Pipeline transporting fuels in liquid form habe to be subjected to an annual leakage test under the supervision of the FPI. This requirement applies to all pipelines that transport oil or oil products such as kerosene, petrol, diesel, etc.
Since these pipelines are almost always installed underground, visual inspections are normally not possible, and volume comparison measurements are unsuitable since they do not offer the required degree of accuracy.
This means that different procedures have to be applied, depending on the configuration of the pipeline or system. The pressure-volume method yields the most accurate information regarding pipeline tightness. Here a pipeline is blocked on both sides and the pressure and temperature are recorded over a period of 24, 48 or 72 hours. This timeframe depends on the accuracy of measurement, especially of the temperature.
If it is not possible to shut down a system for one or several days, the pressure-jump procedure can be used. Here the short-term pressure development in a pipeline is measured at different pressures and the readings are then compared. This procedure is used, for example, for the supply pipelines at Geneva and Zurich airports.
Another method that can be used is the pressure differential measurement, which is applied in systems where two identical pipelines run parallel to one another.