Cameron GENERAL VALVE Twin Seal 400 Series User manual

ENGINEERED & PROCESS VALVES
GENERAL VALVE® Twin Seal™
Double Block and Bleed Plug Valve
GENERAL VALVE®
Installation, Operation and Maintenance Manual
®
™

ENGINEERED & PROCESS VALVES
207/2011 / IOM-GEN-TWIN-03
Installation, Operation and Maintenance Manual

ENGINEERED & PROCESS VALVES
07/2011 / IOM-GEN-TWIN-03 3Installation, Operation and Maintenance Manual
GENERAL VALVE® TWIN SEAL™
Installation. .................................................................................................... 4
Operation. ..................................................................................................... 5
Series 400, 800 & 900
Integral Bushing/Retained Ring Gland ............................................................ 6
Integral Bushing/Bolted Gland ........................................................................ 6
Bushings/One Gland ...................................................................................... 7
Bushings/Two Gland ...................................................................................... 7
Bearings/Duel Retention ................................................................................. 8
Bearings/Internally & Externally Retained ........................................................ 9
Bearings/Internal Retained with Two Glands ................................................... 9
Series 8800 ...................................................................................................10
Operators
Model 375H ..................................................................................................11
Model 500H & 625H ......................................................................................12
Model 376G & 501G .....................................................................................14
Model 625G & 751G & 755G ........................................................................17
Model 1261G & 1261-7G ..............................................................................20
Model 1276G ................................................................................................23
Model 1500G ................................................................................................26
Bleeds
The DTR System Explained .............................................................................29
Miscellaneous
Operation & Maintenance ..............................................................................31
Parts ..............................................................................................................31
TABLE OF CONTENTS

ENGINEERED & PROCESS VALVES
407/2011 / IOM-GEN-TWIN-03
Installation, Operation and Maintenance Manual
INSTALLATION
Orientation
Twin Seal valves may be installed in any position.
Flow Direction
The Twin Seal design is symmetrical. Flow shut-off is
achieved equally on both sides of the plug independent
of flow direction.
Note: The use of a Differential Thermal Relief (DTR) as
described on page 29 does result in a preferred
flow direction.
Clearance for Repair
For easy repair, space should be allowed below the valve for
removal of the lower plate and withdrawal of the seating
slips. See Table 1 for dimensions. Sufficient clear space is
required above the Twin Seal valve, to allow free movement
of the position indicator flag and for removal of the opera-
tor mechanism.
TABLE 1
Clearance required below standard ported valves for
slip removal.
Minimum Clearance
Valve Size
Inch
ASME Class
150
ASME Class
300
ASME Class
600
ASME Class
900
6” 9” 9” 10” 8”
8” 13” 11” 12” 10”
10” 15” 13” 8” 10”
12” 17” 16” 10” 10”
14” 19” 15” 10” xxxx
16” 22” 19” 14” xxxx
18” 23” 13” xxxx xxxx
20” 26” 14” 14” xxxx
24” 28” 17” 12” xxxx
28” 30” 12” xxxx xxxx
30” 30” 28” xxxx xxxx
36” 30” xxxx xxxx xxxx
Note: Allowing more than the specified minimum amount of
clearance will make servicing easier.
Flange Fasteners
Certain Twin Seal flange holes are drilled and tapped, when
there is no possibility of fitting a hexagonal nut behind the
flange. The quantity and size of these tapped holes is shown
in Table 2. Capscrews or stud bolts may be used in
these holes.
TABLE 2
Valve
Size
(inch)
ASME
Class
150
Number of
Tapped
Holes
per Flange
Thread
UNC
Length Required
(inch)
Cap Stud
Screws or Bolts
6 150 4 3/4”-10 2 1/4 3 1/4
8 150 4 3/4”-10 2 1/4 3 1/4
8 300 4 7/8”-9 3 4 1/4
10 150 4 7/8”-9 2 1/4 3 1/4
10 300 4 1”-8 3 4 1/4
12 150 4 7/8”-9 2 1/4 3 1/2
12 300 4 1 1/8”-8 3 1/2 5
14 150 8 1”-8 2 1/2 4
14 600 4 1 3/8”-8 3 3/4 4 3/4
16 150 8 1”-8 2 1/2 3 3/4
18 150 8 1 1/8”-8 3 4 1/4
20 150 8 1 1/8”-8 3 4 1/2
24 150 8 1 1/4”-8 3 1/4 4 3/4
24 600 8 1 7/8”-8 5 1/4 6 3/4
28 150 6 1 1/4”-8 3 1/4 4 1/2
28 300 6 1 1/4”-8 3 1/4 4 1/2
30 150 6 1 1/4”-8 3 1/4 4 1/2
Gear Housing Orientation
On gear-operated models the gear housing and associated
hand wheel may be re-positioned as follows:
A) Place valve in fully open position.
B) Remove gear housing capscrews.
C) Turn hand wheel to further open the valve
which will turn the gear housing. Continue
until hand wheel comes to the desired position
and gear housing mounting holes are aligned.
D) Replace gear housing mounting capscrews.
NB: Short capscrew is inserted below the
worm shaft.

