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Instruction Manual
D103472X012
Specifications
Tables 1 through 4 provide specifications for the various sizes of 667NS2 actuators discussed in this instruction
manual. All torque values given are $5%, unless otherwise specified. See the actuator nameplate for specific
information for your actuator.
Educational Services
For information on available courses for the Fisher 667NS2 actuator, as well as a variety of other products, contact:
Emerson Automation Solutions
Educational Services - Registration
Phone: 1-641-754-3771 or 1-800-338-8158
E-mail: education@emerson.com
emerson.com/fishervalvetraining
Maximum Pressure Limitations
The casing and diaphragm of 667NS2 actuators are pressure operated. This air pressure provides energy to compress
the spring, to stroke the actuator, and lift the diaphragm away from the valve. The following explanations describe the
maximum pressure limits for an actuator. Refer to table 1 for maximum values.
WARNING
To avoid personal injury or parts damage, do not exceed the Maximum Pressures listed in table 1. 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.
D Maximum Diaphragm Pressure for Actuator Sizing: This is the maximum pressure that can be applied at less than
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.
D Maximum Excess Diaphragm Pressure: Additional pressure may be added when the actuator is at full travel. If the
Maximum Excess Diaphragm Pressure is exceeded, damage to the diaphragm or diaphragm casing might result.
Because the actuator has traveled its specified travel, and the diaphragm head is physically stopped from movement,
the energy from any additional air pressure is transmitted to the diaphragm and diaphragm casings. The amount of air
pressure that can be added once the actuator has traveled to the stops is limited by the resultant adverse effects that
may occur. Exceeding this limiting factor could result in leakage or casing fatigue due to the deformation of the
diaphragm casing.
WARNING
To avoid personal injury or parts damage, do not exceed the Maximum Diaphragm Casing Pressure listed in table 1. The
Maximum Diaphragm Casing Pressure must not produce a force on the actuator stem greater than the maximum allowable
actuator output thrust or the maximum allowable stem load.
D Maximum Diaphragm Casing Pressure: If the Maximum Diaphragm Casing Pressure is exceeded, damage to the
diaphragm, diaphragm casing, or actuator might result. For some actuator sizes, the maximum casing pressure is
the sum of the maximum stroking pressure plus a pressure margin to allow for typical regulator settings and/or
relief valve tolerances. For other actuator sizes, the value is lower than the sum of the two pressures.
667NS2 Actuator
March 2022
3
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