Dresser Masoneilan 4700E, Instructions Manual

19

Instruction ES2007 4/98

Models 4700P and 4700E

end of signal range, after making zero adjustment,
decrease signal below low end of signal range and
slowly increase signal to ensure valve plug lifts off seat
at desired signal. If valve is open at low end of signal
range, adjust zero so valve indicates “Open” on travel
indicator scale.

Read field mounting and complete calibration in-
struction (

∑

F or rotary valves) before attempting to

adjust zero.

Span Adjustment (Figure 19 & 20)

If the valve does not fully stroke for a full signal span, the
feedback spring rate is too high. Loosen screw (8) and turn
spring (5) on the spring end (4) to increase the number of
active coils and decrease the spring rate. Conversely, if full
stroke is reached prior to full signal span, turn the spring
to decrease the number of active coils and increase the
spring rate.

Adjustment of +

1

/

4

 turn of the spring changes its rate by

approxi10%.

After making a spring adjustment, it will be necessary to
reset the zero. This is done by turning the zero adjustment
(4B), and tightening zero locknut (4C).

Example: If the number of active coils is increased making
the spring longer, it will be necessary to readjust the zero
nut to compensate for the increased spring length.

When span adjustment has been completed, retighten the
spring locking socket head screw (8).

Caution: When installing positioner with cam in
place, check the position of the spring (5) on
diaphragm S/A (9) to ensure that it is centered on
the diaphragm.

Cam Lobe Change

If it is necessary to change the cam lobe only (without
changing actuator action or positioner action) then proceed
as follows:

Note: Do not disturb cam holder (36) setting on rotary
actuators. [i.e. do not touch set screws (35)]

Caution: If cam is not at low signal line on lobe
(low end of range), do not attempt to remove cam.
The cam must be at low signal line. Select correct
actuator and positioner action and proceed as
follows.

Air to Open/Direct Acting Positioner (Figure 19 & 20)

1.

Shut off supply pressure and signal to positioner.
Valve is now closed and cam (26) is at low signal line
on lobe.

2.

With cam at low signal line remove screw (28) and
washer (27). Note the relative position of the cam
lobe being changed and then remove the cam (26).

3.

Select the desired cam lobe and replace cam (26)
on cam shaft with low signal line of desired lobe
against cam follower. Ensure the newly selected cam
lobe is in the same relative position as the lobe noted
in Step 2.

4.

Replace washer (27) and screw (28). Turn on supply
pressure and signal to positioner. Check zero and
span adjustment. (Refer to zero and span adjustment
section.)

Air to Open/Reverse Acting Positioner (Figure 19)

1.

Shut off supply pressure and signal to positioner.
Valve is now closed and cam (26) is at high signal line
on lobe. Do not remove.

2.

Run an independent regulated air line to the valve
actuator in place of positioner output line. Slowly
apply proper air pressure through the regulator to
open the valve. Do not exceed designated supply
pressure. (Handwheel may be used to open the valve
in place of regulated air line). Align the travel indicator
with the “open” end of travel scale. Do not over travel.
Cam is now at low signal line on lobe.

3.

With cam at low signal line remove screw (28) and
washer (27). Note the relative position of the cam
lobe being changed and then remove the cam (26).

4.

Select the desired cam lobe and replace cam (26)
on cam shaft with low signal line of desired lobe
against cam follower. Ensure that the newly selected
cam lobe is in the same relative position as the lobe
in Step 3.

5.

Replace washer (27) and screw (28). Reduce pres-
sure applied in Step 2 to zero (back off the handwheel
if handwheel was used). Disconnect the independent
regulated air line to actuator and connect positioner
output line. Connect supply pressure and signal to
positioner. Check zero and span adjustment. (Refer
to zero and span adjustment section.)

Air to Close/Direct Acting Positioner (Figure 19 & 20)

1.

Shut off supply pressure and signal to positioner.
Valve is now open and cam (26) is at low signal line
on lobe.