At present, most of the domestic air compressor manufacturers cannot fully meet the requirements stipulated in the engineering law in terms of test and measurement environment, equipment capability and instrument accuracy. Most of them use simple methods for measurement. Through the on-site comparison test, the author uses the simple method to test separately in the three measurement environments. Through the analysis and comparison of the test data, the influence of the three measurement environments on the test results is found to select the most suitable noise measurement method. This comparison test object is a miniature reciprocating piston air compressor of type V- 0 17/ 0 7 . The noise measuring instrument uses HS5661A precision sound level meter with measurement accuracy of ± 0 7dB and test temperature of 25% ± 2 %. , 1 standard atmospheric pressure. It adopts outdoor open space, semi-anechoic chamber and indoor environment to measure. The working time of the space-time press is 0 7MPa, and the exhaust port is led to the outdoor or ditch to ensure the exhaust. The noise of the mouth does not affect the test results. Calculate the average sound pressure level and sound power level of the measured surface according to the provisions of Article 5 2 of GB/T4980-2003. Calculate the average sound pressure level of the surface: L p = 10lg (1 N N i= 1 10 0 1L pi) where L p is the measured surface average A weighted sound pressure level in decibels (dB); this test takes 5 points, ie N = 5, L pi is the measurement point A weighted sound pressure level. Sound power level calculation formula: LW = (L p - K) + 10lg ( S / S0) where L w ± A weighted sound power level ( dB) ; L p ± measured surface average A weighted sound pressure level ( dB ) K ± Environmental correction value (dB); S ± Measurement surface area; S 0 ± Reference area, take 1m 2 . The environmental correction value K is estimated and determined according to the provisions of Appendix E of the GB/T4980-2003 standard. Formula: L p = 10lg( 1+ 4 A/ S)S - measuring the area of ​​the surface; A - the sound absorption of the test chamber A = (S v, m 2; S v - the total surface area of ​​the test chamber (including the wall) , ceiling, floor), m 2. The measurements in the three environments are as follows: (1) Semi-anechoic room measurement The anechoic chamber is a simple semi-anechoic chamber, which is converted from a regular regular room. The semi-anechoic chamber is long in size. The width is 7 13 m). 5 58 m) 2 8 m. The ceiling and surrounding walls are installed. The sound is abrupt, the ground is smooth and the background noise is 31 5 dB(A). (2) Ordinary room indoor measurement The test site is an irregular room. There are some furniture and small machinery in the room. There are aluminum windows on the two walls and iron doors on one wall. The sound insulation effect is good after the doors and windows are closed, and the background noise is 52 1 dB( A). (3) Measurement of open space method The test site is wide, the distance between the air compressor and the surrounding objects is more than 12m, the cement floor area is large enough, and the background noise is 56 0dB (A). Based on the above three test results, it can be seen that the measurement results of the open field method and the indoor method are relatively close. The indoor measurement result is 90 6dB(A) after deducting the environmental correction value K = 5 9 , which is 0 2dB smaller than the measurement result of the open field. It can be seen that when it is difficult to find an open space in the factory with no obstacles within 10m 2 , a room with an area larger than 50m 2 can be used as a test site, and a room with some furniture and small equipment is more suitable for the validity of the measurement results. Because furniture and equipment can effectively reflect the noise in different directions, it is not easy to form the echo effect in the open room. Before the test, the simulation test can be carried out to find the position of the echogenic resonance point in the room. The position where the press is placed deviates from the distance (1 2) m to obtain more efficient data. In the test results of the semi-anechoic chamber, it can be found that the noise value is reduced by nearly 21 dB compared with the open field method. In order to confirm the accuracy of the test results, the author conducted a second semi-anechoic chamber test, and the result was 88. 