Sensus 121 Series User manual

RM-1328 R10
Sensus Metering Systems
Model 121 Regulators
THE GAS INDUSTRY
Installation and
Maintenance
Instructions

Introduction
The Model 121 Regulator represents a combination of capacity,
performance and value... Streamlined body passages provide large
capacity. An external control line is required from lower case to
control piping. The 121 has a fast speed of response, yet is stable
in operation. Soft seats assure positive tight shutoff. Orifices are
replaceable. Springs are color coded. It is also available as
a zero governor or atmospheric regulator, a relief valve or
backpressure regulator, and a vacuum regulator or vacuum breaker.
Installation
1. Examine the regulator for shipping damage.
2. Check nameplate data. Be sure regulator conforms with what
was ordered.
3. Inside of regulator and piping must be clean and free of dirt.
Remove all dirt and debris before installing regulator. Failure to
remove dirt/debris could result in regulator damage or trouble.
4. Remove all shipping screens and covers from the regulator. Do
not let dirt get inside the regulator.
5. Install the regulator. Make sure the inlet and outlet are correctly
connected. High pressure connects to the inlet. The flow arrow
must point downstream.
6. Screwed connections must conform with good piping practice
free of excess thread engagement per ANSI B2.1. Apply pipe joint
compound to male threads only.
7. The model 121 Regulator is usually right side-up as shown on the
Typical Installation drawing (See Page 3.) It may, however, be
installed upside down. When inverted it may be necessary to
readjust the set -point.
Caution: Do not install sideways.
The diaphragm should be horizontal.
8. On indoor installations requiring venting outdoors, run the vent
piping as short and direct as possible with minimum bends and
elbows. Use the same size or larger pipe as the vent connections
on the regulator. With natural gas, or any other hazardous gas,
vent to a safe place outdoors in case gas should accidentally be
discharged. Screen and protect the opening outdoors to guard
against water, ice, dirt, debris or insects. Install the control line.
Connect it into the outlet piping at least 5 pipe diameters
downstream from the regulator.
Cautions:
a. On backpressure regulators and relief valves the external
control line connects into the inlet piping, 5 pipe
diameters upstream from the regulator.
b. Do not install any automatic shutoff device that closes
completely between the regulator and the control line
connection into the piping.
To avoid excessive turbulence, the connection should be clean
and smooth on the inside and be located in straight pipe clear of
valves and fittings. Keep the inside of the control line clean and
protect it from corrosion. Pitch it away from the regulator and
avoid moisture pockets. It must be strong (1/4" for 121-8 and
121-12, 1/2" for 121-16, or larger steel tubing or pipe is
preferred). It must be well protected against breakage.
Regulator will open wide if the control line breaks.
9. Make sure the regulator is correctly connected and adequately
supported. Ensure all pipe joints are tight.
Start-Up
AThe inlet and outlet shutoff valves should both be closed.
If a by-pass is used, the by-pass valve should also be closed.
BNote the set-point (set-point is the outlet pressure the regulator is
adjusted to deliver). Regulator is factory adjusted to the set-point
specified on the order.
Caution: This caution applies where the piping downstream of
the outlet shutoff valve is pressured. That pressure must not
exceed the regulator set-point by more than the pressure
noted (see “Maximum Emergency Pressures”, Page 19).
CSlowly and carefully open the inlet shutoff valve just enough
to allow inlet pressure to build up slowly in the regulator
until it is fully pressured.
Caution: During start-up a pressure gauge must be used
on the regulator outlet pressure and carefully watched.
While inlet pressure builds up, outlet pressure must not
exceed set-point by more than 1 psi. If outlet pressure begins
to exceed set-point by more than 1 psi, close the inlet shutoff
valve. This indicates the regulator is not closing properly.
Check and make necessary corrections before proceeding
with start-up. If regulator outlet pressure exceeds set-point
by more than the pressure noted, refer to “Maximum
Emergency Pressures”, Page 19 for instructions.
DCheck installation for leaks.
ESlowly open the outlet shutoff valve to allow a small flow
(approximately 1000 SCFH). Make sure the flow of gas does
not create a hazard.
Note: If piping downstream of outlet shutoff valve is pressured,
see “CAUTION” under B.
FWith gas flowing, check for correct inlet and outlet pressures.
It may be necessary to further open the inlet shutoff valve to
maintain full inlet pressure.
GMake sure the regulator closes tight (tight lock-up). To do this,
reduce flow to zero by slowly closing the outlet shutoff valve.
Outlet pressure should not exceed set-point by more than 6" w.c.
HFully open inlet and outlet shutoff valves. Do this slowly and
carefully. Watch pressure gauges.
IComplete start-up by making sure there are no leaks.
NOTE
Do not exceed the regulator's pressure ratings. The regulator outlet
has a lower pressure rating than the inlet. Do not expose the
regulator outlet or control line to inlet pressure.
Regulator with external control may be used as an upstream
monitor or upstream regulator in a monitor set. The control
line must connect into the outlet piping downstream of the
downstream regulator.
If the regulator is to be moved to another location, make sure its
construction is compatible with the pressure and flow conditions.
2
Installation and Maintenance
Model 121 Regulators

Installation and Maintenance
Model 121 Regulators
Bypass (if required)
Remote Vent Line (if required)
Vent Cap
1" NPT
Vent
Inlet
Outlet
Control
Connection
Control Line
1/4" NPT (121-8 & 121-12)
1/2" NPT (121-16)
Model 121
5 Pipe
Diameters
8 – 10 Pipe Diameters
3
Temperature Limits
The Model 121 Regulator can be used for flowing temperatures from
-20° F to 150° F.
Buried Service
The Model 121 Regulator is not recommended for buried service.
Set Point Adjustment
AThe 121 is factory adjusted as specified on the order. To change
the set-point, readjust as follows:
1Remove top cap 1.
2Adjust set-point with adjustment button 3 or 3a.
Turn clockwise to increase and counterclockwise to
decrease the outlet pressure.
Note:
a. Only make this adjustment when gas is actually flowing
through the regulator. The flow should be small
(approximately 1000 SCFH). Do not adjust when the
regulator is closed and there is no flow.
b. Do not increase the set-point beyond the upper limit of the
outlet pressure range for the spring 9(refer to spring
tables, Page 4).
c. Always check the outlet pressure with a pressure gauge
while adjusting the set-point.
3When adjustment is complete, replace top cap 1.
Screw it securely into place. Failing to replace cap could
cause unstable regulator operation.
CAUTION
It is the user's responsibility to assure that all regulator vents
and/or vent lines exhaust to a non-hazardous location away from
any potential sources of ignition. Where vent lines are used, it is
the user's responsibility to assure that each regulator is individually
vented and that common vent lines are not used.
To Change Spring
AThe outlet pressure ranges of spring 9are given in the tables on
Pages 4 and 5. To change the spring:
1Remove top cap 1.
2Unscrew and remove adjustment button 3 or 3a
by turning counterclockwise, and remove spring 9.
3Insert new spring. Make sure it is positioned correctly at
the bottom before replacing adjustment button 3or 3a .
4Adjust for the desired outlet pressure per previous section
“Set Point Adjustment.”
5When adjustment is complete, replace top cap 1.
Screw it securely into place. Failing to replace
cap could result in unstable regulator operation.
6New spring range should be marked on regulator.
If old spring range appears on regulator, it should be removed.
CAUTION
The diaphragm case vent must be positioned to protect against
flooding, drain water, ice formation, traffic, tampering, etc.
The vent must be protected against nest building animals, bees,
insects, etc. to minimize the chances for foreign material from
collecting in the vent side of the regulator diaphragm.
Shutdown
ATo Take the regulator out of service, carefully close the inlet
stop valve first. Then close the outlet stop valve. Before
working on regulator, read the next section “General Servicing
Instructions” and the applicable servicing instructions.
CAUTION
Turn gas on very slowly. If an outlet stop valve is used, it should
be opened first. Do not overload diaphragm with a sudden surge
of inlet pressure. Monitor the outlet pressure during start-up to
prevent an outlet pressure overload.
General Servicing Instructions
ABefore any disassembly of the regulator, ensure it is completely
depressured. Pressure must be fully released from the inlet,
the outlet and the control line connection. Failure to adequately
depressure could result in serious personal injury.
BCarefully note the location and position of all disassembled
parts to be certain reassembly is correct. Inspect each part
carefully and replace any that are worn, damaged or otherwise
unsatisfactory.
CUpon completion of servicing, make certain that the regulator
installation is entirely free of leaks.
CAUTION
Regulators are pressure control devices with numerous
moving parts, subject to wear and dependent upon particular
operating conditions. To assure continuous satisfactory
operation, a periodic inspection schedule must be adhered
with the frequency of inspection determined by the severity
of service and applicable laws and regulations.
Typical Installation

