Assembly - Emerson Fisher NS2 Yoke Instruction Manual

ATI Piston Actuator
June 2023
6. For the SRE actuator, dial up the regulator output pressure until the stem connector (key 103) just barely begins to
move up. For the SRR actuator, increase the pressure until the plug is seated, then back off on the pressure until the
stem connector (key 103) just barely beings to move up. At this pressure the valve plug is off the main seat and the
compression is relieved from the stem connector assembly (key 103).
7. Prior to disassembly of the stem connector assembly (key 103), make a mark with a suitable marker just above the
stem connector (key 103) on the piston actuator piston rod. This will aid in reassembly to ensure that proper travel
and seat-load is achieved on the main seat.
WARNING
To avoid personal injury due to the sudden, uncontrolled movement of parts, do not loosen the cap screws when the stem
connector (key 103) when spring force is applied without the aid of control air.
8. With controlled air to the casing, loosen the stem connector cap screws (key 103C). Remove the stem connector
nut-half (key 103B) leaving the magnet target assembly (key 148) in place, if possible. Remove the stem connector
bolt half (key 103A) and feedback arm. Carefully follow the positioner disassembly instructions for any feedback
arm used on the stem connector. Set aside.
9. Loosen the yoke-to-bonnet bolting (keys 101 and 102). Remove nuts (key 102) and washers (key 143).
WARNING
Release of air from the actuator will cause movement of the actuator stem, to avoid personal injury and property damage,
keep hands and tools out of the actuator stem travel path.
10. Lift actuator off the valve by following the recommendations in the Lifting Guidelines section. Shutoff control air
and vent air from piston actuator. Reset portable regulator, secure and disconnect air hose.

Assembly

ATI Piston Actuator with Fisher NS2 Size 80 Yoke
The ATI/Yoke Piston Actuator Assembly is manufactured as an assembly as shown in figure 3. This assembly should be
replaced every 10 years.
Instructions are given below for remounting of the ATI piston actuator assembly. Begin assembly at the appropriate
step.
1. Ensure that the locknuts (key 115) are screwed down on the valve stem. If a mark was made from disassembly, use
this as a guide at step 17 of this section.
2. Coat the threads of the actuator mounting studs (key 101) with Nuclear Grade anti-seize lubricant (key 27) up to
the deformed thread. Thread the actuator mounting studs (key 101) into the valve bonnet until the deformed
thread prevents further insertion.
3. Connect the portable regulator assembly to the piston actuator as shown in figure 4.
4. Using the portable regulator assembly, make sure the adjusting screw of the regulator is completely backed out to
ensure that the regulator outlet pressure will be 0 psig when supply pressure is introduced, then open the
three-way valve to the piston actuator. Open the isolation ball valve to supply plant air to the regulator.
5. For SRE actuators, increase the regulator output pressure until the stem connector (key 103) moves all the way up
into the piston actuator (fully retracted) but do not exceed the Maximum Casing Pressure listed in table 1. SRR
actuators will be fully retracted without air.
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Instruction Manual
D104304X012