AN AIR GRINDER EXHAUST MUFFLER

AN AIR GRINDER EXHAUST MUFFLER Alexander Igolkin, Leonid Rodionov and Aleksandr Kryuchkov Samara State Aerospace University, Moskovskoye shosse 34, 443086 Samara, Russia e-mail:igolkin97@gmail.com The paper deals with the method of the sound pressure level reduction at the work places of the shop floor. During the manned carrier-rocket production process at the industrial enterprise JSK SRC Progress air tools are widely used. One of the pneumatic tool disadvantages is the high level noise. The authors conducted acoustic studies of various equipment work modes in the considered department. The main sources of the noise have been found and their acoustic characteristics have been experimentally determined. The main sources of the noise in department are air grinders. The noise sources spectra have been explored. Special measures are being proposed to noise level reduce at the work places. The most effective measure is the exhaust muffler using. The sketch had made and the prototype of the air grinder produced. The muffler efficiency has been tested in both SSAU lab and at the enterprise department. The efficiency of the exhaust muffler is 16 dba. 1. Introduction Technical progress leads to increasing of noise sources on the work places of various manufacturing and service organization. Various measures to reduce noise are developed [1, 2, 3, 4] and different tools to deal with noises are made [5,6,7,8,9,10]. To reduce the noise of the valve was developed special measures [4, 5, 6, 7]. In the paper [4] was developed special muffler with multiple orifice plate and soundproof case. In the papers [5] and [6] measures using solid friction and valve s poppet modifications to reduce tonal noise of the pilot-operated valve were developed. Without these measures self-exited oscillation of the valve appears [7]. Fluid power (pneumatic and hydraulic) systems are widely spread on various types of manufacture and they deserve special attention [2, 11]. Pneumatic and hydro-mechanical systems noise reduction is presented [2,4,11]. Air tools are widely used during processing details received by casting [5]. Exhaust muffler is the main device to decrease the noise generated by air tool. Some designs of muffler for pneumatic systems are described in the works [12,13,14,15]. 2. Initial noise condition at the workplace The main sources of the noise in department are 10 air grinders and 2 emery wheels. Noise and vibration analyzer Ecophysica [16] was used as the measurement system. Noise measurement results during emery wheel operating are presented in Figure 1. ICSV22, Florence (Italy) 12-16 July 2015 1

L, 100 db Off-loaded air grinder, Leq=101,2 dba Air grinder detail processing, Leq=99,4 dba 25 63 100 1 2 0 630 1k 1.6k 2.5k 4k 6.3k f, Hz Figure 1. The frequency characteristic of the emery wheel sound pressure level. Figure 1 shows that noise level caused by small-sized detail processing has increased by 11 dba. Moreover detail processing increases noise level at frequencies above 1000 Hz, which indicates the appearance of an additional high frequency noise source initiated by detail vibration. The noise spectrum of the air grinder at off-load and loaded regimes is shown in Figure 2. L, 100 db Off-loaded, Leq=76,4 dba Small-sized detail processing, Leq=87,2 dba 25 63 100 1 2 0 630 1k 1.6k 2.5k 4k 6.3k f, Hz Figure 2. The noise spectrum of the air grinder at no load and loaded regimes. Figure 2 presents that overall noise level increases on scale A during detail processing. Noise source ranking shows that the air grinder is more strong noise source (99 dba) than the emery wheel (76 dba). ICSV22, Florence, Italy, 12-16 July 2015 2

