October 2011, Vol. 238 No. 10

Features

Remote CP Monitoring Assists Gas Distribution Company

A UK gas utility has implemented a remote CP monitoring system to help it improve pipeline protection and workforce efficiency. Wales & West Utilities (WWU) is an independent gas distribution business in the UK. It owns, operates, maintains and develops the gas network throughout Wales and southwest England, serving 7.5 million people. Its total length of pipeline network is 35,000 km.

WWU strives for excellence as recognized by its awards and levels of investment. In 2008 it was voted the gas industry’s “Network Operator of the Year” and received the industry’s “Award for Customer Services” in 2009 and 2010. In 2010, it was voted Utility Company of the Year by the Utility Industry Awards. Since 2005 it has invested £50m in information technology and – in the current price review period (2008-2013) – over £2m per week is being spent on improving assets and asset management.

As part of this improvement project, it was decided to implement remote monitoring of WWU’s impressed current cathodic protection system. This article outlines our experiences; we do not say that this is the only or best way but hope that the benefits and lessons learned will assist other gas utilities in their decision-making process.

Objectives
Previous experiences of monitoring CP remotely had proved unsatisfactory for a variety of reasons: 1) The earliest remote monitors had been installed using fixed PSTN phone lines which had become prohibitively expensive to operate and maintain; 2) Some transformer rectifiers in remote areas had been fitted with beacons that flashed in the event of a failure. In principle, these could be observed during aerial surveys; in practice the beacons were themselves unreliable and adverse weather conditions meant that faults could go undetected for prolonged periods; and 3) More recently, remote monitors had been used that were originally developed for other applications and modified for CP. However, they were limited to a single potential measurement and did not interface with the company’s asset management software.

The company’s requirement was for a cost-effective remote CP monitoring system that could 1) provide monitoring at transformer rectifiers and test posts, 2) switch the output of the rectifiers and 3) export CP data directly into the company’s asset management software. Apart from eliminating the manpower used to record measurements, it was felt that the system would greatly improve asset management by providing prompt notification of rectifier and CP faults. It would also make better use of the workforce by diverting their energies from simply monitoring the CP system into repairing and improving it.

System Selection And Financial Justification
Having assessed a number of supplier options and their specifications, the company identified the Merlin system, developed by Abriox, as the one that could completely meet its requirements.

The Merlin system comprised different monitor types, for installation at rectifiers and at test points, together with user software that enabled the pipeline engineer to quickly identify any alarms or deficient measurements. WWU carried out a trial of the system to confirm its suitability, following which a financial case was prepared for the project roll-out.

Financial justification for the remote CP monitoring project was based on removing the need for monthly functional checks at the transformer rectifiers used in impressed current systems. It was estimated the payback period on the investment would be less than three years.

Installation Experience
The installation project was implemented smoothly. Unlike others, the Merlin system had been designed to be compact enough to fit inside existing infrastructure (e.g., rectifier enclosures). UK test points, in particular, have only a small cavity behind the face plate – and the Merlin CP Monitor was the only unit small enough to fit inside it.

[inline:Illustration 2B.JPG=CP Monitor installed at test point.]

Installation of the Merlin Rectifier Monitor and associated solid state Interrupter was standardized for the different rectifier types used by WWU. Once physically installed, both monitor types were very quick and easy to set up – requiring no specialist equipment, simply a mobile phone to send and receive a few text messages. The whole configuration process took just a few minutes per site.

Using GSM communication, the Merlin system was able to offer reliable, low cost messaging. There is almost full GSM coverage in WWU’s area, though the topography of Wales proved challenging and some isolated areas were found to have quite low signal levels. Various solutions were used to overcome this problem: 1) changing the SIM card to a different GSM network, 2) selecting Merlin monitors with external GSM antennas, 3) optimizing the antenna type and 4) mounting the antenna high up on a pole. In remote mountain or valley areas with no (or low/fluctuating levels of) GSM signal, the Abriox Merlin XT monitor with satellite communication was used.

A small number of CP installations were powered from solar panels. In these locations voltage regulators were installed and the spare channels used to monitor battery voltage. Abriox implemented a hardware modification enabling the monitor to be powered from an 11-15V DC supply or alternatively an 18-32V DC supply using a recommended DC-DC convertor.

Benefits
The original objectives of the remote CP monitoring project were achieved. Significant financial savings have been made through better use of WWU’s workforce – monthly functional checks on impressed current systems are discontinued and manpower has been redeployed onto improving the CP system. This has improved efficiency and resulted in significant improvements to the protection offered by the CP system to the pipeline network.

The original plan was to monitor 173 rectifiers and 420 test points. However, due to the success of the project, it proved possible to install ~20% more than these totals. Data from WWU’s three regions (South Wales, North Wales and the South West of England) is automatically exported into the company’s asset management software. Other benefits have included:

1) At test points, the Merlin monitor has proved particularly useful in monitoring AC current and voltage levels. This helps determine if AC corrosion is likely and confirms that the pipeline is safe to work on. The NACE maximum recommended voltage for safe working on pipelines is 15VAC.
2) Alarms have been set for all inputs to ensure that the CP system is working within specified ranges. In the long term this improved protection should prolong the lifetime of the asset.
3) The UK climate is extremely variable and – for the first time – it is possible to monitor rectifier output trends during extended wet and dry periods. Solar station output and battery levels are also now monitored continuously.
4) Constant “off” periods can be set for non-routine operations, such as shelling repairs from corrosion damage or cutting/welding on the main. The transformer rectifiers in the vicinity of the work can be switched off remotely.
5) An additional use for constant rectifier “off” periods is to take fully depolarized readings which can then be compared with polarized readings to observe the potential shift.

With Merlin Interrupters installed at rectifiers, the outputs of all rectifiers on a pipeline can be remotely synchronized, setting “on” and “off” intervals for CIPS and DCVG surveys and making adjustments for anodic and cathodic spikes. This has saved a considerable amount of set-up time and effort. Improved interaction with the workforce has enabled better survey results to be achieved.

There have been some significant benefits that were not originally foreseen:

1) By default, the monitoring system verifies CP readings taken by the third parties and contractors. In a recent instance, incorrect readings were identified that could have masked a potential problem on the pipeline.
2) Many distribution companies with urban areas will have a small number of areas where the workforce feels at risk. Remote monitoring has saved the company from having to send two-man teams into such areas.
3) The system has also been able to identify third-party interference (rebar contact during site works) on a pipeline. It was possible to determine the date and time the incident occurred through changes in the CP readings.

Conclusion
WWU’s decision to implement remote monitoring of its impressed current cathodic protection systems has been fully justified. Through careful system selection and implementation, the project has met all its key objectives, including a significant financial saving. The operational benefits targeted have been realized and – in many cases – exceeded, and the system has delivered a number of additional benefits that were not originally foreseen.

Author
Richard Williams executes the functions of first line manager – pipelines, for Wales & West Utilities in the UK. He was born in Caerphilly, Wales in 1958 and studied electrical and mechanical engineering at the University of Wales, Cardiff. After gaining contracting experience with Dragon Corrosion, he joined British Gas in 1980 as a CP Technician and became a professional member of the Institute of Corrosion in 1990. Since the reorganization of the UK gas sector he has worked for Wales & West Utilities and is responsible for pipeline maintenance and cathodic protection in South Wales.