Pipeline inspection systems such as CCTV are most commonly used to find defects and assess conditions in existing pipelines that have been in service sometimes for many decades. However, in recent years increasingly detailed survey results have been sought by client companies to ensure that their budgets and planning systems are effectively and, possibly more importantly, efficiently utilized.

Currently, Oy DigiSewer Productions Ltd (DSP) is involved in a project for the Hämeenlinnan Seudun Vesi Oy (municipal authority) of the town of Hämeenlinna in Finland, located about 100 km north of Helsinki, to inspect parts of its sewer network. Finland is a country of around 5.4 million people with a public sewerage network totalling around 50,000 km.

The Hämeenlinnan Seudun Vesi Oy is responsible for sewerage networks totalling about 700 km, rain water sewers totalling about 300 km and drinking water pipes covering some 850 km, which serves a population of about 77,000. The Authority operates three main wastewater treatment plants. Currently the cost to Hämeenlinnan Seudun Vesi Oy for providing clean and wastewater services to this population is about €3.2/m3.

The main aim of the current project is to get detailed information about lengths of concrete sewer pipelines which were built between 1950 and 1975 in order to establish what the current conditions are and what maintenance and rehabilitation needs there are throughout these pipe lengths.

Known as the ‘Sewer Cleaning and DigiSewer Inspection Project in the City of Hämeenlinna, Finland,’ the main contractor for the works is Painehuuhtelu Oy PTV of Nurmijärvi, Finland. The pipe condition measurement works are being carried out using the with DigiSewer System.

Ground conditions in the project area under inspection comprise an extensive gravel hogback (ridge) beneath which the pipeline runs. The schedule for the project runs from April 26 to June 15, 2010. The project value is around €30,000 and includes project management, pipeline cleaning, condition measurement, manhole inspection, analysis and reporting of the results and a summary of the results obtained.

The project to measure the condition of the sewer pipelines in questions first involves high-pressure cleaning to ensure that full access to the pipeline is available to the inspection system. Cleaning is being achieved using twin-tank, high-pressure jetting lorry that provides cleaning water at 150 bar pressure at 350 l/min. The capacity of the unit comprises two x 8m3 twin tanks. The cleaning unit is being provided by Eurmark of Finland.

Once any given length is clean and accessible to the DigiSewer measurement/inspection unit, the survey can take place. The DigiSewer unit comprises the DigiSewer measurement unit mounted on an iPEK Rovver tractor unit. Software for the analysis of the data recorded during the survey is the WinCan V8 system.

On completion of the survey and to make handing over of the inspection materials simpler the client is provided with free WinCan Viewer software, which makes interpretation of the results easily understood.
 

The DigiSewer System

The DigiSewer system is designed to be a fast and reliable method of measuring the condition of a pipe and storing this information into a digital format. It provides automatic interpretation of condition data collected to a dimensional accuracy of 1 mm using specially designed data analysis software. This makes the actual survey, data collection and interpretation process operator free. This is achieved because the viewing head of the DigiSewer system is designed to scan the whole of the inner pipe wall around its full 360 degree circumference in the one operation, unlike conventional CCTV, which requires operator intervention to reposition the camera head to view defects, laterals and joints during a survey.

Unlike with conventional CCTV survey systems, DigiSewer tends to be referred to as a condition ‘measurement’ of the pipeline as opposed to an ‘inspection’. This is because the data collection achieved with the DigiSewer system provides a level of accuracy not possible with conventional systems.

The DigiSewer measurement equipment normally runs uninterrupted from one manhole to another, but in the case of the new raw water pipeline the survey runs through the most recently laid pipe section.  Unlike conventional systems, there is no need for the camera operator to stop the survey equipment where defects are found, to record positional data and condition notes on screen to aid later analysis. This is because the data collected by DigiSewer is automatically stored millimeter by millimeter onto a computer or storage device as the survey progresses without operator intervention, making surveys much quicker to complete.

Using the WinScan Viewer, it is also possible to see five different aspect pictures of one single defect at same time. These include the open view, the front view picture, the complete manhole to manhole section on a single screen, a graphic drawing of the manhole to manhole section showing the plan position of any defect and the inclination curve of the pipeline between the manholes.

Also, as compared to conventional CCTV surveys, the speed at which the collected data can be reviewed by analysts can be as much as five time faster. In its latest development DigiSewer is also now compatible to the iPEK SUPERVISION SYSTEM.

Commenting on the works to date, Timo Heinonen managing director of Hämeenlinan Seudun Vesi Oy, said: “The data from the sewer inspection and the condition results it presents us with is very important. Only with this data can we make decisions we can trust with respect to budgets and our planning of maintenance and rehabilitation actions for our sewage network. The age of these old concrete sewers is critical and we need to have an exact yet easy way to handle condition data to support our decisions for the future. This kind of inspection helps a lot in our annual budget planning process.”

Jani Kuikka, managing director of Painehuuhtelu Oy PTV, said: “The DigiSewer system gives inspection contractors like ourselves a fast, reliable and at same time, very trustworthy method of providing easy-to-understand data to our clients; such as municipalities, cities and water companies. Working and reporting with WinCanV8 is an effective and clever tool for our operators as well as being very useful and helpful to our clients as well.”

This article was submitted by Oy DigiSewer Productions Ltd., Nurmijärvi, Finland.

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