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Commissioning of the 1.1 MN·m torque standard machine

29.09.2004

The commissioning of the 1.1 MN·m torque standard machine (Figure 1) repre-sented the successful completion of the 12-year development of the laboratory for the realisation of the quantity of torque which began in 1993. Thus, PTB has measure-ment facilities over 9 decades available which can cover almost all the requirements of industry and research with the necessary measurement uncertainty. Up to now, the only NMI worldwide able to carry out traceable calibrations up to 200 kN·m has been the LNE/Paris.

Calibration of a torque transducer up to 690 kN·m on the 1.1 MN·m torque standard machine of PTB in Braunschweig

Figure 1: Calibration of a torque transducer up to 690 kN·m on the 1.1 MN·m torque standard machine of PTB in Braunschweig for power measurements on a Siemens-Westinghouse gas turbine.

The extension of the measuring range to 1 100 kN·m which has now been achieved makes it possible to calibrate measuring instruments being in operation with a meas-urement uncertainty of 0.1 % above the scale realised with direct load up to 20 kN·m with sufficient accuracy. The installation space of the 1.1 MN·m torque standard ma-chine also allows measuring instruments with a higher nominal torque (currently transducers up to 2.5 MN·m are produced worldwide) to be installed in the facility and calibrated in the sub-range.

Torque is generated via an equal-armed double lever arm with mechanical spindle drives in the lower machine platform. The object to be calibrated is then adapted in series to a reference torque transducer and the applied torque is measured almost free of disturbing components at the pair of tension-compression force transducers arranged in the height-adjustable crosshead. Thanks to additional drives, the me-chanical disturbances (bending moments and transverse forces) generated during loading by, among other things, asymmetries are minimised. The necessary control signals are provided by spring joints which are integrated in the force flow on the measuring side and equipped with strain gauge.

Since May 2004, the standard has been under testing and adjustment. First calibra-tions up to 100 kN·m and later up to 700 kN·m and test results up to 1.1 MN·m con-firmed the functionality of the facility and of the selected functional principle. Regular calibration operation is planned to start in 2005. Already in the middle of the year, a special measuring shaft used for power meas-urements on prototypes of heavy power plant gas turbines could be calibrated for the Siemens Power Generation test field (Figure 2).

Siemens-Westinghouse W501FD in the gas turbine test field in Berlin

Figure 2. Siemens-Westinghouse W501FD in the gas turbine test field in Berlin

Contact person:

Dr. D. Peschel, FB 1.2, AG 1.22, E-mail: diedert.peschel@ptb.de