A-29
Model 199 Differential Pressure Unit (DPU)
Section 4
Table 4.3—Troubleshooting Chart
Trouble
Possible Source
Probable Cause
Corrective Action
High
Indication
Primary
Orifice partially restricted
or too small
Clean out or replace
Piping from
Primary Element
to DPU
Leak in LP side piping
Repair leaks
Bellows Unit
Gas trapped (liquid
service) in LP housing or
liquid trapped (gas ser-
vice) in HP housing
Vent housing
LP housing gasket leaks
Replace gasket
Range spring broken or
DPU tampered with
Return BUA for
repair
Mechanism
Loose links or movements Repair or replace
Out of calibration
Calibrate
Erratic
Indication
Primary
Flow pulsating
Install dampening
device upstream of
DPU run
Piping from
Primary Element
to DPU
Liquid trapped in gas
piping or gas bubble in
liquid piping
Remove (see
Startup Procedure,
Section 3)
Vapor generator incor-
rectly installed
Repipe
Reference leg gassy or
liquid vaporizing
See piping instruc-
tions
Bellows Unit
Obstructed bellows travel
Clean bellows
Gas trapped in DPU HP or
LP housing
Remove (see
Startup Procedure,
Section 3)
Mechanism
Linkage dragging or dirty
Adjust or clean
Pointer dragging on scale
plate
Adjust