The main contribution to the overall sound pressure level, created by the air grinder, makes pneumatic drive exhaust noise, as indicated by the sound pressure characteristic at off-load (Fig. 2). Therefore, the main activity is the development and implementation of the exhaust muffler. Customer supplied its own exhaust muffler for research, effectiveness of which has been determined and the results are shown in Figure 3. L, 120 db 110 100 Off-loaded air grinder (base muffler), Leq=96,2 dba Off-loaded air grinder (without muffler), Leq=101,2 dba Workplace standards, Leq= dba Background, Leq=69,8 dba 31,5 125 200 315 0 0 1.25k 2k 3.15k 5k 8k f, Hz Figure 3. Efficiency studies of the base exhaust muffler. Figure 3 shows that the existing exhaust muffler effectiveness is 5 dba and is insufficient. Sanitary standards on noise at the workplace are not met [17]. Creating an exhaust muffler with effectiveness over 15 dba was main goal to the authors. 3. Development and production of exhaust muffler. Air grinder construction and operation regimes are similar, so one of them was chosen for research. Based on the experience of previous studies [18], the authors developed an original design of the exhaust muffler. Elastic porous material MR (Metal - Rubber) was used as sound-absorbing material. A prototype was made of the following parts (Fig. 4): 1. Air grinder; 2. T-shaped pipe; 3. The sound-absorbing element from the MR; 4,5 Centering aluminum ring; 6. Sound-absorbing (tablet shaped) material MR; 7. Fitting. ICSV22, Florence, Italy, 12-16 July 2015 3

Figure 4. Exhaust muffler prototype. Sound-absorbing material MR [19,20] is set in the space between the rings. Appearance of the prototype is shown in Figure 5. 4. Air grinder study Figure 5. Appearance of the muffler prototype. Experimental air grinder design acoustic efficiency studies were conducted in an anechoic acoustic chamber (Fig. 6) [21]. ICSV22, Florence, Italy, 12-16 July 2015 4

Figure 6. The air grinder location in an acoustic anechoic chamber. Adequate representation of the functioning pneumatic grinder baseline while conducting research in acoustic anechoic chamber should be ensured (sound pressure level frequency characteristics) (Fig. 7). Thus, pressure before the pneumatic tool in studies was 3.9 bar. L, 100 db 30 In the department, Leq=100,6 dba In the laboratory, Leq=96,9 dba 31,5 125 200 315 0 0 1.25k 2k 3.15k 5k f, 8k Hz Figure 7. Simulation baseline result of the no loaded air grinder. Simulation baseline result is somewhat different from the values measured at the workplace (Fig. 7). It is cause by divergence in the inlet pressure in the air grinder. Thus, it is acceptable to conduct research and debugging of the exhaust muffler prototype carried out in laboratory. It is known that the acoustic characteristics and capacity of the sound-absorbing element made from MR is influenced by such parameters as porosity, initial wire diameter and sample thickness [17,25]. Studies were conducted sound absorbing effect of porosity of the sample (pos. 6 in Fig. 4) of the same thickness on efficiency muffler (Fig. 8). The porosity value - "1" is corresponding air tool without muffler. ICSV22, Florence, Italy, 12-16 July 2015 5

L, db 95 85 75 0 Hz Scale A La, 98 dba 96 94 92 88 86 1 0,8 0,7 0,6 Porosity 84 Figure 8. The dependence of the sample acoustic efficiency from its porosity. Figure 8 shows that the most effective sample has a porosity of 0.6. The porosity value lower than 0.6 leads to air consumption reducing. Pneumatic performance (rotation speed) with minimal porosity of the sample is not reduced more than 10%. The test construction results in the laboratory with various sound absorbing elements are shown in Figure 9. L, 110 db 100 Without the muffler, Leq=96,9 dba Tablet shaped MR (porosity 0,6) and lining MR, Leq=82,6 dba Tablet shaped MR (porosity 0,6), Leq=87,9 dba 30 31,5 125 200 315 0 0 1.25k 2k 3.15k 5k f, 8k Hz Figure 9. Efficiency of the exhaust noise reduction. Figure 9 shows that muffler efficiency with tablet shaped MR (porosity - 0.6) is 9 dba. Due to its lack of efficiency sound absorbing lining MR (Pos. 3 in Fig. 4) was additionally used. Installing proposed muffler reduces the noise in the whole range of frequencies. The effectiveness of the experimental muffler design in the laboratory was 14.3 dba. Prototype has been tested at the department territory after conducting research in the laboratory. Sound pressure levels of the air grinder with a prototype muffler compared with the sanitary standards in the department are presented in Figure 10. All tests were conducted at off-load. Experimental muffler design is directed to noise reduction from the exhaust air grinder and does not affect the noise workflow (processing details). Therefore, detail processing was not considered while testing regimes. Designed muffler provides the required efficiency - not less than 15 dba. However, after reducing exhaust noise during testing in the department another noise source was found - the noise from ICSV22, Florence, Italy, 12-16 July 2015 6

