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Noise Control.qxd 5/03/2008 11:51 AM Page 10 RECTANGULAR DUCT ATTENUATORS PERFORMANCE DATA - RS STRAIGHT SPLITTERS Model No Length RS mm Static Insertion Loss, dB Octave Band Centre Frequency (Hz) 63 125 250 500 1K 2K 4K 8K Module widths, mm 07B 900 12 23 36 45 43 36 28 275, 550 07C 1200 16 30 47 50 50 47 39 825, 1100 07D 1500 19 35 49 50 50 49 42 1375, 1650 07E 1800 10 21 41 50 50 50 50 45 1925, 2200 07F 2100 12 25 45 50 50 50 50 50 07G 2400 13 28 48 50 50 50 50 50 10B 900 10 19 31 39 35 27 21 300, 600 10C 1200 13 26 41 48 46 37 26 900, 1200 These notes apply to RS and RT type attenuators 10D 1500 16 30 47 50 50 43 31 1500, 1800 10E 1800 18 35 49 50 50 48 36 2100, 2400 Construction FEATURES 10F 2100 10 20 40 50 50 50 50 37 The units are rigidly constructed and consist of a galvanised sheet metal casing containing a series of centre and side splitters The casing is provided with Pittsburgh corner seams End flanges vary in construction depending on local requirements; please contact your local office for details Where flanges are of angle iron construction, they are not drilled as standard unless ordered with matching flanges The splitters are filled with non-hygroscopic and incombustible material 10G 2400 11 23 44 50 50 50 50 39 12B 900 17 28 35 31 22 17 325, 650 12C 1200 11 22 37 43 40 30 21 975, 1300 12D 1500 13 26 43 47 44 34 24 1625, 1950 12E 1800 15 31 47 50 48 40 28 2275 12F 2100 17 35 50 50 50 43 30 12G 2400 20 39 50 50 50 45 32 15B 900 15 25 31 28 18 13 350, 700 15C 1200 19 33 38 34 23 16 1050, 1400 15D 1500 11 23 39 44 39 26 18 1750, 2100 This material is covered with a gauze scrim and then further covered with galvanised perforated sheet metal 15E 1800 13 27 45 49 46 32 21 15F 2100 15 31 49 50 50 37 24 15G 2400 18 35 50 50 50 41 26 Where attenuators are exposed to the weather, all infill material shall be lined with an impervious film to prevent ingress on moisture See page H-9 for selections from our Q-Seal range Standard attenuators are suitable for duct pressures up to 1kPa Free Area 33% Free Area 38% Free Area 43% such as stainless steel or aluminium, are available on request In addition special finishes such as epoxy coating can be provided Attenuators for Air Distribution System Insertion losses greater than 50dB are not reported as their achievement in practice is difficult Insertion Loss The performance data is based on Australian-sourced and manufactured materials The values quoted in the tables are defined as static insertion loss as defined in BS4718:1971, Methods of Test for Attenuators suitable for higher pressures, or manufactured from special materials (continued next page) PRESSURE LOSS GRAPHS - RT ATTENUATORS RT A Pressure Drop 200 (600mm long) 25 22 12 20 17 10 15 07 Attenuator Model 100 RT Attenuators Length Multiplier RS Attenuators Type Multiplier Code Length Type Multiplier Type Type Multiplier A - 600 1.0 RS07 2.0 B - 900 1.17 RS10 2.0 C - 1200 1.34 RS12 2.6 D - 1500 1.52 RS15 2.6 E - 1800 1.69 F - 2100 1.86 20 G - 2400 2.03 To determine the pressure drop in RS attenuators apply the appropriate factor from the above table to the equivalent RT pressure drop 10 2.0 A RT12D attenuator is required with 8.0m/s face velocity A pressure drop of 64Pa can be determined from Figure By applying a length multiplier of 1.52 found in Figure a resultant