Emerson 168, 168H Instruction Manual
Instruction Manual
Form 2256
December 2008
168, 168H, and 68 Series
168, 168H, and 68 Series Three-Way
Switching Valves
Introduction
The 168 and 168H Series pneumatically operated
three-way snap-acting switching valves (Figure 1) are
used to switch pressures on and off in response to a
predetermined change in an input signal pressure.
In operation, increasing pressure applied to the top of
the diaphragm through port D (see Figure 2) moves
the stem and upper range adjusting nut toward the
trip lever. When the diaphragm pressure reaches
the predetermined upper tripping pressure, the upper
adjusting nut pivots the trip lever to move the rocker
assembly to its alternate position, closing port C
and opening port B. When decreasing pressure to
the diaphragm at port D reaches the lower tripping
pressure, the spring moves the stem and lower range
adjusting nut to return the rocker to its original position,
closing port B and opening port C.
W1932
Figure 1. Exterior of 168 Series Switching Valve
D
The 68 Series (Figure 4) three-way snap-acting body
assemblies can be used alone, or to form the valve
body portions of 168 or 168H Series switching valves.
With the addition of the lever knob (key 11, Figure 4)
to a Type 68-1 body assembly, a Type 68-2 manual
switching valve body assembly is formed.
Only personnel qualied through training or experience
should install, operate, and maintain these valves. If
there are any questions concerning these instructions,
contact your local Sales Ofce before proceeding.
DIAPHRAGM
DIAPHRAGM
SPRING
B
C
BODY
BODY SPRING
TRIP LEVER
INLET PRESSURE
OUTLET PRESSURE
ATMOSPHERIC PRESSURE
LOADING PRESSURE
A
M1045
ROCKER
ASSEMBLY
UPPER RANGE
ADJUSTMENT NUT
STEM
LOWER RANGE
ADJUSTMENT NUT
Figure 2. Construction Details of
168 Series Switching Valve
www.emersonprocess.com/regulators
D100275X012
168, 168H, and 68 Series
Specications
Maximum Allowable Pressures
Diaphragm
168 Series: 100 psi (6,90 bar)
Flow Coefcients
Cg: 7
Representative C1: 35
168H Series: 150 psi (10,3 bar)
Body: See Table 1
Operative Temperature Limits
(1)
-10° to 150°F (-23° to 66°C)
Port Diameter
3/32-inch (2,38 mm)
1. This term is dened in ISA Standard S51.1-1979.
Table 1. Maximum Pressures and Spring Part Numbers
DIAPHRAGM PRESSURE
COMPLETE
SWITCHING
VALVE TYPE
NUMBER
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 150 10,3 1U878037022, Metallic 68-2
168-1
168-2
168-3
168-4
168H-1
168H-2
168H-3
168H-4
CHANGE BETWEEN
SWITCHING POINTS
Minimum Maximum
Psi bar Psi bar Psi bar Psi bar
10
0,69
58
10
0,69
10
0,69
7
0,48
20
1,38
20
1,38
20
1,38
16
1,10
38
58
38
100
65
100
65
4,00
2,62
4,00
2,62
6,90
4,48
6,90
4,48
DIAPHRAGM
PRESSURE RANGE
2 to 60
2 to 40
2 to 60
2 to 40
50 to 150
35 to 100
50 to 150
35 to 100
0,14 to 4,14
0,14 to 2,76
0,14 to 4,14
0,14 to 2,76
3,45 to 10,3
2,41 to 6,90
3,45 to 10,3
2,41 to 6,90
Pressure Connections
1/4-inch NPT female
Approximate Weights
68 Series: 0.5 pound (0,23 kg)
168 Series: 3 pounds (1,36 kg)
168H Series: 5 pounds (2,27 kg)
KEY 8, FIGURE 3
DIAPHRAGM SPRING
PART NUMBER AND
COLOR CODE
1U877127142, green
1U879727142, yellow
1U877127142, green
1U879727142, yellow
1U877127142, green
1U879727142, yellow
1U877127142, green
1U879724142, yellow
MAXIMUM
ALLOWABLE
BODY
PRESSURE
150
10,3
150
10,3
40
2,76
40
2,76
150
10,3
150
10,3
40
2,76
40
2,76
KEY 2D, FIGURE 4
BODY SPRING PART
NUMBER AND
COLOR CODE
1U878037022, Metallic
1U878037022, Metallic
1U854537022, Yellow
1U854537022, Yellow
1U878037022, Metallic
1U878037022, Metallic
1U854537022, Yellow
1U854537022, Yellow
BODY
ASSEMBLY
TYPE
NUMBER
68-1
68-1
68-3
68-3
68-1
68-1
68-3
68-3
Installation
Maximum allowable pressures for the diaphragm and
body are given in the Specications section above and
Table 1 respectively. If pressure to the unit is capable
of exceeding these values, install relief valves or other
overpressure protection devices in the pressure lines.
