Installation; Three-Way Valve Applications Note - Fisher 685SE Instructions Manual

685SE/685SR Piston Actuator
June 2017

Installation

WARNING
Always wear protective gloves, clothing, and eyewear when performing any installation operations to avoid personal
injury.
To avoid personal injury or property damage caused by bursting of pressure­retaining parts, be certain the cylinder
pressure or other pressure ratings do not exceed the limits listed in table 1. Use pressure­limiting or pressure­relieving
devices to prevent cylinder pressure or other pressures from exceeding these limits.
Check with your process or safety engineer for any additional measures that must be taken to protect against process
media.
If installing into an existing application, also refer to the WARNING at the beginning of the Maintenance section in this
instruction manual.
Dropping the actuator and any attached accessories and/or valve may cause personal injury and/or equipment damage. For
all mounting procedures use an adequately sized chain, sling, hoist, or crane to handle the actuator and any attached
accessories and/or valve. Use caution during lifting and handling to prevent slippage, swinging, faulty equipment
connections, or sudden shock loads.
CAUTION
Special care must be taken when installing an actuator in a horizontal service orientation. To avoid cantilever loads on the
valve stem and yoke, it is the customer's responsibility to ensure proper support for a horizontal actuator.
When an actuator and control valve are shipped together as a control valve assembly, the actuator is normally
mounted on the valve. Follow the valve instructions when installing the valve in the pipeline. If the actuator is shipped
separately or if it is necessary to mount the actuator on the valve, perform the actuator mounting procedures in this
instruction manual. Refer to the individual product instruction manuals for the installation or mounting of a FIELDVUE
DVC6200 digital valve controller or 3610 positioner.
If the actuator is being installed without a positioner, the cylinder loading pressures should be supplied through a
4­way solenoid valve or a switching valve. Pressure connection locations are indicated below:
D 685SE Actuators: Side of the outer spring cartridge and bottom of the lower head.
D 685SR Actuators: Top of the upper head and side of the outer spring cartridge.
The supply pressure medium should be clean, dry filtered air. If the supply source is capable of exceeding the
maximum actuator operating pressure or positioner supply pressure, appropriate steps must be taken during
installation to protect the positioner and all connected equipment against over pressurization.
The control valve should be located where it will be accessible for servicing. Room should be left above and below the
control valve to permit removal of the actuator and valve plug.
Three­Way Valve Applications Note
In three­way valve applications where the actuator fully strokes at a frequency of once per minute or faster, and the
stroking speed is rapid (less than 0.5 seconds per stroke), there is a possibility that the stem can fracture at the plug if
the actuator cylinder pressure is greater than 5.5 bar (80 psig). This can cause loss of control of process fluid and
further damage to the actuator. Consideration should be given to the use of high­strength, fatigue­resistant stem
materials in these applications.
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Instruction Manual
D103799X012