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JJG 797-2013Verification Regulation of Calibration Instrument for Torque Wrenches (English PDF)

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Issued by

General Administration of Quality Supervision, Inspection and

Level / Type

National · Mandatory

Issue date

April 27, 2013

Implementation date

October 27, 2013

Scope

JJG 797-2013 (Verification Regulation of Calibration Instrument for Torque Wrenches) is available as an English-translated PDF.

JJG 797-2013 — This Regulation applies to the initial verification, subsequent verification and usage inspection of electronic, mechanical and hydraulic calibration instrument for torque wrenches (hereinafter referred to as torque instrument).

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Document preview — JJG 797-2013

National Standard of the People's Republic of China

Issued by: General Administration of Quality Supervision, Inspection and

Introduction
1 Scope
2 Terminology
2.1 Standard torque wrench
2.2 Average arm length
2.3 Minimum arm length
3 General introduction
4 Measuring performance requirements
5 General technical requirements
5.1 Appearance
5.2 Technical performance
5.3 Use and replacement of indication instrument
5.4 Indication instrument
6 Measuring instrument control
6.1 Verification condition
6.2 Verification item and verification method
6.3 Process of verification result
6.4 Verification period
Appendix A Content format of verification certificate and verification
Results
Appendix B Verification record of calibration instrument for torque
Wrenches
Appendix C Verification steps
Appendix D Arm length for reference and literature

1 Scope

This Regulation applies to the initial verification, subsequent verification and usage inspection of electronic, mechanical and hydraulic calibration instrument for torque wrenches (hereinafter referred to as torque instrument).

2 Terminologies

2.1 Standard torque wrench

The torque wrench which has high accuracy and is used to conduct quantity-value transfer for calibration instrument for torque wrenches.

2.2 Average arm length

The average length of torque wrench's arm, within a certain range.

2.3 Minimum arm length

The minimum length of torque wrench's arm, within a certain range.

3 General introduction

Torque instruments are the instruments used to verify (calibrate) various types of manual torque wrenches. Torque instruments can be generally divided into mechanical, hydraulic and electronic types (it usually uses strain torque sensor) according to the working principle. It mainly includes two kinds according to the structure. one is the calibration instrument for torque wrench with a loading structure, another one is the calibration instrument for torque wrench without a loading structure.

Mechanical and hydraulic torque instruments coaxially concatenate the wrench of torque wrench to be verified AND the torsion elastomer of torque instrument.

When imposing torque directly or indirectly on the tail section of torque wrench, specifications and user's requirements.

5.3.2 Torque sensor and indication instrument shall support the use of each

other. Generally, they shall not be replaced randomly. If they need to be replaced, the re-verification is needed.

5.4 Indication instrument

5.4.1 Analogue instrument

5.4.1.1 Scale and mark of each indication dial shall be clear, explicit and easy

to read. The zero and maximum value of each scale shall be explicitly marked.

5.4.1.2 It shall have reset mechanism to indicate zero and holding mechanism

of torque's indication value.

5.4.1.3 The engraved lines on the dial shall be uniform, the width of pointer shall be approximately equal to the width of engraved lines. The resolution shall be determined according to the RATIO of the width of pointer AND the spacing (scale spacing) between the centers of 2 adjacent engraved lines. The recommended ratio is 1/2, 1/5 and 1/10. When the scale spacing is not less than 1.25mm, 1/10 dial scale value may be estimated and read.

5.4.1.4 During the process of imposing torque, the pointer shall be smooth, and have no abnormal phenomenon such as impact and stagnation. Active pointer and passive pointer shall be coincide with the engraved lines of the dial, and be parallel to the surface of dial.

5.4.1.5 The friction of active pointer shall be able to make passive pointer stay in any position. When conducting verification with or without passive pointer, its relative error of indication value shall not exceed the relative error of indication value as specified by the corresponding accuracy grade. When the torque of fixed-value type torque wrench is suddenly removed, the amount of change of active pointer shall not be greater than 1/5 of the relative error of maximum torque indication value of the corresponding accuracy grade.

5.4.2 Digital instrument

5.4.2.1 The connection between torque sensor and indication device shall be reliable. And it shall have certain ability to resist to electromagnetic interference.

5.4.2.2 Each operation switch, button, knob and jack shall have words or symbols marked on it, and the operation shall be flexible and reliable.

5.4.2.3 The indication of figures shall be clear and accurate. And it shall have functions of continuation, peak holding and zero-adjustment.

5.4.2.4 The minimum figure increment shall be 1×10n, 2×10n or 5×10n, in which n is a positive integer, a negative integer or zero. Each grade shall includes zero and maximum value of its scale range. And it shall indicate the declining symbols of less-than zero position (for example, displayed by the symbol "+" or "-").

5.4.2.5 For those with function of digital signal output, the output data shall be consistent with the indication value.

5.4.2.6 When torque instrument is without loading, if the indication value

change is not greater than 1 increment, then the resolution is 1 increment of the last significant figure displayed; if the indication value change is greater than one increment, then the resolution is the half of range of the indication value change.

6 Measurement instrument control

Measurement instrument control includes. the initial verification, subsequent verification and inspection when in use.

6.1 Verification condition

6.1.1 Environmental condition

According to the specification of torque instrument grade, verification of 0.3 grade and 0.5 grade shall be at room temperature of (20 + 5) °C, verification of 1.0 grade and 2.0 grade shall be at room temperature of (20 + 10) °C, and under the condition of a relative humidity not greater...

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This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 23 pages — is available in the English PDF.

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