Protective electrical bonding

This increase can lead to unexpected corrosion problems/failure, as well as undesirable legal ramifications. Although it is possible to eliminate stray current corrosion (Fig. 10b) with the help of proper design features, the solution is not simple. The best solution to stray current problems is electrical bonding of nearby structures, as shown in Fig. 11. Installation of additional anodes and possibly additional rectifier results in protection of both structures [38]. 

Fault protection is protection against electric shock rmder single fault conditions and is provided by protective equipotential bonding and automatic disconnection of the supply (by a fuse or MCB) in accordance with lEE Regulations 411.3 to 6. 

In Chapter 13 of the lEE Regulations we are told that where the metalwork of electrical equipment may become charged with electricity in such a manner as to cause danger, that metalwork will be connected with earth so as to discharge the electrical energy without danger. The application of protective equipotential bonding is one of the important principles for safety. 

The object of the test is to ensure that the CPC is correctly connected, is electrically sound and has a total resistance which is low enough to permit the overcurrent protective device to operate within the disconnection time requirements of Regulation 411.4.6, should an earth fault occur. Every protective conductor must be separately tested from the consumer s main protective earthing terminal to verify that it is electrically soimd and correctly connected, including the protective equipotential bonding conductors and supplementary bonding conductors. 

Seven primary corrosion prevention methods are available to reduce the corrosion of metals material selection, electrical isolation, electrical bonding, environmental modification, inhibitors, coatings, and cathodic protection. Corrosion prevention methods are often used in conjunction with one another. Coatings are used to reduce current requirements in cathodic protection. Zinc is used as a cathodic protection system in coatings. The effects of two or more corrosion prevention systems can be synergistic or antisyner-gistic. Two effects are synergistic if the combination of the two is more effective than the sum effect of the two. 

The second design step addresses electrical continuity and the use of insulating flanges. These parameters will essentially define the structural area of influence of the CP system. To ensure protection over different structural sections that are joined mechanically, electrical bonding is required. In complex structures, insulated flanges can restrict the spread of the CP influence. 

Aluminum and its alloys should be anodized and painted, except in areas of electrical bonding. In such areas and where anodizing is not possible, a ehemical film treatment may be used, although it does not afford corrosion protection equivalent to anodizing. When possible, chemical films should be given the additional protection of organic coatings. 

The joint area of the electrical bond should be provided with a protective finish after bonding (organic coating, sealant, paint system). 

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