Crown Duct Slab with a bright Class ‘O’ foil
facing is suitable for the thermal insulation of rectangular water
storage tanks and feed and expansion tanks. For weatherproofing,
PIB sheeting may also be
applied. For additional mechanical strength, metal sheeting should
be used. The recommended minimum thicknesses of Crown Duct Slab for
use on water tanks are shown in the table opposite.
Installation
Crown Duct Slab is cut to
fit so that the slabs on the short sides of the tank overlap the
slabs on the long sides of the tank. The insulation is bonded to
the ductwork by means of a suitable adhesive, in accordance with
the manufacturer’s instructions. All the junctions between pieces
of insulation to be close butted and sealed with self adhesive
aluminium tape at least 100mm wide.
Crown Duct Slab can be used
up to continuous operating temperatures of 230°C and down to below
ambient temperatures provided that a 100% vapour barrier is
maintained. The surface temperature of the facing should not exceed
80°C.
The thermal conductivity
of the insulation varies with temperature, as shown in the
table.
| Mean temperature
(°C) |
Thermal
conductivity (W/mK) |
| 10 |
0.032 |
| 25 |
0.034 |
| 50 |
0.038 |
| 75 |
0.042 |
| 100 |
0.047 |
| 125 |
0.053 |
Tested in accordance with BS 874: 1973 (1980)
Recommended minimum thickness of insulation for
tanks
|
Application |
Water temperature (°C) |
Insulation thickness (mm) |
| For protection against
freezing |
- |
25 |
| Storing chilled and
cold water supplies |
0 |
100 (50+50) |
| 5 |
75 (25+50) |
| 10 |
50 |
| Where gas is used: |
| Domestic hot water storage |
– |
75 (25+50) |
| Heating system
storage |
75 |
75 (25+50) |
| 100 |
75 (25+50) |
| 150 |
100 (50+50) |
Note:
These figures are derived from
BS
5422: 2001. For other fuels contact
the Knauf Insulation Technical Advisory Centre.
Acoustic performance
Crown Duct Slab will
provide effective control of noise, the actual performance varies
with insulation thickness and surface finish.