Roxul Industrial Insulation Process - Manual (Page 47)

1.2.10 expansion joints
In thermal insulation systems, large differences
between the piping and the cladding temperature
can occur. The materials used for the pipe,
insulation, insulation support and cladding also
have different thermal expansion coefficients.
This leads to different thermal elongations of the
various components in the insulation system,
which must be allowed for using constructive
measures. The elongation “Δl” can be determined
as follows:
Δl = l ⋅ Δt ⋅ a
In this formula, l corresponds to the length of the
pipe, Δt corresponds to the difference in
temperature between the cold and warm pipe (or
cladding) and a corresponds to the linear thermal
expansion coefficient (see tables in Chapter 3).
If bellow expansion joints for thermal length
compensation have been built into the pipe, the
insulation system will also bellow along with the
pipe movements, potentially compromising the
insulation. The expansion bellows are covered
with a sheet that is then insulated (see diagrams
on the right). With temperatures above 550 °F
(300 °C), do not use galvanized sheets due to the
risk of galvanic corrosion (cracking).
To compensate for thermal expansion of the
cladding, install the expansion joints shown below.
1.2 Insulation of piping
Example for the thermal elongation of steel
Δ l (inch per foot) Δ t (°F) Δ t (°C)
0.004 50 28
0.008 100 56
0.012 150 83
0.016 200 111
4"
(100 mm)
4" (100 mm)
1. Pipe - 2. ProRox ® insulation - 3. Cladding -
4. Aluminum foil - 5. Cover sheet - 6. Wrap (mat) pin with
clip - 7. Spacer
1. Pipe - 2. ProRox ® insulation - 3. Cladding -
4. Sheet-metal screw or rivet - 5. Swage -
6. Metal strap - 7. Circumferential seam
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