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Flow Measurement at a Compressor Station

Flow Measurement at a Compressor Station

Flow metering on compressor operations is critical for the proper balancing of the compressors, to thus notice possible surge issues before they occur and to monitor compressor efficiency and performance. 

Differential pressure flow meter devices should not be the flow measurement system of choice due to the pressure drop they are causing, whilst turbine flow meters and other mechanical meters do not perform well in pulsating conditions. Vibrations and mechanical stresses can also be problematic for Pitot tubes inserted into a pipe via welded-on fittings.

FLEXIM's ultrasonic clamp-on flow meters offer a valuable alternative as pulsating flow is not an issue and they do not cause any pressure drop.

Response time to changes in flow is an important flow meter performance criterion in compressor operations. A typical response time for Differential Pressure flow meter devices is 100 to 200 ms to reflect app. 63% of a flow change.

FLEXIM's clamp-on flow meters can add value with faster response.  A response time of 10 ms to reflect 100% of a flow rate change is possible offering a much better and faster possibility to react and change the performance settings of a compressor and avoiding possible damages due to surges.

The compressor flow intake measurement ensures a balanced and sufficient gas load. Maintenance issues or possible compressor surge issues are thereby noticed well in advance of costly equipment damage.

Application example at a natural gas compressor station:

In the western region of Germany, a natural gas corporation extracts 6.5 billion m³ of natural gas per year from about 120 wells. The pressure of the reservoirs can vary between 25 and 80 bar, depending upon the degree of depletion.
At the compressor station, the extracted natural gas is compressed to a pressure of 80 bar through two gas turbines driven by high-pressure compressors before it is sent to the processing plant. Two orifice plates / differential pressure meters measure the flow upstream from the compressors.

Depending upon the actual delivery rate of the well heads, it can happen that some gas has to be recirculated via a bypass in order to ensure optimal operation of the compressor. In this case, the flow measured of the permanently installed differential pressure meters no longer corresponds to the effective rate of gas being tapped. However, both the production dispatcher and the operator of the processing plant require reliable information as to the exact amount of extracted gas being forwarded.

FLEXIM's non-invasive flow measurement using the clamp-on technique is an elegant solution for this measuring task. Since the transducers do not come in contact with the medium, they are not subject to wear caused by corrosive substances, such as hydrogen sulfide, in the gas stream. No changes need to be made to the piping. Installation can take place without interruption of the production process.

Avantages

  • High measurement dynamics (from 0 up to 250.000 Nm³/h)
  • Integrated conversion to standard volume flow or standard mass flow according to ISO 12213-1
  • Uncomplicated retrofitting without cutting into the pipe or interrupting the process
  • Non-contact measurement avoids material compliance procedures

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