bearings in the air grinder. Further noise reduction is possible due to the repair or replacement of bearings in the air grinder. L, 110 db 100 Workplace standards, La= dba Background, La=66,7 dba With the muffler, La=83,1 dba Without the muffler, La=99,8 dba 31,5 63 125 2 0 1k 2k 4k f, Hz 8k Acknowledgements Figure 10. The results of sound pressure level measurements at the workplace. This work was supported by the Ministry of Education and Science of the Russian Federation. Future work As a recommendation to further noise reduction at the workplace it is necessary to furnish the room acoustic sound-absorbing material [21,22], which has a sufficient efficiency at high frequencies. References 1 Kryuchkov, A.N., Shakhmatov E.V., Samsonov, V.N., Druzhin, A.N. and Makaryants, G.M. Design Technique and Future-Proof Scheme of the Ship Pipe Anti-Noise Tool, Fundamentalnaya i Prikladnaya Gidrofizika, 7(3), 67-79, (2014). 2 Igolkin A.A., Kryuchkov, A.N., Makaryants G.M. Prokofiev A.B., Prokhorov, S.P., Shakhmatov E.V. and Shorin V.P. Snizheniye kolebaniy i shuma v pnevmogidromekhanicheskikh sistemakh, Samara State Aerospace University named after academician S.P. Korolev (National Research University), Samara, Russia, 314, (2005). 3 Ivanov, N.I. and Nikiforov, А.S. Foundations of Vibroacoustics, Polytechnika, Saint Petersburg, Russia, 482, (2000). 4 K.V. Blumin, K.V., Gafurov, S.A., Zubrilin, I.A., Makaryants, G.M., Kruchkov, A.N. and Shakhmatov, E.V. Design Methodology of Hydrodynamic Noise Silencer, Proceedings of the 20th International Congress on Sound & Vibration, Bangkok, Thailand 7-11 July, (2013). 5 Igolkin, A.A., Kryuchkov, A. N. and Shakhmatov E.V., Acoustic Performances of Air Tool, Proceedings of the 17th International Congress on Sound and Vibration, Cairo, Egypt, 18-22 July, (2010). 6 Makaryants, G.M., Sverbil, V.Y., Shakhmatov, E.V., Makaryants, M.V., Stadnik, D.M. and Tumanov, D.V. Tonal Noise Reduction of Safety Pneumatic Valve of Indirect Action with Self-Excited Oscillations, Sudostroenie. 5, 49-51, (2012). ICSV22, Florence, Italy, 12-16 July 2015 7

