Nace CP 1 - Page 504

TM0497-2002
24 NACE International
STATIONARY METER
AND WIRE REEL
UNPROTECTED PIPE
+
_
REFERENCE ELECTRODE POSITION
FOR RELATED READINGS
TEST CONNECTION
TO PIPELINE
NOTE: Cathodic protection not applied.
Figure B2a
Reference Electrode Intervals for Potential Survey Using Stationary Meter and Wire Reel.
UNPROTECTED PIPE
REFERENCE ELECTRODE POSITION
FOR RELATED READINGS
TEST CONNECTION
TO PIPELINE
MOVING METER
AND WIRE REEL
+
_
Figure B2b
Reference Electrode Intervals for Potential Survey Using Moving Meter and Wire Reel.
0
100 200 300 400 500 600 700 800
-400
-500
-600
Pipe-to-Electrolyte Potential (mV)
AREAS EXPERIENCING CORROSION
-700
CATHODIC PROTECTION NOT APPLIED
Linear Distance
Figure B2c
Variation of Pipe-to-Electrolyte Potential with Survey Distance
FIGURE B2
Pipe-to-Electrolyte Potential Survey of a Noncathodically Protected Pipeline
Significant errors in the potential measurements can occur when surveys are undertaken as shown if there is a
break in the lead wire insulation or if leakage occurs through the
insulation.