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Projects: Projects for Investigator
Reference Number	NIA_NGGT0043
Title	MiniLog Stray Current Monitoring Devices for Cathodic Protection Re-Life
Status	Completed
Energy Categories	Fossil Fuels: Oil Gas and Coal(Oil and Gas, Refining, transport and storage of oil and gas) 100%;
Research Types	Applied Research and Development 100%
Science and Technology Fields	PHYSICAL SCIENCES AND MATHEMATICS (Metallurgy and Materials) 50%; ENGINEERING AND TECHNOLOGY (Mechanical, Aeronautical and Manufacturing Engineering) 50%;
UKERC Cross Cutting Characterisation	Not Cross-cutting 100%
Principal Investigator	Project Contact No email address given National Grid Gas Transmission
Award Type	Network Innovation Allowance
Funding Source	Ofgem
Start Date	01 January 2013
End Date	01 January 2015
Duration	24 months
Total Grant Value	£20,000
Industrial Sectors	Technical Consultancy
Region	London
Programme	Network Innovation Allowance
Investigators	Principal Investigator	Project Contact , National Grid Gas Transmission (100.000%)
Web Site	http://www.smarternetworks.org/project/NIA_NGGT0043
Objectives	The objective of the project is to demonstrate and evaluate the benefits of the Minilog product. This will enable National Grid to close out CP defects which have arisen following routine CIPS activities. There is currently a significant backlog of defects which require investigation, and manual investigation of these defects is not practical. Minilog would potentially prove the off-potential and effectiveness of the CP system by providing a larger catalogue of detailed data rather than relying solely on expert interpretation to confirm wether or not the readings require further investigation. This will also provide more effective working time across the team to improve overall performance. The project will be successful if the polarised potential of the sections of pipeline with stray current can be identified. This will allow for accurate, reliable, and consistent defect analysis of stray current defects.
Abstract	Steel pipelines provide a very low resistance electrical path to remote earth. Therefore they are often influenced by numerous sources of both AC and DC stray current including high voltage overhead cables, DC transit systems, impressed current CP (cathodic protection) systems, DC (direct current) machinery and effects during sunspot activity known as Tellurics. Transient stray current effects are superimposed on top of the applied CP system and create significant CP measurement difficulties. The effectiveness of CP systems is assessed by periodic measurement of the pipe to soil potential over the entire pipeline; this requires the applied CP system to be switched "ON" and "OFF" very rapidly to eliminate a measurement error due to the volt drop associated with CP current flowing in the ground. However stray current cannot be switched off and may continue to deliver protective CP current to the pipeline. The consequence of all this is that it can be very difficult to assess whether the applied CP is effective or not. Minilog gives the facility to switch the pipe to coupon bond and record a robust and reliable "OFF" reading, (i.e. an error free measurement), without the influence of stray current. A coupon as mentioned above, is a buried metallic element of known size which represents an uncoated area of pipeline, and can be used as a tool to measure the potential at a specific location because unlike the pipeline it does not have the ability to act as a large conductor due to its size. CP data can only be classified against National Grid’s set criterion through expert interpretation; this leaves the possibility for misinterpretation of data, which could result in the pipeline being classified as satisfactory when in reality it might not be. The follow on effects of this could mean that In-Line Inspection (ILI) inspections are carried out less frequently, allowing corrosion to propagate. The benefit of using Minilog is that the level of CP applied can be assessed against the required protection criterion with a high level of confidence and the evidence retained for audit purposes. Subjective assessment is eliminated, and unnecessary costly excavations of coating defects in the areas influenced by stray current to prove by inference that the CP system is effective are not required. Along a section of pipe where the level of potential is severely fluctuating due to stray current, it is possible to monitor the actual effectiveness of the CP system at a localized point by taking measurements from coupons installed on many CP test posts along the section of pipeline affected by stray current, thus removing the problem of the pipe being a large conductor. The Minilog system will allow CP technicians to take readings from these coupons over a period of time to build up a better picture of the actual CP conditions rather than a single manual reading, which would only give a value for the time of the reading. Traditionally, to measure the ‘on’ and ‘off’ CP readings, a CP technician would have to travel to several TR (transformer rectifier) locations to fit interrupters which temporarily switch the CP system on and off. This then allows the technician to record how the stray current is affecting the true CP reading at a specific location between these TRs, namely where the CIPS (closed interval protection survey) data is showing large amounts of stray current interference. Byswitching the CP system on and off the stray current issue is removed because the reading for ‘off’ potential is only being taken from the metallic coupon rather than the pipeline itself. This process takes time and will only permit on and off readings at the time spent at the specific location, so it does not allow for a suite of data to be collected over a period of time. The MiniLog allows the CP technician to visit each site just twice. Once to fit the device into the test post the same way as they would with their standard testing equipment, and once more to retrieve the equipment at the end of the trial. This trial would take place typically over a 48 hour period taking readings every few seconds to allow our team to see a complete and accurate picture of the CP effectiveness at the given location. The device doesn’t require interrupters to be fitted as it takes the ‘off’ potential reading by disconnecting the coupon from the pipeline and therefore the CP system, much the same as the interrupters do in the more traditional method. The benefits of using Minilog are that it not only switches between the pipeline and the coupon automatically without the need to travel to several locations, but it is also discreet enough to fit inside a standard CP test post and be left unattended for a period of time, allowing more definitive evidence to be collected. The classification of CP defects where stray current is evident can only be done using interpretation by CP experts, so it is clear that by building up a larger catalogue of data over a longer period of time this interpretation will be far more reliable, and will undoubtedly be an effective way of categorizing areas where further investigation is required, or proving that the section of pipeline is within the CP protection limits set out in ECP2, the National Grid standard. More time is required than was initially anticipated for the analysis and internal review before progressing to the last stage of work on this project.Note : Project Documents may be available via the ENA Smarter Networks Portal using the Website link above
Publications	(none)
Final Report	(none)
Added to Database	14/09/18