Metal ductwork with a
lining of Crown Acoustic Duct Liner glass mineral wool with glass
cloth facing, mechanically fixed to internal face of duct. Crown
Acoustic Duct Liner is the ideal fire-safe sound absorption
material for the internal lining of air handling equipment and duct
systems, or for use as a general purpose noise control product
where a faced surface, free from risk of erosion is
essential.
Installation
Measure Crown Acoustic
Duct Liner and cut to shape allowing 50mm excess at downstream
transverse joints. Trim off 50mm of insulation to leave a 50mm
facing overlap. All longitudinal joints to be close-butted. All
internal surfaces to be free from dust and grease. Apply mechanical
fastenersin accordance with manufacturers’ instructions at no more
than 450mm centres, and to commence no more than 75mm from joints,
corner breaks etc. Apply a suitable adhesive to the duct surface,
prior to positioning Crown Acoustic Duct Liner over the fixing
pins. Seal all longitudinal joints with a proprietary sealant.
Apply caps/washers to fixing pins and remove excess pin length.
Position the overlap of facing at the transverse joints downstream
of airflow and secure under a metal strip, fixed through the
insulation by screws or rivets at maximum 75mm centres. Secure the
initial and final edges of lined section by similar metal strips.
Coat exposed insulation edges with sealant and secure behind return
flanges of the casing.
Performance
Acoustic performance
As a guide, the length of
duct to be lined with Crown Acoustic Duct Liner should be 10 times
the mean duct width. If the duct is serving a ‘quiet room’, then
the length of treated duct should be 20 times the mean duct width.
For recommended thickness of Crown Acoustic Duct Liner for specific
applications consult our Technical Advisory Centre. The table below
shows typical sound absorption coefficients for Crown Acoustic Duct
Liner.
Sound absorption
characteristics
| Thickness
(mm) |
Frequency (Hz) |
NRC |
| 125 |
250 |
500 |
1000 |
2000 |
4000 |
| 25 |
0.1 |
0.35 |
0.65 |
1 |
1 |
1 |
0.75 |
| 50 |
0.3 |
0.9 |
1 |
1 |
0.95 |
0.85 |
0.96 |
| 75 |
0.45 |
0.9 |
1 |
1 |
0.95 |
0.9 |
0.96 |
Notes: The table shows typical sound
absorption coefficients for Crown Acoustic Duct Liner. The
NRC is
the average coefficient over the frequency range 250-2000 Hz. Test
Method BS EN20354: 1993
(1992).
Fire performance
The base glass mineral
wool of Crown Acoustic Duct Liner is classified as noncombustible
to Euroclass A1 to
BS
EN
ISO 13501-1, to
BS 476: Part 4: 1970
(1984) and achieves a Class 1 surface spread of flame to
BS 476: Part 7: 1997
and is Class ‘O’ to the Building Regulations. The glass cloth
facing complies with the Class ‘O’ requirements of the Building
Regulations when tested to
BS 476: Part 6: 1989 and Part 7:
1997.
Thermal performance
Crown Acoustic Duct Liner
will provide a basic level of thermal insulation and has a thermal
conductivity of 0.037 W/mK.
Air velocity
Crown Acoustic Duct Liner is
ideal for lining duct sections operating at air velocities of up to
30m/s. The increase in air resistance when compared with unlined
steel sheet is negligible.
Other Advantages
- Combines lightness, strength and ease of use
- The aluminium foil facing ensures a positive vapour seal
- Corrosion free
- No deterioration of performance over time
- Resilient, strong and flexible
Sound
attenuation (dB) on a 1 metre run of lined straight
ducting
| Duct
Details |
Frequency (Hz) |
| 125 |
250 |
500 |
1000 |
2000 |
4000 |
| 125mm wide duct lined with 25mm
Crown Acoustic Duct Liner |
0.5 |
1 |
7.5 |
16.5 |
22.5 |
19.5 |
| 250mm wide duct lined with 25mm
Crown Acoustic Duct Liner |
– |
0.5 |
5 |
9.5 |
10 |
3 |
Note: Tested in accordance with BS 4718: 1971.