pressure drop of 97Pa can be determined 60 40 Pressure Drop, Pa H Free Area 27% Example:- 3.0 4.0 6.0 10.0 20.0 30.0 Face Velocity, m/s H-10 NOISE CONTROL PRODUCTS © FANTECH 2008 Noise Control.qxd 5/03/2008 11:51 AM Page 11 RECTANGULAR DUCT ATTENUATORS (Contd.) Selection procedure PERFORMANCE DATA - RT TAPERED SPLITTER To satisfactorily select an attenuator the following information is required Model No RT 07A 07B 07C 07D 07E 07F 07G 10A 10B 10C 10D 10E 10F 10G 12A 12B 12C 12D 12E 12F 12G 15A 15B 15C 15D 15E 15F 15G 17A 17B 17C 17D 17E 17F 17G 20A 20B 20C 20D 20E 20F 20G 22A 22B 22C 22D 22E 22F 22G 25A 25B 25C 25D 25E 25F 25G (a) Attenuator insertion loss required (b) Air flow passing through the attenuator (c) The maximum allowable air flow resistance (pressure loss) (d) Physical size constraints Select as follows:(a) From the insertion loss table select the attenuator that offers the closest match to the required insertion loss Note that a small free area and long length provides the greatest attenuation, but also the greatest pressure loss (b) Select the module width closest to the preferred size Note:To achieve the required attenuation it is essential the module widths shown in the right hand column of the table are adhered to There are no restraints on the height increments up to the maximum of 2400mm for a single attenuator Attenuators of a greater height would be supplied in modules (c) Refer to the pressure loss graph and determine the air flow resistance for the selected attenuator model at the selected width, height and length (d) If the pressure loss is low compared to the design constraints increase the face velocity i.e reduce the width and/or attenuator height (e) Calculate the attenuator regenerated noise level to ensure that it is consistent with the application Refer to data on regenerated noise on page H-13 Installation Special care must be taken when installing attenuators to ensure maximum performance is achieved Attenuators are best located where duct work passes through walls bridging high to low noise level areas They should not be located in the immediate blast area of fans or close to bends as this will adversely effect the noise regeneration and pressure loss In some instances it may be necessary to isolate the attenuator from duct-borne vibration to achieve maximum efficiency Standard attenuators are not thermally insulated and may require additional external lagging when handling conditioned air © FANTECH 2008 Length, mm 600 900 1200 1500 1800 2100 2400 600 900 1200 1500 1800 2100 2400 600 900 1200 1500 1800 2100 2400 600 900 1200 1500 1800 2100 2400 600 900 1200 1500 1800 2100 2400 600 900 1200 1500 1800 2100 2400 600 900 1200 1500 1800 2100 2400 600 900 1200 1500 1800 2100 2400 Static Insertion Loss, dB Octave Band Centre Frequency (Hz) 63 125 250 500 1k 2k 4k 13 23 31 30 19 10 19 33 39 34 27 13 24 40 43 38 33 16 29 46 47 42 35 19 34 50 49 45 37 10 23 40 50 49 46 43 11 25 44 50 50 48 45 11 18 28 24 15 16 28 35 29 21 11 21 39 42 35 27 13 25 43 44 39 31 16 30 49 47 43 35 18 35 50 48 45 42 20 39 50 50 50 44 10 13 24 23 11 15 27 33 26 18 10 20 34 38 31 22 12 24 41 42 36 26 14 29 45 45 40 31 16 32 50 47 43 38 19 38 50 50 46 39 11 22 16 10 13 21 27 21 14 18 31 34 27 18 10 21 35 39 31 20 14 27 43 44 35 26 15 29 47 46 41 33 17 34 49 50 43 34 10 20 13 13 21 26 19 12 17 27 31 23 14 10 20 33 36 27 17 12 25 38 