4
Atmospheric Regulator or Zero Governor
Size Outlet Pressure Range Springs
3/4", 1" and 1-1/4" 121-8 1-1/2" w.c. vacuum (–1-1/2" w.c.) to + 1-1/2" w.c. Main Spring (Red-Black) 143-82-021-00
Counterspring (Black-Red) 121-10-021-50
1-1/2", 2" and 2-1/2" 121-12 1" w.c. vacuum (-1" w.c.) to + 1-1/2" w.c. Main Spring (Red-Black) 143-82-021-00
Counterspring 120-10-021-10
3" and 4" 121-16 1-1/4" w.c. vacuum (-1-1/4" w.c.) to + 1-1/4" w.c. Main Spring only 121-62-021-54
Outlet Pressure Ranges and Springs
Maximum Nominal
Outlet Spring Spring Inlet Diaphragm
Size Pressure Range Color Part Number Pressure Size
1-1/2" to 3-1/2" w.c. Blue-Black 143-82-021-01 (main spring)
Black-Red 121-10-021-50 (counterspring)
1-1/2" to 12" w.c. Green-Black 143-82-021-02 (main spring)
Black-Red 121-10-021-50 (counterspring)
3/4", 1" and 1-1/4" ** 3-1/2" to 6-1/2" w.c. Red-Black 143-82-021-00 60 psi 8"
Model 121-8 5" to 8-1/2" w.c. Blue-Black 143-82-021-01
6" to 14" w.c. Green-Black 143-82-021-02
12" to 28" w.c. Green (2" O.D.) 143-16-021-05
1 psi to 2 psi Orange (2" O.D.) 143-16-021-06
2 psi to 4-1/4 psi Black 143-16-021-07
3/4", 1" and 1-1/4" ** 3 psi to 6-1/2 psi Cadmium* 143-16-021-08
Model 121-8HP 6 psi to 10 psi Cadmium* 143-16-021-08 (outer) 60 psi 8"
White 143-16-021-13 (inner)
1-1/2" to 3-1/2" w.c. Red 143-16-021-03 (main spring)
_120-10-021-10 (counterspring)
1-1/2" to 12" w.c. Maroon 121-42-021-00 (main spring)
_120-10-021-10 (counterspring)
1-1/2", 2" and 2-1/2" 3-1/2" to 6-1/2" w.c. Red (2" O.D.) 143-16-021-03 60 psi 12"
Model 121-12 5" to 8-1/2" w.c. Blue (2" O.D.) 143-16-021-04
6" to 14" w.c. Green (2" O.D.) 143-16-021-05
12" to 28" w.c. Orange (2" O.D.) 143-16-021-06
1 psi to 2 psi Black 143-16-021-07
1-1/2 psi to 3 psi Cadmium 143-16-021-08
1-1/2", 2" and 2-1/2" 1 psi to 2 psi Orange (2" O.D.) 143-16-021-06 60 psi 8"
Model 121-8 2 psi to 4-1/4 psi Black 143-16-021-07
1-1/2", 2" and 2-1/2" 3 psi to 6-1/2 psi Cadmium* 143-16-021-08
Model 121-8HP 6 psi to 10 psi Cadmium* 143-16-021-08 (outer) 60 psi 8"
White 143-16-021-13 (inner)
3-1/2" to 6-1/2" w.c. Red (3" O.D.) 121-62-021-50
3" and 4" 5" to 8-1/2" w.c. Blue (3" O.D.) 121-62-021-51 15 psi (4" 121)
Model 121-16 6" to 14" w.c. Green (3" O.D.) 121-62-021-52 40 psi (3" 121 16"
14" to 28" w.c. Orange (3" O.D.) 121-62-021-53
1/2 psi to 1-1/4 psi Yellow 121-62-021-56
3" and 4" 1 psi to 2 psi Black 143-16-021-07 15 psi (4" 121)12"
Model 121-12 1-1/2 psi to 3 psi Cadmium 143-16-021-08 40 psi (3" 121
*Requires High Pressure Spring Adjustment.
** 3/4" x 3/4" not available.
Installation and Maintenance
Model 121 Regulators

Installation and Maintenance
Model 121 Regulators
5
Differential Regulator
Maximum Maximum Maximum
Differential Spring Body Diaphragm Pressure Diaphragm Case
Size Pressure Range Spring Color Part Number Pressure Differential Pressure
3-1/2" to 6-1/2" w.c. Red-Black 143-82-021-00
3/4", 1" and 1-1/4" 5" to 8-1/2" w.c. Blue-Black 143-82-021-01
121-8* 6" to 14" w.c. Green-Black 143-82-021-02 60 psi 2 psi 35 psi
12" to 28" w.c. Green 143-16-021-05
1 psi to 2 psi Orange (2" O.D.) 143-16-021-06
3-1/2" to 6-1/2" w.c. Red (2" O.D.) 143-16-021-03
1-1/2", 2" and 2-1/2" 5" to 8-1/2" w.c. Blue (2" O.D.) 143-16-021-04
121-12 6" to 14" w.c. Green (2" O.D.) 143-16-021-05 60 psi 2 psi 20 psi
12" to 28" w.c. Orange (2" O.D.) 143-16-021-06
1 psi to 2 psi Black 143-16-021-07
3-1/2" to 6-1/2" w.c. Red (3" O.D.) 121-62-021-50
3" and 4" 5" to 8-1/2" w.c. Blue (3" O.D.) 121-62-021-51 15 psi (4" 121) 1 psi 10 psi
121-16 6" to 14" w.c. Green (3" O.D.) 121-62-021-52 40 psi (3" 121)
12" to 28" w.c. Orange (3" O.D.) 121-62-021-53
3" and 4" 1 psi to 2 psi Black 143-16-021-07 15 psi (4" 121) 2 psi 20 psi
121-12 1-1/2 psi to 3 psi Cadmium 143-16-021-08 40 psi (3" 121)
*3/4 " x 3/4" not available.
Back Pressure Regulator or Relief Valve
Relief or Back Maximum Diaphragm
Size Pressure Range Spring Color Part Number Case Pressure
3" to 5-1/2" w.c. Red-Black 143-82-021-00
5" to 7-1/2" w.c. Blue-Black 143-82-021-01
3/4" thru 2-1/2" 6" to 13" w.c. Green-Black 143-82-021-02
121-8* 10" to 15" w.c. Blue (2" O.D.) 143-16-021-04 10 psi
12" to 25" w.c. Green (2" O.D.) 143-16-021-05
18" w.c. to 2 psi Orange (2" O.D.) 143-16-021-06
1 psi to 4 psi Black 143-16-021-07
3/4" thru 2-1/2" 3 psi to 6 psi Cadmium** 143-16-021-08
121-8** 6 psi to 10 psi Cadmium (outer)** 143-16-021-08 20 psi
White (inner) 143-16-021-13
3" to 5-1/2" w.c. Red (2" O.D.) 143-16-021-03
1-1/2", 2" and 2-1/2" 5" to 7" w.c. Blue (2" O.D.) 143-16-021-04
121-12 6" to 12" w.c. Green (2" O.D.) 143-16-021-05 10 psi
12" to 25" w.c. Orange (2" O.D.) 143-16-021-06
1-1/2" thru 4" 20" w.c. to 1-3/4 psi Black 143-16-021-07
121-12 1-1/2" to 2-3/4" psi Cadmium 143-16-021-08
3" to 4-1/2" w.c. Red (3" O.D.) 121-62-021-50
3" and 4" 3" to 6" w.c. Blue (3" O.D.) 121-62-021-51
121-16 5" to 11" w.c. Green (3" O.D.) 121-62-021-52 5 psi
10" to 24" w.c. Orange (3" O.D.) 121-62-021-53
14" w.c. to 1-1/4 psi Yellow 121-62-021-56
**Require High Pressure Spring Adjustment (121-8HP). *3/4" x 3/4" not available.

