Stray currents protection against

The U -detonators which are now employed in mining in the Germany need a pulse of 16 mW -s/ohm the earlier detonators required only 3 mW s/ohm. Thus new detonators afford much better protection against stray currents. Locations exposed to electrostatic stray charges (thunderstorms) and which are therefore particularly dangerous, are equipped with low-sensitivity detonators, which require as much as 2500 mW-s/ohm for actuation and may therefore be considered safe ( HU -detonators). 

The best protection against stray current is, therefore, provided by concrete. Those methods that can improve the resistance of concrete to carbonation or chloride contamination, which are illustrated in Chapters 11 and 12, are also beneficial with regard to stray-current-induced corrosion. It should be observed that this may not be the same for preventative techniques, since conditions leading to corrosion initiation due to stray current are different, in terms of potential, from those leading to corrosion initiation due to carbonation or chloride contamination. For instance, the use of stainless steel or galvanized-steel bars, which improves the resistance to pitting corrosion in chloride-contaminated concrete (Chapter 15), does not substantially improve the resistance to stray current in chloride-free and non-carbonated concrete [4]. In any case, a high concrete resistivity will reduce the current flow due to stray current. 

A grounding lead should be installed across the sections of pipe that have been parted to protect against stray currents generating a spark. These currents could be generated by energy sources that have not been properly de-energized, such as cathodic protection of the pipe system or nearby equipment... 

Protection that concrete offers to steel against stray current ceases when corrosion of the reinforcement has initiated, e. g. due to carbonation, chloride contamination, or the stray current itself In this case, any current flowing through the steel will increase the corrosion rate at the anodic site, similarly as in buried steel structures. Figure 9.8 shows that even small driving voltages can lead to an increase in the corrosion rate on the anodic area (from to Furthermore, it has been observed that if steel is subjected to pitting corrosion in chloride-contaminated concrete, the anodic current increases the size of the attacked area [5]. 

API RP 2003, Protection Against Ignitions Arising Out of Static, Lightning, and Stray Currents, 6th ed., September 1998... 

Electric Drainage means of electric protection of an underground system against the corrosive action of stray currents arising from a d.c. electric traction system employing one or more connections (drainage bonds) made between the system to be protected and the return circuit of the traction system (rail, return current feeder, negative busbar of the sub-stations). 

API Recommended Practice 2003 (1998) Protection against ignitions arising out of static, lightning and stray currents. 6th ed. (American Petroleum Institute). 

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