ENGINEERED & PROCESS VALVES
07/2011 / IOM-GEN-TWIN-03 5Installation, Operation and Maintenance Manual
Valve figure No. C411; C811; C911;
8811; C1611; C1500
C421; C821; C921;
8821; C1621; C1521
C441; C841; C941;
C1641; C1541
C851; C1651;
C1551 Comments
ASME Class 150 300 600 900
Shell Test Pressure
(Valve Open)
(pisg)
(kg/cm2)
500
35
1200
85
2250
158
3350
235
No leakage permitted
Seat Test Pressure (Valve Closed) (psig)
(kg/cm2)
300
21
800
56
1600
113
2400
168
Test upstream &
downstream seats. No
leakage permitted
Supplimentary (API 598) Air Seat Test
Pressure (Vavle Closed)
(psig)
(kg/cm2)
80
6
80
6
80
6
80
6
Test upstream &
downstream seats. No
leakage permitted
Pressure Test
Twin Seal valves can be hydrostatically pressure-tested after installation, to full API 6D limits per Table 3 below.
Table 3
The Twin Seal valve is a non-lubricated, resilient seal, plug-
type valve which has a mechanical means of freeing the plug
before it is rotated from the closed to the open position.
In opening the valve, the plug is raised, thus retracting the
seating segments or slips through their tapered dovetail
connections. Only after the slips are fully retracted perpen-
dicularly from the body seat is the plug rotated to the open
position.
Conversely, in closing the valve, the plug and slips are
rotated freely, with no seal-to-body contact until the slips
are positioned over the ports. Then the plug is driven down
between the slips and the tapered surfaces wedge out the
slips for a positive upstream as well as downstream shut-off.
For maximum upstream sealing, do not back off the hand
wheel. Warning: Do not over torque by using cheater bars.
The small Twin Seal valves are handwheel operated, and
require up to 3 turns to open or close. Up to 2 3/4 turns
expand or retract the slips, while 1/4 turn rotates the plug.
Large valves operate in a similar manner, except that they
have enclosed weather-proof worm gearing.
At the top of the valve, a position indicator flag shows the
exact plug position. It appears in line with the flow when
the valve is open, and perpendicular to the flow when the
valve is closed.
OPERATION
Since Twin Seal valves hold bubble-tight, for ease of
opening in liquid service, it is important to prevent trapped
body pressure from exceeding the working pressure of the
valve. Therefore, a relief system is required to prevent pres-
sure buildup in the body cavity.
AB
CD

ENGINEERED & PROCESS VALVES
607/2011 / IOM-GEN-TWIN-03
Installation, Operation and Maintenance Manual
INTEGRAL BUSHING/RETAINING RING GLAND
INTEGRAL BUSHING/BOLTED GLAND
Typical Arrangement of:
2” C811
2” C821
3” CA811
3” CA821
The smallest of the Twin Seal valves
do not require discrete bushings
due to minimal hydro seating forces
within the valve. Also note that due
to the size of the operator, the gland
is held in by a retaining ring backed
up by the operator housing.
Typical Arrangement of:
4” C811
The units do not require discrete
bushings due to small hydro
seating forces and by incorporating
a slightly larger operator a bolt gland
can be employed.

ENGINEERED & PROCESS VALVES
07/2011 / IOM-GEN-TWIN-03 7Installation, Operation and Maintenance Manual
BUSHINGS/ONE GLAND
BUSHINGS/TWO GLAND
Typical
Arrangement of:
3” C851
3” C861
4” C851
6” C851
Higher pressure class
valves employ the
balanced plug design
to minimize plug
hydro forces which in
turn requires
two glands.
Typical Arrangement of:
2” C841 6” C911 12” C811
2” C851 6” C921 12” C821
2” C861 6” C941 12” A1911
2” C911 8” C411 12” C921
2” C921 8” C421 14” C811
2” C941 8” C811 14” C821
3” C841 8” C821 14” C911
3” C911 8” C841 16” C411
4” C821 8” C911 16” C811
4” C841 8” C921 16” C821
4” C911 10” C411 16” C911/21
4” C921 10” C421 18” C411
4” C941 10” CA811 18” C811
6” C411 10” C821 20” C411
6” C421 10” C911 20” C421
6” C821 10” C921 20” CA811
6” C841 12” C411 24” C411
6” CA811 12” C421 24” C421

ENGINEERED & PROCESS VALVES
807/2011 / IOM-GEN-TWIN-03
Installation, Operation and Maintenance Manual
BEARINGS/DUAL RETENTION
BEARINGS/DUAL RETENTION
Typical
Arrangement of:
12” C941
14” C841
16” C921
18” CA821
18” C911
20” CA821
20 CA841
20” C841
20” CA911
20” CA921
24” CA811
24” C811
24” C821
24” CA821
24” C911
28” C811
28” CC821
30” CC811
30” C821
As valve size increases so does the plug load, therefore, these sizes require bearings.
Typical
Arrangement of:
36” CA811
This valve requires
bearings. The inner
bearing retainer is
slightly different than
the one above.

