261 / 416
H
H-7
NOISE CONTROL PRODUCTS
© FANTECH
2016
RECTANGULAR DUCT ATTENUATORS
Face Velocity at
Pressure Drop
20Pa
600mm 900mm 1200mm
1
2
3
4
5
6
Length of attenuator
..A..
..B..
..C..
..D..
..E..
..F..
..G..
1500mm 1800mm 2100mm 2400mm
1
2
3
4
5
6
7
RT.. Series & RT.. QS Series
Attenuator face velocity
@ 20Pa pressure loss (m/s)
600mm 900mm 1200mm
Length of attenuator
..A..
..B..
..C..
..D..
..E..
..F..
..G..
1500mm 1800mm 2100mm 2400mm
RT20../QS..
RT15../QS..
RT12../QS..
RT10../QS..
R3T30..
R3T22..
R3T17..
R3T15..
RT07../QS..
R3T.. Series
Attenuator face velocity
@ 20Pa pressure loss (m/s)
3.3
R3T15.. R3T17.. R3T22.. R3T30..
RT07.. RT10.. RT12.. RT15.. RT20..
RT07..
QS
RT10..
QS
RT12..
QS
RT15..
QS
RT20..
QS
450
900
1350
1800
2250
475
950
1425
1900
2375
525
1050
1575
2100
600
1200
1800
2400
275
550
825
1100
1375
1650
1925
2200
300
600
900
1200
1500
1800
2100
2400
325
650
975
1300
1625
1950
2275
350
700
1050
1400
1750
2100
400
800
1200
1600
2000
2400
275
550
825
1100
1375
1650
1925
2200
300
600
900
1200
1500
1800
2100
2400
325
650
975
1300
1625
1950
2275
350
700
1050
1400
1750
2100
400
800
1200
1600
2000
2400
R3T.. Series (mm)
RT.. Series (mm)
RT.. Q Seal Series (mm)
Face Velocity at
Pressure Drop
50Pa
11
10
9
8
7
6
5
4
3
2
600mm 900mm 1200mm
Length of attenuator
..A..
..B..
..C..
..D..
..E..
..F..
..G..
1500mm 1800mm 2100mm 2400mm
RT20../QS..
RT15../QS..
RT12../QS..
RT10../QS..
RT07../QS..
Attenuator face velocity
@ 50Pa pressure loss (m/s)
9
8
7
6
5
4
3
2
600mm 900mm 1200mm
Length of attenuator
..A..
..B..
..C..
..D..
..E..
..F..
..G..
1500mm 1800mm 2100mm 2400mm
Attenuator face velocity
@ 50Pa pressure loss (m/s)
R3T30..
R3T22..
R3T17..
R3T15..
RT.. Series & RT.. QS Series
R3T.. Series
Width table
6
6
7
5
Select the product code which is aligned with the 2100mm long, 37% open, 23 dB(A). In this case the product code is RT12F.
6
Refer to the correct pressure loss (20Pa) graph and attenuator series ( RT Series for the RT12F model)
7
Draw a vertical line on the graph that corresponds to the length of the attenuator model chosen at step
4
(i.e. 2100mm long
or 'F' length code). The face velocity on the RT12../QS curve that corresponds to the model is 3.3m/s
Face Velocity
8
Calculate the minimum face area for your attenuator selection; Face Area = Air flow = 7.0m
3
/s = 2.12m
2
9
To calculate the width of a rectangular attenuator of unknown dimensions, use the formula;
Width = Face Area x Aspect Ratio = 2.12m
2
x 1.5 = 1.78m
*Common aspect ratios vary between 0.5 and 3.0. When a silencer width is larger than its height aspect ratio >1.0. An aspect ratio of 1.5 is a good default.
In the width table below, pick the closest width available for a RT12.. series attenuator. In this case, 1.95m (1950mm) is the selected
width.
To calculate the height of the attenuator, use the formula; Height = Face Area = 2.12m
2
= 1.09m
The final model code of the attenuator selected is RT12F-195-109
Width
1.95m
3.3m/s
7
9