CADENZA

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Nickolas Goodwin
6 years ago
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1 Attenuator with aerodynamically shaped splitters for rectangular ducts GENERAL has been developed to meet today s high requirements for sound attenuation and is especially suitable for use in duct systems. QUICK FACTS Rectangular sound attenuator with connections equal to outer casing Good aerodynamic characteristics Low pressure drop due to tapered splitters Environmentally friendly sound attenuating material: CLEANOLON -AL Available with inspection hatch Available in fire-insulated version with 50 mm mineral wool insulation Washable surface CLEANOLON -AL Connection dimensions from 400 x 300 to 2200 x 2200 mm Included in Magic CAD and Point databases Registered design. The company reserves the right to make design changes without prior notice. 1

2 DESIGN is manufactured as standard in galvanized steel sheet. The sound attenuating material, CLEANOLON -AL, is tested to Swedish standards with regard to cleaning, fibre-loosening, ageing properties, wet cleanable, emissions etc. is supplied as standard with C-clip connection to connecting ducts. FUNCTION The low pressure drop through is achieved by shaping the splitter elements in accordance with the basic laws of aerodynamics using continuous tapering. The low pressure drop may be exploited to: reduce the space required through selecting a smaller attenuator reduce the pressure setting of the fan if the size is retained reduce inherent sound generation in the system due to lower air velocities and pressure setting facilitate the adaptation of the sound attenuator to the duct system contains all the positive characteristics of earlier Swegon sound attenuators. By taking into consideration the properties of the construction materials and utilizing the basic principles of flow theory, Swegon have optimized the sound attenuator with regard to: the acoustic properties of the sound attenuating materials the thickness of the splitters the width of the slots the length of the splitters the surface covering cleanabillity By combining the above factors, Swegon can always offer the best sound attenuation and lowest pressure drop according to customer requirements. ACCESSORIES T1: Non-insulated inspection hatch T2: Fire-insulated inspection hatch T3: The sound attenuators is supplied fire-insulated with 50 mm mineral wool.n.b. The attenuator s H measurement is then increased by 100 mm. T4: Perforated steel sheet covering can be supplied as loose splitters without any housing. Please contact Swegon for further information. CUSTOMER MODIFICATIONS In addition to the accessories and special versions described in the catalogue, it is possible to modify the attenuator to suit the customer requirements. Swegon can, in consultation with the customer, optimize the attenuator with regard to sound attenuation, size, adaptation to the air handling unit and choice of materials (e.g. stainless steel, aluminium/zinc and so on). Please contact Swegon for further information. PLANNING, GENERAL The TECHNICAL DATA shown for are valid for the standard version. Dampers, duct bends or other equipment in the vicinity of the attenuator will increase its pressure drop and inherent sound and may also affect the attenuation. Data shown here are based on an even flow of air in and out of the sound attenuator. Refer also to the section on SYSTEM POWER AND PRESSURE- DROP. The inherent sound generated increases when perforated steel sheet is used to cover the splitters. Refer to the section on INHERENT SOUND GENERATION. MAINTENANCE Under normal operating conditions, is a maintenance free sound attenuator. If there are requirements for internal cleaning, can be factory fitted with an inspection hatch: see accessories. All the slots are then accessible through the hatch. In many cases it may however be suitable to position the inspection hatch in the duct near to the sound attenuator. ENVIRONMENT "Environment declaration" is available on Swegon s website on the Internet or may be ordered from one of our sales offices. INSTALLATION The C-clip on this product are only intended for connection to ducts. The product is to be installed suspended with supports under its entire width. 2