40 32 21 14 28 44 44 37 24 16 33 46 50 39 26 10 18 10 11 18 20 14 15 23 28 19 12 18 28 33 22 13 11 23 34 38 26 16 13 27 40 44 31 16 14 29 43 48 33 19 14 10 16 18 12 13 19 25 17 10 16 25 29 20 10 21 30 34 22 11 12 25 36 40 26 14 12 27 40 42 30 16 11 14 16 11 6 12 16 22 15 15 22 26 18 19 25 30 18 10 23 31 36 24 11 11 25 36 38 28 13 8k 17 22 26 28 32 41 43 13 16 20 21 25 30 32 14 16 18 20 23 26 11 13 14 17 19 21 11 12 14 14 16 6 9 10 10 12 7 7 10 6 7 Module widths, mm 275, 550 825, 1100 1375, 1650 1925, 2200 Free Area 27% 300, 600 900,1200 1500,1800 2100, 2400 Free Area 33% 325, 650 975,1300 1625,1950 2275 Free Area 38% 350, 700 1050, 1400 1750, 2100 Free Area 43% 375, 750 1125, 1500 1875, 2250 Free Area 47% 400, 800 1200, 1600 2000, 2400 Free Area 50% 425, 850 1275, 1700 2125 Free Area 53% 450, 900 1350, 1800 2250 Free Area 56% NOISE CONTROL PRODUCTS H-11 H Noise Control.qxd 5/03/2008 11:51 AM Page 12 RECTANGULAR DUCT ATTENUATORS Suggested Specification HOW TO DETERMINE WEIGHT Attenuators shall be as manufactured by Q-Tech Acoustics Pty Ltd and shall have the performance as scheduled The casing shall be manufactured from high quality galvanised mild steel sheet with Pittsburgh corner seams Mild steel end flanges shall be provided pop-riveted and sealed to the case These shall be finished with zinc-rich primer or hotdipped galvanised after fabrication if requested Select the factor from Tables b & c below for the respective attenuator model, width and height Acoustic splitters shall have a folded profile or semi-circular inlet fairing with tapered discharge profile to minimise pressure drop and regenerated noise, similar to Q-Tech RT series Where nominated, straight splitter attenuators can be used similar to Q-Tech RS series Airways shall be straight and parallel The infill material shall be either rockwool or fibreglass as specified by the manufacturer The infill material shall be covered with a gauze scrim to prevent erosion of the fibres, then encased in galvanised perforated sheet metal H Where attenuators are exposed to the weather they shall be of the Q-Seal type All infill materials shall be lined with an impervious film to prevent the ingress of moisture The infill material when tested in accordance with AS1530.3:1989 shall have the following indices:- Ignitability Spread of flame Heat evolved Smoke developed Apply the appropriate factor in Table a for your required length to obtain attenuator weight Example Model RT17D Height Factor, Tables b & c Factor for 1500L, Table a Attenuator weight Table b Model RT/S07 RT/S10 RT/S12 RT/S15 RT/S17 RT/S20 RT/S22 RT/S25 275 300 325 350 375 400 425 450 550 600 650 700 750 800 850 900 Table c Height mm 300 450 600 750 900 1050 1200 1350 1500 1650 1800 1950 2100 2250 2400 17 22 27 32 39 44 49 54 60 65 70 75 80 85 90 32 39 47 54 61 69 76 84 91 98 106 113 121 128 136 = 1500W × 1050H × 1500L = 118 = 2.15 = 118 × 2.15 = 253.7 kg 825 900 975 1050 1125 1200 1275 1350 Table a Length, mm 600 900 1200 1500 1800 2100 2400 Standard Widths - W, mm 1100 1375 1650 1200 1500 1800 1300 1625 1950 1400 1750 2100 1500 1875 2250 1600 2000 2400 1700 2125 1800 2250 Factor 1.00 1.43 1.79 2.15 2.65 3.01 3.36 1925 2100 2275 2200 2400 Height Factor (See above for length factor) 45 58 71 84 97 54 70 85 100 116 64 82 99 117 135 74 94 114 134 154 83 106 128 150 173 93 118 142 167 192 103 130 157 184 210 113 142 171 