Rocksilk Mattress is a
non-combustible rock mineral wool faced on one side with galvanised
or stainless steel wire mesh to form a firm but flexible general
purpose insulating mattress. It is available in two densities: SD1
is 100 kg/m3 and HD1 is 125 kg/m3.
The galvanised wire mesh is 0.82mm x 25mm (22 swg x 1”). Both
grades are also available in a water repellent grade and/or with a
stainless steel mesh, 0.9mm x 25mm, subject to enquiry.
Typical Construction
Rocksilk Mattress is
specifically for the thermal insulation of large vessels, boilers
and high temperature plant.
Note: Vessels can include large and small rectangular,
cylindrical and irregular pieces of equipment, high towers for
chemical process plants, large storage tanks and spheres as well as
boilers and steam turbines.
In selecting the most suitable product, the following criteria must
be considered.
- Maximum service temperature
- Degree of insulation efficiency required
- Robustness of insulation necessary to support the applied
finish and withstand the environment.
Generally, the higher the
temperature, the higher the density required. However, it may be
prudent to select a density of slab higher than that necessary for
the temperature where a more robust insulant is required to support
the covering and other loads which may at times be imposed, such as
foot traffic on top of large tanks. For cylindrical vessels up to
1120mm outside diameter, Knauf Insulation recommend that they
should be insulated as pipes where preformed pipe insulation is
available.
For weatherproofing,
PIB
sheeting may also be applied. For additional mechanical strength,
metal sheeting should be used.
Installation
Rocksilk Mattress is to be closely
butted together and the edges of the outer layer of wire netting
laced together with wire. Joints in multiple layers should be
staggered. Rocksilk Mattress should be impaled over pins and
secured with 50mm flat square washers and capped with spring clip
washers. Metal pins or forked studs to be welded/screwed to the
surface of the vessel at the following pitches:
- Vertical surfaces at an approximate square pitch of 450mm
- Upward facing surfaces 600mm
- Overhanging or downward facing surfaces 300mm.
When using pins with spring clip
washers the length of the pin to be 12mm shorter than the thickness
of the insulation to avoid hot spots on the cladding. This is
normally achieved by compressing the mineral wool insulation with
the spring washer by 12mm and cropping the pin back to the
washer.
Forked studs to be longer than the insulation thickness and turned
back and recessed into the insulation by approximately 10mm.
Performance
Operating temperatures
Rocksilk Mattress can be used up to
continuous operating temperatures of:
- Up to 600ºC: SD Grade
- Up to 750ºC: HD Grade
Note: Galvanised wire mesh in
contact with temperatures above 350ºC may suffer
embrittlement.
Fire performance
The rock mineral wool of Rocksilk
Mattress is non-combustible to
BS
476: Part 4: 1970 (1984).
Thermal performance
Rocksilk Mattress has a thermal
conductivity of 0.033 W/mK at 10ºC.
Insulation thicknesses should be set by the specification, but
otherwise meet the recommendations given in
BS
5422: 1990/2001
Acoustic performance
The use of Rocksilk Mattress can
significantly reduce the noise generated by liquid and granular
materials being transported at high velocity in pipework.
Permanence
Rocksilk Mattress is non-wicking
when tested to
BS
2972: 1989:
Section 12. When exposed to 90% relative humidity and 20ºC,
Rocksilk Mattress absorbs less than 0.004% of moisture.
Other Advantages
- Corrosion free when used with austenitic stainless steel
- Reduced thermal bridging
- No deterioration of performance over time
- Speed of installation
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