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4.6.7 Diaphragm replacement
The diaphragm may require replacement without having to
make other repairs. If the regulator is easy to access and
isolate, it can be replaced while leaving the regulator installed
in the piping provided it can be isolated. In this case, isolate
the regulator and vent all pressure. Ensure isolation valves
are locked to prevent accidental pressurization while working
on the regulator. Remove the actuator following the instruc-
tions in section 4.6.3
Replace and install the diaphragm and reassemble the
actuator as shown in section 4.6.2 – 4.6.6. Check calibration
once more when the regulator is returned to service.
4.6.4 Body removal:
Unscrew the nuts (27) and remove the blindhead (1).
Remove the nuts (27a) of the inlet flange (flanged regula-
tors), or the screws (32) of the regulators with threaded ends;
remove the high pressure body (24) keeping the plug in a suit-
able position. Remove the plug.
4.6.5 Parts inspection
All the components are now ready to be inspected. Replace
any worn items. Clean all parts.
Pay particular attention to the condition of the disc and plug,
both elastomeric and metal, and the seat area of the high-
pressure body.
If the seat is worn, it may be able to restore it by lapping using
a metal disc and abrasive paste.
If preferred, the regulator may be returned to an authorized
Masoneilan repair center to be reconditioned.
The diaphragm should be replaced if it shows any damage. The
same applies to Teflon diaphragm protector (if equipped).
Gaskets and O-rings (8) should not be re-used.
4.6.6 Reassembly
Carry out the dismounting operations in reverse order.
Push the stem of the plug into the guide and put the high
pressure insert into position with the pin (31). For regulators
with flanged ends, put the flange into position; tighten the
nuts or screws uniformly. Install the Diaphragm(s) (see 4.6.3.)
taking care to properly arrange the Teflon protectors, if
equipped. Make sure the seats of the O-rings are perfectly
clean before installiing them.
Assemble:
- for single diaphragm versions: bracket, diaphragm plates,
diapragm and spring guide disks (with relative gaskets), nut.
- for double diaphragm versions: bracket, diaphragm,
diaphragm plate, lower diaphragm, intermediate ring and
actuator ring, upper diaphragm, spring guide (with relative
gaskets), nut.
Before installing the nut and tightening, position the
diaphragm/s so that when the diaphragm-bracket assembly
is fully rotated to the right and left, each hole rotates by the
same angle as the matching hole on the actuator flange. This
means that the bracket is at right-angles to the high pressure
body.
Tighten the nut (and the lock nut for double diaphragm). Match
the holes of the diaphragm(s) with the holes in the actuator
flange and reinstall the spring, spring holder and spring case.
Install the blindhead (1). Turn the adjustment screw the
number of turns noted down during disassembly.
Exact calibration must then be checked when the regulator is
returned to service.
Instructions
EY0171-0172 – 10/08
171 and 172 Series
Self-Operating Pressure Regulators
Fig. 12 Example of installation layout –
Group 1 regulators: 172-50 Single Diaphragm
Fig. 13 Example of installation layout –
Group 2 regulators: 172-50 Double Diaphragm
DV-215-171_172 series Inst-v13.indd 9
11/5/08 12:13:40 PM