Attention to detail
Neil Dalby of BAC Corrosion Control Limited discusses remote monitoring of pipelines protected by impressed current cathodic protection systems
Corrosion of metallic structures, whether they are pipelines, jetties or storage tanks, can be costly for an operating company. Targets are being set constantly by such operating companies to reduce leakages, and pipeline integrity, which brings to the forefront the problem of extending the pipeline's overall life span.
One way to control the corrosion is the application of coatings, in conjunction with impressed current cathodic protection (ICCP). This is used to protect the parts of the structure where the protective coating has failed, whether it is partial or total failure.
Most companies are becoming aware of ICCP theory along with that of sacrificial anode cathodic protection, and the obvious cost savings. Companies are also finding themselves having to comply with statutory health and safety executive requirements, and the introduction of ICCP is a must on order to meet regulations and laws.
The success of the cathodic protection relies on an impressed current from a DC power supply being imposed on to the structure. This can be done using various sources including transformer rectifiers that require AC power supply, or solar-powered generators.
For structures to maintain the correct levels of cathodic protection, differing amounts of current are required depending on various
external factors. These include resistivity of the surrounding soil, or distance from anode to structure.
The monitoring of protection criteria is extremely time-consuming, and they are therefore often only checked on an annual basis by field technicians. Whatever the interval of checking, the results are only valid for the time of taking and could be out of criteria between visits.
Remote monitoring systems have been around for many years, but now BAC Corrosion Control Limited, based in Telford has designed and tested a product in partnership with Italian company Technosystem, of Milan.
The idea of this product, Cathodic-on-Line (CCOL), is to remotely monitor the potential and current of the cathodic protection systems. Various levels of sophistication of monitoring are available utilising the ability to measure polarised potentials, which are a more valid measurement in line with current standards and practices.
The main advantage of CCOL is that it caters solely for the relevant quantifiable data and, unlike other monitoring systems, CCOL does not waste the unit's capabilities on irrelevant measuring possibilities that are not used. The system allows for various levels of cathodic protection data monitoring, logging, graphing and alarm warnings
by text message and the internet for display, monitoring and
Installation is simple with a requirement for the installation of a small data logger and GSM modem unit complete with battery packs at the monitoring location. All that is otherwise needed on site is three cable connections in order to monitor potential and current.
There are two options for monitoring. The portal records the minimum, maximum and average data over a 24-hour period and displays it the following day. Alternatively, the portal is programmable to record additional data according to customer requirements over a 24 hour (or longer) period. This allows monitoring at possible interference points such as DC rail crossings or other pipelines.
The increased recording options are either data-sampling at a rate of 1sec, which is then transmitted every minute, giving minimum, average and maximum values, or similar data transmitted every 15min over a period of up to a month. Data is archived each year and the customer is provided with a copy of the data on a CD, and additionally the data is stored in BAC's own archives for a further four years.
All that is required to view the monitored data from the portal is an internet facility. From the website, data from the units can be viewed for minimum, average, maximum values, standard deviation, out-of-limit value (set according to customer requirements) and out-of-limit time to be inspected as data or as graphs - all in real time while online.
Data can also be exported as an ASCII file to other programmes such as spreadsheets or word-processing packages for offline review and reporting. For each operating unit, data can be uploaded to the website, which could include instructions on how to get to the site or information from the last physical inspection.
If an operating unit enters alarm criteria,
pre-set by the customer, an e-mail is automatically sent to a specified address as soon as the data has been sent by the operating unit to the control room. A report can also be sent to a designated mobile phone as a report to inform field engineers of alarms.
The advantages include:
n precise and continuous knowledge of the status of the cathodic protection current and potential,
Several trials have been carried out in the UK, including Transco Pipelines in southern England, which measured stray current from rail DC traction systems, and several major water companies. Currently 6,000 units have been installed and are operating for Italgas monitoring cathodic protection installations in over 3,000km of gas pipelines.
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