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Exploring the attribution of crane (hanging) scales

Are crane scales automatic or non-automatic scales? This question seems to have started with R76 International Recommendation for Non-Automatic Weighing Instruments. Article, stating “free-hanging scales, such as hanging scales or suspension scales”, is finalized.

Furthermore, the term “non-automatic scale” in R76 Non-Automatic Weighing Scales states: a scale that requires the intervention of an operator during the weighing process to determine the acceptability of the weighing result. This is followed by two additional remarks, Remark 1: Determination of the acceptability of a weighing result includes human activity by the operator that affects the weighing result, e.g., actions taken when the value is stabilized or when adjusting the weighing load, as well as determining whether to accept the observed value of the weighing result or whether a printout is required.

Non-automated weighing processes allow the operator to take action to influence the weighing result if the result is not acceptable (i.e., adjusting the load, unit price, determining whether the load is acceptable, etc.). NOTE 2: When it is not possible to determine whether a scale is nonautomatic or automatic, the definitions in the International Recommendations for Automatic Weighing Scales (IRs) OIMLR50, R51, R61, R106, R107, R134 are preferred over the criteria in NOTE 1 for making judgments.

Since then, the product standards for crane scales in China, as well as the calibration procedures for crane scales, have been prepared in accordance with the provisions of the International Recommendation R76 for non-automatic scales.

(1) Crane scales are devices that allow weighing of objects while they are being lifted, saving not only the time and labor required for weighing, but also the space occupied by separate weighing operations. What’s more, in many continuous production processes, where weighing is necessary and fixed scales cannot be used, crane scales are very useful for lifting and transporting objects. High productivity, product quality and safety are playing an increasingly important role.

To study the accuracy of crane scales, the influence of the weighing environment should be fully considered. The dynamic environment during weighing, wind, changes in gravitational acceleration, etc. affect the weighing results; for the hook head suspension or similar measurements of the impact of the tension of the sling; the swing of the goods weighing the accuracy of the impact can not be ignored; in particular, the goods to do the conical pendulum movement when the impact of the time, which is any purely mathematical treatment of the dynamic measurement method can not be resolved.

(2) The International Recommendations for Non-Automatic Weighing Instruments, in Appendix A, only describes the test methods for conventional non-automatic weighing instruments, but does not describe any test methods for hanging scales. When the National Weighing Instrument Measurement Technical Committee revised the verification procedure of “Digital Indicator Scale” in 2016, it considered the special characteristics of hanging scales. Therefore, when revising JJG539 “Digital Indicator Scale” calibration procedure , the test methods for the performance of hanging scales were specifically added in a targeted manner. However, these are still in accordance with the test methods in the stationary state, deviating from the actual use of the situation.

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