Roxul Industrial Insulation Process - Manual (Page 114)

Thermal conductivities for industrial/mechanical
insulation can be measured according to the test
methods below.
Guarded hot plate apparatus test
method
The thermal conductivity of flat products, boards
(slabs) and wired mats can be measured with the
guarded hot plate apparatus according to
ASTM C177 or EN12667.
The core components of the apparatus usually
consist of two cold-surface units and a guarded
hot-surface unit. The insulation material to be
measured is sandwiched between these units.
The thermal conductivity is calculated at the mean
temperature between the hot and the cold side
and expressed at the hot face temperature.
Hot pipe apparatus test method
The thermal conductivity of pipe sections and
flexible wraps (mats) can be measured with the
hot pipe apparatus according to ASTM C335 or
EN ISO 8497.
The core consists of a hot pipe with a length of
10 feet (3m). The thermal conductivity is
calculated at the mean temperature between the
hot and cold side and expressed at the mean
temperature. The main difference is that the hot
pipe apparatus test method includes the seams
within the insulation. This explains why the
measured values will be higher than the guarded
hot plate apparatus test.
A distinction is drawn between the definition of
thermal conductivity.
Laboratory thermal conductivity
Thermal conductivity is measured under
laboratory conditions with the guarded hot plate
apparatus or hot pipe apparatus test method.
Nominal (or declared) thermal conductivity
Thermal conductivity specified by the manu-
facturer, allowing for production related
variations in quality and possible ageing, for
example caused by gas exchange in closed cell
insulation materials.
Practical thermal conductivity
Declared thermal conductivity including the
influence of joints, design uncertainties,
temperature differences, convection, changes
in density, moisture absorption and ageing.
These effects are taken into consideration using
supplementary factors.
Operational thermal conductivity
Practical thermal conductivity, whereby the
supplementary values for insulation related
bridges, such as bearing and support structures
are included in the value.
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