657 Actuator (30-70 and 87)
Instruction Manual
Form 1900
February 2007
8
4. Calculate the percent of deadband by:
Deadband, psi
Deadband = —————————————— = nn%
Bench Set Span, psi
Loading Connection
The loading pressure connections are made at the
factory if the valve, actuator, and positioner come as
a unit. Keep the length of tubing or piping as short as
possible to avoid transmission lag in the control
signal. If a volume booster, valve positioner or other
accessory is used, be sure that it is properly
connected to the actuator. Refer to the positioner
instruction manual or other manuals as necessary.
For actuators shipped separately or whenever the
actuator pressure connections are installed, use the
following steps:
1. Connect the loading pressure piping to the NPT
female connection in the top of the diaphragm
casing.
2. For sizes 70 and 87 actuators, if necessary,
remove the 1/4 inch NPT bushing if a 1/2 inch NPT
female connection is needed to increase connection
size. The connection can be made with either piping
or tubing.
3. Cycle the actuator several times to be sure that
the valve stem travel is correct when the correct
pressure ranges are applied to the diaphragm.
WARNING
If valve stem travel appears to be
incorrect, refer to the Bench Set
Spring Adjustment procedures at the
beginning of this section. To avoid
personal injury or product damage, do
not place the valve into service if it is
not reacting correctly to diaphragm
loading pressure changes.
Maintenance
Actuator parts are subject to normal wear and must
be inspected and replaced when necessary. The
frequency of inspection and replacement depends
on the severity of service conditions.
WARNING
Avoid personal injury or property
damage from sudden release of
process pressure or bursting of parts.
Before performing any maintenance
operations:
D Always wear protective gloves,
clothing, and eyewear when
performing any maintenance
operations to avoid personal injury.
D Disconnect any operating lines
providing air pressure, electric power,
or a control signal to the actuator. Be
sure the actuator cannot suddenly
open or close the valve.
D Use bypass valves or completely
shut off the process to isolate the
valve from process pressure. Relieve
process pressure from both sides of
the valve. Drain the process media
from both sides of the valve.
D Vent the power actuator loading
pressure and relieve any actuator
spring precompression.
D Use lock-out procedures to be
sure that the above measures stay in
effect while you work on the
equipment.
D The valve packing box may
contain process fluids that are
pressurized, even when the valve has
been removed from the pipeline.
Process fluids may spray out under
pressure when removing the packing
hardware or packing rings, or when
loosening the packing box pipe plug.
D Check with your process or safety
engineer for any additional measures
that must be taken to protect against
process media.
Actuator Maintenance
This procedure describes how the actuator can be
completely disassembled and assembled. When
inspection or repairs are required, disassemble only
those parts necessary to accomplish the job; then,
start the assembly at the appropriate step.
Key numbers refer to figures 6, 7, or 8 unless
otherwise indicated. Figure 6 shows the sizes 30
through 60 actuators, figure 7 illustrates the sizes 70
actuator, and figure 8 shows the size 87 actuator.
