Fisher 657 - Manual (Page 5)

Instruction Manual
D100307X012
657 Size 80 and 100 Actuators
December 2010
5
When adjusting travel of a reverse‐acting (push‐down‐to‐open) valve, apply a slight pressure on the actuator
diaphragm. This moves the valve plug off the seat, reducing the chance of damaging the valve plug or seat during
adjustments.
1. Back the stem locknuts away from the stem connector, and slightly loosen the stem connector cap screws.
CAUTION
Do not use wrenches or other tools directly on the valve stem. Damage to the stem surface and subsequent damage to the
valve packing may result.
2. Tighten the locknuts together, using a wrench, then screw the valve stem either into the stem connector to
lengthen travel or out of the stem connector to shorten travel.
3. Cycle the actuator to check the travel. If actual travel is not equal to the specified travel, adjust and check travel
until correct. Tighten the stem connector cap screws when correct travel is obtained.
4. Raise the travel indicator disk by threading the stem locknuts against the stem connector.
Spring
Make spring adjustments when the loading pressure range applied to achieve specified travel is not equal to the
pressure range stamped on the actuator nameplate. Refer to the Bench Set pressure range on the nameplate when
the valve contains no pressure and the packing is loosely inserted in the bonnet. Refer to the Max. Allow. Supply on the
nameplate when the valve is controlling the specified pressure drop and the packing is tightened to stop leaks around
the stem.
Monitor loading pressure carefully when making adjustments. Do not exceed the pressure specifications of either the
loading regulator or the actuator casings.
Each actuator spring has a fixed pressure span. Changing the spring compression shifts the span up or down to make
valve travel coincide with the loading pressure range.
Size 80
Remove cover band (key 60, figure 4), insert a rod of approximately 12.7 mm (1/2‐inch) diameter into a hole in the
adjusting screw (key 12, figure 4), and rotate the adjusting screw with the rod. Rotating the screw from left to right
will increase the loading pressure required to start actuator stem travel; opposite rotation will decrease the pressure
required to start travel.
Size 100
CAUTION
The actuator must be in the vertical position when adjusting spring to avoid damage to thrust bearing (key 35, figure 5) and
to properly position spacers required for adjustment.
Remove the shroud plate (key 107, figure 5), and loosen the jam nut (key 115, figure 5).