Cameron BARTON 289A - Page 65

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Section 4 Model 199 Differential Pressure Unit (DPU)
Table 4.3—Troubleshooting Chart
Trouble
Possible Source
Probable Cause
Corrective Action
Low or No
Indication
Primary Element
or Differential
Pressure Source
Orice installed backwards
or oversized
Replace orice
Flow blocked upstream
from run
Clean out run or
open valve
Loss of liquid in reference
leg (liquid level)
Rell reference leg
Density changes in pro-
cess media or reference
leg
Rell reference leg
with same density
liquid as process
media
Piping from
Primary Element
to DPU
Pressure tap holes
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 shut-
off valves
Piping leaks, HP side Repair leaks
Bellows Unit Housing(s) lled up with
solids, restricting bellows
movement
Clean out housing(s)
Gas trapped (liquid ser-
vice) or liquid trapped (gas
service) in housing(s)
Vent housing(s)
HP Housing gasket leaks Replace gasket
DPU tampered with Return BUA for
repair
Mechanism Loose links/movements Tighten or replace
Out of calibration Calibrate
Corrosion or dirt in mecha-
nism
Clean or replace
Pointer loose Tighten pointer