Emerson 122A Instruction Manual

Instruction Manual
Form 2279

March 2013

Type 122A Three-Way Switching Valve

WARNING

!

Failure to follow these instructions or
to properly install and maintain this
equipment could result in an explosion,

 re and/or chemical contamination

causing property damage and personal
injury or death.

Fisher® switching valves must be
installed, operated, and maintained
in accordance with federal, state, and
local codes, rules and regulations,
and Emerson Process Management
Regulator Technologies, Inc. (Regulator
Technologies) instructions.

Type 122A

If the switching valve vents gas or a
leak develops in the system, service
to the unit may be required. Failure
to correct trouble could result in a
hazardous condition.

Installation, operation, and maintenance

procedures performed by unquali ed

personnel may result in improper
adjustment and unsafe operation. Either
condition may result in equipment
damage or personal injury. Only

quali ed personnel shall install, operate,

and maintain the Type 122A three-way
switching valve.

Introduction

Scope of the Manual

This instruction manual includes installation,
adjustment, maintenance, and parts ordering
information for the Type 122A three-way
switching valve.

W3141-1

Figure 1. Type 122A Three-Way Switching Valve

Description

The Type 122A three-way switching valve (see
Figure 1) is a high-capacity, 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.

www.fisherregulators.com

D100263X012

Type 122A

Specications

The Specications section lists the specications for Type 122A three-way switching valve. Factory specication

is stamped on the nameplate fastened on the valve at the factory.

Maximum Inlet Pressure

150 psig / 10.3 bar

Set Pressure Ranges

See Table 1

Maximum Control Pressure to Diaphragm

150 psig / 10.3 bar

Temperature Capabilities

-20 to 150°F / -29 to 66°C

(1)

(1)

Flow Coefcients

(2)

C

g

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

C

1

(1)

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

(1)

Control Connection

1/4 NPT

Approximate Weight

5 pounds / 2.3 kg

1. The pressure/temperature limits in this Instruction Manual 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.

Table 1. Set Pressure Ranges

PRESSURE BUILD-UP

SET PRESSURE RANGES

psig bar psi bar Inches mm Inches mm

3 to 15
5 to 20
5 to 35

30 to 60
40 to 100
60 to 150

0.21 to 1.0

0.35 to 1.4

0.35 to 2.4

2.1 to 4.1

2.8 to 6.9

4.1 to 10.3

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

WIRE DIAMETER

0.168

0.187

0.218

0.234

0.283

0.240

4.27

4.75

5.54

5.94

7.19

6.10

SPRING

FREE LENGTH

2.94

2.81

2.50

2.57

2.31

2.63

74.6

71.4

63.5

65.2

58.7

66.8

SPRING PART

NUMBER

1D892327022
1D751527022
1D665927022

1D7455T0012
1E543627142
1P901327142

SPRING

COLOR

Red

Cadmium

Blue

Green
Yellow
Brown

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

2

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 set point
chosen. The set pressure is easily changed by
adjusting the screw at the top of the valve.

INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE

ADJUSTING SCREW

Type 122A

STEM

PORT D

PORT A

SPRING

DIAPHRAGM

UPPER VALVE SEAT

PORT C

VALV E

W0157

INLET PRESSURE

OUTLET PRESSURE

ATMOSPHERIC PRESSURE

LOWER VAVE SEAT

PORT B

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

3