Other Metal Structures

Scrap steel In some fortunate instances a disused pipeline or other metal structure in close proximity to the project requiring cathodic protection may be used. However, it is essential in cases of scrap steel or iron groundbeds to ensure that the steelwork is completely electrically continuous, and multiple cable connections to various parts of the groundbed must be used to ensure a sufficient life. Preferential corrosion can take place in the vicinity of cable connections resulting in early electrical disconnection, hence the necessity for multiple connections. 

Fig. 6. Portable soil-washing machine shown here at a highway maintenance site used for removal of lead particles from the residue created when bridges and other metal structures are sand-blasted to remove old paint containing lead. There are numerous applications for such portable plants. (Westinghouse Electric Corporation)...

Others. Other metal structured packinge reported in the literature include Ralupak (3) and Rombopak (291. Plastic structured packing. 

Galvoline [Dow], TM for a cored magnesium ribbon used as a continuous anode for the cathode protection of buried pipelines and other metal structures. Combustible. 

Design considerations include the proximity to other metallic structures and existing CP systems, the type of grounding, the estimated remaining service life of the tank, the type and temperature of the stored product, the amount of product stored, the cycling rates, the method of tank bottom plate construction, the type of tank foundation, the type of secondary containment, if any, and the backfill soil characteristics. 

It may be desirable to electrically isolate a cathodically protected structure from all other metallic structures, such as connecting lines, pump stations, terminals, etc. If the installation is not isolated, these connections also will be cathodically protected, and current requirements frequently will be excessive. Electrical insulation of pipelines and other structures is accomplished by dielectric isolation. Small lines may be insulated by insulating couplings or unions. If feasible, insulated flanges should be assembled and electrically tested with an ohmmeter before being connected into a line. 

Metal buildings and other metal structures should be connected at the base to one or more ground electrodes by two or more independent connections (see Figure 2-8). Building structural steel can be used as the main conductor of the lightning protection system if it is inherently continuous or bonded together to provide electrical continuity. 

Cathodic protection is widely used in classic and atomic power plants, oil refineries, chemical works, and for the protection of gas and water pipelines and other metal structures. Excellent results are obtained by this method during anticorrosion electrochemical protection of reactors, tanks, pipelines (external and internal surfaces), pumps, coolers, heat exchangers, etc. Con-... 

If the line of soil pins used when making four-pin resistivity measurements is closely parallel to a bare underground pipeline or other metallic structure, the presence of the bare metal may cause the indicated soil resistivity values to be lower than it actually is. Because a portion of the test current will flow along the metallic structure rather than through the soil, measurements along a line closely parallel to pipelines should therefore be avoided. 

Lesser interference with the other metallic structures is caused because of a relatively low current output. 

The structure to be protected must be free from all interconnected metal work in order to limit the flow of electric current on the structure. This is made possible by electrical insulation. It is the condition of being electrically isolated from other metallic structures. The term insulation is used interchangeably with isolation. The use of isolated flanges and joints is common in pipelines. 

Infrastructural steel and other metal structures used in bulk quantities for construction need to be protected from corrosion caused from diffusion of water, oxygen. 

When the gradients are pulsed, residual fields called eddy currents are induced in the cryostat and other metallic structures. These fields decay with time constants typically in the order of tens of milliseconds, but for eddy currents in the cold cryostat vessel wall they may be hundreds of milliseconds long. Eddy currents can have a devastating effect upon image... 

The condition of being electrically separated from other metallic structures or the environment. Electrical resistivity... 

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