Hi-tech vision underground
A project in Finland to survey condition and maintenance needs of old sewer pipelines has benefited from the use of the DigiSewer system, which records data with incredible accuracy.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 utilised.
Currently Oy DigiSewer Productions (DSP) is involved in a project for the Hämeenlinnan Seudun Vesi Oy in Finnish town Hämeenlinna, located about 100km north of Helsinki, to inspect parts of its sewer network. Finland is a country of around 5.4M people with a public sewerage network totalling around 50,000km.
Hämeenlinnan Seudun Vesi Oy is responsible for sewerage networks totalling about 700km, rainwater sewers amounting to 300km and drinking water pipes covering some 850km, 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.
Gravel hogback 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, 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. The pipe condition measurement works are
being carried out using the 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 ran from April 26 to June 15, 2010. The scheme, worth €30,000, 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 involved high pressure cleaning to ensure full access to the pipeline is available to the inspection system. Cleaning was achieved using a twin tank, high pressure-jetting lorry that provided cleaning water at 150 bar pressure at 350l/min. The capacity of the unit comprises two 8m3 twin tanks.
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 that makes interpretation of the results easily understood.
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 1mm 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 360o 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.
Positional data 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 millimetre by millimetre 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, 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.
Timo Heinonen, the managing director of Hämeenlinan Seudun Vesi Oy, comments: "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, adds: "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."