1
2
9
3
21b
Fig. 1
Adjustment and Vent Connection
21b for Differential Regulators,
Atmospheric Regulators and
Zero Governors
27
37
16b
a
c
a
b
e11
1a
3a
High
Pressure
Spring
Adjustment 4
5
7a
7b
9
45
21
22
23
25
24
26
29
35
38
32
19
16a
15
14
13
d
b12
13
h
fg
d
c
2a
2
21a
1/4"NPT
Control
line
connection
1"
NPT
Vent
connection
6
3/4" – 1" – 1-1/4"
Standard, Differential, Atmospheric or Zero Governors
16b
15
14
13
12
a
b
11
a
c
h
3
1
35
22
23
21
24
25 26
27
29
37 38
32
19
16a
c
d
f
d
1/4" NPT
Control
line
connection
b
13
21a
2
45 1" NPT Vent
connection
9
121-8 – Standard
121-8 HP – High Pressure
Pipe Sizes
(inlet x outlet) Screwed, NPT
3/4" x 1"
3/4" x 1-1/4"
1" x 1"
1" x 1-1/4"
1-1/4" x 1-1/4"
Installation and Maintenance
Model 121 Regulators

a
bc
fh
11
16b
2
3
9
45
21
22
23
24 25
26
27
29
14a
14b
13
38
37 32
20 16a
15
35
ab
cd
12
13
d
21a
1
1" NPT Vent
connection
1" NPT
Control
line
connection
7
h
11
13
1a 3a
High
Pressure
Spring
Adjustment
4
2a
2
21a
a
b
c
d
ef
g
27 25
26
24
23
22 21
45
21
9
7b
7a
5
1" NPT Vent
connection
1/4" NPT Control
line connection
121-8 – High Pressure – Back Pressure
3/4" – 1" – 1-1/4"
Back Pressure
Installation and Maintenance
Model 121 Regulators
121-8 – Back Pressure

8
Installation and Maintenance
Model 121 Regulators
Condensed Parts List 3/4", 1" and 1-1/4"
Illustration Description Part
Number Number
1Seal Cap 143-16-005-00
1a Seal Cap 121-10-005-52
2Tetraseal (or O-Ring) 905241
2-1/4" x 2-3/8"
2a Tetraseal (or O-Ring) 906534
1-1/2" x 1-5/8"
3Adjustment Spring Button 143-16-009-00
3a Spring Adjusting Screw 906537
4Jam Nut 1/2"-13 921005
5Housing Cover 121-10-005-51
7a Top Spring Button 121-10-009-51
7b Thrust Bearing, stainless ball, 930510
3/8" diameter
9Spring, see table “Spring Ranges”
121-8 Standard Diaphragm
Assembly (3-1/2" w.c. to 4-1/4" 121-10-550-52
psi outlet pressure)
11a Elastic Stop Nut 52-NTE-066 908561
11b Bottom Spring Button 121-10-220-50
11 11c Diaphragm Pan 121-10-017-50
11d Diaphragm, Buna-N 121-10-150-50
11d Diaphragm, Viton 121-10-150-52
11f Seal Washer 121-10-178-50
11h Diaphragm Stud, 091-16-058-02
Stainless Steel
121-8 HP High Pressure Diaphragm
Assembly (3 psi to 10 psi 121-10-550-55
outlet pressure)
11a Elastic Stop Nut 29-NE-066 903955
11b Bottom Spring Button 121-10-022-53
11c Diaphragm Pan 121-10-017-50
11 11d Diaphragm, Buna-N 121-10-150-50
11d Diaphragm, Viton 121-10-150-52
11e Upper Plate 121-10-022-52
11f Seal Washer 121-10-178-50
11g Lower Plate 121-10-079-52
11h Diaphragm Stud, 091-16-058-02
Stainless Steel
121 Seal Diaph Assembly Buna-N 121-10-564-51
121 Seal Diaph Assembly Viton 121-10-564-52
12a Piston 121-10-053-51
12 12b Seal Diaphragm, Buna-N 121-10-364-50
12b Seal Diaphragm, Viton 121-10-364-51
12c Plate 121-10-010-50
12d Stem, Stainless Steel 121-10-016-53
13 O-Ring, Buna-N, 3/8" x 1/2" 934007
O-Ring,Viton, 3/8" x 1/2" 902418
14 Wave Washer 905479
15 Molded Valve, Buna-N (45-50 Duro) 121-10-311-50
Molded Valve, Viton-A (65-75 Duro) 121-10-311-51
Condensed Parts List 3/4", 1" and 1-1/4"
Illustration Description Part
Number Number
16a Retaining Ring 904447
16b Valve Holder, split (pair required), 121-16-130-51
Stainless Steel
19 Orifice, 1-1/4" dia., brass 143-16-023-03
Orifice, 1-1/4" dia., stainless steel 143-16-023-14
26 Gasket 121-16-063-51
32 Tetraseal (or O-Ring) 2-3/8" x 2-1/2" 904081
Repair Kits, consisting of Buna-N
Main and Seal Diaphragms,
Buna-N Molded Valve plus Wave
46 Washer and Retaining Ring, Buna-N
O-Rings, Tetraseals and Gaskets:
For 121-8 121-10-598-50
For 121-8 HP 121-10-598-51
For Back Pressure Models
Item 12d above, Stem,
12 Stainless steel – substitute 121-10-016-55
Stem, Back Pressure
Item 14 above, Wave Washer – 121-16-102-52
14 substitute 121-16-103-51
Poly-U Disk Retainer 121-10-023-50
Item 19 above, Orifice – substitute
19 Orifice, Back Pressure (Brass) 121-10-023-51
Orifice, Back Pressure
(Stainless Steel)
Item 46 above, Repair Kits –
46 substitute
For 121-8 Back Pressure 121-10-598-54
For 121-8 HP Back Pressure Contact Sensus
Add Item 47
47 Valve, Seal Diaphragm and 121-10-511-54
Stem Assembly

