Calibration
of torque application tools according to DIN EN ISO 6789
Image showing EC calibration bench

For the calibration of manually operated torque tools the international standard EN ISO 6789 is decisive (2003). Accordingly calibration has to be understood as those “activities which under given conditions determine the mutual allocation between the stated or indicated values of a torque application tool and the associated values of a calibration device.” Aim of the measures is the appraisal and documentation of the difference amount between given value and actual value of a torque tool using calibrated measuring instruments.


Re-calibration

According to EN ISO 6789 defined as “the requirements to be fulfilled during the calibration of manually operated torque application tools to a defined service life.” Hence torque wrenches are to re-calibrated in a determined interval periodicly.


Procedure

Torque application tools must be examined according to calibration conditions described in EN ISO 6789 point 6.3 and fulfill the requirements of point 5.1.5 (tolerance limits). For closer information on this please consult EN ISO 6789.


Calibration device

The maximum permissable measuring inaccuracy of the calibration device amounts to 1% of the indicated value. The measuring inaccuracy is to calculated according to the “Guide for to calculate evaluation OF Uncertainty in Measurement” (GUM) with an extension factor k = 2. For closer information on this please consult EN ISO 6789.


Interval

Torque application tools are to be regarded also as inspection devices. If the user accomplishes procedures for the control of inspection, measuring and test equipment, the torque application tools must be included into these procedures. The calibration interval is to defined due to certain usage factors, e.g.

  • required accuracy
  • frequency of usage
  • typical load during usage
  • environmental conditions during procedure
  • storage conditions

The period is to be adapted according to the defined procedures for the control of inspection, measuring and test equipment and under evaluation of experiences won by the re-calibration. If the user does not accomplish procedures for the control of inspection, measuring and test equipment, a life of 12 months or approximately 5,000 loads can be taken as reference value for a re-calibration interval. For the first re-calibration the period of the validity begins with the first use of the torque application tool.


Calibration Service

Maintenance, calibration and adjustment are accomplished in our internal workshop according to EN ISO 6789. We offer also servicing contracts for those date-supervised calibration of your torque wrenches. At interest contact us please. We will gladly inform you in detail.