Maintenance - Emerson Fisher 2502 Instruction Manual

2502 Controllers
June 2017
Figure 11. Fisher 2502F Controller with Differential Relief Valve
FIXED
PIVOT
PIVOTING
CROSS
NOZZLE
SPRINGS
RESET
BELLOWS
CJ4081‐A
CU7387‐B
C0311‐2
A sudden increase in the output pressure will cause a rapid pressure increase in the proportional bellows and in the
outer relief valve chamber. If the outer chamber pressure exceeds that in the inner relief valve chamber by the amount
of the relief pressure setting, the relief diaphragm will move off the orifice in the relief valve, and the pressure in the
outer chamber will bleed into the reset system. This action provides quick relief of excessive proportional pressure and
reduces the time required by the system to return to the control point.

Maintenance

2502 controllers are used in combination with 249 sensors.
WARNING
Always wear protective eyewear, gloves and clothing whenever possible when performing maintenance to avoid personal
injury.
Personal injury or property damage due to sudden release of pressure, contact with hazardous liquid, fire, or explosion can
be caused by puncturing, heating, or repairing a displacer that is retaining process pressure or liquid. This danger may not
22
MOVABLE
PROPORTIONAL
ARM
BELLOWS
BEAM AND
FLAPPER
FIXED RESTRICTION
INLET END
OF RELAY VALVE
LEVEL SET
ADJUSTMENT
INNER CHAMBER
EXHAUST END
LARGE DIAPHRAGM
OF RELAY VALVE
OF ASSEMBLY
SMALL
DIAPHRAGM
OF ASSEMBLY
Instruction Manual
RELIEF VALVE
DIFFERENTIAL
RELIEF VALVE
CAM
RELIEF
RESET VALVE
DIAPHRAGM
OUTER
CHAMBER
PROPORTIONAL
VALVE
SUPPLY PRESSURE
OUTPUT PRESSURE
NOZZLE PRESSURE
EXHAUST
PROPORTIONAL PRESSURE
RESET PRESSURE
D200126X012
DIAPHRAGM
ASSEMBLY
RESTRICTION