Emerson 122A Data Sheet

Bulletin 71.7:122A

Type 122A Three-Way Switching Valve

Introduction

The Type 122A valve (see Figure 1) is a high­capacity, economical three-way pneumatic switching
valve for on-off applications. This valve can be
used for diverging or converging gaseous service,
diverging liquid service with gas-loaded liquids, and
converging liquid service. Six spring ranges are
available for control pressures from 3 to 150 psig
(0,21 to 10,3 bar).

Features

• Convenient Installation—Compact construction

permits easy handling and installation.

December 2009

• Easy Leak Detection—Vent hole between body
and actuator stem seals allows rapid detection of
body or actuator leakage.

• Easy Maintenance—With the bottom piping
disconnected, the valve can be completely
disassembled without removing it from the line.

Principle of Operation

Refer to Figure 2. The ow through the Type 122A

valve is normally from port A to C, with the spring
force holding the valve plug down on port B
(diverging service).

As the pressure under the diaphragm is increased
through port D, it acts against the force of the spring.
When the control pressure overcomes the force of
the spring, the valve begins to stroke, opening port B.
Once the pressure under the diaphragm reaches
setpoint plus build-up, the valve completes its stroke
and the port C seat ring is closed. The valve will only
fully stroke when build-up above setpoint is achieved.

The point at which the valve completes its stroke
and the pressure change necessary to do this
are dependent on the spring rate and the setpoint
chosen. The set pressure is easily changed by
adjusting the screw at the top of the valve.

W3141-1*

Figure 1. Type 122A Three-Way Switching Valve

Installation

The Type 122A valve may be installed in any position.
Be certain the spring case vent opening is pointing
down and is protected against the entrance of the
moisture and any other material that may plug the
vent. The Type 122A valve should not be used in
installations where water hammer can be experienced.
Dimensions are shown in Figure 3.

Overpressure Protection

Type 122A Three-Way Switching Valves have
maximum outlet pressure ratings that are lower than
their maximum inlet pressure ratings. A pressure­relieving or pressure-limiting device is needed if inlet
pressure can exceed the maximum outlet pressure
rating. Overpressuring any portion of a switching
valve or associated equipment may cause leakage,

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D200075X012

Bulletin 71.7:122A

INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE

Specications

Body Sizes and End Connection Styles

Connections A and C: Available in 3/4 or 1 body
sizes with NPT end connections
Connection B: 3/4 NPT

Maximum Inlet Pressure

(1)

150 psig (10,3 bar)

Set Pressure Ranges

See Table 1

Maximum Control Pressure to Diaphragm

(1)

150 psig (10,3 bar)

Temperature Capabilities

(1)

-20° to 150°F (-29° to 66°C)

Construction Materials

Valve Body: Cast iron
Bottom Connector: Steel
Spring Case: Aluminum
Lower Diaphragm Case: Cast iron
Disk and Disk Holder Assembly: Nitrile (NBR)
and Aluminum or Nitrile (NBR) and Stainless steel

1. The pressure/temperature limits in this Bulletin and any applicable standard or code limitation should not be exceeded.

2. At an inlet pressure of 25 psig (1,7 bar) and with full pressure drop across the body.

Orice: Aluminum or Stainless steel
Diaphragm: Neoprene (CR)
Gaskets: Composition
O-Rings: Nitrile (NBR)
Washers: Zinc-plated steel and
302 Stainless steel
Spring: Zinc-plated steel

Flow Coefcients

(2)

C

g

Connection A to B: 138
Connection A to C: 131
C

1

Connection A to B: 28.0
Connection A to C: 32.5

Control Connection

1/4 NPT internal

Vent Connection

1/4 NPT internal with screen

Approximate Weight

5 pounds (2 kg)