ENGINEERED & PROCESS VALVES
07/2011 / IOM-GEN-TWIN-03 9Installation, Operation and Maintenance Manual
BEARINGS/INTERNALLY & EXTERNALLY RETAINED
BEARINGS/INTERNALLY & RETAINED WITH TWO GLANDS
Typical
Arrangement of
10” CB841
10” C941
12” CB841
16” CA841
16” C941
20” CA921
24” C841
These valve sizes
require bearings
Typical
Arrangement of
8” C851
10” C851
High pressures require
hydrostatically
balanced plugs and
two glands.

ENGINEERED & PROCESS VALVES
10 07/2011 / IOM-GEN-TWIN-03
Installation, Operation and Maintenance Manual
GENERAL VALVE® Twin Seal™ SERIES 8800
Typical Arrangement of:
2” 8851
2” 8861
3” 8851
6” 8821
8” 8811
8” 8821
10” 8811
10” 8821
12” 8811
12” 8821
Typical Arrangement of:
14” 8811
16” 8811
18” 8811
20” 8811
24” 8811
NB: With the exception of
14”, 20” & 24” Models 8811G,
remaining sizes all incorporate
an internal coupling to connect
valve with the operator.
76 PIPE PLUG
4 PLUG
62 O-RING
49 GASKET
2 BONNET
6 GLAND
77 LOCATING PIN
62B BACKUP RING
62A O-RING
63 PACKING
72 CAP SCREW
5 SLIPS
1
BODY
62
O-RING
49
GASKET
3
LOWER
PLATE
76
PIPE PLUG
1
BODY
3
LOWER PLATE
75
NUT
76
PIPE PLUG
76 PIPE PLUG
5 SLIPS
62 O-RING
49 GASKET
62B BACKUP RING
71 STUD
71 STUD
62A O-RING
62B O-RING
63 PACKING 75 NUT
75A LIFTING LUG
6 GLAND
72 CAP SCREW
4
PLUG
71
STUD

ENGINEERED & PROCESS VALVES
07/2011 / IOM-GEN-TWIN-03 11 Installation, Operation and Maintenance Manual
GENERAL VALVE® Twin Seal™ MODEL 375H
Item
No.
375 H
Part No.
Description Req’d
1 21-419 Operator Housing 1
2 22-417 Upper Stem 1
3 22-418 Lower Stem 1
4 27-418 Indicator Shaft 1
5 27-419 Indicator Flag 1
6 28-406 Handwheel 1
7 45-411 Key 1
8 46-425 Bushing 1
9 48-405 Roller 1
10 50-402 Grease Retainer 1
11 62-32 O-Ring 1
12 64-415 Protector 1
13 64-417 Insignia Plate 1
14 65-402 Grease Seal 1
15 66-409 Ball Bearing 1
16 72-5 Capscrew 4
17 74-6 Screw 1
18 74-9 Set Screw 1
19 75-434 Nut 1
20 76-411 Lube Fitting 1
21 77-407 Guide Pin 1
22 77-423 Drive Pin* 1
23 77-453 Roll Pin 1
24 78-413 Retaining Ring 1
25 78-414 Retaining Ring 1
375 H is Used on Models:
2” C811
2” C821
3” CA811
3” CA821
OPERATOR DISASSEMBLY
1. Unscrew (17) and remove indicator flag (5).
2. Remove the stem protector (12).
3. Remove the handwheel nut (19),
handwheel (6), key (7) and grease
retainer ring (10).
4. Remove the retainer ring (25) and pull out
the upper stem (2) with lower stem (3),
bearing (15), roller (9) and indicator shaft
subassembly (4) out through the top of
the housing (1).
5. Remove set screw (18) from bottom of
lower stem and push indicator shaft sub-
assembly (4) out through the bottom of
the lower stem.
6. Separate the stems and remove the
retaining ring (24) and the bearing (15)
from the upper stem.
7. Remove grease seal (14) and bushing (8)
(if required) from top of upper stem (2).
8. Remove O-Ring (11) from inside housing.
OPERATOR ASSEMBLY
1. Install O-Ring (11) in housing (1).
2. Place the bearing (15) on the top of the
upper stem (2). Install retaining ring (24).
3. Apply a liberal coating of grease to all
surfaces of upper stem (2) and inside and
outside of lower stem (3).
4. Thread the upper stem and lower stem
together such that the drive pin (22) in the
upper stem comes against the shoulder at
the TOP of the lower stem (3) and the
detent recess in the upper stem is exactly in
line with roller opening in the lower stem.
NOTE: This operation may require several
attempts as the threads are multiple start
and do not always assemble correctly with
the first try.
5. Install the indicator shaft sub-assembly (4)
up through both stems. Align the detent
hole in the indicator disc with the threaded
hole in the lower stem and fasten with
set screw (18). Set screw must be below the
outside surface of the lower stem.
6. Place the roller (9) in the side opening of
the lower stem. A liberal application of
grease will hold the roller in position.
7. Place the stem assembly into the housing
taking care that roller is aligned with roller
groove in housing. Push the entire
assembly down until the bearing rests on
the shoulder in the housing.
8. Install the retaining ring (25) in the top of
the housing (1).
9. Install grease retainer (10) in handwheel (6)
and place handwheel and key (7) on upper
stem. Install bushing (8) and grease seal
(14) in handwheel nut (19). Screw the nut
on the upper stem and tighten down on
handwheel securely.
10. Install stem protector (12).
11. Install indicator flag (5) and secure
with screw(17).
Cross Section
19
17
20
25
15
22
9
18
21
4
5
12
14
8
6
10
24
7
2
3
1
16
23
13
11
17
5
12
4
19
7
25
10
24
15
22
9
1
2
3
18
21
16
5
8
6
11
Exploded View
* not available separately.

