Specifications

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2013 Deepwater Corrosion Services Inc. Specications subject to change without notice
ROV-II operation manual
8 Document 354-MN01-ENG Rev. C
• Stab the probe onto the structure and determine which reading displays the most positive
voltage; this is normally the failed reference electrode. The good reference electrode will have the
most negative reading.
For example, (-) 900 mV is more negative than (-) 800 mV. (-) 900 mV would indicate the good
reference electrode; (-) 800 mV would indicate the failed reference electrode.
• Record the cell-to-cell value.
• Only use the voltage readings from the good reference cell for the rest of that dive.
Figure 3 - Identifying a failed reference electrode
5.5 Proximity mode ground check
When the probe is being used in proximity mode, the user needs to verify that the platform ground
wire and probe tip will yield the same reading at any point on the main structure.
• Stab the steel structure with the probe and record the voltage reading.
• Take the reading again using the platform reference ground wire instead of the probe tip. The
readings should be identical.
If the readings vary by more than 3 mV, check the platform ground wire connection.
6. Operation
Most companies have their own survey procedures to follow. The following guidelines are given as
guidance only.
6.1 Wet check
6.1.1 When interfaced to an ROV, it’s important to perform a wet check before every dive. Sig-
nal errors caused by umbilical power cable interference could introduce reading errors.
6.1.2 With the probe wired to the ROV, immerse the system to a depth of at least –30 feet (–10
m), and with the vehicle still in its Tether Management System (TMS), bring up one electrical sys-
tem at a time and note the potential of the tip. (It will vary some depending on immersion time).
If there is a problem, the potential will change rapidly or will spike when the circuit is powered.
Repeat for all electrical and hydraulic systems. If a problem is detected, it should be xed. Usu-
ally, the cause is a poor ground connection or a faulty leaking underwater connector. The system
at fault can be switched off if it will not hinder operation.
6.2 Recording cathodic protection potentials
If wired correctly, the cathodic protection potentials should have a negative polarity. Accurate read-
ings will be steady as long as the probe is not moving. If readings are erratic, this is a sign of a con-
nection problem and the cause should be isolated and xed.
Most negative reading:
Indicates good electrode
Most positive reading:
Indicates failed electrode