3 PLANNING Dimensions/sound attenuation 1. Calculate the required sound attenuation either manually or with the aid of Swegon sound calculation software ProAc (available on our website) 2. Select the sound attenuator which fulfils the sound attenuation requirements for low frequencies (especially 125 Hz) from TECHNICAL DATA. Also check the attenuation in the higher frequencies. 3. Check the H-measurement of the attenuator to optimize the pressure drop, taking into consideration the system power. 4. The p-value that is obtained from TECHNICAL DATA is used to determine the pressure drop for the attenuator. The higher the p- value, the higher the pressure drop see Nomogram Check the inherent sound generation for the attenuator Pressure drop 1. Calculate the gross frontal area B x H (m 2 ) 2. Refer to Nomogram 1 for the relevant airflow. 3. Go vertically up to the p value obtained from TECHNICAL DATA for the selected attenuator. 4. Read off the pressure drop for duct-duct installation. 5. When selecting alternatives other than duct-duct, the pressure drop is corrected with the aid of Graph 1. Nomogram 1. Determining the pressure drop Pa The pressure drop in Nomogram 1 is multiplied by the value obtained from Graph 1, depending on the installation of the attenuator. Example: An attenuator is located next to an air handling unit in a fan room. The airflow is 4 m 3 /s and the attenuator is installed in a duct with a width of 1000 mm. The attenuator 1016 with a p-value of 3.2 has been selected from TECHNICAL DATA. The attenuator has a width of 1000 mm and a height of 1100 mm. The gross frontal area will be 1.1 m 2. Nomogram 1 gives a pressure drop of approximately 25 Pa. If the attenuator had been installed duct-chamber, the pressure drop would have been multiplied by 2.3 as read off from Graph 1. The pressure drop then obtained would have been approximately 58 Pa. Graph 1. Correction for other installations m 2 Curve 1: Chamber-duct, Curve 2: Duct-chamber, Curve 3: Chamber-chamber 3

4 SYSTEM POWER AND PRESSURE DROP Attenuator installed before or after a bend The corrections below must be multiplied by the pressure drops shown in the graphs Attenuator before bend Attenuator after bend Distance Corr.factor Distance Corr.factor 3xD 1,1 1xD 1,2 2xD 1,2 0 (direct) 1,3 1xD 1,35 0 (direct) 1,5 Attenuator installed before or after a chamber The total pressure drop through an attenuator is obtained by multiplying the correction factor from Graph 1 by the pressure drop from Nomogram 1. Attenuator installed before or after a branch An attenuator installed after a branch can be compared with one installed after a chamber. Refer to curve 1 in Graph 1. The total pressure drop through the attenuator is obtained by multiplying the correction factor by the pressure drop from Nomogram 1. Figure 1. Attenuator before or after a bend Distance and D refer to the distance between the attenuator and bend and the largest side of the attenuator respectively. The total pressure drop = pressure drop of attenuator from Nomogram 1 x correction factor. An attenuator installed before a branch can be compared in a similar way with one installed before a chamber. Refer to curve 2 in Graph 1. The total pressure drop through the attenuator is obtained by multiplying the correction factor by the pressure drop from Nomogram 1. Attenuator installed by an air handling unit It is difficult to make accurate corrections for an attenuator installed next to an air handling unit. This depends primarily on the fact that different manufacturers of air handling units have varying fan outlets. The most common arrangement is a relatively small outlet (giving a high exit velocity) combined with a large duct connection (with air velocities of around 4 6 m/s). Generally speaking the angle between the outlet and the duct should not exceed 15º. To ensure good distribution of the airstream, a diffuser plate in front of the outlet may be used with good result. Attenuator installed by a damper An attenuator installed next to a damper can give large pressure drops. As the damper angle is increased, larger differences in the air velocity profile are generated. This results in increased air velocities between the attenuator splitters with an increased pressure drop as a result. Attenuators installed in series The basic rule when installing attenuators in series is to avoid changing the velocity profile between the attenuators. If the straight section of duct between attenuators can be made sufficiently long (4 x D), in the best case it is possible to calculate the pressure drop as specified for each separate attenuator. One important aspect is to ensure that the splitters do not cover any air slots. Please contact Swegon when installing attenuators in series. 4