9
Servicing – 3/4", 1", 1-1/4"
General Instructions
1. Make sure the regulator is entirely depressured before servicing.
2. Carefully note location and position of all disassembled parts
to be certain reassembly is correct. Inspect each one carefully
and replace those that are worn or damaged or otherwise
unsatisfactory.
3. A moderate application of lubricant to O-Ring 13 will help
assure free stem movement and a tight seal. Similar application
of lubricant to other O-Rings or Tetraseals will help assure
their tightness. Do not use petroleum based lubricants.
4. Bolted connections should be tightened evenly and firmly.
Carefully tighten diaphragms into place. Bolts must be tight
enough to prevent leakage, but not so tight that the diaphragm
material is crushed or damaged.
5. Upon completion of servicing, make certain that regulator
installation is entirely free of leaks.
To Service Valve – 15
1. Remove bolts 38 and remove bottom cap 37 and Tetraseal 32.
2. Remove Retaining Ring 16a.
3. Remove both halves of valve holder 16b.
4.Remove valve 15 (wave washer 14 will likely remove with
the valve. Retain it for reassembly – To reassemble,
replace parts in reverse sequence.
To Service Main Diaphragm – 11d
1. Remove top cap 1, and release and remove adjustment 3 or 3a .
On high pressure model remove cap 1a, release adjustment 3a,
and remove cover 5and button 7a. Mark or measure position
of adjustment 3or 3a. Use this to return adjustment to this
setting during assembly.
2. Remove spring 9.
3. Remove bolts 22 and upper case 21.
4. Rotate diaphragm assembly 11 counterclockwise (this unscrews
11h from 12d) and remove.
5. To disassemble diaphragm assembly, remove nut 11a.
Carefully note location and position of all parts to be certain
of correct reassembly. Abrasive side of emery cloth washers
face against diaphragm. – To reassemble, replace parts
in reverse sequence. Make sure the screwed connection
between 11h and 12d is loose by approximately 1/2 turn.
To do this, carefully rotate diaphragm assembly 11 clockwise
until this screwed connection bottoms (do not jam it together).
Then, back-off diaphragm assembly 11 counter-clockwise
approximately 1/2 turn. The 11h and 12d screwed connection
must not be tight.
Servicing
To Service Orifice – 19
1. Remove valve 15 per section “To Service Valve-15”.
2. Unscrew orifice 19 using 1-5/8" hex socket wrench.
When replacing orifice use a moderate amount of pipe
dope on orifice threads.
To Service Seal Diaphragm – 12b
1. Remove valve 15 per section “To Service Valve-15”.
2. Remove diaphragm assembly 11 per section
“To Service Main Diaphragm-11d”.
3. Remove bolts 25 and lower diaphragm case 24.
4. Remove bolts 29 and center piece 27, and then remove
seal diaphragm assembly 12.
5. To disassemble 12, unscrew piston 12a from stem 12d.
Use a spanner wrench in notch in skirt of piston
(this can also be done by inserting a standard 7/32"
Allen wrench in the notch).
–To reassemble, replace parts in reverse sequence.
Make certain that fabric side of seal diaphragm 12b
faces upward and “rubber” side faces downward toward body.
Do not pinch loop in seal diaphragm 12b between 35
and centerpiece 27.
Periodic Inspection:
Regulators are pressure control devices with numerous moving
parts subject to wear that is dependent upon particular operation
conditions. To assure continuous satisfactory operation,
a periodic inspection schedule must be adhered with the
frequency of inspections determined by the severity of service
and applicable laws and regulations.
Installation and Maintenance
Model 121 Regulators

10
Installation and Maintenance
Model 121 Regulators
Servicing – 3/4", 1", 1-1/4"
Back Pressure Models General Instructions
1. Make sure the regulator is entirely depressured before servicing.
2. Carefully note location and position of all disassembled parts
to be certain reassembly is correct. Inspect each one carefully
and replace those that are worn or damaged or otherwise
unsatisfactory.
3. A moderate application of lubricant to O-Ring 13 will help
assure free stem movement and a tight seal. Similar application
of lubricant to the other O-Rings or Tetraseals will help assure
their tightness. Do not use petroleum base lubricants.
4. Bolted connections should be tightened evenly and firmly.
Carefully tighten diaphragms into place. Bolts must be tight
enough to prevent leakage, but not so tight that the diaphragm
material is crushed or damaged.
5. Upon completion of servicing, make certain that regulator
installation is entirely free of leaks.
To Service Valve – 15
1. Remove bolts 29 and remove upper case assembly.
2. Remove Retaining Ring 16a.
3. Remove both halves of valve holder 16b.
4. Remove valve 15 (washer 14A and holder 14B will likely
remove with the valve. Retain for reassembly).
– To reassemble, replace parts in reverse sequence.
To Service Main Diaphragm – 11d
1. Remove top cap 1, and release and remove adjustment 3.
On high pressure model remove cap 1a, release adjustment 3a,
and remove cover 5and button 7a. Mark or measure position
of adjustment 3or 3a. Use this to return adjustment to
this setting during reassembly.
2. Remove spring 9.
3. Remove bolts 22, nuts 23, and upper case 21.
4. Rotate diaphragm assembly 11 counterclockwise
(this unscrews 11h from 12) and remove.
5. To disassemble diaphragm assembly, remove nut 11a.
Carefully note location and position of all parts to be certain
of correct reassembly. Abrasive side of emery cloth washers
face against diaphragm.
– To reassemble, replace parts in reverse sequence.
Make sure the screwed connection between 11h and 12d is
loose by approximately 1/2 turn. To do this, carefully rotate
diaphragm assembly 11 clockwise until this screwed connection
bottoms (do not jam it together). Then, back-off diaphragm
assembly 11 counterclockwise approximately 1/2 turn.
The 11h to 12d screwed connection must not be tight.
To Service Orifice – 20
1. Remove top cap 1, and release and remove adjustment 3.
On high pressure model remove cap 1a, release adjustment
3a, and remove cover 5and button 7a. Mark or measure
position of adjustment 3or 3a. Use this to return adjustment
to this setting during reassembly.
2. Remove spring 9.
3. Remove bolts 38 and bottom cap 37 along with Tetraseal 32.
4. Unscrew orifice 20 using 1-5/8" hex socket wrench.
When replacing orifice use a moderate amount of pipe
dope on orifice threads.
– To reassemble, replace parts in reverse sequence.
To Service Seal Diaphragm – 12b
1. Remove bolts 29, upper case assembly, and then remove
seal diaphragm, and stem assembly 12.
2. To disassemble 12, screw piston 12a from stem 12d.
Use a spanner wrench in notch in skirt of piston
(this can also be done by inserting a standard 7/32"
Allen wrench in the notch).
– To reassemble, replace parts in reverse sequence.
Make certain that fabric side of seal diaphragm 12b faces
upward and “rubber” side faces downward toward body.
Do not pinch loop in seal diaphragm 12b between 35
and centerpiece 27.
Periodic Inspection:
Regulators are pressure control devices with numerous moving
parts subject to wear that is dependent upon particular operation
conditions. To assure continuous satisfactory operation,
a periodic inspection schedule must be adhered to with the
frequency of inspections, determined by the severity of service
and applicable laws and regulations.

12d
14
1315
12f
19
12d
14
19
12e
15
Installation and Maintenance
Model 121 Regulators
2
1
3
9
45
21
22
23
24 25
26
27 29a
29 30 33
34
35
32 37
38 19a 19
13
14
15
d
c
b
a
12
13
h
f
d
c
b
a
11
21a
18
16b
16a
1" NPT Vent
connection
1/4" NPT Vent
connection
e
21
45
22
23
24
27
1
a
c
df
11
9
3
2
21a
25
26
29a
29
h
b
1" NPT Vent
connection
1/4" NPT Control
line connection
4
3a
5
7a 7b
9
21
45
21 22
23
24 25
26
29
1a
2a
2
29a
21a
abced
f
g
h11
High Pressure
Spring Adjustment
27
1" NPT Vent
connection
1/4" NPT
Control
line
connection
121-12 – Standard
121-8 – Standard
V-Port Wing Option
Standard Retainer Option
121-8 HP – High Pressure
1-1/2" – 2" – 2-1/2"
Standard, Differential, Atmospheric or Zero Governors
11
2
1
3
9
29a
Fig. 1
Adjustment 3 and Vent Connection
21b for Differential Regulators,
Atmospheric Regulators and
Zero Governors
Pipe Sizes
(inlet x outlet) Screwed, NPT
1-1/2" x 1-1/2"
1-1/2" x 2"
2" x 2"
2-1/2" x 2-1/2"
Flanged ANSI 125 lb. FF
2" x 2"