7 Makaryants, G.M., Prokofiev, A.B., Sverbilov, V.Y., Shakhmatov, E.V. and Makaryants, M.V. Self-Oscillations of the Poppet Relief Pneumatic Valve Due to Instability of the Airflow around an Inlet Port, Proceedings of the 18th International Congress on Sound and Vibration, Rio de Janeiro, Brazil, 10-14 July, (2011). 8 Igolkin, A.A., Rodionov, L.V. and Shakhmatov, E.V., Noise Decrease in Premises at the Expense of Application Dampers, Safety in technosphere. 4, -43, (2008). 9 Kolesnikov, V.A., Shakhmatov E.V. and Foyt, V.V. Damper, RUS Patent 2115842, Russian Federation: Samarskij gosudarstvennyj aehrokosmicheskij universitet im.s.p.koroleva, (1996). 10 Shakhmatov, E.V., Kryuchkov, A.N., Prokofiev, A.B., Golovin, A.N. and Belov, G.O. Using of Pressure Fluctuations Absorber to Reduce Vibroacoustic Loading of Hydromechanical Systems, Sudostroenie, 3, 45-47, (2011). 11 Gimadiev, A.G., Shakhmatov, E.V. and Shorin, V.P. Designing Dampers for Control-System Hydraulic Circuits, Power Engineering New York, 25(4), 116-122, (1987). 12 Shakhmatov, E.V., Kryuchkov, A.N Bogdanov, S.A., Seyfetdinov, R.B. and Belov, G.O. Glushitel' shuma, RUS Patent 71144, Russian Federation: Gosudarstvennoye obrazovatel'noye uchrezhdeniye vysshego professional'nogo obrazovaniya Samarskiy gosudarstvennyy aerokosmicheskiy universitet imeni akademika S.P. Koroleva, (2007). 13 Shakhmatov, E.V., Kryuchkov, A.N. and Igolkin, A.A. Pnevmoglushitel' s vysokochastotnym oblucheniyem, RUS Patent 713, Russian Federation: Gosudarstvennoye obrazovatel'noye uchrezhdeniye vysshego professional'nogo obrazovaniya Samarskiy gosudarstvennyy aerokosmicheskiy universitet imeni akademika S.P. Koroleva, (2007). 14 Nabiev, R.R., Khamatdinov. Z.Z., Nabiullin, V.Kh. and Valeev, R.F. Pneumatic Engine Noise Silencer, RUS Patent 21947, Russian Federarion: Obshchestvo s ogranichennoj otvetstvennost'ju firma "Tekhnoservis",Otkrytoe aktsionernoe obshchestvo "Uralo-Sibirskie magistral'nye nefteprovody im. D.A.Chernjaeva", (2000). 15 Kojakov, V.F.,Kojakov. O.V. and Kojakov, S.V.Silencer, RUS Patent 20446, Russian Feredation: Kojakov Vasilij Fedorovich, (1993). 16 GOST 23337-78, Noise. Methods of Noise Measurement in Residential Areas and in the Rooms of Residential, Public and Community Buildings, 22, (1982). 17 SN 2.2.4/2.1.8.562-96 Shum na rabochikh mestakh, v pomeshcheniyakh zhilykh, obshchestvennykh zdaniy i na territo-rii zhiloy zastroyki, 8, (1996). 18 Shakhmatov, E.V., Kryuchkov, A.N., Bogdanov, S.A. and Nazarov, O.V. Zvukopogloshchayushchaya konstruktsiya s perforirovannym zapolnitelem v vide skladchatoy struktury, RUS Patent 61353, Russian Federation: Gosudarstvennoye obrazovatel'noye uchrezhdeniye vysshego professional'nogo obrazovaniya Samarskiy gosudarstvennyy aerokosmicheskiy universitet imeni akademika S.P. Koroleva, (2007). 19 Igolkin A.A., Izzheurov, E.A., Safin A.I., Shakhmatov E.V. The Use of Porous Material «Metallorubber» in Hydraulic Gas Systems of Power Plants for Noise Damping and Temperature Stabilizing, Sudostroenie. 5, 46-48, (2012). 20 Igolkin, A.A., Izzheurov, E.A., Shakhmatov, E.V. and Hongyuan J. Acoustic Performances of Metal Rubber, Proceedings of the 18th International Congress on Sound and Vibration, Rio de Janeiro, Brazil, 10-14 July, (2011). 21 Kokh, A.I., Krjuchkov, A.N., Sejfetdinov, R.B. and Shakhmatov, E.V. Muffled Acoustic Chamber, RUS Patent 2387761, Russian Federation: Gosudarstvennoye obrazovatel'noye uchrezhdeniye vysshego professional'nogo obrazovaniya Samarskiy gosudarstvennyy aerokosmicheskiy universitet imeni akademika S.P. Koroleva, (2010). 22 Lenchine,V.V., Makaryanz, G.M. and Shakhmatov, E.V. Database for Choosing of Materials for Acoustic Furnishing of Premises, Proceedings of the Samara Scientific Center of the Russian Academy of Sciences, 1(1), 137-1, (1999). ICSV22, Florence, Italy, 12-16 July 2015 8