Maintenance; Troubleshooting - Fisher 2502 Series Level-Trol Instruction Manual

2502 Series
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 cham-
ber 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

The 2502 Series controllers are used in combination
with 249 Series sensors. Due to the care Fisher Con-
trols takes in meeting all manufacturing requirements
(heat treating, dimensional tolerances, etc.), use only
replacement parts manufactured or furnished by Fish-
er Controls.
16
Figure 13. Type 2502F Controller with Reset Relief Valve
WARNING
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 be readily apparent when disas-
sembling the sensor or removing the
displacer. Before disassembling the
sensor or removing the displacer, ob-
serve the more specific warning pro-
vided in the sensor instruction manual.

Troubleshooting

When troubleshooting, open loop conditions must exist
unless otherwise stated. When monitoring the process
variable, use the most accurate level indicting device
readily available. The output signal measuring device
should have a corresponding accuracy.