GB/T 20062-2017Mobile cranes—Limits and measurement methods for operating noise (English PDF)

3.1 Time-averaged A-weighted Sound Pressure Level

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5.2 Measurement Environment

5.2.1 The test site shall comply with the stipulations of GB/T 3767.

5.2.2 At the microphone position, the averaged background noise level should be lower than the measured sound pressure level by more than 15 dB, and at least 6 dB lower.

5.2.3 The ambient temperature during the test is between -10 °C ~ + 35 °C.

5.2.4 During the test, the wind speed 1.5 m from the ground shall not be greater than 8 m/s.

5.2.5 During the test, if the wind speed exceeds the maximum allowable wind speed range provided by the microphone manufacturer, a windproof device shall be added to the microphone.

5.3 Positioning of Crane Noise Measurement Center

The noise measurement surface of the crane is a hemispherical surface (see Figure 1), with a radius of 16 m. If the crane is not suitable for this radius, it may also be selected in accordance with GB/T 3767.

For cranes equipped with two engines, then, the crane noise measurement center is the geometric center of the engine used for lifting operations and shall coincide with the center of the hemisphere. During the measurement, the driving direction of the crane is along the + X direction; the boom is along the - X direction. If the crane driving direction is consistent with the working direction of the boom (for cranes without rotating function), then, the crane (whole body) is along the - X direction.

For cranes equipped with one engine, which is simultaneously provided for driving and operation, then, the crane noise measurement center is the middle position of the engine and the hoisting machine and shall coincide with the center of the hemisphere.

5.4 Layout of Microphone

5.6.2 Working conditions of lifting

The crane lifts 50% of the rated weighted; select an appropriate boom length; the measurement duration is 15 s ~ 20 s.

5.6.3 Working conditions of turning

When the crane is unloaded and has the shortest basic boom, adjust the boom to the position at 40° ~ 50° with the horizontal plane; rotate by 90° to the left; immediately reversely rotate to the initial position. The measurement time is the time required for one work cycle.

5.6.4 Working conditions of luffing

When the crane is unloaded and has the shortest basic boom, lift the boom from the maximum working range to the minimum working range, and immediately descend to the initial position. The measurement time is at least 20 s.

5.6.5 Telescopic working conditions of boom

When the crane is unloaded, adjust the fully retracted boom to a position at 40° ~ 50° with the horizontal plane; fully extend the first grade of the telescopic cylinder, then, immediately return to the fully retracted state.

5.8 Determination of Measurement Results

5.8.1 All intermediate calculation results (such as: sound pressure level and area calculation, etc.) shall retain one decimal place. The measurement accuracy of the parameters in the tests shall comply with the stipulations of GB/T 21457.

5.8.2 When the difference between two of the three A-weighted measurement values does not exceed 1 dB, no measurement is necessary. Otherwise, the measurement shall be continued, until the difference between two values does not exceed 1 dB. Use the arithmetic mean value of the two higher values that differ by no more than 1 dB as the report value.