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Section 4
Model 752 and 752A Differential Pressure Transmitters
Table 4.3—DPU Troubleshooting
Problem
Possible
Source
Probable Cause
Corrective Action
High
Output
Primary
Element
Orifice partially restricted or too
small;
Loss of liquid in reference leg
(liquid level)
Clean out or
replace;
Refill reference leg
Piping from
Primary
Element to
Transmitter
Leak in LP side piping
Repair
Bellows Unit
Gas trapped in LP housing in
liquid service or liquid trapped in
gas service;
LP housing gasket leaks;
Range spring broken or body
tampered with
Vent housing;
Replace gasket;
Return unit for
repair
Erratic or
Intermittent
Operation
Primary
Element
Flow pulsating
Install dampening
device upstream of
meter run
Piping from
Primary
Element to
Transmitter
Liquid trapped in gas piping or
gas bubble in liquid piping;
Vapor generator installed wrong;
Reference leg gassy or liquid
vaporizing
Remove trapped
liquid or gas bubble;
Repipe;
See piping instruc-
tions
Bellows Unit
Obstructed bellows travel;
Gas trapped in HP or LP housing
See
Remove trapped
gas
Out of
Calibration
Bellows Unit
Dirt in bellows;
Damaged bellows
Clean external
bellows surface or
return damaged
DPU for repair
