Emerson Process Management FISHER 657 - Manual (Page 7)

Instruction Manual
D100306X012
657 Actuator (30-70 and 87)
December 2010
7
5. Calculate the actual friction force:
Friction
Force, = 0.5
pounds Difference
in pressure
readings, psig

Effective
diaphragm area,
inches
2
Refer to table 1 for the effective diaphragm area.
When determining valve friction, you can make diaphragm pressure readings at a travel position other than mid‐travel
if you desire. If you take readings at zero or at the full travel position, take extra care to ensure that the readings are
taken when the travel just begins or just stops at the position selected.
It is difficult to rotate the spring adjustor (key 12, figure 6, 7, and 8) when the full actuator loading pressure is applied
to the actuator. Release the actuator loading pressure before adjusting. Then re‐apply loading pressure to check the
adjustment.
Spring Verification
Ensure that the actuator stem is at the top of its travel as shown in figure 4 and not connected to the valve. (Note:
Some spring compression is required to move the diaphragm to the top of its travel.) The steps provided are the same
for direct or reverse acting valves.
WARNING
When moving the actuator stem with diaphragm loading pressure, use caution to keep hands and tools out of the actuator
stem travel path. Personal injury and/or property damage is possible if something is caught between the actuator stem and
other control valve assembly parts.
Also, provide a certified pressure gauge suitable to accurately read the diaphragm pressure from 0 psig through the
upper bench set pressure marked on the nameplate. Apply loading pressure to the diaphragm.
CAUTION
Stroke the actuator a few times to ensure that the pressure gauge is working correctly, and that the actuator is functioning
properly. To prevent product damage, it is important to be sure that the actuator assembly is not binding or producing any
loading friction on the actuator stem movement.
1. If not already accomplished, provide a temporary means of applying an adjustable loading pressure to the actuator
during bench set adjustments.
2. Set the diaphragm loading pressure at 0 psig. Then, slowly raise the pressure from 0 psig towards the lower bench
set pressure while checking for the first movement of the actuator stem. The actuator stem should show
movement at the lower bench set pressure. If movement occurs before or after the lower pressure is reached,
adjust the spring adjuster (see figure 4) into or out of the yoke until the actuator stem's movement is first detected
at the lower bench set pressure.
3. Be sure the spring adjuster is adjusted to meet the requirements of step 2 above.
4. Apply the upper bench set loading pressure to the diaphragm. This pressure extends the actuator stem down
towards the valve. (Note: the actuator stem may slide over the valve stem as shown in figure 4.) At the end of the
actuator stem, use a marker or a piece of tape to mark the valve stem (see figure 4). (Note: If the actuator stem
does not pass over the valve stem, provide a method to mark this point of stem travel.)