Fisher 2506 - 2516, 2516 F Receiver;Controllers

Instruction Manual
D200129X012
2506/2516 Receiver/Controller
June 2017
18
As long as the process level remains constant, the transmitter input pressure to the receiver/controller remains
constant. Inside the receiver/controller, the bellows beam/flapper assembly remains in a steady‐state position.
The position of the bellows beam allows the supply pressure to bleed through the nozzle as fast as it enters the relay
through the fixed restriction. A change in transmitter input pressure repositions the beam/flapper assembly with
respect to the nozzle.
On a direct action receiver/controller, an increase in transmitter input pressure causes a pressure increase in the
sensing bellows assembly, tending to push the beam toward the nozzle. This restricts the escape of supply pressure
through the nozzle, thus increasing the pressure on the large diaphragm in the relay. This opens the relay valve to the
supply pressure allowing an increase in output pressure to the control valve.
A decrease in transmitter input pressure decreases the pressure in the input bellows assembly by moving the beam
away from the nozzle. This allows the supply pressure to bleed through the nozzle faster than it can enter through the
fixed restriction in the relay. The relay valve opens, exhausting the output pressure which vent through the relay
exhaust port. This action decreases output pressure to the control valve.
2516, 2516F Receiver/Controllers
The action of a proportional‐plus‐reset controller (figure 13) is similar to that of a proportional controller except that
feedback from the controller output pressure is piped to a reset bellows as well as to the proportional bellows.
Figure 13. Fisher 2516 and 2516F Direct Action Receiver‐Controller Schematic
B2116
REMOTE SETPOINT
BELLOWS
TRANSMITTER INPUT
TRANSMITTER INPUT
REVERSING SWITCH
BELLOWS VENT OR REMOTE
SETPOINT CONNECTION
PROPORTIONAL BELLOWS
BEAM/FLAPPER
ASSEMBLY
RESET
BELLOWS
RESET BELLOWS
RESET VALVE
RESET
VALVE
OUTPUT
PRESSURE
PROPORTIONAL
VALVE
PROPORTIONAL VALVE
SENSING BELLOWS
RESTRICTION
OUTPUT PRESSURE
TO CONTROL VALVE
SUPPLY
SUPPLY PRESSURE
RELAY LOADING
PRESSURE
2516 RECEIVER/CONTROLLER
2516F RECEIVER/CONTROLLER
OUTPUT PRESSURE
RELAY BLEED PRESSURE
PROPORTIONAL PRESSURE
RESET PRESSURE
RESET RELIEF
VALVE SPRING
ADJUSTING
SCREW
DIFFERENTIAL
RELIEF VALVE
RELIEF VALVE
DIAPHRAGM
NOZZLE
BEAM/FLAPPER
ASSEMBLY
You can adjust the reset valve on the 2516 and 2516F to channel some or all of the proportional pressure into the reset
bellows that opposes the proportional bellows action. This arrangement automatically reduces the effect of any
proportional overcorrection by a set amount per time interval, as long as there is a deviation from the control point.