lindab | we simplify construction Pressure control valve OLR Technical data Sample calculation When dimensioning an overflow diffuser, calculate the decrease in the wall’s noise-reducing properties. For these calculations, the area of the wall and sound reduction figure R must be known. This is adjusted in relation to the diffuser’s D n,e value. D n,e is the diffuser’s R value given at a transmission area of 10 m 2 , as specified in ISO 140-10. The D n,e value can be converted into the R value for other transmission areas using the table below. A rea [m 2 ] C orrection [dB] 10 2 1 0 -7 -10 The diagram below indicates the decrease in the wall’s reduc- tion figure, based on the diffuser, in a given octave band: Reduction of R_wall [dB] Area of wall [m²] / Number of valves [-] 20 1m² 2m² 5m² 10m ² 20m ² 15 30m ² 40m ² 50m ² 10 100m ² 5 0 -10 -5 0 5 10 15 20 R_wall - D n,e [dB] As a rough estimate the calculation can be performed direct- ly using the wall’s R w value. Example: R w (wall) D n,e,w (diffuser) Area of wall Number of diffusers 50 dB 44 dB R w - D n,e,w = 6 dB 20 m 2 1pcs. 20 m 2 /1pcs. = 20 m 2 Indicated reduction of R w (wall): R w value for wall with diffuser: 5 ~50-5 = 45 dB The calculation can also be performed using the following formula: R res = 10 Log S wall + (10m² 10 -0,1·Dn,e ) (S wall 10 -0,1 · Rwall ) where: - R res is the resulting reduction figure for wall and diffuser. - S is wall area. - D n,e is the diffuser’s D n,e value. - R wall is the wall’s R value without diffuser. Technical data Capacity Volume flow q v [l/s] and [m 3 /h], total pressure drop Δ p t [Pa] and sound effect level L WA [dB(A)] are specified for a diffuser on either side of the wall. Dimensioning diagram ǻ p t [Pa] OLR 400 100 600 800 1000 70 50 40 30 35 20 30 15 25 10 7 15 20 60 70 30 100 20 40 50 60 70 100 150 200 300 400 L WA dB(A) 150 500 200 700 q V [l/s] 250 q V [m 3 /h] Element-normalised reduction figure D n,e Table 1: Cavity wall with 120 mm insulation. Centre frequency Hz Size 125 250 500 1K 2K 400 *31 37 41 46 55 600 *29 35 38 43 52 800 *28 34 37 42 51 1000 *26 33 36 41 50 D n,e,w 46 43 42 41 Table 2: Cavity wall with 35-70 mm insulation. Centre frequency Hz Size 125 250 500 1K 2K 400 *31 37 39 42 52 600 *29 35 37 40 49 800 *28 34 35 39 48 1000 *26 33 34 38 47 D n,e,w 44 42 40 39 Table 3: Positioning over a frame in a cavity 70 mm insulation. Centre frequency Hz Size 125 250 500 1K 2K 400 *31 37 36 41 52 600 *29 35 33 39 49 800 *28 34 32 38 48 1000 *26 33 31 37 47 wall with D n,e,w 42 39 38 37 Table 4: Solid wall without insulation. Size 125 400 *31 600 *29 800 *28 1000 *26 Centre frequency Hz 250 500 1K 2K 37 32 37 45 35 30 35 43 34 28 33 42 33 27 32 41 * minimum values D n,e,w 38 36 34 33 2 Lindab reserves the right to make changes without prior notice 2021-02-10
Download PDF file