A-16
Appendix A Model 224 Differential Pressure Unit
Table A.3—Troubleshooting Tips
Problem Possible
Source
Probable Cause Corrective Action
Low or No
Indication
Bellows Unit Housing fi lled with solids restricting bel-
lows movement
Clean out housing
Gas (liquid service) or liquid (gas service)
trapped in housing
Vent housing
High pressure housing gasket leaks Replace gasket
DPU tampered with Return BUA for repair
High
Indication
Primary
Source
Orifi ce partially restricted or too small Clean out or replace
Primary
Element to
DPU piping
Piping leaks on low pressure side Repair leaks
Bellows Unit Gas (liquid service) or liquid (gas service)
trapped in housing
Vent housing
Low pressure housing gasket leaks Replace gasket
Range spring broken or DPU tampered
with
Return BUA for repair
Erratic
Indication
Primary
Element
Flow pulsating Install dampening
device upstream of
DPU run
Erratic
Indication
Primary
Element to
DPU piping
Liquid (gas service) or gas bubble (liquid
service) trapped in piping
Remove
Vapor generator incorrectly installed Re-pipe
Reference leg gassy or liquid vaporizing See piping instructions
Bellows Unit Obstructed bellows travel Clean bellows
Gas trapped in DPU high pressure or low
pressure housing
Remove (see startup
procedure)
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