ISO 21857:2021

Description

This document establishes the general principles for the evaluation and minimization of the effects of stray current corrosion on external surfaces of buried or immersed pipeline systems caused by AC and DC electrical interference.

Other stray current effects such as overheating, and interference with welding operations are not covered in this document.

A brief description of AC effects, general principles and some guidelines, are provided.

NOTE 1 See ISO 18086 for the effects of alternating current on buried or immersed pipelines.

Systems that can also be affected by stray currents include buried or immersed metal structures such as the following:

a) pipeline systems;

b) metal sheathed cables;

c) tanks and vessels;

d) earthing systems;

e) steel reinforcement in concrete;

f) sheet steel piling.

This document gives guidelines for

– the design of cathodic protection systems that might produce stray currents,

– the design of pipeline systems, or elements of pipeline systems, which are buried or immersed, and which can be subject to stray current corrosion, and

– the selection of appropriate protection or mitigation measures.

Internal corrosion risks from stray currents are not dealt with in detail in this document but principles and measures described here can be applicable for minimizing the interference effects.

NOTE 2 The impact of electromagnetic interference on above-ground appurtenances of pipeline systems is covered in EN 50443, IEC 61140, IEC 60364-4-41, IEC 60479-1, IEC 60364-5-52, IEC/TS 61201 and IEC/TR 60479-5.

This document can also be used for pipeline systems outside of the petrochemical and natural gas industries and other buried or immersed structures.

NOTE 3 EN 50162 provides guidance for railway related structures.