ENGINEERED & PROCESS VALVES
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Installation, Operation and Maintenance Manual
GENERAL VALVE® Twin Seal™ MODEL 500H & 625H
Item
No.
500 H
Part
No.
625 H
Part
No.
Description
1 21-411 21-407 Operator
Housing
2 22-408 22-411 Upper Stem
3 41-405 41-406 Drive Pin*
4 22-409 22-413 Lower Stem
5 26-408 26-405 Housing Cap
6 27-406 27-406 Indicator Flag
7 27-404 27-438 Indicator Shaft
8 28-409 28-401 Handwheel
9 41-403 41-403 Guide Pin
10 41-404 41-404 Detent Pin
11 45-401 45-413 Key
12 46-424 46-424 Bushing
13 47-401 47-401 Spring
14 48-401 48-403 Roller
15 62-17 62-17 O-Ring
OPERATOR DISASSEMBLY
1. Unscrew (26) and remove indicator flag (6).
2. Remove the stem protector (18).
3. Remove bearing retainer nut (27).
4. Remove the handwheel (8) and key (11).
5. Unbolt and remove the housing cover (5).
6. Unbolt and remove the guide pin (9), with detent pin (10) and spring (13).
7. Pull the upper stem (2) with lower stem (4), roller (14), bearing (20) and indicator shaft
(7) out through the top of the housing (1). If the bearing is snug in the housing, replace
the handwheel and key. Turn the handwheel clockwise to raise the lower stem as far as
possible. Insert a 3/8” diameter bar through the two holes in the bottom of the housing.
Turn the handwheel clockwise and jack the bearing clear of the housing.
8. Remove the set screw (16) and push the indicator shaft subassembly (7) out through the
bottom of the lower stem.
9. Remove the lower stem (4) from the upper stem (2).
10. Remove the retaining ring (30) and bearing (20) from the upper stem.
11. Remove the O-Ring (16) from the inside of the housing and grease seal (19) and bushing
(12) (if required) from the top of the upper stem (2).
Item
No.
500 H
Part
No.
625 H
Part
No.
Description
16 62-18 62-22 O-Ring
17 64-414 64-405 Plastic Plug
18 64-411 64-412 Protector
19 65-401 65-401 Grease Seal
20 66-402 66-403 Ball Bearing
21 72-4 72-4 Capscrew
22 72-5 72-6 Capscrew
23 72-6 72-11 Capscrew
24 72-21 72-21 Capscrew
25 74-1 74-3 Set Screw
26 73-28 74-6 Screw
27 75-427 75-429 Hex Nut
28 76-411 76-411 Lube Fitting
29 77-402 77-403 Coupling Pin
30 78-403 78-404 Retaining Ring
31 93-413 93-413 Cover
Exploded View
* not available separately.