The 68 Series body assemblies can be installed in any
position. Position a 168 or 168H Series switching valve
so that moisture and other foreign material cannot enter
either the vent (key 17, Figure 3) or the small hole in the
end of the stem protector (key 10, Figure 3).
When the switch is in service, inspect the vent opening
periodically to ensure that it is not plugged.
Before installing, be certain that the valve body
portion and adjacent pipes are free of pipe scale and
other foreign material. Use accepted piping practices
when installing.
2
For the 168 and 168H Series switching valves, a
mounting bracket (key 15, Figure 3) is available. This
mounting bracket is suitable for use with a 2-inch
(50,8 mm) (nominal) pipestand. Mounting parts that
can be used to attach a 168 or 168H Series switching
valve to the yoke of a control valve actuator are
also available.
Pipe the common pressure line to port A (the
connection in the end of the valve body portion). With
one port (either B or C) plugged, the unit can be used
as an on/off switch. Note that ow cannot pass from
port B to port C or from port C to port B.
168, 168H, and 68 Series
168 and 168H Series Adjustment
Determine the desired upper and lower switching
pressures (the high and low values of diaphragm
pressure at which the valve is to switch). Refer to
Table 1 to ensure that these pressures are within the
diaphragm pressure range and that the diaphragm
pressure change between the switching pressures is
within the minimum and maximum limits shown.
Adjust the unit as follows. Key numbers used in this
procedure are shown in Figure 3 except where indicated.
1. Remove screws and stem protector (keys 11
and 10).
2. To set the lower switching pressure:
2.1 Apply a pressure to the diaphragm case (key 1)
equal to the lower switching point.
2.2 Loosen locknut (key 9). Use a screwdriver
to move the trip lever (key 2C) so that the
visible end points away from the spring case
(key 2A). It might be necessary to back the
adjusting nut (key 7) and locknut away from
the trip lever to do this.
168 and 168H Series Manual
Reset Operation
Without Manual Reset Switch
With one adjusting nut removed, the unit will switch
with high (or low) diaphragm pressure and will remain in
that position until the stem protector (key 10, Figure 3) is
removed and the trip lever (key 2C, Figure 4) is manually
moved to its normal position. Remove the range
adjusting nut (and its locknut) located nearer the spring
case (key 2A, Figure 3) if switching at low diaphragm
pressure only is desired. Remove the other adjusting
nut and locknut if switching with high diaphragm
pressure only is desired. The remaining adjusting nut
can be adjusted by the appropriate steps given in the
Adjustment section.
To reset the unit after it has switched, remove the
machine screws and stem protector (keys 11 and 10,
Figure 3), and use a screwdriver to return the trip lever
(key 2C, Figure 4) to its normal position.
With Manual Reset Switch
2.3 Rotate the adjusting nut toward the trip lever
until the nut just moves the trip lever to the
alternate position.
3. To set the upper switching pressure:
3.1 Apply a pressure to the diaphragm case (key 1)
equal to the upper switching pint.
3.2 Loosen the locknut on the upper range
adjusting nut. Use a screwdriver to move
the trip lever (key 2C) so that its visible
end points toward the spring case (key 2A).
It may be necessary to back the adjusting
nut and locknut away from the trip lever to
do this.
3.3 Rotate the upper range adjusting nut toward
the trip lever until the nut just moves the trip
lever to its alternate position.
4. Tighten each locknut against its respective
adjusting nut.
5. Replace stem protector and machine screws
(key 11).
When a manual reset switch (see Figure 3) is used
on a unit in the single-pressure trip mode (either high
or low pressure setpoint requiring only one adjusting
nut), the end of the reset lever (key 20) in contact
with the trip lever (see section DD, Figure 3) should
be on the opposite side of the trip lever from the
adjusting nut.
If it is necessary to change the reset lever position,
remove the self tapping screws (key 23). Slide the lever
out of the stem protector slots, and position it on the
other side of the trip lever and re-insert. Re-attach the
indicator tag with the self-tapping screws, making sure
the arrow on the tag points in the same direction as
that required to reset the switch.
3
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