Nace CP 1, Руководство по эксплуатации

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RP0176-2003
20
NACE International
9.6 The test equipment used for obtaining each electrical
value should be maintained in good operating condition and
checked annually for accuracy. Reference electrodes
should be checked more frequently for possible inaccuracy
because of contamination, bad electrical connections, or
deterioration of wire insulations.
9.7 Diver-assisted or ROV inspections may be conducted
in conjunction with other underwater work to ensure that the
CP system is effective.
9.8 Remedial measures should be taken promptly when
periodic surveys and inspections indicate that protection is no longer adequate or will soon become inadequate. These
measures may include:
9.8.1 Repairing, replacing, or adjusting components of
CP systems.
9.8.2 Providing supplementary CP facilities in areas
where additional protection is necessary.
9.8.3 Repairing defective insulating devices or contin-
uity bonds.
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Section 10: Splash Zone Corrosion Control Measures
10.1 Introduction
10.1.1 This section lists corrosion control measures
that minimize the deterioration of steel members in the
splash zone. Some procedures may not be applicable
in all areas of the world because of varying service
conditions.
10.1.2 Corrosion of attached pipelines or risers in the
splash or submerged zone is outside the scope of this
standard.
10.1.3 Additional thickness of steel is usually provided
in the splash zone.
10.2 Placement
10.2.1 Unless the setting depth of the structure can be
ensured, consideration should be given to additional
protection beyond the normal splash zone interval to
provide a margin of safety.
10.3 Steel Wear Plates and Corrosion Allowance
10.3.1 Wear plates should compensate for the antici-
pated corrosion and wear during the life of the struc-
ture. Wear plates are usually 13 to 19 mm (0.50 to
0.75 in.) thick.
10.3.2 Wear plates are needed because damage can
occur to coatings or sheathings used in the splash
zone.
10.3.3 In addition to providing a corrosion allowance,
wear plates add stiffness and strength, thereby provid-
ing greater impact resistance.
10.3.4 Wear plates are usually coated or sheathed for
additional corrosion protection.
10.3.5 Corrosion allowance by additional steel thick-
ness may be used instead of wear plates. The thick-
ness should be calculated based on estimated lifetime
of the installation and anticipated corrosion rate. It is
normally not less than 6 mm (0.25 in.). The corrosion
rate in the splash zone is typically in the range 0.2 to
0.4 mm (0.007 to 0.015 in.)/year.
10.4 Alternative Corrosion Control Measures for Steel in
the Splash Zone
10.4.1 UNS
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N04400 (Nickel-copper alloy 400) or
UNS C70600 (90/10 copper-nickel alloy) sheathing
10.4.1.1 UNS N04400 sheathing, typically 1 to 5
mm (40 to 200 mils) thick (18 to 4 AWG,
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or UNS
C70600 sheathing, typically 4 to 5 mm (160 to 200
mils) thick, should be attached to tubular members
in the splash zone either by banding or welding.
Welding is preferred because the annulus be-
tween the steel member and the sheathing is
sealed.
10.4.1.2 The metal sheathing should be protected
from impact damage. Alloy-clad steel plate may
aid in preventing damage.
10.4.2 Vulcanized chloroprene
10.4.2.1 Vulcanized chloroprene is typically ap-
plied in thicknesses of 6 to 13 mm (0.25 to 0.50
in.).
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(7)
Metals and Alloys in the Unified Numbering System (latest revision), a joint publication of ASTM International and the Society of
Automotive Engineers (SAE), 400 Commonwealth Drive, Warrendale, PA 15096.
(8)
American Wire Gauge (AWG): A particular series of diameters and thicknesses established as a standard in the United States and used
for nonferrous sheets, rods, and wires. Also known as the Brown and Sharpe Gauge.