12-6
4. Place the upper end of the stem into a vice using
the stem flats to hold in place. Use caution to not
damage the stem or its threads. Thread the plug
head into the bellows stem using a wrench on the
flats of the head. (Torque
1
/
2
through 2-inch valves
to 540 in-lbs, and 3-inch valves to 2500 in-lbs.)
5. At the inside corner where the plug head meets the
plug stem, tack weld the head to the stem with two
1
/
8
-inch welds 180 degrees apart.
6. Install a new seat ring gasket, seat ring, seat retainer
and new bellows assembly gasket into valve body.
7. Insert the bellows assembly into the valve body,
being careful to not damage the plug head.
8. Insert a new bellows housing gasket onto the
bellows assembly. Next, carefully lower the bel-
lows housing over the bellows assembly and onto
the valve body and bonnet flange studs. Be certain
the tell-tale tap is located opposite of the positioner.
9. Install the bonnet flange nuts and tighten finger-tight.
10. Insert the packing spacer, lantern ring, new pack-
ing and upper stem guide into the packing box.
11. Turn the actuator back onto the bellows stem,
without turning the stem inside the bellows seal
housing. Be certain the gland flange and bonnet
flange are in place before engaging the bellows
stem and actuator stem threads. Leave approxi-
mately three to five bellows stem threads exposed
or until a
1
/
8
-inch gap remains between the yoke
bottom and bonnet. With air-to-open valves, re-
tract the stem by applying air pressure to the
bottom of the actuator. This will allow the yoke
clamp and gland flange bolting to be attached and
tightened firmly. The packing box nuts should be
just over finger tight.
12. For air-to-close valves, skip this step and go to step
13. For air-to-open valves, check for proper plug
seating as follows: When proper seating occurs, the
bonnet flange will be forced up against the finger tight
bonnet bolting with such force that it will be impos-
sible to wiggle the flange. If proper seating does not
occur, the bonnet flange can be wiggled with light
hand force. Should this occur, place air under the
actuator piston and retract the actuator to approxi-
mate mid-stroke position. Remove the yoke clamp
and gland flange bolting and turn the actuator off the
bellows stem one additional thread and repeat the
above seating procedure. When the bonnet flange
becomes tight against the finger-tight body bolting,
plug is properly seated. If necessary, repeat above
procedure until proper seating occurs. Re-attach
and tighten the yoke clamp and gland flange bolting.
13. Move the plug to the extended (or closed) position.
Begin tightening the bonnet flange bolting in a
manner that will keep the bonnet flange square/
parallel with the body. Tighten the first bolt
1
/
6
-turn,
Figure 3: Exploded view:
Guardian II Metal Bellows Seal
Standard
Mark One
Parts
Hard
Guide
Guide
Housing
Plug
Head
Shrouded
Bellows
Assembly
Soft
Guide
Retainer
Soft
Guide
