Clasification Society Rulefinder 2016 - Version 9.25
Clasification Society Rules and Regulations - Rules and Regulations for the Classification of Offshore Units, January 2016 - Part 8 CORROSION CONTROL - Chapter 2 Cathodic Protection Systems - Section 3 Impressed current anode systems

Section 3 Impressed current anode systems

Parent topic: Chapter 2 Cathodic Protection Systems

3.1 General

3.1.1 Impressed current anode materials may be of leadsilver alloy or platinum over such substrates as titanium, niobium, tantalum, or of mixed oxides-activated titanium. Anode materials and anode designs specified in BS EN 13173 or BS EN 12495 are also permitted.

3.1.2 The design and installation of electrical equipment and cables is to be in accordance with the requirements of Pt 6, Ch 2 Electrical Engineering.

If hazardous areas are present on the facility, the impressed current cathodic protection system and equipment is to comply with the requirements ofPt 6, Ch 2 Electrical Engineering (in particular Pt 6, Ch 2, 5 Supply and distribution), Pt 7, Ch 2, 8 Electrical equipment for use in explosive gas atmospheres, Pt 7, Ch 2, 9 Additional requirements for electrical equipment on oil storage units for the storage of oil in bulk having a flash point not exceeding 60°C (closed-cup test), Pt 7, Ch 2, 10 Additional requirements for electrical equipment on units for the storage of liquefied gases in bulk and Pt 7, Ch 2, 11 Additional requirements for electrical equipment on units intended for the storage in bulk of other flammable liquid cargoes, IEC 60079 series and IEC 60092-502.

IEC 60092-502 Clause 5.7 ‘Cathodically protected metallic parts’ states ‘No impressed current cathodic protection shall be provided for metallic parts in hazardous areas, unless it is specially designed for this application and acceptable to the appropriate authority’.

The insulating elements required for the cathodic protection, for example, insulating elements in pipes and tracks, should if possible be located outside the hazardous area. See IEC 61892-7 Section 5.6.6.

3.1.3 All equipment is to be suitable for its intended location. Cables to anodes are not to be led through tanks intended for the storage of low flashpoint oils. Where cables are led through cofferdams of oil storage units they are to be enclosed in a substantial steel tube of about 10 mm thickness.

3.1.4 The arrangement for glands, where cables pass through shell boundaries, are to include a small cofferdam.

3.1.5 Cable and insulating material should be resistant to chloride, hydrocarbons and any other chemicals with which they may come into contact.

3.1.6 The electrical connection between the anode cable and the anode body is to be watertight and mechanically and electrically sound.

3.1.7 Where the power is derived from a rectified a.c. source, adequate protection is to be provided to trip the supply in the event of:
  1. A fault between the input or high voltage windings of the transformer (i.e. main voltage) and the d.c. output of the associated rectifier; or
  2. The ripple on the rectified d.c. exceeding 5 per cent. The requirements for transformers and semi-conductor equipment are given in Pt 6, Ch 2, 9 Rotating machines.

3.1.8 Anodes may be installed by mounting in insulating holders attached directly to the submerged structural member provided the general requirements given in Pt 8, Ch 2, 2.13 Anode installation regarding attachments to the structure are complied with.

3.1.9 Suitable dielectric shields are to be fitted in order to avoid high negative potentials.

3.1.10 A warning light or other warning indicator is to be arranged at the control position from which divers are controlled to indicate that the impressed current cathodic protection system has been switched off when divers are in the water.

3.2 Protection after launching and during outfitting

3.2.1 Where protection is primarily by an impressed current cathodic protection system, sufficient sacrificial anodes are to be fitted, capable of polarising the critical regions of the structure from the time of initial immersion until full commissioning of the impressed current system.

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