m                                       SPECIAL Ratnayaka (Assistant Director)                                       W.M. ...
3. Calibration of torquewrench calibration devices          The guideline DKD-R 3-8: 2003specifies characteristics, calibr...
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Torque Standards


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Torque Standards

  1. 1. m SPECIAL Ratnayaka (Assistant Director) W.M. Wasantha Sri Lanka Standards Institution, Sri Lanka Torque Standards 1. Introduction tooling problems before they arise perhaps Torque is the tendency of a force due to tool wear or broken components. to rotate an object about an axis, fulcrum, or Also, design studies of torque transducers pivot. Informally, torque can be thought of are very important in optimization of their as "rotational force". Torque being a very design for various engineering applications. important physical parameter, plays a very vital role in various applications like aviation, 2. Calibration of hand torque14 automobile, power and agriculture industries. tools The importance of the torque measurements Hand torque tools are generally is to control the fastening force on assembly used in the fields of research and parts and to measure mechanical power. developments, inspections, quality controls Torque is, generally, measured by as well as servicing where there is a need to May-June 2012/Vol.14, No.67 mechanical type torque meters/wrenches know correct torque settings. This type of and these torque tools need to be calibrated tool can also be used in a production using torque wrench calibration devices. environment to apply torque and check the Regular calibration of torque tools guarantees tightness of fasteners. The standard guideline repeated accuracy and traceability to ISO 6789: 2003 specifies the classification, international standards. Calibration also requirements for calibration, test method and ensures torque equipment is operating peak marking of hand torque tools. performance and can highlight potential Also, BS 7882: 2008 specifies requirements for the calibration and classification of torque measuring devices, including those used for the calibration of hand torque tools to ISO 6789: 2003. The information to be given on the certificate of calibration is also listed. A calibration procedure was prepared for calibration of hand torque tools with the help of knowledge acquired during theoretical and practical sessions and it was evaluated to check validity to implement in each participants country. Figure 1 - Hand torque tool calibration
  2. 2. 3. Calibration of torquewrench calibration devices The guideline DKD-R 3-8: 2003specifies characteristics, calibration,classification, calibration certificate &duration of validity of torque wrenchcalibration devices. Preparation of thecalibration and calibration procedure werestudied in detail with the help of lectures andpractical sessions. A torque transducer was calibratedusing a torque transfer wrench as the Figure 2 - Calibration of hand torque toolstandard. Measurement results were calibration devicesevaluated and uncertainty budget wasprepared according to the procedure given calibrated and calibration certificates werein the DKD-R 8-3: 2003 guideline. A issued for all of them.calibration procedure was prepared andevaluated to implement in each participants 5. Conclusioncountry to calibrate torque wrench calibration All participants of the torque group 15devices. were able to completed training programe May-June 2012/Vol.14, No.67 successfully. The training programme4. Designing of torque included theoretical and practical sessions.measuring devices The aim of the theoretical part is to The lecture series and practical understanding the importance of torquesessions under the title of "designing of measurements, the mechanism of torquetorque measuring devices" were very tools, classification of torque tools, calculationimportant to understand basic principals of of uncertainty budget and calibrationmodern torque transducers. certificate. The aim of the experimental part Basic theory of designing and is to give experiences to participants. Thecalculation of torque measuring devices overall aim of the programme, transferringwere studied. According to the calculated the knowledge to the Asia pacific countries,values, four torque transducers were was achieved successfully.designed, simulated and verified using thesoftware "solid work". The alloy steel sensingbody and other accessories were preparedin a machine shop and strain gauges werebonded to the sensing body in the practicalsessions. The bridge circuit of the sensingbody was prepared to connect the transducerto the indicator directly. Finally, cross forceeffect of each transducer was analyzed inorder to optimize the design. All four participants prepared theirown torque transducer. Two of them bendingmodel with the capacity of 10 N.m and others Figure 3 - Torque transducers designedare tortional model with the capacity of 500 during the trainingN.m. All four torque transducers were