Description of 19/30361619 DC 2019

This document establishes the general principles to be adopted to minimize the effects of stray current corrosion on external surfaces of buried or immersed pipeline systems caused by direct-current (d.c.).

ISO 18086 provides detailed information on the effects of alternating current on bubried or immersed pipelines. A brief description of alternating current (a.c.) effects is provided in this document.

The document is intended to offer guidance for:

• the design of cathodic protection systems which may produce stray currents;

• the design of pipeline systems, or elements of pipeline systems, which are to be buried or immersed and which may be subject to stray current corrosion;

• the selection of appropriate protection or mitigation measures.

The effects of a.c. induced voltages are not dealt with in detail in this document because they are covered in ISO 18086. General principles and guidelines are, however, provided.

Stray current corrosion can also occur internally in systems containing a conducting electrolyte e.g. near insulating joints or high resistance pipe joints in pipelines transporting conductive fluids.

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.

Stray currents can also cause other effects such as overheating. These other effects are not covered in this document.

A.C. currents can induce voltages on above-ground appurtenances of pipeline systems. These are not covered in detail in this document. They are covered in EN 50443, EN 61140, IEC 60364-4-41, IEC/TS 60479-1, IEC 60364-5-52, IEC /TS 61201, and IEC/TR 60479-5. EN 50122-1 gives guidance on d.c. touch potential limits.

Systems which may be affected by stray currents include buried or immersed metal structures such as:

1. pipeline systems;

2. metal sheathed cables;

3. tanks and vessels;

4. earthing systems;

5. steel reinforcement in concrete;

6. sheet steel piling.

This document provides details only for pipeline systems, although the principles can be applied to other buried structures. The EN 50162 series of standards also provide guidance for railway related structures.

An affected structure carrying stray currents, e.g. a pipeline or cable may itself affect other nearby structures.

About BSI

BSI Group, also known as the British Standards Institution is the national standards body of the United Kingdom. BSI produces technical standards on a wide range of products and services and also supplies certification and standards-related services to businesses.