Roxul Industrial Insulation Process - Manual (Page 80)

Insulation of
flue gas duct
s
In the case of non-steady operation, for example,
when starting up the installation causes
fluctuating flue gas temperatures , measures
must be taken if necessary to allow even heating
of the reinforcement profiles. The temperatures
on the duct wall, as well as on the inside of the
reinforcement element, increase rapidly when
the installation is started up, whilst the outside
of the profile remains cold at first and only heats
up after a longer delay. This leads to temperature
differences, which can cause undue stressing of
the component. The extent of the temperature
differences depends on numerous parameters.
A few examples follow:
The operating speed influences the speed at
which temperature of the flue gas increases
and the temperature difference in the
reinforcement element.
High temperature differences occur in the case
of large profiles.
The shape of the reinforcement profiles
influences an even temperature distribution.
Thick walled profiles, for example, do not warm
up as evenly as thin walls.
The different thermal conductivities of the
materials used and the heat transfer rates lead
to an uneven temperature distribution.
To reduce the temperature differences, the
insulation must be structurally designed to enable
as much heat as possible to be transported by
means of radiation and convection from the duct
wall to the external flange of the reinforcement
profiles. The following shows the design details
for a profile insulation system.
This type of design is generally recommended for
profiles measuring up to ≤ 10" (240 mm) in height.
max.
4"
(1
00
mm
)
1. Duct wall - 2. ProRox ® insulation - 3. Reinforcing ribs - 4. Welding pins with clips - 5. Metal cladding
Insulation of reinforcing ribs
1. Duct wall - 2. ProRox ® insulation - 3. Metal cladding:
corrugated sheet - 4. Reinforcing element -
5. Supporting construction and spacer - 6. Aluminum
foil (optional) - 7. Welding pins/clips
Insulation of reinforcing ribs
77