ENGINEERED & PROCESS VALVES
07/2011 / IOM-GEN-TWIN-03 13 Installation, Operation and Maintenance Manual
625 H is Used on Models:
2” C851 2” C941
2” C861 4” C941
3” C851 6” C911
3” C861 6” C921
4” C841
4” C851
6” C821
8” C811
10” CA811
500 H is Used on Models:
2” C841 2” C921
3” C841 3” C911
4” C811 4” C911
4” C821 4” C921
6” CA811
OPERATOR ASSEMBLY
1. Place the bearing (20) on upper stem (2). Install a retaining ring (30) to lock bearing in place.
2. Apply a liberal coat of grease to all surfaces of upper stem (2) below the bearing, and to all surfaces of the lower stem (4). Thread
the upper stem (2) into the lower stem (4) such that the drive pin (3) in the upper stem comes against the shoulder at the TOP
of the lower stem and the detent recess in upper stem is exactly in line with the roller opening in lower stem.
NOTE: This operation may require several attempts as the threads are multiple start and do not always assemble correctly
with the first try.
3. Install the indicator shaft assembly (7) up through both stems. Align the detent hole in the indicator disc with the threaded hole
in the lower stem and fasten with set-screw (25). Set screw must be below the outside surface of the lower stem.
4. Install O-Ring (16) in housing (1).
5. Place roller (14) in opening of lower stem. A liberal application of grease will hold it in position.
6. Place the stem assembly into the housing - taking care that roller is aligned with roller groove in housing. Push entire assembly
down until bearing rest on shoulder in housing.
7. Apply a smooth even coating of Form-a-Gasket® to surface of guide pin boss on housing (1).
8. Insert guide pin (14) with detent pin (10) and spring (13) to fully engage slot in lower stem and secure with capscrews (21).
9. Apply a smooth even coating of Form-a-Gasket® to top surface of housing (1).
10. Install O-Ring (15) in housing cover (5) and secure to housing (1) with capscrews (22).
11. Install the handwheel (8) and key (11).
12. Install the bearing retainer nut (27) and tighten securely.
13. Install grease seal (19) and bushing (12) in top of upper stem (2).
14. Install stem protector (18).
15. Install indicator flag (6) and secure with screw (26).
Cross Section

ENGINEERED & PROCESS VALVES
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Installation, Operation and Maintenance Manual
GENERAL VALVE® Twin Seal™ Model 376G & 510G
376 G is Used on Models:
2” C811 2” C821
3” CA811 3” CA821
501 G is Used on Models:
2” C841 2” C921
3” C841 3” C911
4” C811 4” C911
4” C821 4” C921
6” CA811
8
34
18
21
23
2
9
4
19
27
16
13
5
14
21
3
32
10
1
27
15
26
29
11
12
28
7
17
20
24
25
31
6
24-444
30
Section B-B
Section A-A
Exploded View 29
11
9
11
49-648-020
7
6 20
17
1224
26
25
PLASTIC
SHIM
34
24
25
31
8
21
2
23
4
18
16 3
5
19
21
23
13
1
14
27
28 32 UPPER
30
33
35
22
32 LOWER
10
15
(376 ONLY)
Cross Section

ENGINEERED & PROCESS VALVES
07/2011 / IOM-GEN-TWIN-03 15 Installation, Operation and Maintenance Manual
OPERATOR DISASSEMBLY
1. Remove the indicator pin (34) and pull the indicator stem (8) up through the gear housing (2).
2. Remove the stop screw (35) and dowel pin (33). Drive out the upper coupling pin (32) and remove the coupling (10).
3. Remove the capscrew (29), washer (11), handwheel (9) and key (12).
4. Remove the four capscrews (27) and the gear housing cover (7).
5. Remove four capscrews (27) and lift off the gear housing (2). It may be necessary to turn the worm shaft counterclockwise to back
the worm clear of the gear while lifting off the gear housing. The worm shaft (6) and the tapered bearing cup (24) and cone (25)
on each end may now be removed from the gear housing (2).
6. The operator stem (3), upper stem (4), bearings (23), and roller (16) may now be lifted out of the operator housing.
NOTE: The cam bushing (13) and stem bushing (14) are a press fit in the operator housing and should not be removed. Should
the cam bushing require replacement, the operator housing must be returned.
GENERAL VALVE® Twin Seal™ Model 376G & 510G
Item
No.
376G
Part No.
501G
Part No. Description Req’d
1 21-583 21-555 Operator Housing 1
2 21-584 21-554 Gear Housing 1
3 22-524 22-508 Operator Stem 1
4 23-560 23-525 Upper Stem 1
5 77-465 77-464 Pin* 1
6 24-451 24-445 Worm Shaft 1
7 26-632 26-580 Gear Housing Cover 1
8 27-545 27-504 Stem Indicator 1
9 28-441 28-442 Handwheel 1
10 32-476 32-469 Coupling 1
11 44-465 44-453 Handwheel Washer 1
12 45-431 45-431 Key 1
13 46-557 46-501 Cam Bushing 1
14 46-558 46-502 Stem Bushing 1
15 46-559 - Pilot Bushing 1
16 48-405 48-401 Roller 1
17 62-71 62-34 O-Ring 1
Item
No.
376G
Part No.
501G
Part No Description Req’d
18 62-83 62-70 O-Ring 1
19 62-398 62-79 O-Ring 1
20 62-91 62-91 O-Ring 1
21 62-371 62-339 O-Ring 2
22 - 64-424 Caplug
23 66-483 66-476 Ball bearing 2
24 66-481 66-477 Cup Bearing 2
25 66-482 66-478 Cone Bearing 2
26 69-414 69-414 Spinner Handle 1
27 72-5 72-5 Capscrew 8
28 72-16 72-10 Capscrew 4
29 72-21 72-26 Capscrew 1
30 76-891 76-594 Plug 1
31 76-612 76-612 Lube Fitting 1
32 77-422 77-417 Coupling Pin 2
33 77-480 77-418 Dowel Pin 1
34 77-451 77-440 Indicator Pin 1
35 98-790 98-663 Stop Screw 1
* not available separately.

