Protection against corrosion by stray current from direct current systems
This standard establishes the general principles to be adopted to minimize the effects of stray current corrosion caused by direct-current (d.c.) on buried or immersed metal structures. The standard is intended to offer guidance for: ? the design of direct current systems which may produce stray currents; ? the design of metal structures, which are to be buried or immersed and ? which may be subject to stray current corrosion; ? the selection of appropriate protection measures. The standard mainly deals with external stray current corrosion on buried or immersed structures. However stray current corrosion may also occur internally in systems containing an electrolyte e.g. near insulating joints or high resistance pipe joints in a water pipeline. These situations are not dealt with in detail in this standard but principles and measures described here are generally applicable for minimizing the interference effects. Stray currents may also cause other effects such as overheating. These are not covered in this standard. D.C. systems that can cause currents to flow in the earth or any other electrolyte, whether intentional or unintentional, include: ? d.c. traction systems; ? trolley bus systems; ? d.c. power systems; ? d.c. equipment at industrial sites; ? d.c. communication systems ; ? cathodic protection systems; ? high voltage d.c. (HVDC) transmission systems; ? d.c. track circuit signalling systems. For stray currents from traction systems EN 50122-2 gives requirements for minimizing their production and for the effects within the railroad. Systems which may be affected by stray currents include buried or immersed metal structures such as: a) pipelines; b) metal sheathed cables; c) tanks and vessels; d) earthing systems; e) steel reinforcement in concrete; f) steel piling. An affected structure carrying stray currents, e.g. a pipeline or cable may itself affect other nearby structures (see Clause 8). This standard does not address the effect of a.c. stray current. Where a.c. stray current is suspected, care should be taken when taking measurements on any components due to risk of large induced voltages. If a.c. stray current interference is present the criteria described in this standard will not apply.
: 9 470,0 Ft
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