Cathodic Protection - Monitoring and Maintenance

This is the sixth in a series of presentations by the South East Branch of PIG in the field of external pipe corrosion and cathodic protection.

This presentation explains the requirements and the practicalities of pipeline cathodic protection monitoring and maintenance for non-specialists.

It explains why the monitoring is necessary and what maintenance is recommended. The main pipeline above-ground survey techniques are discussed.

An example of the very latest technical developments in the reporting of routine monitoring and maintenance surveys is given.

IEEE Transactions on Power Delivery

Corroconsult’s Technical Director is a co-author of a new paper published in the IEEE Transactions on Power Delivery.  It was published on 09 April 2022.

The paper is a collaboration between Dr. David Boteler (Land and Minerals Sector,  Natural Resources, Ottawa, Canada), Prof. C. Charalambos (University of Cyprus, Nicosia, Cyprus) and Ken Lax (Corroconsult UK Ltd).

Previously unexplained instances of AC corrosion may be due to the effects of harmonics, which may not have been taken into account in the mathematical modelling and the interference mitigation design.  The presence of harmonics may not be apparent when taking voltage and current density measurements.

The paper gives a worked example of how to perform the calculations, which will be helpful for cathodic protection and pipeline electrical interference specialists.

Abstract:

Electromagnetic interference to pipelines and railways from AC sources has long been a cause for concern. Methods and standards have evolved to enable calculations of the voltages produced under different conditions. These take into account the AC frequency, the soil resistivity and the pipeline characteristics. However, the approximations presented in some standards fail to take into account the phase relationship of the currents in the AC conductors and how that affects the induced currents in the earth. This paper re-examines these issues by introducing a revised complex image method for 3-phase systems that provides a simple and accurate way to include the influence of induced currents in calculations of the induced emf in nearby conductors. Normal positive sequence 3-phase currents produce fields in neighbouring conductors that tend to cancel. For the associated image currents in the earth, the cancellation is so complete that they have no influence on the induced emf. A different situation occurs with the zero sequence currents that occur during fault conditions and triplen harmonics. These currents are in phase, so there is none of the cancelling effect and the contributions from each conductor add to give a larger induced emf in a neighbouring conductor.

Published in: IEEE Transactions on Power Delivery ( Volume: 37, Issue: 2, April 2022)

Page(s): 851 - 859

Date of Publication: 09 April 2021

ISSN Information:

DOI: 10.1109/TPWRD.2021.3072355

Contact Corroconsult UK Ltd for further information.

Pin Brazing for Cathodic Protection Applications - A Beginner's Guide

Pin Brazing is ideally suited for many applications including continuity bonding between pipes, across flanges, connection of cathodic protection test and current carrying cables and connection of bracelet galvanic anodes etc.

The Pin Brazing equipment is very robust, easy to operate, easy to maintain and ideal for on site works.

The kit is powered by a 36V DC battery pack (or suitable welding generator when using the generator gun) capable of delivering 240A for use with fused brazing pins, ceramic ferrules and cable lugs.

With the earth device in place the gun trigger is depressed and after approximately 1.5 to 2 seconds the circuit is mechanically broken as the fuse wire breaks, and the brazing pin is held into the molten pool of brazing alloy that rapidly cools into a homogenous and very strong connection.

This short video demonstrates the three key steps to applying a successful pin braze to a structure for cathodic protection cabling.

The video has been presented in slow motion to better highlight each of the processes.

A Pipeline Designer's Guide to Cathodic Protection

As part of our ongoing free webinar series with The Pipeline Industries Guild, our latest presentation “Pipeline Designer’s Guide to Cathodic Protection” is now available on YouTube.

The aim of the presentation is to provide information to pipeline designers on the factors that can influence the effectiveness of the external corrosion protection system - coatings, cathodic protection and electrical interference.

The technical information is given in such a way that it is understandable to people that are not corrosion specialists.