200 229 122 154 185 217 248 132 166 200 234 267 142 178 214 250 286 152 190 228 267 305 161 202 243 283 324 171 214 257 300 343 181 226 271 317 362 110 131 152 174 195 216 237 259 280 301 322 344 365 386 407 To determine weights of Q-Seal rectangular attenuators multiply the weight of standard units by 0.89 HOW TO ORDER - W H Air Flow L - RT - tapered splitter RS - straight splitter Airway width in cm 07 - 75mm 15 - 150mm 22 - 225mm 10 - 100 17 - 175 25 - 250 12 - 125 20 - 200 Length code A - 600mm D - 1500mm G - 2400mm B - 900 E - 1800 C - 1200 F - 2100 Variations to standard G - galvanised flanges S - stainless steel E - epoxy coating QS - impervious lining (Default is standard construction) Casing width in cm Casing height in cm H-12 NOISE CONTROL PRODUCTS © FANTECH 2008 Noise Control.qxd 5/03/2008 11:52 AM Page 13 RECTANGULAR DUCT ATTENUATORS REGENERATED NOISE DATA Figure Figure Spectrum corrections for airway velocity module Airflow Airway Velocity m/sec 200 mm Airway width (in mm) Octave Band Centre Frequency, Hz 63 125 250 500 1k 2k 4k 8k -2 -6 -7 -10 -12 -16 -19 -22 -3 -5 -8 -7 -8 -10 -13 -15 -3 -6 -10 -7 -7 -8 -10 -12 100 mm Tapered Splitter: shown with modules If airway width were 150mm and length 1500mm, the silencer would be an RT15D % Free Area 60 An attenuator can be a source of noise in itself This noise is termed ‘regenerated noise’ and is a function of the airway velocity within the attenuator and its size To determine the regenerated noise of an attenuator the following procedure should be followed:- Example Figure Air flow = 11.2 m3/s 50 Selected attenuator having dimensions of = RT17D - 150 - 105 1500W × 1050H × 1500L 40 Percentage free area from Fig = 47 % 30 Airway velocity, m/s = 100 Air flow, m /s ´ % Free Area Unit Area, m = 11.2 100 ´ 1.50 ´ 1.05 47 20 07 10 12 15 17 20 22 25 Attenuator Model No = 57 dB 80 Number of modules =4 Correction for no of modules, Fig = +6 dB 70 ig h he er Sp litt 20 50 0 60 40 10 00 00 t Figure 50 40 10 20 40 Airway Velocity, m/s 14 The number of modules is obtained from the module widths column of the right hand side performance of the data tables on page H-11 In this example the width is 1500mm, which is the fourth dimension shown, indicating there are four modules Regenerated noise is therefore as follows:- 10 Octave Band Centre Frequency, Hz = base level + corr for no of modules = 57 + = 63 dB Total sound power level, Lw Figure 12 dB Increase H Base sound power Level, Lw, Fig 90 Base Sound Power Level, LW = 15.13 m/s No of Modules © FANTECH 2008 10 20 63 125 250 500 1k 2k 4k 8k Total sound power level, Lw 63 63 63 63 63 63 63 63 Correction for airway velocity of 15.13 m/s from Figure -3 -5 -8 -7 -8 -10 -13 -15 Regenerated noise spectrum, Lw 60 58 55 56 55 53 50 48 NOISE CONTROL PRODUCTS H-13 ... satisfactorily select an attenuator the following information is required Model No RT 07A 07B 07C 07D 07E 07F 07G 10A 10B 10C 10D 10E 10F 10G 12A 12B 12C 12D 12E 12F 12G 15A 15B 15C 15D 15E 15F... thermally insulated and may require additional external lagging when handling conditioned air © FANTECH 2008 Length, mm 600 900 1200 1500 1800 2100 2400 600 900 1200 1500 1800 2100 2400 600 900... RT17D Height Factor, Tables b & c Factor for 1500L, Table a Attenuator weight Table b Model RT/S07 RT/S10 RT/S12 RT/S15 RT/S17 RT/S20 RT/S22 RT/S25 275 300 325 350 375 400 425 450 550 600 650