1dB(A), the error of the two tests is less than 1dB, indicating that the result is reliable and effective. The anechoic chamber was converted from a normal room, and the doors and windows of the room were closed with a wooden board about 10 mm thick. Only one small door was allowed to enter and exit, and a large number of foam tips were placed on the walls and ceiling. Smooth and smooth, the area is about 35m 2 . The semi-anechoic chamber is suitable for the noise test of small air compressors, and the overall modification cost is not high, which is beneficial to the air compressor manufacturer to carry out the model development test. The test environment is subject to the least interference factors, and the test results can be reproduced. High sex, small measurement dispersion is small. In summary, if the production enterprise has an open space for noise testing, and pay attention to factors such as wind speed and background noise in the test environment, which can greatly affect the noise test, the exit test of the air compressor noise project can be carried out, but When environmental factors affect the accuracy of test results, the test should be stopped in time or multiple test methods should be used to ensure the accuracy of the data. If the noise of the surrounding workshop is affected by the noise of the surrounding workshop and the noise of the motor vehicles inside and outside the factory, the indoor method should be selected for testing. The room as the test room should be fixed, and the position of the furniture and machinery in the room should be fixed, which is conducive to maintaining The consistency of test environment factors is beneficial to the reproducibility of multiple test results, and is also conducive to the comparison of test data between different models. The semi-anechoic chamber method can provide good environmental factor guarantee for the accuracy of test results. It can achieve better environmental hardware support for new product R&D and identification, and old product noise improvement, but it can be used in factory inspection and testing. It is slightly inconvenient. It is recommended that qualified production enterprises can assist in the use of indoor or outdoor test methods on the basis of setting up a semi-anechoic chamber to improve the inspection efficiency under the premise of ensuring the accuracy of test results. This air compressor noise comparison test, especially the comparison test of the semi-anechoic indoor air filter muffler, the noise sound power level of the V- 0 17/ 0 7 air compressor in the case of installing a muffler At 88 7 dB(A), after removing the muffler, it is 95 3 dB(A). Obviously, the use of the air inlet muffler significantly reduces the noise of the air compressor. The structure and quality of the muffler are directly related to the noise reduction result. Influence: If the noise is obviously increased during the test of the air compressor, first check whether the muffler is dirty, whether the internal filter paper is damaged, and if it should be replaced immediately, to ensure the test data is objective and effective. As a general-purpose mechanical product widely used in production fields, scientific research institutions, laboratories, etc., air compressor products emit low-frequency noise for a long time, which may cause adverse reactions such as upset and tinnitus of workers around the equipment, and the noise control is also For the long-term research of air compressor manufacturers, in order to control noise, it is necessary to obtain reliable and accurate data through effective measurement methods. It is hoped that the data in this paper and the test data can provide useful reference for noise testing of air compressors. experience. Unstandard ag bearings, Non-standard AG bearings,planter bearings NingBo Greenly Machinery Co.,LTD , https://www.greenlyagparts.com
Mobile air compressors (hereinafter referred to as air compressors) are widely used in the production field. The working noise level often directly affects the production environment of the operator or the operator. The corresponding product standard is the noise limit of the air compressor. A clear requirement is required. GB/T4980-2003 National Standards for the Determination of Noise of Volumetric Compressors issued by the General Administration of Quality Supervision, Inspection and Quarantine, specifies the noise measurement method for volumetric air compressors. The body of the standard specifies the engineering method for the measurement of noise sound power levels. The summary method is specified in the appendix. The standard 4 2 1 provisions specify the requirements of the measurement environment, including three cases: a test chamber with a free sound field on the reflective plane, such as a semi-anechoic chamber; an outdoor field on the radiating plane with the above properties, at any distance from the microphone There is no reflector within 10m, and the size of the reflection plane should be at least 2m beyond the projection of the measurement surface on the reflection plane. For ordinary rooms, a reflection plane with the above properties is required, and the environmental correction value is determined according to the method specified in the standard 5.3. K, in order to correct the measured value to the result of free sound field conditions. The environmental correction value K should be no more than 7dB.