Next Generation Transformer-Rectifiers for Cathodic Protection Applications

Corroconsult UK Limited are proud to announce a new product line.

This next generation of transformer-rectifiers offer the user absolute control over the TRs configuration in real-time with the added benefit of in-built remote monitoring of key measurements.

The TRs can be viewed and configured in real-time through web based applications that are compatible with Windows / Macintosh / Android / iOS platforms.

Each initial order is provided with a lifetime single user access to the online database (additional lifetime user licenses can be purchased separately). There are no hidden ongoing subscription costs.

Each unit can be designed specifically to client requirements and is assembled and tested in the UK by Corroconsult personnel in accordance with the Company Quality Management System (ISO 9001-2015).

Take control of your impressed current cathodic protection (ICCP) systems.

Contact us for a live demonstration via video conferencing.

The Importance of Electrical Isolation

Defining "Electrical Isolation" for a Cathodic Protection System

With respect to cathodic protection systems, the term "electrical isolation" relates to confining the (cathodic) protective current to the structure being protected.

In terms of electrical separation this could mean isolating;

• Two (or more) cathodic protection systems from one another
• Buried / immersed structures from above ground appurtenances
• Cathodically protected structures from earthing systems
• Owner / Operator interfaces

Electrical isolation is a key factor in the successful application of cathodic protection where it has been included at the design stage. For the purposes of this blog article we assume that the structure is intended to be electrically isolated.

That is not to say that electrical isolation is always required, as long as the designed system has taken this into account.

There are times when it may not be desirable, or even practical, to isolate protected from unprotected structures. Examples are refineries, industrial plants, large tank farms and similar complex facilities. 

How to Electrically Isolate the Cathodically Protected Structure

Commercial fittings for providing electrical isolation of pipework include;

• Insulating Flange Kits (IFK)
• Monolithic Isolation Joints (IJ)
• Non-metallic pipe sections

Cathodically protected structures can be electrically isolated from earthing systems via;

• Decoupling Devices

Other solutions, e.g. non-conductive membranes, are available as methods of electrical isolation depending on the system in question.

Insulating Flange Kits (IFK)

The kit comprises of the following;

• Insulating Gasket
• Non-Metallic Sleeves for Assembly Bolts
• Non-Metallic Washers
• Metallic Washers
• Nuts & Bolts

Monolithic Isolation Joints (IJ)

The isolation joint is fabricated as a ready to install section of pipework.

The joint consists of;

• Forged Rings
• External Coating
• Internal Coating
• Adhesive Sealant
• Di-Electric Filler
• Insulating Rings
• O Rings

Decoupling Devices

Corroconsult recommend only solid-state devices, as this eliminates the maintenance requirements and hazardous electrolytes of electrochemical polarisation cells.

Solid-state DC decoupling devices can be used for;

• Electrically isolating from from utility earthing (grounding) systems
• Electrically isolating from electrical equipment earthing (grounding) systems
• Induced AC voltage mitigation
• Isolation joint protection

How can electrical isolation be compromised?

Incorrect Installation

An incomplete kit installation for an IFK will result in the flanged joint being electrically continuous.

Earthing / Grounding

The most common failure of installed electrical isolation is through incorrect earthing of cathodically protected structures.

New ISO 20313 Standard Released - Cathodic Protection of Ships

The new ISO 20313 standard for the Cathodic Protection of ships chaired by Ken Lax was published on 30 January 2018.  This is a major achievement for the working group and especially for the UK mirror group participants (Pat Lydon, Winston Shepherd and Andrew Willis). 

The plenary meeting of ISO Technical Committee (TC) 8 and Sub Committee (SC) 8 – Ship design met on 31 January 2018 and complimented the working group on meeting all the deadlines and producing a good standard. 

The working group has now been disbanded, although the Chairman of TC8 SC8 requested Ken to remain on the sub-committee to provide assistance.

The new Standard is available for download here: https://www.iso.org/standard/67645.html