22
23
25
24
26 27 30 33
34
35 15
16a
16b
13
19
18
38
37
32
2
3
945
a
b
c
d
f
h
11
29c
29
a
b
c
d
12
1
21
19a
14b
14a
21a
1" NPT Vent
Connection
2
1
3
9
21a
abc
df
h
11
29a 29
45
21
24
1" NPT Vent
Connection
22
23
g
25
26
27
2a
1a
2
21a
a
b
c
d
e
f
g
11
h
25 26
27
29a
29
3a
4
5
7a
7b
9
21
45
21
22
23
24
High Pressure
Spring Adjustment
1" NPT Vent
connection
1/4" NPT
Control
line
connection
121-12 – Back Pressure
121-8 HP – High Pressure – Back Pressure
121-8 – Back Pressure
Installation and Maintenance
Model 121 Regulators
1-1/2" – 2" – 2-1/2"
Standard, Differential, Atmospheric or Zero Governors
12
Pipe Sizes
(inlet x outlet) Screwed, NPT
1-1/2" x 1-1/2"
1-1/2" x 2"
2" x 2"
2-1/2" x 2-1/2"
Flanged ANSI 125 lb. FF
2" x 2"

13
Installation and Maintenance
Model 121 Regulators
Condensed Parts List 1-1/2", 2" and 2-1/2"
Illustration Description Part
Number Number
1Seal Cap 143-16-005-00
1a Seal Cap 121-10-005-52
2Tetraseal (or O-Ring) 2-1/4" x 2-3/8" 905241
2a Tetraseal (or O-Ring) 1-1/2" x 1-5/8" 906534
3Adjustment Spring Button 143-16-009-00
3a Spring Adjusting Screw 906537
4Hex Steel Nut 921005
5Housing Cover 121-10-005-51
7a Top Spring Button 121-10-009-51
7b Thrust Bearing, stainless ball, 930510
3/8" diameter
9Spring, see table “Spring Ranges”
121-12 Diaphragm Assembly 121-16-550-51
(3-1/2" w.c. to 2 psi outlet pressure)
11a Elastic Stop Nut 52-NTE-066 908561
11b Bottom Spring Button 121-10-022-50
11 11c Diaphragm Pan 121-16-017-50
11d Molded Diaphragm, Buna-N 121-16-150-53
11d Diaphragm, Viton 121-16-150-55
11f Seal Washer 121-10-178-50
11h Diaphragm Stud, stainless steel 121-16-058-52
121-8 Standard Diaphragm
Assembly 121-10-551-52
(1 psi to 4-1/4 psi outlet pressure)
11a Elastic Stop Nut 29-NE-066 903955
11 11b Bottom Spring Button 121-10-022-50
11c Diaphragm Pan 121-10-017-50
11d Diaphragm, Buna-N 121-10-150-50
11d Diaphragm, Viton 121-10-150-52
11f Seal Washer 121-10-178-50
11h Diaphragm Stud, stainless steel 091-16-058-02
121-8 HP High Pressure
Diaphragm Assembly 121-10-550-55
(3 psi to 10 psi outlet pressure)
11a Elastic Stop Nut 29-NE-066 903955
11b Diaphragm Plate 121-10-022-53
11 11c Diaphragm Pan 121-10-017-50
11d Diaphragm, Buna-N 121-10-150-50
11d Diaphragm, Viton 121-10-150-52
11e Upper Plate 121-10-022-52
11f Seal Washer 121-10-178-50
11g Lower Plate 121-10-079-52
11h Diaphragm Stud, stainless steel 091-16-058-02
121 Seal Diaph Assembly, Buna-N 121-16-564-51
121 Seal Diaph Assembly, Viton 121-16-564-52
12a Piston 121-16-053-51
12b Seal Diaphragm, Buna-N 121-16-364-50
12 12b Seal Diaphragm, Viton 121-16-364-51
12c Plate 121-16-010-53
12d Stem, stainless steel 121-16-016-53
12e Retainer 121-16-016-00
12f V-Port Wings 121-16-012-52
O-Ring, Buna-N 3/8" x 1/2" 934007
13 O-Ring, Viton 3/8" x 1/2" 902418
14 Wave Washer 905479
Condensed Parts List 1-1/2", 2" and 2-1/2"
Illustration Description Part
Number Number
15 Molded Valve, Buna-N (45-50 Duro) 121-16-311-50
Molded Valve, Viton-A (65-75 Duro) 121-16-311-51
16a Retaining Ring 904447
16b Valve Holder, split (pair required) 121-16-130-51
stainless steel
18 Tetraseal (or O-Ring) 904207
2-1/2" x 2-11/16"
19 Orifice, 2-5/32" dia., stainless steel 121-16-023-51
Orifice, 2-5/32" dia., stainless steel 121-16-023-52
19a Retaining Ring, stainless 904656
26 Gasket 121-16-063-51
29a Copper Washer 121-16-178-51
30 O-Ring, 3-1/8" x 3-1/2" 934041
32 Tetraseal (or O-Ring) 3-1/4" x 3-1/2" 904078
33 Seal Diaphragm Ring 121-16-008-50
34 Gasket 121-16-104-50
45 Travel Indicator Contact Sensus
Repair Kits, consisting of Buna-N Main and Seal
Diaphragms, Buna-N Molded Valve plus Wave
Washer and Retaining Ring, Buna-N O-Rings,
46 Tetraseals and Gaskets:
For 121-12 121-16-598-50
For 121-8 121-86-598-50
For 121-8 HP 121-86-598-51
For Back Pressure Models
Item 12d above, Stem,
12 Stainless Steel – 121-16-016-55
substitute Stem, Back Pressure
Item 14 above,
14 Wave Washer – substitute
Poly-U Disk 121-16-102-52
Retainer 121-16-103-51
Item 46 above,
Repair Kits – substitute
46 For 121-12 Back Pressure 121-16-598-52
For 121-8 Back Pressure 121-86-598-54
For 121-8 HP Back Pressure 121-86-598-55
Add item 47
47 Valve, Seal Diaphragm and 121-16-511-51
Stem Assembly

