The second technical presentation of 2021 was held on 11th February and featured a talk by Jay Warner, from Dairyland Electrical, who discussed, DC Decouplers – Why Are They Needed? and Improving Speed and Accuracy of CIPS Measurements with 
PCRX Decouplers.
Pipelines and storage tanks are commonly bonded to electrical earthing systems to reduce the effects of unwanted AC voltage and lightning hits on the structure. For example, AC mitigation systems provide a path to earth to reduce induced AC from nearby high voltage AC power lines as well as protecting against AC faults and lightning. Also, electrical equipment connected to the structure must be electrically earthed to meet electrical code safety requirements. Each of these connections to earth provides a path for cathodic protection (CP) current to flow from the anode bed back to the rectifier. Thus, in addition to protecting the structure, the CP system protects the earthing system and everything else to which it is electrically bonded. Protecting a bare metal earthing system requires much more current than protecting a coated pipeline and in many such cases CP systems are not able to maintain adequate potentials for corrosion control. The solution is to install DC decouplers in series with the bonding connections between the cathodically-protected structure and the earthing systems. Decouplers are designed to block CP current while allowing steady state AC, AC faults, and lightning current to pass freely. This allows the CP system to focus on protecting just the pipe, as it was designed to do, while the pipe remains safely earthed. The presentation included a brief description of solid-state DC decoupler devices and their operation and reviewed the common applications for decouplers used in conjunction with 
CP systems.
Example of gradient control mat isolation.
Jay also described some of the challenges often encountered with obtaining accurate CP potentials on protected structures during interrupted surveys. Capacitors, which are essential components of decouplers used with AC mitigation systems, can in some situations influence instant-off measurements and lead the operator toward incorrect conclusions. The influence of decoupler capacitance on instant-off measurement response was explained and several field installation examples were presented in which PCRX camouflage technology was used to overcome the capacitive effects during interrupted surveys.
After many interesting questions from the audience, the chair thanked Jay for his informative talk.
Example of AC Mitigation Equipment.
Typical decouplers.
The branch AGM was held prior to the March meeting which by tradition was the President’s talk. At the AGM, the branch chair, Ben Moorhouse discussed the performance of the branch over the past year, and said that although the pandemic had prevented the in-person evening meeting from taking place, the branch had successfully moved its technical presentations to online events. This was deemed very successful, as it allowed the branch to have internationally-based speakers, and also attendees from outside the UK. It was hoped to resume the normal meetings at the Lancaster Hall hotel for the 2021/2022, as networking was an important part of the branch activity. The possibility of also steaming the presentations online, so that interested non-UK members could join in was being explored. The treasurer reported that costs since April last year had been virtually zero, and that for the branch financial year 2019/2020, approximately £6500 (which included a surplus of £3,100 from the 2019 Christmas lunch was refunded to head office. The secretary reported that we had gained to supporting company members. The meeting finished with the chair proposing the branch committee (which was unchanged) for this year, and this was agreed by the members present.
Bill Hedges then delivered his President’s talk on the developments within the Institute and plans for the future. He described the history and the workings of the Institute, its governance structure and its membership prolife, including the types of individual and company membership and introduced the new Corporate membership class, which is being trialled by BP. There are currently about 1,650 individual members which has been increasing over the last 3 years, 26 Gold sustaining company and 102 other sustaining member companies. There is a drive to recruit and retain members, and Bill highlighted the benefits to be gained from being a member, including networking, career development, reputation and collaboration and financial benefits, and explored these features in detail. He then moved on to the areas of current activity, digital modernisation with increased social media presence, improvements to the website, increased and improved training programmes and our global partnerships, and again explored these topics in detail. Bill then explained the external drivers which were affecting our industry, and of course our members, and finished with a request for members to become more involved.
Institute of Corrosion President, Bill Hedges.
This presentation was well received by the 65 attendees.
Both these presentations have been uploaded to the ICorr website, and can be viewed at https://www.icorr.org/london/
Full details of future branch events can be found on the diary page of the magazine, and on the ICorr website.
