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Extension of the metrological capacities of the petroleum test rig

19.04.2010

The petroleum test rig is an integral part of PTB's system of primary standards in the field of volume and flowrate measurement; it works specifically with fluids other than water. The extensions which have been carried out considerably improve the operation of the test rig and now enable us to investigate the transferability of measurement results which have been obtained using the Hydrodynamic Test Field with water to other fluids under comparable measurement conditions.

The petroleum test rig was set up in 1950 already; it understood itself as an independent volumetric standard measuring device for white spirit and spindle oil and was equipped with four volumetric tanks having capacities between 100 and 5,000 litres.

Owing to the long-term metrological concept of the "Liquid Flow" Department, it is progressively becoming integrated into the global system of fluid primary standards and is to be used especially for research purposes in order to develop medium-independent transfer standards [1]. Fundamental modifications and improvements were therefore necessary. Besides the automation of the fluid level measurement – which was already described in a piece of research news from last year – on one of the standard tanks, especially the operating parameters of the test rig, the installation conditions for the test objects and the measuring arrangements have been optimised.

For example, besides the so-called static start/stop operation, the "flying" start/stop operation has now been realised. In the case of the static start/stop operation, the signal acquisition of the measuring instrument starts exactly when the meter section is opened and the liquid starts flowing. Start-up and rundown procedures on the test object and the adjustment of the desired flowrate are carried out during the measuring operation, i.e. during the signal acquisition on the test object, and thus can lead to considerable errors which mostly cannot be controlled. In the case of the "flying" start/stop operation, the desired flowrate is already applied to the measuring instrument to be tested before the actual measuring operation starts. The measuring operation is started by a fast diversion of the fluid flow from the bypass into the volumetric tank and is terminated by switching back the corresponding diverting mechanism into its original position.

The diverting mechanism for the large meter section DN150 for the  "flying" start/stop operation is located in the centre of the photo. The  mechanism consists of a double ball valve which conveys the fluid flow  from the bypass pipe (left section) into one of the volumetric tanks  (right section) during the measuring operation, and back into the bypass  pipe after the measurement has been completed.

Figure 1: The diverting mechanism for the large meter section DN150 for the "flying" start/stop operation is located in the centre of the photo. The mechanism consists of a double ball valve which conveys the fluid flow from the bypass pipe (left section) into one of the volumetric tanks (right section) during the measuring operation, and back into the bypass pipe after the measurement has been completed.

Besides optimising the measuring operation by means of "flying" start/stop operation, also

  • the parameter ranges of the measurands "flowrate", "volume" and "pressure" have been extended by the realisation of a direct pump operation,
  • the two meter sections have been extended from 2.7 m to more than 7 m in order to improve the flow conditions and
  • the semi-automatic PC control has been centralised.

 

Table 1: Extended parameter ranges of PTB's petroleum test rig

  Nominal diameter Flowrate Pressure
Small meter section = 80 mm = 160 m³/h = 10 bar
Large meter section = 150 mm = 240 m³/h = 10 bar

After commissioning the test facility, the subsequent task will be to investigate the optimised operation modus as to the measurement uncertainty which can now be achieved and, thus, to experimentally prove and document the improvement of the measurement capabilities.

[1] Gudrun Wendt, Rainer Engel, Jörg Riedel: Sicherstellung der Rückführbarkeit der Mengen- und Durchflussmessung von Flüssigkeiten. PTB-Mitteilungen 119 (2009), Heft 1, pp. 23-27

Contact person:

Jörg Riedel, Dept 1.5, WG 1.53, e-mail: joerg.riedel@ptb.de