Principle Of Operation; 3582 Valve Positioners - Emerson Fisher 3582 Instruction Manual

3582, 582i, and 3583
actuator should be at its midtravel position. If not,
first check for loose linkage or improper cam
installation. A minor nozzle height adjustment might
be necessary to make the desired input signal value
correspond to the starting point of travel.
3. Apply an input signal equal to the low value of the
input signal range. For example, for a 3582 valve
positioner with a 0.2 to 1.0 bar (3 to 15 psig) input
signal range, set the input signal at 0.2 bar (3 psig).
Loosen the nozzle locknut and adjust the nozzle until
the actuator moves to the proper end of its travel.
Changing the nozzle position is intended only as a
means of zero trim adjustment. Whenever nozzle
position is changed, the zero reference point is
changed.
4. Apply an input signal equal to the high value of
the input signal range and observe the actuator stem
travel. If the stem travel is short of its expected
range, increase the travel by moving the flapper
assembly to a higher number on the beam. If the
desired stem travel occurs before the input signal
reaches the high value of the input signal range,
decrease the travel by moving the flapper assembly
toward a lower number on the beam.
5. Repeat steps 3 and 4 until the correct travel is
achieved. Each time the flapper position is changed
in step 4, repeat step 3 to provide proper zero.
Moving the flapper assembly toward zero on the
beam scale decreases stem travel. Table 13 lists the
minimum stem travel available for different travel pin
settings. For example, with a travel pin setting of 2
the minimum stem travel possible, for the full input
signal range, would be 11 mm (0.4375 inch).
The positioner will fully vent or
pressurize the actuator to supply
pressure at the ends of actuator travel
when the positioner is calibrated
correctly. Failure to properly calibrate
the positioner may result in reduced
seat loading.
26
Note
Table 13. Minimum Travel with Given Pin Position
TRAVEL PIN
POSITION ALONG
ROTARY SHAFT ARM
1-1/8
1-1/2
2
2-1/2
3
4

Principle of Operation

3582 Valve Positioners

The 3582 (3582, 3582NS and 3582A, C, D, and G
pneumatic valve positioners) accepts a pneumatic
input signal from a control device. Figure 17 is an
operational schematic for a direct-acting pneumatic
valve positioner.
As shown in figure 17, in a diaphragm-actuated,
sliding stem control valve package with a 3582 valve
positioner, supply pressure is connected to the 83L
relay. A fixed restriction in the relay limits flow to the
nozzle so that when the flapper is not restricting the
nozzle, air can bleed out faster than it is being
supplied.
The input signal from the control device is connected
to the bellows. When the input signal increases, the
bellows expands and moves the beam. The beam
pivots about the input axis moving the flapper closer
to the nozzle. The nozzle pressure increases and,
through relay action, increases the output pressure
to the actuator. The increased output pressure to the
actuator causes the actuator stem to move
downward. Stem movement is fed back to the beam
by means of a cam. As the cam rotates, the beam
pivots about the feedback axis to move the flapper
slightly away from the nozzle. The nozzle pressure
decreases and reduces the output pressure to the
actuator. Stem movement continues, backing the
flapper away from the nozzle, until equilibrium is
reached.
When the input signal decreases, the bellows
contracts (aided by an internal range spring) and the
beam pivots about the input axis to move the flapper
away from the nozzle. Nozzle pressure decreases
Instruction Manual
June 2010
MINIMUM TRAVEL AVAILABLE
mm Inch
6 0.25
8 0.3125
11 0.4375
13 0.5
16 0.625
22 0.875