Specifications

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2013 Deepwater Corrosion Services Inc. Specications subject to change without notice
ROV-II operation manual
6 Document 354-MN01-ENG Rev. C
5. Calibration
5.1 General
As with any subsea measurement device, it is important to calibrate the ROV-II probe to ensure that
the reference electrodes are working properly and that there is no damage to the probe. If the probe
is not calibrated, readings may be incorrect and the dive may have to be repeated.
Since the ROV-II probe uses two reference electrodes, the user always has two independent voltage
readings of the tip contact. This provides an advantage over probes that use a single reference elec-
trode because the cell-to-cell value can be checked at any time during operation to verify the probe
is calibrated and working properly. The cell-to-cell value is simply the difference in voltage between
the two readings; this value should never exceed 5 mV topside and 10mV subsea. For example, if
both voltage readings are the same, the cell-to-cell value is 0 (zero) mV.
5.2 Using calibration for troubleshooting
Certain problems could cause the probe to be out of calibration. A common cause, particularly on
diver surveys, is damage to the cable insulation. This causes an offset in the voltage readings, which
would usually be interpreted as inadequate protection levels. Other causes include one or more
defective reference cell electrodes, wire damage within the probe or mud that has gotten inside the
probe. Calibration can be used to quickly diagnose a defective reference electrode or cable damage
and should be performed before, during, and after every use.
NOTE: Company calibration specications must be met, but we strongly advise also using the at-
tached procedures.
5.3 Topside/bucket calibration
There are two types of bucket calibrations that can be performed:
• Zinc coupon calibration
• Cell-to-cell calibration
Wiring schematics for these two bucket calibrations are shown in Figures 4-5.
CAUTION:
Never use a metallic container for storage or for performing calibrations.
5.3.1 Fill a non-metallic bucket or container approximately 18 in. (45 cm) deep with seawater or
simulated solution with a specic gravity between 1.021 and 1.028.
5.3.2 Place the probe in the bucket, allowing the body to ll with seawater. The entire probe,
including the tip, must be immersed.
CAUTION:
DO NOT immerse the Seacon RMG-3FS connector in water unless it is mated with the
dummy plug.
5.3.3 Wait 30 minutes for the electrode elements to reach equilibrium (rst time use only).
5.3.4 To perform a zinc coupon calibration:
• Immerse the zinc calibration coupon. Stab the probe tip rmly onto the zinc coupon.
• Using a digital voltmeter set on 2.00 V DC scale, contact pin socket #1 (the large socket; refer
to Figure 2) with the positive voltmeter lead. This pin socket measures the probe tip.
• At the same time, contact pin socket #2 (rst clockwise of the large pin socket) with the nega-