14
Servicing – 1-1/2", 2", 2-1/2"
General Instructions
1. Make sure the regulator is entirely depressured before servicing.
2. Carefully note location and position of all disassembled parts
to be certain reassembly is correct. Inspect each one carefully
and replace those that are worn or damaged or otherwise
unsatisfactory.
3. A moderate application of lubricant to O-Ring 13 will help assure
free stem movement and a tight seal. Similar application of
lubricant to other O-Rings or Tetraseals will help assure their
tightness. Do not use petroleum base lubricants.
4. Bolted connections should be tightened evenly and firmly.
Carefully tighten diaphragms into place. Bolts must be tight
enough to prevent leakage, but not so tight that the diaphragm
material is crushed or damaged.
5. Upon completion of servicing, make certain that regulator
installation is entirely free of leaks.
To Service Valve – 15
1. Remove bolts 38 and remove bottom cap 37 and Tetraseal 32.
2. Remove Retaining Ring 16a.
3. Remove both halves of valve holder 16b.
4. Remove valve 15 (wave washer 14 will likely remove with the
valve. Retain for reassembly. – To reassemble, replace parts
in reverse sequence.
To Install V-Port Wing – 12f
1. Remove valve 15 per assembly “To Service Valve - 15”.
2. Remove wave washer 14.
3. Remove retainer 12e. It will not be used.
4. Reinstall wave washer 14.
5. Install V-Port wing 12f on stem with v-notch side against the
wave washer and flat area exposed.
6. Reassemble remaining parts in reverse sequence.
To Service Main Diaphragm – 11d
1. Remove top cap 1, and release and remove adjustment 3.
On high pressure model remove cap 1a, release adjustment 3a,
and remove cover 5and button 7a. Mark or measure position
of adjustment 3or 3a. Use this to return adjustment to this
setting during reassembly.
2. Remove spring 9.
3. Remove bolts 22 and upper case 21.
4. Rotate diaphragm assembly 11 counterclockwise (this unscrews
11h from 12d) and remove.
5. To disassemble diaphragm assembly, remove nut 11a.
Carefully note location and position of all parts to be certain
of correct reassembly. Abrasive side of emery cloth washers face
against diaphragm.
– To reassemble, replace parts in reverse sequence.
Make sure the screwed connection between 11h and 12d is
loose by approximately 1/2 turn. To do this, carefully rotate
diaphragm assembly 11 clockwise until this screwed connection
bottoms (do not jam it together). Then back-off diaphragm
assembly 11 counterclockwise approximately 1/2 turn.
The 11h to 12d screwed connection must not be tight.
To Service Orifice – 19
1. Remove valve 15 per section “To Service Valve-15”.
2. Remove main diaphragm assembly 11 per steps 1 through 4
“To Service Main Diaphragm-11d”.
3. Remove seal diaphragm assembly 12 per steps 3 and 4 under
“To Service Seal Diaphragm-12b”.
4. Remove Retaining Ring 19a.
5. Remove orifice 19 through top opening.
To reassemble, replace parts in reverse sequence.
(On reassembly, ensure that 19a is fully seated in its groove.
Also, beveled edge of 19a faces downward toward bottom
cap 37.)
To Service Seal Diaphragm – 12b
1. Remove valve 15 per assembly “To Service Valve-15”.
2. Remove main diaphragm assembly 11 per steps 1 through 4
“To Service Main Diaphragm-11d”.
3. Remove bolts 25 and lower diaphragm case 24.
4. Remove bolts 29 and centerpiece 27, and then remove seal
diaphragm assembly 12.
5. To disassemble 12, unscrew piston 12a from stem 12d.
Use a spanner wrench in notch in skirt of piston
(this can also be done by inserting a standard 7/32"
Allen wrench in the notch).
To reassemble, replace parts in reverse sequence.
Make certain that fabric side of seal diaphragm 12b faces
upward and “rubber” side faces downward toward body.
Do not pinch loop in seal diaphragm 12b between ring 33
and centerpiece 27. Also, rounded edge of 33 faces upward
toward seal diaphragm 12b.
Periodic Inspection:
Regulators are pressure control devices with numerous moving
parts subject to wear that is dependent upon particular operation
conditions. To assure continuous satisfactory operation,
a periodic inspection schedule must be adhered to with the
frequency of inspections, determined by the severity of service
and applicable laws and regulations.
Installation and Maintenance
Model 121 Regulators

Installation and Maintenance
Model 121 Regulators
Servicing – 1-1/2", 2", 2-1/2" Back Pressure Models
General Instructions
1. Make sure the regulator is entirely depressured before servicing.
2. Carefully note location and position of all disassembled parts
to be certain reassembly is correct. Inspect each one carefully
and replace those that are worn or damaged or otherwise
unsatisfactory.
3. A moderate application of lubricant to O-Ring 13 will help assure
free stem movement and a tight seal. Similar application of
lubricant to other O-Rings or Tetraseals will help assure their
tightness. Do not use petroleum base lubricants.
4. Bolted connections should be tightened evenly and firmly.
Carefully tighten diaphragms into place. Bolts must be tight
enough to prevent leakage, but not so tight that the diaphragm
material is crushed or damaged.
5. Upon completion of servicing, make certain that regulator
installation is entirely free of leaks.
To Service Main Diaphragm – 11d
1. Remove top cap 1, and release and remove adjustment 3.
On high pressure model remove cap 1a, release adjustment 3a,
and remove cover 5and button 7a. Mark or measure position
of adjustment 3or 3a. Use this to return adjustment to this
setting during reassembly.
2. Remove spring 9.
3. Remove bolts 22, nuts 23 and upper case 21.
4. Rotate diaphragm assembly 11 counterclockwise
(this unscrews 11h from 12) and remove.
5. To disassemble diaphragm assembly, remove nut 11a.
Carefully note location and position of all parts to be certain
of correct reassembly. Abrasive side of emery cloth washers
face against diaphragm.
To reassemble, replace parts in reverse sequence.
Make sure the screwed connection between 11h and 12d is
loose by approximately 1/2 turn. To do this, carefully rotate
diaphragm assembly 11 clockwise until this screwed connection
bottoms (do not jam it together). Then, back-off diaphragm
assembly 11 counterclockwise approximately 1/2 turn. The 11h
to 12d screwed connection must not be tight.
To Service Seal Diaphragm – 12b
1. Remove main diaphragm assembly 11 per steps 1 through 4
“To Service Main Diaphragm-11d”.
2. Remove bolts 29 and centerpiece 27, then remove seal
diaphragm, valve and stem assembly 12.
3. To disassemble 12, unscrew piston 12a from stem 12d.
Use a spanner wrench in notch in skirt of piston (this can also
be done by inserting a standard 7/32" Allen wrench in the notch).
– To reassemble, replace parts in reverse sequence.
Make certain that fabric side of seal diaphragm 12b faces
upward and “rubber” side faces downward toward body.
Do not pinch loop on seal diaphragm 12b between ring 33
and centerpiece 27, Also rounded edge of 33 faces upward
toward seal diaphragm 12b.
To Service Valve – 15
1. Remove main diaphragm assembly 11 per steps 1 through 4
“To Service Main Diaphragm-11d”.
2. Remove seal diaphragm, valve and stem assembly to service
seal diaphragm 12b.
3. Remove Retaining Ring16a.
4. Remove both halves of valve holder 16b.
5. Remove valve 15 (washer 14 and holder 14a will likely
remove with the valve. Retain for reassembly.)
– To reassemble, replace parts in reverse sequence.
To Service Orifice – 19
1. Remove main diaphragm assembly 11 per steps 1 through 4
“To Service Seal Diaphragm-11d”.
2. Remove seal diaphragm, valve and stem assembly 12 per
steps 2 and 3 under “To Service Seal Diaphragm-12b”.
3. Remove Retaining Ring 19a through top opening .
4. Remove orifice 19 through bottom opening.
– To reassemble, replace parts in reverse sequence.
(On reassembly, be sure that 19a is fully seated in its groove.
Also, beveled edge of 19a faces upward toward adapter 27).
Periodic Inspection:
Regulators are pressure control devices with numerous moving
parts subject to wear that is dependent upon particular operation
conditions. To assure continuous satisfactory operation,
a periodic inspection schedule must be adhered to with the
frequency of inspections, determined by the severity of service
and applicable laws and regulations.
15

16
Installation and Maintenance
Model 121 Regulators
2
1
3
4
525
21
22
23
25
27
29
33
35 32
37
38 19a
19
18
17
16b
16a
15
15a
14
a
b
c
d
12
13
2a
8
7
9
10
21a a
b
c
d
f
h
11
45
26
28
32
34
24
1" NPT Vent
connection
3" 121 as shown.
4" uses a spacer, approx.
1" O.D. x 3/4" I.D. x 3/16" thick
2
1
3
9
45
21
22
23
24
25
26 27 28
13
a
b
c
d
f
h
11
21a
1/4" NPT
Control
line connection
2
1
3
26
5
4
21a
h
f
d
c
b
a
11
13
a
b
c
d
12
14
15a
15
16a
16b
17
18
19
19a
38
37
32
35
21
45
22
23 24
25 26
27 28
29 32
33 34
2a
8
7
9
10
1/4" NPT
Control line
connection
2a
1
3
9
45
21
a
b
c
d
f
h
11
21a
22
23
24
28272625
1" NPT Vent
connection
1/4" NPT
Control line
connection
3" – 4" Standard
3" – 4"
Back Pressure
Pipe Sizes
(inlet x outlet)
Flanged ANSI
125 lb. FF
3" x 3"
4" x 4"

