A-15
Model 580A Differential Pressure Switch
Appendix A
Immediately stop all disassembly, tighten the housing bolts, and
return the unit to the factory or authorized service center for repair.
Tag the unit and specify "Gas in the Bellows."
4.
Carefully remove the pressure housing bolts and pressure housings.
IMPORTANT: It is recommended that new O-rings be used whenever pressure hous-
ings are replaced.
5.
Install the pressure housings onto the new BUA and attach with appropri
-
ate housing bolts (see
Table A.2, page A-14
,
for torque requirements).
6. Reattach the mounting bracket to the DPU.
7. Re-attach the DPU to the process monitoring instrument and install the
instrument into service in reverse order of removal. For instructions on
attaching the Model 580A Differential Pressure Switch drive arm to the
torque tube, see
Section 3, page 11
.
8.
Calibrate the instrument per the instructions in
Section 3, page 11
.
DPU Troubleshooting
Table A.3 provides a description of commonly reported problems, probable
causes, and corrective actions for use in troubleshooting issues involving the
Model 224 DPU.
See
Table 3.1, page 23
,
for Model 580A Differential Pressure Switch trouble-
shooting information
.
Table A.3—Troubleshooting Tips
Problem
Possible
Source
Probable Cause
Corrective Action
Low or No
Indication
Primary
Element or
DPU
Orifice installed backwards or oversized
Replace orifice
Flow blocked upstream from run
Clean out run or open
valve
Loss of liquid in reference leg (liquid level)
Refill reference leg
Density changes in process media or
reference leg
Refill reference leg with
same density liquid as
process media
Piping from
Primary
Element to
DPU
Pressure tap holes plugged and/or piping
plugged
Clean out piping
Bypass valve open or leaking
Close bypass valve(s)
or repair leaks
Liquids or gases trapped in piping
Vent piping
Block or shutoff valves closed
Open block or shutoff
valves
Piping leaks on high pressure side
Repair leaks