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Section 3
Model 289A Differential Pressure Indicating Switch
Troubleshooting
For troubleshooting tips, see Table 3.2 below. For information related to the
DPU, see the Model 199 DPU user manual in Appendix A.
Table 3.2—Troubleshooting
Problem
Possible
Source
Probable Cause
Corrective
Action
Low or No
Indication
Primary
Element or
DPU
(Refer
to DPU
Manual)
Orifice installed backwards or over
-
sized
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
Primary
Element
to DPU
Piping
(Refer
to DPU
Manual)
Pressure tap holes plugged and/or
piping plugged
Clean out piping
Bypass valve open or leaking
Close bypass
valve(s) and/or
repair leaks
Liquids or gases trapped in piping
Vent piping
Block or shutoff valves closed
Open block or
shutoff valves
Piping leaks on HP side
Repair leaks
Bellows
Unit
(Refer
to DPU
Manual)
Housing filled with solids restricting
bellows movement
Clean out hous-
ing
Gas (liquid service) or liquid (gas ser-
vice) trapped in housing
Vent housing
HP housing gasket leak
Replace gasket
DPU tampered with
Return BUA for
repair
Indica-
tor, Alarm
Switch
Mechanism
Loose linkage or movement
Tighten or replace
Out of calibration
Calibrate
Pointer loose
Tighten pointer
Dirty or corroded mechanism
Clean or replace
Wiring interfering with movement
Re-route wiring
Dirty mechanism
Clean mechanism