Emerson Fisher OS2 Instruction Manual page 12

Type OS2
Mechanism Box (BM1 or BM2)
Disassembly for NPS 1 through 6 / DN 25 through
150 Body Sizes (Refer to Figure 14)
Warning
!
avoid personal injury or damage to
property from sudden release of pressure
or uncontrolled gas or other process fluid.
Before disassembling, carefully relieve
all pressures. Use gauges to monitor
inlet and outlet pressures while releasing
these pressures.
The only parts that are replaceable on
the Type OS2 are the equalizer bypass
component, manometric sensing device
(Types BMS1 and BMS2) and the sealing
components. The seat ring on the Type OSE
is pressed into the body and is not
field removable.
The position of the travel stop (Figure 13)
depends on the Type of assembly and
body size. The travel stop must be in the B
position (Figure 13) for nPS 1 and 2 / Dn 25
and 50 body sizes. For all other body sizes,
the travel stop must be in the C position
(Figure 13).
The cover is held on by one screw which can be unscrewed
manually or by using a socket (maximum recommended
torque is 1.8 ft-lbs / 2.4 N•m).
1. Open the mechanism cover and replace the cover screw
O-ring by removing the circlip.
CaUTiOn
Trip the mechanism if it is not already
released by moving Pin D1 (see Figure 7) to
remove as much spring tension on the stem
as possible.
2. Trip the mechanism by carefully turning the tripping
plate (Pins D1 and D2) clockwise (refer to Figures 5
and 6).
3. Remove the clip (refer to Figure 8). Turn and detach
the clevis from the stem by pulling the pin from the
sliding clevis.
12
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4. Remove the two cap screws (key 39) holding the
mechanism box (key 16) to the bonnet (key 15) and
remove the mechanism box.
5. Remove the nuts (key 23, for NPS 4 and 6 / DN 100
and 150 only) or cap screws (key 21) holding the bonnet
(key 15) to the body (key 1).
6. The bonnet (key 15), valve plug (key 5H) (with equalizer
bypass, key 5A in NPS 1 through 6 / DN 25 through
150 body sizes), main spring (key 12) and small stem
bushing (key 24) will lift out of the body as a unit. Set the
unit on a hard flat surface with the valve plug (key 5H)
at the bottom and press down on the bonnet (key 15) to
compress the main spring (key 12), allowing the stem to
be unhooked from the coupling head.
7. Use a spanner wrench (a wrench is supplied with one
of the replacement parts kits) to unscrew the equalizer
bypass (key 5A) from the valve plug (key 5H) (refer
to Figures 10 and 11). The NPS 1 / DN 25 body size
equalizer bypass (key 5A) holds the plug O-ring (key 32)
to the valve plug (key 5H). On the NPS 2 and 3 / DN 50
and 80 body sizes, the equalizer bypass (key 5A) holds
the plug disk and the plug O-ring (key 32) to the valve
plug (key 5H). The NPS 4 and 6 / DN 100 and 150 body
sizes valve plug disk and valve plug are held together
by six cap screws. On these body sizes, remove the cap
screws and valve plug disk to replace the plug O-ring
(refer to Figure 11).
The equalizer bypass (key 5a) is a common
part between valve plug sizes from nPS 1
through 6 / Dn 25 through 150 body sizes.
The equalizer bypass (key 5a) is not
serviceable and must be replaced as a unit.
8. To remove the equalizer bypass (key 5A) from
the coupling and coupling head, drive out the roll
Pin (key 5C) on the coupling (refer to Figure 10).
Disassembly for NPS 8 and 10 / DN 200 and 250
Body Sizes (Refer to Figures 13 and 15)
1. Remove the mechanism box (BM) cover (key 96).
2. Remove the travel stop (see Figure 13).
3. Unscrew the nuts (keys 97 and 98).
4. Remove the resetting latch (key 100).
5. Remove the bolt (key 113) and the spacer (key 114).
6. Remove the cam (key 121) and yoke (key 108).
7. Unscrew the two screws (key 117).
8. Retain the square nut (key 53) situated at the extremity
of the stem valve (key 20).
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