ENGINEERED & PROCESS VALVES
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Installation, Operation and Maintenance Manual
OPERATOR ASSEMBLY
1. Install O-Ring (21) in the stem bushing (14) in the operator housing (1). Place bearing (23) in the top of the operator housing (1).
2. Apply a liberal coating of grease to all surfaces of the operator stem (3) and the upper stem (4). Thread the operator stem into
the upper stem such that the dowel pin (5) comes against the shoulder at the BOTTOM of the upper stem and the detent recess in
the operator stem is exactly in line with the roller opening at the bottom of the upper stem. This operation may require
several attempts as the threads are multiple start and do not always assemble correctly with the first try.
3. Place the roller (16) in the opening of the upper stem (4) and the detent recess of the operator stem (3). An application of grease
will hold it in position.
4. Position the operator housing such that when viewed from above, the raised portion of the cam is in the lower left quadrant of
the housing bore (see cross-section illustration). With the roller on the left side, place the upper stem, operator stem and roller
(which have been assembled together–see steps 2 & 3) into the operator housing (1), down through the stem bushing (14) and
cam roller bushing (13) until the shoulder of the upper stem (4) is against the bearing (23).
5. Install bearing (23) in the gear housing (2). Install the O-Ring (21) in the top of the gear housing (2).
6. Install the tapered roller bearing cup (24) in the recess of the gear housing with the large diameter of the taper facing out.
7. Install tapered roller bearing cup (24) and cone (25) on the handwheel end of the worm shaft (6). Place bearing cone (25) on the
opposite end of the worm shaft with the large diameter of the taper against the shaft shoulder. Apply a liberal amount of grease
to all parts.
8. Install the worm shaft in the gear housing. Make certain that the rear bearing cone has properly entered the rear bearing cup.
9. Install O-Rings (17) and (20) in the gear housing cover (7) and assemble to the gear housing (2) with four of the capscrews (27).
Run the screws in just enough to keep parts in place but do not tighten at this time.
10. Install O-Ring (19) in the top of the operator housing. Place the gear housing on the operator housing with the worm gear on the
left side as viewed from the top (same side as the roller) and fasten with four of the capscrews (27).
NOTE: Worm shaft must be moved out slightly to allow parts to assemble. Tighten capscrews (27) in gear housing cover (7).
11. Assemble handwheel (9), key (12), washer (11) and capscrew (29) on the worm shaft.
12. Place a drift punch through the hole in the top of the operator stem to prevent it from turning. With the punch at 90° to the
worm shaft, turn the handwheel clockwise and run the upper stem down as far as it will go. Place the coupling (10) on the
bottom of the operator stem with the horizontal portion of the L-shaped groove at the bottom. Turn the coupling until the
coupling pin hole in the operator stem is aligned with the top hole in the coupling, and the vertical groove without the ramp is
aligned with the stop screw boss in the housing. Drive the coupling (32) into the hole in the top of the coupling and the bottom
hole of the operator stem. Install the stop screw (35) and the dowel pin (33).
NOTE: The coupling (10) has an L-shaped groove on both sides. The vertical portion of one of the grooves has a ramp at the top.
The coupling must be installed such that the side without the ramp is adjacent to, and engages the stop screw. (The ramp is used
to actuate the automatic body bleed valve when installed).
13. Install O-Ring (21) in the top of the gear housing and O-Ring (18) in the top of the lower stem (3). Place the indicator stem (8) on
the top of the operator stem and down through the gear housing. Install the indicator pin (34).

