It is commonly known, that any kind of leakages produces an acoustic noise, which can be detected by sensors. The attenuation of the acoustic signal during its traveling from the sources often makes it possible to detect leaks from remote locations.

The pig technology overcomes this problem, instead of sound traveling from the source to fixed sensors, the pig transports this sensor through the pipeline to the position of the possible sensors.

In 1992 the OMV (Austrian Oil Company) and TUV Austria (Testing and Inspection Institute) start to develop a completely self- contained pig, which should be able to check all kinds of liquid pipelines from 100 mm up.

An autonomous travel unit, which produces no additional noise by its traveling, contains the necessary power supply, the sensor(s), the data acquisition, conditioning and storage unit. After lab tests, where we checked and adjusted the sensitivity of the pig for different types and sizes of leaks and different liquids, we send out pig through a test loop with the possibility to build in different leakages (e. g. drilled pin-holes, pitting and cracks). During these tests we could demonstrate, that the pig is able to detect leakage rates as small as 5 or 10 lh-1, depending on the working pressure and the transportation liquid of the line. Through the special design we can discriminate real sources (leakages) from each kind of disturb and random noise and we have also a clear indication about its location.

We performed our first field experiences on connection pipelines between a refinery and a tank farm, with bridges and underground rivers crossing and could demonstrate that we are able to map out the condition of the line with an accuracy lower than 0.5% between artificial and natural markers also under worth conditions.

After our successful experiences with the small vehicles between 100 and 300 mm, we developed a 400/450 mm pig with some additional features. This means, we are able to detect, store and analyse 2 acoustic channels, temperature and pressure within the run. Since summer 1995 also this pig is in service successfully and therefore we are able to offer a complete set of pigs between 100 mm up to 450 mm and service hours upto 100 hours and storage possibility upto 400 km.

According to our experience on more than 600 km pipeline we are convinced, that this set of pig produces a lot of economical and ecological benefits for the pipeline owner.