17
Installation and Maintenance
Model 121 Regulators
Condensed Parts List 3" and 4"
Illustration Description Part
Number Number
3" and 4" Model 121
1Seal Cap for 121-16 138-02-005-01
Seal Cap for 121-12 143-16-005-00
2Seal Cap Gasket for 121-16 120-08-066-00
Tetraseal for 121-12, 2-1/4" x 2-3/8" 905241
3Adjustment Spring Button for 143-16-009-00
for 121-12
8Thrust Washer 141-10-160-01
9Spring see table “Spring Ranges”
121-16 Diaphragm Assembly 121-62-550-50
11a Elastic Stop Nut 52-NTE-066 903955
11b Bottom Spring Button 121-62-022-50
11 11c Diaphragm Pan 121-62-017-50
11d Diaphragm, Buna-N 121-62-150-50
11d Diaphragm, Viton 121-62-150-52
11f Seal Washer 121-10-178-50
11h Diaphragm Stud, stainless steel 121-16-058-52
121-12 Diaphragm Assembly
(3-1/2" w.c. to 2 psi outlet pressure) 121-16-550-51
11a Elastic Stop nut 29-NE-066 903955
11b Bottom Spring Button 121-10-022-50
11 11c Diaphragm Pan 121-16-017-50
11d Molded Diaphragm, Buna-N 121-16-150-53
11d Diaphragm, Viton 121-16-150-55
11f Seal Washer 121-10 178-50
11h Diaphragm Stud, stainless steel 121-16-058-52
13 O-Ring, Buna-N, 3/8" x 1/2" 934007
O-Ring, Viton, 3/8" x 1/2" 902418
14 Wave Washer 905481
16a Retaining Ring 904448
16b Valve Holder, split (pair required), 121-22-130-51
stainless steel
17 O-Ring, Buna-N, 5/8" x 3/4" 902922
O-Ring, Viton, 5/8" x 3/4" 902698
26 Tetraseal (or O-Ring) 4-3/8" x 4-5/8" 904085
28 Tetraseal (or O-Ring) 2-3/4" x 3" 904079
Repair Kits, consisting of Buna-N
Main and Seal Diaphragm, Buna-N
Molded Valve plus Wave Washer
and Retaining Ring, Buna-N
46 O-Rings, Tetraseals and Gaskets
3" 121-16 121-60-598-50
3" 121-12 121-20-598-50
4" 121-16 121-62-598-50
4" 121-12 121-22-598-50
For Back Pressure Models
Item 14 above,
14 Wave Washer – substitute
Poly-U Disk 121-22-102-52
Retainer 121-22-103-50
17
Condensed Parts List 3" and 4"
Illustration Description Part
Number Number
3" Model 121 only
12a Piston 121-20-053-50
12b Seal Diaphragm, Buna-N 121-20-364-50
12 12b Seal Diaphragm, Viton 121-20-364-51
12c Plate 121-20-010-50
12d Stem, stainless steel 121-20-016-51
15 Molded Valve, Buna-N (45-50 Duro) 121-20-311-50
Molded Valve, Viton-A (65-75 Duro) 121-20-311-51
15a Valve Wing 121-20-018-50
Valve Wing, stainless steel 121-20-018-51
18 Tetraseal (or O-Ring) 3-3/4" x 4" 904200
19 Orifice, 3-1/4" dia., steel 121-20-023-50
Orifice, 3-1/4" dia., stainless steel 121-20-023-51
19a Retaining Ring, stainless 904660
32 Tetraseal (or O-Ring) 5" x 5-1/4" 934328
33 Seal Diaphragm Ring 121-20-008-50
34 Gasket 121-20-104-50
45 Travel Indicator 091-00-365-00
(specify scale 091-00-008-02)
For Back Pressure Models
12 Item 12d above, Stem - substitute
Stem, Back Pressure 121-20-016-53
47 Add item 47
Valve, Seal Diaphragm and 121-20-511-50
Stem Assembly
4" Model 121 only
12a Piston 121-22-053-50
12b Seal Diaphragm, Buna-N 121-22-264-50
12 12b Seal Diaphragm, Viton 121-22-364-51
12c Plate 121-22-010-50
12d Stem, steel 121-22-016-53
12d Stem, stainless steel 121-22-016-51
15 Molded Valve, Buna-N (45-50 Duro) 121-22-311-50
Molded Valve, Viton-A (65-75 Duro) 121-22-311-51
15a Valve Spacer 121-22-038-50
18 Tetraseal (or O-Ring) 4-3/4" x 5" 950625
19 Orifice, 4-7/32" dia., steel 121-22-023-50
19a Retaining Ring 904229
20 Orifice, 4-7/32" dia., Stainless steel 121-22-023-52
Retaining Ring, stainless 121-22-130-52
20a Pliers for Retaining Ring 19a OB5
Truarc 0600
32 O-Ring 6-1/4" x 6-1/2" 934337
33 Seal Diaphragm Ring 121-22-008-50
34 Gasket 121-22-104-50
45 Travel indicator 091-00-365-00
(specify scale 091-00-008-002)
For Back Pressure Models
12 Item 12d above, Stem - substitute 121-20-016-53
Stem, Back Pressure
Add item 47
47 Valve, Seal Diaphragm and Stem 121-20-511-50
Assembly