ENGINEERED & PROCESS VALVES
07/2011 / IOM-GEN-TWIN-03 17 Installation, Operation and Maintenance Manual
GENERAL VALVE® Twin Seal™ Model 625G, 751G & 755G
Exploded View
625G is Used on Models:
2” C851 2” C941
2” C861 2” 8851
3” C851 2” 8861
3” 8851 4” C941
3” C861 6” C911
4” C841 6” C921
6” C821 6” 8821
8” C811 8” 8811
10” CA811 10” 8811
751G is Used on Models:
6” C841 8” C911
8” C821 10” C911
10” C821 12” 8811
12” C811 14” 8811
14” C811
755G is Used on Models:
6” C851 8” C941
8” CA841
41
34
17
18
7
32
8
21
26, 28
24
16
4
33
5
20
11
39
13
25
36
9
10
27
43
29
6
19
2
35
1
31
14
3
12
22
38
15, 42
23
40, 30
26 28
32
7 8 21
29
13
17
34
18
11
39
24
25
16
10
36
9
27
6
2
4
10
19
43
5
20 312
14
31
38
44
37
35
23
1
15/42
30/40
22
Cross Section

ENGINEERED & PROCESS VALVES
18 07/2011 / IOM-GEN-TWIN-03
Installation, Operation and Maintenance Manual
GENERAL VALVE® Twin Seal™ Model 625G, 751G, & 755G
OPERATOR DISASSEMBLY
1. Unscrew (39) and remove indicator flag (11).
2. Remove stem protector (24).
3. Unbolt and remove gear housing cover (9).
4. Remove bearing retainer nut (16).
5. Remove bearing carrier (10) and upper bearing (27).
6. Remove upper retaining ring (43).
7. Remove capscrew (34), washer (17), handwheel (13) and key (18).
8. Unbolt and remove bearing cap (8).
CAUTION: DO NOT DAMAGE PLASTIC SHIMS.
9. Screw out the worm shaft (7). Front bearing cone (26) and cup (28) and rear bearing cone (26) will come out with the worm shaft.
Rear bearing cup (28) can then be removed from gear housing (2).
10. Remove the worm gear (6) and key (19).
11. Unbolt and remove the gear housing (2).
12. Unbolt and remove the guide pin (14).
13. Pull the upper stem (4) with lower stem (3), roller (20), lower bearing (27) and indicator shaft (12) out through the top of the
housing (1). If the bearing is snug in the housing, install the worm gear with its key on the upper stem upside down (hub up).
Turn the gear counter clockwise to raise the lower stem as far as possible. Insert a 1/2” diameter bar through the two holes in the
bottom of the housing. Using a pipe wrench on the gear hub, turn clockwise and jack the bearing clear of the housing.
14. Remove the set screw (38) and push the indicator shaft sub-assembly (12) out through the bottom of the lower stem.
15. Remove the lower stem (3) from the upper stem (4).
16. Remove the retaining ring (43) and lower bearing (27) from the upper stem.
Item
No.
625G
Part No.
751G
Part No.
755G
Part No. Description
1 21-422 21-623 21-623 Operator Housing
2 21-408 21-405 21-443 Gear Housing
3 22-440 22-555 22-555 Lower Stem
4 22-439 22-554 22-554 Upper Stem
5 41-406 41-401 41-401 Drive Pin*
6 23-402 23-403 23-406 Worm Gear
7 24-404 24-404 24-403 Worm Shaft
8 26-401 26-401 26-401 Bearing Cap
9 26-413 26-403 26-403 Gear Housing Cover
10 26-412 26-411 26-423 Bearing Carrier
11 27-406 27-406 27-406 Indicator Flag
12 27-429 27-435 27-435 Indicator Shaft
13 28-404 28-402 28-402 Handwheel
14 41-407 41-498 41-498 Guide Pin
15 77-403 41-410 41-410 Coupling Pin
16 75-462 42-401 42-401 Hex Nut
17 44-401 44-401 44-401 Washer
18 45-402 45-402 45-402 Woodruff Key
19 45-403 45-406 45-406 Straight Key
20 48-403 48-413 48-413 Roller
21 62-13 62-13 62-13 O-Ring
22 62-22 62-209 62-209 O-Ring
23 64-405 64-402 64-402 Plastic Plug
Item
No.
625G
Part No.
751G
Part No.
755G
Part No Description
24 64-411 64-411 64-411 Protector
25 65-401 65-401 65-401 Grease Seal
26 65-401 65-401 65-401 Bearing Cone
27 66-412 66-410 66-410 Bearing Ball
28 66-458 66-458 66-458 Bearing Cup
29 69-414 69-414 69-414 Spinner Handle
30 72-11 - - Stud
31 72-4 72-4 72-4 Capscrew
32 72-5 72-5 72-5 Capscrew
33 72-10 72-6 - Capscrew
34 72-8 72-8 72-8 Capscrew
35 72-9 72-9 72-9 Capscrew
36 72-14 72-14 72-26 Capscrew
37 72-21 72-21 72-21 Capscrew
38 74-3 74-4 73-28 Set Screw
39 74-6 74-6 74-6 Screw
40 - 73-130 73-130 Hex Nut
41 76-612 76-612 76-612 Lube Fitting
42 - 78-406 78-406 Retaining Ring
43 78-404 78-408 78-408 Retaining Ring
44 93-413 93-413 93-413 Cover

