Specifications

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2013 Deepwater Corrosion Services Inc. Specications subject to change without notice
ROV-II operation manual
9 Document 354-MN01-ENG Rev. C
7. Taking cathodic protection potential readings
Stab the tip-contact probe onto the point on the structure where the reading is required. When a
good contact is made, the displays will show a steady reading.
CAUTIONS
• Avoid stabbing painted or coated surfaces whenever possible. Try to take readings on
bare steel or on spots specially designated for cathodic protection measurement.
• If necessary, anodes can be stabbed. However, it is best to stab the anode band if possible.
• Avoid trying to stab through heavy, hard marine growth.
• The probe unit should be kept out of the mud, which will contaminate the electrodes.
• If the readings are not steady or do not match the criteria in Table 1, the cause is prob-
ably due to a high-resistance contact. DO NOT RECORD THESE NUMBERS. Continue to
stab until readings are within the range specied in Table 1. See troubleshooting section if
problems persist.
• NEVER operate the system with any of the connectors un-mated unless the dummy
plugs are installed.
8. Data interpretation
For carbon steel structures in seawater, the readings obtained should be within the ranges in Table
1. Exceptions may occur if the probe is stabbed onto an isolated section of a corrosion-resistant
alloy such as stainless steel, copper or nickel. In these cases, readings less negative than the indi-
cated range may be noted. If so, ensure that the readings are steady and within the ±5 mV allowable
tolerance.
Table 1 - Normal cathodic protection ranges for bare carbon steel in seawater
Range (mV) Interpretation Action
-500 or more positive
Error
Remake contact & verify
Measure two other points around the
component
Abort & refer to troubleshooting section
-501 to -649
Isolated from cathodic protection
Remake contact & verify
Record data
-650 to -799
Not cathodically protected
-800 to -849
Marginal cathodic protection
-850 to -1049
Cathodically protected
Record data
-1050 to -1149
Anode potential
-1150 or more negative
Error
Remake contact & verify.
Measure two other points around the
component
Abort & refer to troubleshooting section