5 INHERENT SOUND GENERATION An attenuator does not only decrease noise levels, it also generates sound itself at high air velocities and pressure drops. Normally there are no problems as long as the recommended operating area in Nomogram 1 is adhered to. For more accurate calculations there are curves drawn in Nomogram 1 showing inherent sound generation. Please refer to ProAc, where not only inherent sound generation is shown but also pressure drop. The L wt values shown are sound power levels for with a reference value of W at an airflow of 1 m 3 /s. By correcting L wt with K 1 for, the sound power level for each Octave band is obtained. For with perforated steel sheet, first add 12 db to the L wt value shown and then correct with K 2. Hz K 2K 4K 8K K K Example: An attenuator is installed next to an air handling unit in a fan room. The airflow is 4 m 3 /s and the attenuator is installed in a duct with a width of 1000 mm. The attenuator 1016 with a p value of 3.2 has been selected from TECHNICAL DATA. The attenuator has a width of 1000 mm and a height of 1100 mm. The gross frontal area will be 1.1 m 2. Nomogram 1 gives L wt = 38 Pa. Correct with K 1 to obtain separated octave bands and for 4 m 3 /s as in Graph 2. Hz K 2K 4K 8K L wt K m 3 /s L w Corrections for air flows other than 1 m 3 /s are made by using Graph 2 below. Inherent sound generated must be 8 10 db lower in each octave band than the requirement for sound power level after the attenuator. Graph 2. Corrections for other air flows 5

6 TECHNICAL DATA B-measurement: 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1800, 2000, 2200 H-measurement: 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2200 B and H measurements marked in yellow and in bold type are standard. Total installation measurements in H plane: H + 40 mm L-measurement: see table in TECHNICAL DATA FIRE INSULATION In many cases, the attenuator is installed in a fire-insulated duct system. In those cases where ventilation ducts are fire insulated with 50 mm of mineral wool, the attenuator can either be insulated directly at site or insulated at the factory. This is available for as an accessory. Figure 2. INSPECTION HATCH In some circumstances there are requirements for inspection hatch on or next to an attenuator. This is available as an accessory for, the inspection hatch enabling access to all air slots. Technical data are not affected when the accessory T1 is used. A choice can be made between either insulating the inspection hatch alone ( T2) or insulating the whole attenuator ( T3). Technical data are not affected when T2 or CA- DENZA T3 are used. Figure 4. with fire-protective insulation 50 mm of mineral wool Figure 3. with inspection hatch T1 In those cases where is to be equipped with an inspection hatch, this means that the inspection hatch will be located on the upper or lower side of the attenuator (i.e. the B measurement is defined as the width). If for reasons of shortage of space the incpection hatch needs to be located on a side of the attenuator, the B-measurement will then be defined as the height (see figure above). Enough space to open the inspection hatch must be allowed. Fully open, the inspection hatch requires a distance of 700 mm. 6

7 TECHNICAL DATA B-measurement Code Length Static set attenuation (db) as in ISO 7235:91 P-value (mm) (mm) k 2K 4K 8K

8 TECHNICAL DATA continuing B-measurement Code Length Static set attenuation (db) as in ISO 7235:91 P-value (mm) (mm) K 2K 4K 8K

9 DIMENSIONS AND WEIGHTS B-measurement: 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1800, 2000, 2200 H-measurement: 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, B and H measurements marked in yellow and in bold type are standard. Total installation measurements in H plane: H + 40 mm L-measurement = see table TECHNICAL DATA Weight = contact your nearest Swegon office. SPECIFICATION Product Rectangular sound attenuater a aaaa bbbb x cccc x dddd Version: Code: As in technical data Measurements: B x H x L ACCESSORIES T1 = Non-insulated inspection hatch T2 = Fire-insulated inspection hatch T3 = The sound attenuator is supplied fire-insulated with 50 mm mineral wool. T4 = Perforated steel sheet covering N.B. If the attenuator is equipped with an inspection hatch, sufficient space must be allowed to open the hatch. Fully open the hatch requires a distance of 700 mm. Figure 5. s splitters are designed in accordance with the basic laws of aerodynamics. SPECIFICATION EXAMPLE Swegon rectangular sound attenuator of type, with the following functions: Aerodynamically shaped splitters for low pressure drop Type-approved CLEANOLON -AL insulation Sound attenuation in db (stated clearly for different frequency bands) Pressure drop in Pa (stated clearly) Size a aaaa bbbb x cccc x dddd xx. units Order example Straight sound attenuator, code 0636, fulfilling the sound attenuation requirements as calculated. The attenuator is to be equipped with a noninsulated inspection hatch. The installation space is limited vertically to max mm, which means that there is sufficient space to open the hatch (700 mm). Order code: a x600x1850 T1 9

CALMO

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