Instruction manual
Type MR105
13
Actuator Maintenance
Perform this procedure if it is desired to inspect or
replace the diaphragm or other internal parts or if it
is desired to change the outlet pressure range of the
regulator by changing the control spring.
!
WARNING
To avoid possible personal injury from
spring or pressure-loaded actuator,
make certain the adjusting screw is
completely backed off or the spring case
pressure is vented prior to disassembly.
Otherwise, the spring load or loading
pressure could forcefully eject the
spring case.
Replacing Main Spring
1. Loosen the jam nut (key 72). If pressure-loaded
actuator is used, remove also the sealing washer
(key 71). Using a hand wrench (not an impact
gun), unscrew the adjusting screw (key 73) and
remove it from the spring case (key 70).
2. Loosen and remove the cap screws (key 67) and
lift off the spring case (key 70) from the spring case
spacer (key 66 for Low-Pressure Actuator), upper
casing welding assembly (key 87 for Low-Pressure
Pressure-Loaded Actuator) or upper diaphragm
casing (key 63 for High-Pressure Actuator).
3. Remove the upper spring seat (key 69) and control
spring (key 68). Replace the control spring if desired.
4. For pressure-loaded actuator, replace the upper
casing welding assembly top O-ring (Low-Pressure
Actuator) or upper diaphragm casing O-ring (High-
Pressure Actuator) (key 64) if necessary. Install
the new O-ring in the groove on the top surface
of the upper casing welding assembly (key 87)
for Low-Pressure Actuator or upper diaphragm
casing (key 63) for High-Pressure Actuator. If
spring (key 68) and spring case spacer/upper
diaphragm casing O-ring (key 64) replacement
has been completed and no further maintenance
in the actuator and its internal parts is necessary,
proceed to step 23 for Low-Pressure Actuator or
step 20 for High-Pressure Actuator.
For Low-Pressure Actuator Diaphragm Replacement
5. Remove the cap screws (key 57) and hex nuts
(key 58) connecting the casings (key 63 or 87
and key 62) and diaphragm (key 56). Lift off the
upper diaphragm casing (key 63) or upper casing
welding assembly (key 87).
6. Unscrew the jam nuts (key 48) and remove them
from the actuator stem (key 40).
7. Remove the Belleville spring washer (key 49),
lower spring guide (key 52) and diaphragm plate
(key 55) from the actuator stem (key 40).
8. Lift off the diaphragm (key 56) from the actuator
stem (key 40) and inspect it for damage.
Replace if necessary. If no further maintenance
or inspection is required, proceed to step 18 to
reassemble the actuator.
Note
Exercise care to ensure that the actuator
diaphragm head bore without pinching,
cutting or damaging in any way the
lower diaphragm head O-ring (key 51).
9. Carefully remove the lower diaphragm head
(key 53) from the actuator stem (key 40) so that
the actuator stem threads do not damage the
O-ring inside the lower diaphragm head. Replace
the lower diaphragm head O-ring (key 51)
if necessary.
10. Remove the cap screws (key 65) connecting the
lower diaphragm casing (key 62) and internal
stiffener plate (key 84) to the bonnet (key 61).
Lift the stiffener plate and lower casing off of
the bonnet.
11. If it is desired to replace the bonnet and stem
O-rings (keys 60 and 47) and bearings (key 46),
disconnect the control line attached to bonnet
(key 61). Unscrew the bonnet from the valve body
(key 1). Remove stem (key 40) from the bonnet by
pulling on the end of the stem without threads.
12. Remove the wiper (key 45, detail Z) on the
threaded (orice side) end of the bonnet (key 61)
to reach the bearing (key 46) and stem O-ring
(key 47). Install the new stem O-ring and bearing
and put back the wiper.
13. Turn the bonnet (key 61) over and install another
stem O-ring (key 47) and bearing (key 46, detail X)
in the top side of the bonnet. Inspect the bonnet
O-ring (key 60) installed in the groove located
on the top surface of the bonnet (key 61) for any
damage and replace if necessary.
14. Lubricate the bore on both ends of the bonnet
(key 61). Install the bonnet over the actuator
stem (key 40) and thread into the valve body
(key 1). Tighten the bonnet into the body until the
connecting pipe holes in the bonnet are located
90° from the valve body ends for correct tubing