W0157

INLET PRESSURE
OUTLET PRESSURE

ATMOSPHERIC PRESSURE

STEM

PORT D

PORT A

PORT B

ADJUSTING SCREW

SPRING

DIAPHRAGM

UPPER VAVE SEAT

PORT C

VALVE

LOWER VAVE SEAT

Figure 2. Type 122A Three-Way Switching Valve Operational Schematic

2

Table 1. Set Pressure Ranges

Bulletin 71.7:122A

SET PRESSURE

RANGES

Psig bar Psig bar Inches mm Inches mm

3 to15
5 to 20
5 to 35

30 to 60
40 to 100
60 to 150

0,21 to 1,0
0,34 to 1,4
0,34 to 2,4

2,1 to 4,1
2,8 to 6,9

4,1 to 10,3

parts damage, or personal injury due to bursting of

PRESSURE BUILD-UP

ABOVE SETPOINT

REQUIRED FOR

FULL STROKE

10

13.5
22

30
54
66

0,69
0,93

1,5

2,1
3,7
4,6

SPRING

PART

NUMBER

1D892327022
1D751527022
1D665927022

1D7455T0012
1E543627142
1P901327142

SPRING

COLOR

Red

Cadmium

Blue

Green
Yellow
Brown

SPRING WIRE DIAMETER SPRING FREE LENGTH

0.168

0.187

0.218

0.234

0.283

0.240

4,27
4,75
5,54

5,94
7,19
6,10

Ordering Information

2.94

2.81

2.50

2.57

2.31

2.63

pressure-containing parts or explosion of accumulated
gas. Switching valve operation within ratings does
not preclude the possibility of damage from external
sources or from debris in the pipeline. A switching
valve should be inspected for damage periodically and
after any overpressure condition.

Refer to the Specications section. Review the
description to the right of each specication and in

the referenced table and specify the desired choice
wherever there is a selection to be made. Also be
sure to specify the desired set pressure.

4.12 Ø
(105)

74,7
71,4
63,5

65,3
58,7
66,8

AR1545-A
A1164-1

VENT

1/4 NPT
CONTROL CONNECTION

3/4 OR 1 NPT

1.81
(46)

3.62
(92)

7.88 (MAX)
(200)

2.19

(56)

2.12

(54)

3/4 NPT

INCHES

(mm)

Figure 3. Dimensions

3

Bulletin 71.7:122A

Ordering Guide

Body Size (Connections A and C) (Select One)

3/4 NPT

1 NPT

Quantity (Specify) __________

Disk and Disk Holder Assembly (Select One)

Nitrile (NBR) and Aluminum***
Nitrile (NBR) and Stainless steel***

Seat Rings (Select One)

Aluminum***
Stainless steel***

Set Pressure Range (Select One)

3 to 15 psig (0,21 to 1,0 bar), Red***
5 to 20 psig (0,34 to 1,4 bar), Cadmium***
5 to 35 psig (0,34 to 2,4 bar), Blue***
30 to 60 psig (2,1 to 4,1 bar), Green***
40 to 100 psig (2,8 to 6,9 bar), Yellow***
60 to 150 psig (4,1 to 10,3 bar), Brown***

Regulators Quick Order Guide

* * * Readily Available for Shipment

* * Allow Additional Time for Shipment

* Special Order, Constructed from Non-Stocked Parts. Consult

Your local Sales Ofce for Availability.

Availability of the product being ordered is determined by the component
with the longest shipping time for the requested construction.

Specication Worksheet

Application (Please designate units):

Specic Use

Line Size

Gas Type and Specic Gravity

Gas Temperature
Does the Application Require Overpressure Protection?
Yes No If yes, which is preferred:
Relief Valve Monitor Regulator Shutoff Device
Is overpressure protection equipment selection assistance
desired?

Pressure (Please designate units):

Maximum Inlet Pressure (P
Minimum Inlet Pressure (P

1max

1min

)

)
Downstream Pressure Setting(s) (P2)
Maximum Flow (Q

max

)

Performance Required:

Accuracy Requirements?
Need for Extremely Fast Response?

Other Requirements:

Industrial Regulators

Emerson Process Management
Regulator Technologies, Inc.

USA - Headquarters
McKinney, Texas 75069-1872 USA
Tel: [phone]
Outside U.S. 1-972-548-3574

Asia-Pacic

Shanghai, China 201206
Tel: [phone]

Europe
Bologna, Italy 40013
Tel: [phone]

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Dubai, United Arab Emirates
Tel: [phone]

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business of Emerson Process Management.

The contents of this publication are presented for informational purposes only, and while every effort has been made to ensure their accuracy, they are not to be construed as warranties or

guarantees, express or implied, regarding the products or services described herein or their use or applicability. We reserve the right to modify or improve the designs or specications of such

products at any time without notice.

Emerson Process Management does not assume responsibility for the selection, use or maintenance of any product. Responsibility for proper selection, use and maintenance of any Emerson
Process Management product remains solely with the purchaser.

Natural Gas Technologies

Emerson Process Management
Regulator Technologies, Inc.

USA - Headquarters
McKinney, Texas 75069-1872 USA
Tel: [phone]
Outside U.S. 1-972-548-3574

Asia-Pacic

Singapore, Singapore 128461
Tel: [phone]

Europe
Bologna, Italy 40013
Tel: [phone]
Gallardon, France 28320
Tel: [phone]

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