A success story

On 15 October 2024, MERO in Vohburg has now been successfully inspecting pipelines with our leak detection pigs for 25 years.

The company MERO Germany GmbH (Vohburg an der Donau), as well as TAL, the German Transalpine Oil Pipeline in Kösching, had already identified the need for leak detection pigs around 1995. Firstly, for a new pipeline at MERO and secondly to replace obsolete systems that could no longer be repaired due to a lack of spare parts.

The company EDAG (Ingolstadt) had engineers working for TAL as service providers at the time, so TAL was able to pass on the above requirements to EDAG. EDAG then decided to develop new pigs. This development was supported by TAL and MERO, who were able to bring the new systems up to the functional standard by means of pig lock tests and many test runs in the MERO pipeline. TÜV Süd (Munich) was involved throughout the entire development phase to improve the set of rules for the recording functions and parameters.

For a long time, FFT and EDAG had the same owners and the largest sites in Fulda. Close cooperation was therefore a matter of course. The electronics and software specialists worked hand in hand and developed the Leak Detection Pig at EDAG. The development team moved the product to FFT in 2010, as FFT and EDAG no longer have the same owner. The system is still being further developed, manufactured and sold by FFT today.

Four times a year, TÜV Süd carries out a thorough inspection of the pipelines, known as the DD test (differential pressure test). During this test, the pressure in the pipeline is gradually increased to the maximum while certain section valves are closed. This allows the individual sections of the pipeline to be checked for any loss of pressure. This test ensures that leaks are detected, documented and repaired at an early stage. This prevents oil, for example, oil escaping from the pipeline into the environment. The DD test takes about a week and requires a temporary shutdown of the pipeline, during which time no oil is transported.

However, if the pipeline operator can successfully conduct a pig run every month and provide TÜV Süd with proof of the pipeline's tightness, the number of DD tests to be carried out is reduced from 4 times to once a year. This is exactly what MERO has been doing for 25 years. As a result, MERO has been able to save a total of 75 weeks of DD testing and thus avoid approximately 1.5 years of pipeline downtime.

The ultrasonic leak detection pigs used are designed to detect creeping leaks in the pipeline. These are the most dangerous leaks as they can remain undetected for years without proper methods.

The leak detection pig is inserted into the pipeline once a month and is pushed through the pipeline by the oil column with its own power supply and without an active drive.

The pressurised crude oil in the pipeline contains tiny gas bubbles that grow into larger bubbles when the pressure drops. It is precisely this pressure drop that occurs in the flow channel of a leak. (Law of aerodynamics: the pressure in flowing gases and liquids is lower than that in stationary gases and liquids). These gas bubbles then burst in the neighbouring soil. The resulting ultrasonic noise is transmitted back into the pipeline through the leak channel.

The main function of the leak detection pig is therefore to detect noise in this frequency range. In addition to the sound information, the date, time, internal pipeline pressure, temperature and route information are also stored. There are a number of other conditions that must be met for the sound to be generated. For example, the internal pipeline pressure must be greater than 5 bar and the back pressure of the soil flooded by the pumped fluid must be at least 0.1 bar at 1.2 m overburden.

All of this information is processed by FFT's pressure-resistant, encapsulated electronic unit - a microcontroller with its own memory. Once the pig has been removed and cleaned, the data can be read out and analysed using specially developed software.