Installation of Clamp-On Gas Flow Meters in the Middle Pressure Distribution Net

The natural gas network of a German public utility company encompasses an underground pipeline system of approx. 70 miles. The gas is distributed thru middle pressure (650 mbar, appr 6-8 psig) pipelines and is then delivered to the end users via metering stations at appr. ambient pressures.

For a network analysis, for planning future expansions and for rapid localization and repair of possible disturbances, the company needed to measure the flow at various points in the network. These measurements are not subject to custody transfer calibration requirements, but were carried out as operational measurements. In the past turbine meters had been used at the gas transfer and metering stations. The turbine meter models installed were not equipped with counters. Retrofitting or converting the gas transfer and metering stations would have been very costly.

The utility decided to go with the cost effective alternative: non-intrusive gas flow measurement using the FLEXIM clamp-on ultrasonic technology. Now, the gas flow is measured before it reaches the gas transfer and metering station. To do this, it is enough to expose the PE pipeline at the measuring point in order to mount the clamp-on ultrasonic transducers on the pipe. No process interruption is necessary. By selecting appropriate measuring points with long straight lengths up- and downstream, a high measuring precision can be achieved.

The non-intrusive, acoustic measuring procedure is not subject to mechanical wear and therefore offers a long lifetime and high reliability. The recording of even the smallest leakage volume is possible.