It is the job of the sampling probes to take a representative sample from the pipeline. It is important to ensure that this sample is extracted from the central third of the pipeline. One advantage of the retractable probes is that there is no risk of damage being caused to them when pigging is taking place in the pipeline. There is also the option of reducing pressure directly at the sampling probe. This is especially advisable if sample preparation and gas analysis are not carried out directly next to the sampling point.

As a general rule, implementing a reduction in pressure reduces the sample pressure to between 10 kPa and 500 kPa. Heated pressure regulators must be used if the dew point could be fallen below in the process.

In the sample preparation system, pressure reducers and flowmeters can be used to set the sample flow and pressure that will ultimately be required. Electronic monitoring of the sample flow transmits an alarm signal to the SITRANS CV/MicroSAM if necessary. The filters ensure that the sample is appropriately clean. An optional double block and bleed (DB&B) arrangement of the solenoid valves can ensure extremely safe isolation between the sample streams and the calibration gas. All versions of the sample preparation system are available for one, two or three flows plus the calibration flow.

The prepared sample is then analyzed in the natural gas analyzer and the calorific value, standard density and Wobbe index are calculated. Connecting the SITRANS CV/MicroSAM to a flow computer enables an energy value to be calculated from the measured quality and quantity with consideration of the pressure, temperature and flow measurement. SITRANS CV is preferably used in connection with flow computers. For the use of MicroSAM, please consult the parent company.

In order to regularly carry out calibration and supply carrier gas to the SITRANS CV/MicroSAM, gases that are typically found in shelving or cabinet structures must be made available. Heating the gas cylinders prevents condensation from building up in them. The gas cylinder transfer station enables the cylinders to be exchanged during operation. Individual cylinders can be connected and disconnected by means of valves.

The communication functionalities of the SITRANS CV can be extended using a SIMATIC Extension Unit. It is then possible to connect a further Modbus master and/or up to 16 AO. For the generation of analog outputs in combination with MicroSAM, we recommend the I/O Extender solution (see catalog PA 01, section 3)