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Instruction Manual
D100311X012
Figure 2. Schematic Representation of Fisher 667 Actuator
Table 2. Maximum Pressure Limitations
PRESSURE LIMITATIONS
Maximum Casing
bar
Pressure for Actuator
psig
Sizing
bar
Maximum Excess
Diaphragm Pressure
psig
Maximum Diaphragm Casing
Pressure
Maximum Pressure Limitations
WARNING
To avoid personal injury or parts damage, do not exceed the Maximum Pressures listed in table 2. Exceeding any of the
maximum pressures can result in uncontrolled movement of parts, damage to actuator parts and the control valve, and
loss of control of the process. Use pressure‐limiting or pressure‐relieving devices to prevent casing pressure from
exceeding these limits.
The casing and diaphragm of 667 actuators are pressure operated. This air pressure provides force to compress the
spring and stroke the actuator. The following explanations describe the maximum pressure limits for 667 actuators.
Refer to the nameplate, warning tag, and table 2 for maximum values.
D Maximum Casing Pressure for Actuator Sizing: This is the maximum pressure that can be applied to provide full
travel of the actuator. If this stroking pressure is exceeded before the upper diaphragm plate contacts the travel
stop, damage to the stem or other parts might result. The Maximum Diaphragm Casing Pressure for a specific
actuator construction may be less than the Maximum Casing Pressure for Actuator Sizing. See table 2.
D Maximum Excess Diaphragm Pressure: This is the additional pressure that may be added when the actuator is at full
travel. If the Maximum Excess Diaphragm Pressure is exceeded once the actuator has reached full travel, damage to
the diaphragm or diaphragm casing might result.
DIAPHRAGM
AIR
LIFTS
AF3833‐A
A6127
667 REVERSE‐ACTING DIAPHRAGM ACTUATOR
Standard Cast Iron Construction
3.4
50
1.4
20
Upper bench set plus Maximum
Excess Diaphragm Pressure or 4.1 bar
(60 psig), whichever is less.
SPRING
PUSHES
DOWN
ACTUATOR
STEM
ACTUATOR SIZE
80
All Steel Construction
4.9
70
1.4
20
Upper bench set plus Maximum
Excess Diaphragm Pressure or 5.5 bar
(80 psig), whichever is less.
667 Size 80 and 100 Actuators
May 2011
100
6.9
100
1.7
25
Upper bench set plus Maximum
Excess Diaphragm Pressure or 7.9 bar
(115 psig), whichever is less.
3
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