Application Note

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Pipeline Cathodic Protection

Application Background

Cathodic protection has been known about and applied to metal structures since last century. The principle of cathodic protection is simple. Corrosion is reduced by two methods.

anodes to be polarized to the potential of the local cathodes therefore stifling corrosion cells.

Pipelines are generally protected by impressed current systems and there are many expert cathodic protection companies worldwide advising pipeline operators on cathodic protection.

The first method is to connect the metal of the structure to a more easily corroded metal, called a sacrificial anode such that the sacrificial anode corrodes faster than the metal of the structure. Small vessels have these to protect propellers from corrosion and water heaters have these to minimise corrosion in water heater tanks.

The second method is to apply opposing current (this is called an impressed current system) forcing the local

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Application DetailMany oil and gas pipelines traverse very remote regions and there is a need to make sure the cathodic protection systems remain in operation to maintain pipeline integrity. These systems typically have rectifier stations at various points along the pipeline which take primary alternating current power, perhaps from a local power supply of a local generator, and rectify it to provide a low voltage and high current to apply to an anode buried in the ground.

Through this method the pipeline is protected from corrosion, however there is a need to monitor the performance of these systems as follows:

• therectifierstationstatusneedstobemonitored,toensure the voltage and current applied is correct

• thepipeline/structureneedstobemonitoredatmanypoints to ensure the small potential is correct along the pipeline to the next rectifier station

The rectifier station may have a small RTU with a Modbus interface to allow it to be controlled and monitored by a central SCADA system, and this would be common in high population areas where there is plenty of power and communications structure. The rectifier station may also have a simpler system of analog and digital inputs on the rectifier status, perhaps also local power generator status and fuel status and other local parameters.

For the rectifier station a Neon Remote Terminal or Module canmonitoreitherModbuschannelsand/orindividualanalog and digital inputs and outputs. There may be a needtomakeadjustmentstotheappliedvoltage/currentand these can be enabled to be remotely managed. This system would typically be housed in a metal structure, with termination strips and a solar panel and battery and a solar recharge system to the power supply is independent from the rectifier station power supply.

Telemetry would be needed to provide the rectifier station status and possible control from the pipeline operations centre. This could be cell phone based or satellite modem based, more likely satellite modem based as the pipeline is likely to traverse very remote areas. Perhaps the rectifier station would need to communicate with the central Neon Server every 15 minutes to communicate readings to be displayed on a Central Neon Server and also report out status to a central pipeline SCADA or other management system.

The other measurement points along the pipeline also need to be measured, and this is a very simple occasional measurement of a very low voltage level of the pipeline structure when compared to earth.

For the measurement station points a very small Neon Remote module could be used, with a small lithium battery pack, or a very small solar panel strip supply for convenience, as the power requirements are low.

Telemetry would be needed to provide the occasional voltage readings from the measurement points, but quite infrequently, perhaps read the voltage hourly, store it locally, and then and transmit the data to the central neon server daily, to minimise the power consumption and satellite airtime charges.ICCP Rectifier

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Typical Configuration

Application Specific Instruments/Inputs

Options Unidata Part Number Description

Low voltage sensors Custom part Low voltage sensors

Neon Telemetry - NRT / RTU / Field Units

Options Unidata Part Number Description

Cellular RTU GPRS 2011E-AB0 Neon Metering Module GSM+Ant+Batt

Cellular RTU 3G 2013D-AB0 Neon Metering Module 3G+Ant+Batt

Cellular RTU GPRS-Industrial 2014E-AB0 Neon Remote Terminal-Terrestrial+Ant+Batt

Cellular RTU 3G-Industrial 2016D-AB0 Neon Remote Terminal-Terrestrial+Ant 3G+Bat

Low Earth Orbit Satellite - Globalstar 2015D-AB0 Neon Remote Terminal-Satellite Globalstar+Ant+3 Bat

Ethernet 2017E-0B0-1 or 3 NRT Ethernet - 1 or 3 Ethernet Ports with Batteries

Equatorial Orbit Satellite - Inmarsat 2018E-AB0-1 NRT Ethernet with Inmarsat M2M Modem & 1 Ethernet Port & Bat

WI-FI 2019E-AB0-1 NRT Ethernet Wi-Fi - 1 Ethernet Port & Batteries

LCD Display 2500E NRT LCD Display

Field Termination Strip 2103E 2014E, 2015D, 2016D & 2017E NRT FTS

NRT Firmware Option 2303A-8M 8M Extended Memory

NRT Firmware Option 2303A-8M-CAM 8M Extended Memory & Camera Option

NRT Firmware Option 2303A-CAM Camera Option

Neon Application Software - Customer Server

Options Unidata Part Number Description

Neon Applications Software 2302A Neon Server Software Licence Incl 5 NAL

Neon Applications Software 2302A-10 Additional 10 NRT Access Licence

Neon Applications Software 2302A-20 Additional 20 NRT Access Licence

Neon Applications Software 2302A-50 Additional 50 NRT Access Licence

Neon Hosting Service - Unidata Server

Options Unidata Part Number Description

Neon Hosting Service 2301A Neon Data Initial Subscription Setup Fee

Neon Hosting Service 2301A-01 Neon Data Service Fee for 1-50 NRT

Neon Hosting Service 2301A-02 Neon Data Service Fee for 51-100 NRT

Neon Hosting Service 2301A-10 Neon Data Service Fee Metering

Conventional Dataloggers / Field units

Options Unidata Part Number Description

Prologger 7001E-11 Green logger 1M + Alkaline Battery

Field Termination Strip Prologger 7100E 7001E FTS

Starlog Datalogger Management Software

Options Unidata Part Number Description

Starlog V4 Management Software 6308A-AUE STARLOG V4 Full Licence Key