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BS EN ISO 18086:2020:2021 Edition

BS EN ISO 18086:2020:2021 Edition

$189.07

Corrosion of metals and alloys. Determination of AC corrosion. Protection criteria

Published By Publication Date Number of Pages
BSI 2021 48
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This document specifies protection criteria for determining the AC corrosion risk of cathodically protected pipelines.

It is applicable to buried cathodically protected pipelines that are influenced by AC traction systems and/or AC power lines.

In the presence of AC interference, the protection criteria given in ISO 15589‑1 are not sufficient to demonstrate that the steel is being protected against corrosion.

This document provides limits, measurement procedures, mitigation measures, and information to deal with long-term AC interference for AC voltages at frequencies between 16,7 Hz and 60 Hz and the evaluation of AC corrosion likelihood.

This document deals with the possibility of AC corrosion of metallic pipelines due to AC interferences caused by conductive, inductive or capacitive coupling with AC power systems and the maximum tolerable limits of these interference effects. It takes into account the fact that this is a long-term effect, which occurs during normal operating conditions of the AC power system.

This document does not cover the safety issues associated with AC voltages on pipelines. These are covered in national standards and regulations (see, e.g., EN 50443).

PDF Catalog

PDF Pages PDF Title
2 National foreword
4 European foreword
7 Foreword
8 Introduction
9 1 Scope
2 Normative references
3 Terms and definitions
13 4 Cathodic protection persons competence
5 Assessment of the AC influence
5.1 General
14 5.2 Assessment of the level of interference
6 Evaluation of the AC corrosion likelihood
6.1 Prerequisite
6.1.1 General
15 6.1.2 AC voltage on the structure
6.2 AC and DC current density
6.2.1 General
6.2.2 AC current density
6.2.3 High cathodic DC current density
16 6.2.4 Low cathodic DC current density
6.2.5 Current ratio “Ia.c./Id.c.”
6.2.6 Soil resistivity
6.3 Corrosion rate
6.4 Pipeline coatings
17 6.5 Evaluation of the metal loss
7 Acceptable interference levels
8 Measurement techniques
8.1 Measurements
8.1.1 General
8.1.2 Selection of test sites
18 8.1.3 Selection of measurement parameter
8.1.4 Sampling rate for the recording of interference levels
8.1.5 Accuracy of measuring equipment
8.1.6 Installation of coupons or probes to calculate current densities
8.2 DC potential measurements
19 8.3 AC voltage measurements
8.4 Measurements on coupons and probes
8.4.1 Installation of coupons or probes
20 8.4.2 Current measurements
8.4.3 Corrosion rate measurements
21 8.5 Pipeline metal loss techniques
9 Mitigation measures
9.1 General
9.2 Construction measures
9.2.1 Modification of bedding material
9.2.2 Installation of isolating joints
22 9.2.3 Installation of mitigation wires
9.2.4 Optimization of pipeline and/or powerline route
9.2.5 Power line or pipeline construction
9.3 Operation measures
9.3.1 Earthing
23 9.3.2 Adjustment of cathodic protection level
9.3.3 Repair of coating defects
24 10 Commissioning
10.1 Commissioning
10.2 Preliminary checking
10.2.1 General
25 10.2.2 Coupon AC voltage and current startup
10.2.3 Verification of effectiveness
10.2.4 Installation and commissioning documents
26 11 Monitoring and maintenance
27 Annex A (informative) Simplified description of the AC corrosion phenomenon
29 Annex B (informative) Coupons and probes
34 Annex C (informative) Coulometric oxidation
35 Annex D (informative) Influence of soil characteristics on the AC corrosion process
36 Annex E (informative) Other criteria that have been used in the presence of AC influence
40 Annex F (informative) Parameters to take into account to choose a DC decoupling device
42 Annex G (informative) Method to determine the reference electrode location to remote earth
44 Annex H (informative) Simultaneous measurement on coupon current densities with high rate
46 Bibliography

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BS EN ISO 18086:2020
$189.07