ENGINEERED & PROCESS VALVES
07/2011 / IOM-GEN-TWIN-03 19 Installation, Operation and Maintenance Manual
OPERATOR ASSEMBLY
1. Place one of the two bearings (27) on upper stem (4). NOTE: This bearing is assembled such that the wide surface of the inner race
seats on the upper stem shoulder. Install a retaining ring (43) to lock the bearing in place. NOTE: The retaining ring comes against
narrow surface of inner race.
2. Apply liberal coat of grease to all surfaces of the upper stem below the bearing. Thread the upper stem (4) into the lower stem
(3) such that stop pin (5) in the upper stem comes against the shoulder at the TOP of the lower stem and the detent recess in
upper stem is exactly in line with the roller opening in lower stem. This operation may require several attempts as the threads are
multiple start and do not always assemble correctly with the first try.
3. Install the indicator shaft assembly (12) up through both stems. Align the detent hole in the indicator disc with the threaded hole
in the lower stem and fasten with set screw (38). Set screw must be below the outside surface of the lower stem.
4. Install O-Ring (22) in housing (1).
5. Place roller (20) in opening of lower stem. A liberal application of grease will hold it in position.
6. Place the stem assembly into the housing–taking care that roller is aligned with roller groove in housing. Push entire assembly down
until bearing rests on shoulder in housing.
7. Apply a smooth even coating of Form-a-Gasket® to surface of guide pin boss on housing (1).
8. Insert guide pin (14) to full engage slot in lower stem and secure with capscrews (31).
9. Place gear key (19)
10. Install tapered roller bearing cup (28) in rear bearing recess of gear housing (2) with large diameter of taper facing out.
11. Install tapered roller bearing cup (28) and cone (26) on handwheel end of worm shaft (7). Place bearing cone (26) on opposite end
with large diameter of taper against shaft shoulder.
12. Install worm shaft in gear housing. Make certain that rear bearing cone has properly entered rear bearing cup (28).
13. Install O-Ring (21) in bearing cap (8).
14. Apply a smooth even coating of Form-a-Gasket® to bearing cover boss on gear housing. Fasten bearing cap (8) in place with
capscrews (32). Be sure to install the plastic shims between gear housing and bearing cap.
15. Install worm gear (6) in gear housing with hub down (toward smaller opening).
16. Apply Form-a-Gasket® to top flange of operator housing (1). Place gear housing (2) with assembled parts on top of operator
housing guiding worm gear keyway over key (19) in upper stem (3).
17. Install retaining ring (43) to secure worm gear (6).
18. Fasten gear housing (2) to operator housing (1) with capscrews (35). CAUTION: NOTE THAT THE SHORT CAP SCREW (33) IS
INSTALLED DIRECTLY UNDER THE CENTER OF THE WORM SHAFT (7).
19. Fill gear housing (2) with grease up to top of worm gear.
20. Install bearing (27) in bearing carrier (10). NOTE: The widest surface of the outer race goes against the shoulder in the
bearing carrier.
21. Apply a smooth even coating of Form-a-Gasket® over top surface of gear housing (2).
22. Place bearing carrier (10) on top of gear housing (2). Install two capscrews (36) 180° apart to temporarily align the bearing carrier.
They need only be partially screwed in.
23. Install lock nut (16) on upper stem and tighten snug with a wrench. Remove the two capscrews (36).
24. Install the grease seal (25) in the gear housing cover (9). Slide the cover over the indicator shaft (12) and secure to top of
gear housing (2) with capscrews(36).
25. Install stem protector (24).
26. Install indicator (11) and secure with socket head capscrew (39).

ENGINEERED & PROCESS VALVES
20 07/2011 / IOM-GEN-TWIN-03
Installation, Operation and Maintenance Manual
GENERAL VALVE® Twin Seal™ Model 1261G 1261-7G
1261G is Used on Models:
12” C821 8” C921
14” C821 10” CA921
16” C811 12” CA911
16” 8811 14” C911
18” C811 16” C911
18” 8811
20” CA811
20” 8811
24” 8811
Exploded View
1261-7G is Used on Models:
8” C851 12” CA921
10” CB841 18” C911
12” CB8411 20” CA911
16” CA821
18” CA821
24” CA811
29
17
611
34
16
30
8
28
39
28
27
2
28
27
37
8
22
10
24
33
7
15
25
2
18
35
40
26
3
1
12
32
13
4
21
41
14
23
11
31
19
36
42
38
5
30
8
17
6
2827
20
28
27
29
16
34
11
37
22
7
15
9
33
24
25
39 5
2
39
40
26
26
18
3
4
13
32
23
41
14
35
1
21
12
19
38
10
42
36
31
23
41
Cross Section
43 NOT
SHOWN