18
Servicing – 3", 4"
General Instructions
Same general instructions as listed on page 9.
To Service Valve – 15
1. Remove bolts 38 and remove bottom cap 37.
2. Remove Retaining Ring 16a.
3. Remove both halves of valve holder 16b.
4. Remove valve 15, and wing 15a or spacer
(wave washer 14 will likely remove with the valve. Retain it
for reassembly. – To reassemble, replace parts in reverse
sequence.
To Service Main Diaphragm – 11d
1. Remove top cap 1.
2. Release adjustment 3 (count the turn of adjustment 3and use
for returning the adjustment to this setting during assembly).
3. Remove bolts 10 and housing 5(3" and 4" 121-16 only).
4. Remove spring 9.
5. Remove bolts 22 and upper case 21.
6. Rotate diaphragm assembly 11 counterclockwise
(this unscrews 11h from 12d) and remove.
7. To disassemble diaphragm assembly, remove nut 11a.
Carefully note location and position of all parts to be certain
of correct reassembly. Abrasive side of emery cloth washers
face against diaphragm.
– To reassemble, replace parts in reverse sequence.
Make sure the screwed connection between 11h and 12d is
loose by approximately 1/2 turn. To do this, carefully rotate
diaphragm assembly 11 clockwise until this screwed connection
bottoms (do not jam it together). Then back-off diaphragm
assembly 11 counterclockwise approximately 1/2 turn. The 11h to
12d screwed connection must not be tight.
To Service Orifice – 19
1. Remove valve 15 per section “To Service Valve – 15”.
2. Remove seal diaphragm assembly 12 per step 2 under “To
Service Seal Diaphragm – 12b”.
3. Remove Retaining Ring 19a.
4. Remove ring 33 and orifice 19 through top opening. – To
reassemble, replace parts in reverse sequence. (On reassembly,
be sure that 19a is fully seated in its groove. Also, beveled edge
of 19a faces downward toward bottom cap 37).
To Service Seal Diaphragm – 12b
1. Remove valve 15 per section “To Service Valve – 15”.
2. Remove bolts 29 and upper case assembly. Then remove seal
diaphragm assembly 12.
3. To disassemble 12, unscrew piston 12a from stem 12d. Use a
spanner wrench in notch in skirt of piston (this can also be done
by inserting a standard 7/32" Allen wrench in the notch).
– To reassemble, replace parts in reverse sequence. Make certain
that fabric side of seal diaphragm 12b faces upward and “rubber”
side faces downward toward body. Do not pinch loop in seal
diaphragm 12b between ring 33 and centerpiece 27.
Also, rounded edge of 33 faces upward toward seal diaphragm
12b. Make sure the screwed connection 11h and 12d is loose
by approximately 1/2 turn. To do this, carefully rotate seal
diaphragm assembly 12 clockwise until this screwed connection
bottoms (do not jam it together). Then, back-off seal diaphragm
assembly 12 counter-clockwise approximately 1/2 turn. The 11h
to 12d screwed connection must not be tight.
Servicing – 3", 4"
Back Pressure Models General Instructions
Same general instructions as listed on page 9.
To Service Valve – 15
1. Remove bolts 29 and remove upper case and assembly 33.
2. Remove Retaining Ring 16a.
3. Remove both halves of valve holder 16b.
4. Remove valve 15 and wing 15a or spacer (washer 14 and
holder 14b will likely remove with valve. Retain for reassembly).
– To reassemble, replace parts in reverse sequence.
To Service Main Diaphragm – 11d
1. Remove top cap 1.
2. Release adjustment 3(count the turns of adjustment 3and use
for returning the adjustment to this setting during reassembly)
3. Remove bolts 10 and housing 5(3" and 4" 121-16 only)
4. Remove spring 9.
5. Remove bolts 22 and upper case 21.
6. Rotate diaphragm assembly 11 counterclockwise
(this unscrews 11h from 12d) and remove.
7. To disassemble diaphragm assembly, remove nut 11a.
Carefully note location and position of all parts to be certain
of correct reassembly. Abrasive side of emery cloth washers
face against diaphragm.
– To reassemble, replace parts in reverse sequence.
Make sure the screwed connection between 11h and 12d is
loose by approximately 1/2 turn. To do this, carefully rotate
diaphragm assembly 11 clockwise until this screwed connection
bottoms (do not jam it together). Then back-off diaphragm
assembly 11 counterclockwise approximately 1/2 turn. The 11h
to 12d screwed connection must not be tight.
To Service Orifice – 19
1. Remove valve 15 per section “To Service Valve – 15”, item 1.
2. Remove Retaining Ring 19a and ring 33 through top opening.
3. Remove orifice 19 through bottom opening.
– To reassemble, replace parts in reverse sequence.
(On reassembly, be sure that 19a is fully seated in its groove,
and beveled edge of 19a faces downward toward bottom cap 37.)
Installation and Maintenance
Model 121 Regulators

4
2
1
3
5
9
To Service Seal Diaphragm – 12b
1. Remove valve 15 per section “To Service Valve – 15”, item 1.
2. Remove bolts 29 and upper case assembly and then remove
seal diaphragm assembly 12.
3. To disassemble 12, unscrew piston 12a from stem 12d.
Use a spanner wrench in notch in skirt of piston (this can also
be done by inserting a standard 7/32" Allen wrench in the notch).
– To reassemble, replace parts in reverse sequence.
Make certain that fabric side of seal diaphragm 12b faces
upward and “rubber” side faces downward toward body.
Do not pinch loop in seal diaphragm 12b between ring 33 and
centerpiece 27. Also, rounded edge of 33 faces upward toward
seal diaphragm 12b. Make sure the screwed connection
between 11h and 12d is loose by approximately 1/2 turn. To
do this, carefully rotate seal diaphragm assembly 12 clockwise
until this screwed connection bottoms (do not jam it together).
Then back-off seal diaphragm assembly 12 counterclockwise
approximately 1/2 turn. The 11h to 12d screwed
connection must not be tight
Variations
Vacuum Breaker
Vacuum Breakers are vacuum limiting devices. In their general function, they can be compared
to relief valves or back pressure regulators.
The breaker outlet and control line are piped to the vacuum. The breaker inlet connects to a lesser
vacuum, to atmosphere or to a positive pressure. The maximums for the positive pressure are
60 psi for 3/4" through 2-1/2" sizes, 40 psi for 3" and 15 psi for 4". The vacuum breaker is normally
closed and excess vacuum creates a valve opening movement which increases flow from the inlet
and thereby relieves or “breaks” the excess.
All of the pipe sizes listed on Page 24 are available 3/4" through 4". Note on the cutaway drawing
that the main spring is reversed to provide the upward closing force on the valve. Except for certain
parts used in the spring assembly, everything else is interchangeable with standard 121 regulators.
Vacuums and Springs
Vacuum Range
w.c. vacuum Spring
Size (– w.c.) Spring Color Part Number
3" to 6-1/2" Red-Black 143-82-021-00
5" to 8-1/2" Blue-Black 143-82-021-01
3/4", 1" and 1-1/4" 8" to 14" Green-Black 143-82-021-02
121-8 12" to 20" Blue (2" O.D.) 143-16-021-04
18" to 30" Green (2" O.D.) 143-16-021-05
30" to 56" Orange (2" O.D.) 143-16-021-06
3" to 6-1/2" Red (2" O.D.) 143-16-021-03
1-1/2", 2" and 2-1/2" 5" to 8-1/2" Blue (2" O.D.) 143-16-021-04
121-12 8" to 14" Green (2" O.D.) 143-16-021-05
12" to 28" Orange (2" O.D.) 143-16-021-06
28" to 56" Black 143-16-021-07
3" and 4" 3" to 5-1/2" Red (3" O.D.) 121-62-021-50
121-16 4" to 7-1/2" Blue (3" O.D.) 121-62-021-51
7" to 14" Green (3" O.D.) 121-62-021-52
3" and 4" 12" to 28" Orange (2" O.D.) 143-16-021-06
121-12 28" to 56" Black 143-16-021-07
Installation and Maintenance
Model 121 Regulators
19

To Service Vacuum Breaker or Vacuum Regulator
1. Remove cover cap 1. Measure depth from top of cover to ferrule 5 for assembly.
2. Hold Stem 2from turning using screwdriver on end of stem.
3. Unlock nut 3from nut 4and remove nut 3.
4. Slowly remove nut 4maintaining pressure on spring ferrule 5to prevent ejection of the spring from
the upper case.
CAUTION: Do not allow stem 2to unscrew during removal of nut 4.
5. Remove spring 9.
6. To service vacuum breaker, follow procedure for standard regulators by size.
7. To service vacuum regulator, follow procedure for back pressure regulators by size.
Installation and Maintenance
Model 121 Regulators – Variations
Vacuums and Springs
Vacuum Range
w.c. vacuum Spring
Size (– w.c.) Spring Color Part Number
3" to 6-1/2" Red-Black 143-82-021-00
3/4", 1" and 1-1/4" 5" to 8-1/2" Blue-Black 143-82-021-01
121-8 8" to 14" Green-Black 143-82-021-02
12" to 20" Blue 143-16-021-04
18" to 30" Green 143-16-021-05
1-1/2", 2" and 2-1/2" 3 to 6-1/2" Red 143-16-021-03
121-12 5" to 8-1/2" Blue 143-16-021-04
8" to 14" Green 143-16-021-05
1
3
5
9
4
2
Vacuum Regulator
Vacuum Regulators are used to maintain a certain negative pressure (vacuum) in enclosed spaces
such as tanks, vessels, chambers, piping systems, etc. In general, these are piped to the regulator
inlet and control line connections and the regulator outlet piped to the inlet of a vacuum pump
or other vacuum source.
Available pipe sizes are 3/4" thru 2-1/2", as listed on Page 24. Note on the cutaway drawing that
the spring assembly is arranged for an upward force on the valve. Also, the valve itself is normally
open and moves downward to close rather than upward as in the standard 121. With the exception
of certain parts involved in the foregoing, everything else is interchangeable with standard
121 regulators.
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