single Indents
Dowels (b)
Travel
Stops (c)
“A” “B”
“A” “B”
Figure 8 Bottom Mounted Stop Block Assembly
11.3 General Notes when Fitting to Valves
There are three congurations that may be encountered when tting actuators, with
travel stops, to valves and they require two methods of assembly. Double-Acting and
Fail-Safe clockwise actuators use the same method while the Fail-Safe counterclockwise
actuators use a different method. The direction of travel is when viewing the pinion shaft
from above the actuator at the slotted end of the pinion drive shaft.
11.3.1 Double-Acting
Double-Acting actuators use pressurized air to drive the pinion shaft in alternate directions
to open and close the valve.
11.3.2 Standard Conguration Fail-Safe Clockwise
Air power between the pistons rotates the pinion in a counterclockwise direction.
When the air pressure is removed the springs drive the actuator pinion clockwise.
This is normally to close the valve but can also be used to open the valve on air failure
if required.