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HDPE drainageInstallation guidelines
Pipe fixing system
6 Pipe fixing system
6.1 Choice of pipe fixing system
The choice of the pipe f ixing system is essential to install the pipe systemcorrectly. Depending on the temperature of the medium, the ambient
temperature and the building constraints there are the following options:
1 Installation in guide brackets with correction for axial movement of
the pipe by means of:
- Snap-expansion sockets
- Deflection leg
- A combination of both
2 Rigid installation
3 Embedding in concrete
4 HDPE systems below ground
6.2 Installation in guide brackets
With compensation for axial movement of the pipe with snap-
expansion sockets
The axial movement is caused by the linear expansion of the pipe.
The total expansion ∆l triggered by the temperature difference can be
calculated using formula 6.2.1 or can be taken from diagram 6.2.1.
∆lt= L pipe . αt . t max . 103
The maximum length change which can be accommodated by the
expansion sockets can be found in table 6.2.1.
Equation 6.2.1
Length change caused by temperature
difference
∆l t = lenght change (mm)
L pipe = total lenght of pipe (m)
αt = linear expansion coefficient (mm / mºK)
t max = temperature difference in ºC
Diagram 6.2.1 Length change caused by temperature difference
d1
(mm)
Total
length
(mm)
Min. insertion
depth 20ºC
(mm)
Max.
expansion
(mm)
32 130 74 56
40 132 76 56
50 132 76 56
56 132 76 56
63 132 76 56
75 132 76 56
90 134 78 56
110 134 78 56
125 135 79 56
160 140 84 56
200 230 120 110
250 250 125 125
315 270 126 144
Table 6.2.1 length change with expansion sockets
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Installation guidelines
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HDPE drainage
Pipe fixing system
The general rule regarding the number of expansion sockets to be used is
as follows:
Every expansion socket can accommodate the expansion and contraction
of a 5 meter pipe. In every pipe section the required expansion sockets
have to be installed. The number can be derived as follows (see example):
Example:
Length pipe section (L1+L2 +L3) = 18m
Installation temperature: 5°C
Temperature medium: +15°C / +75°C
Temperature difference: 75-5 = 70°K
Total expansion: 18 m x 0.18 mm/mK . 70K = 227mm
In a pipe section of 110 mm diameter this results in 227/56 = ~4.1 = 5
expansion sockets.
This general rule can be used for pipe sections of 5 meter length andlong term temperature differences ≤ 37,5°C.
With short term temperature differences, for example the emptying of a
bathtub, a reduction factor of 0.5 can be applied to the temperature
difference. In the example this would result in 0.5x227/56 = ~2.1 =
3 expansion sockets.
The general rules can be applied for pipe lengths ≤ 5 meter in most drai-
nage applications. With extreme high temperatures possibly in combi-
nation with a complex route the number of expansion sockets needs to
be calculated.
6.3 Installation in guide brackets
With correction for axial movement of the pipe with a
deflection leg
For computing the length of the deflection leg the formula 6.3.1 can be
used or table 6.3.2 and 6.3.3, depending on temperature of installation
and operation.
LB ≥ 10 x √∆l x d1,2
First the length change ∆L has to be determined at a temperature
difference ∆tmax (see paragraph 6.2.1).
Illustration 6.2.2 Pipe section with expansion sockets
Illustration 6.3.1
Installation with deflection leg
Equation 6.3.1
bepaling buigbeenlengte
L A= Bracket distance
LB= Lenght deflection legL= Pipe lenght
GL= Guide bracket
∆l= Length change
LB = Length of deflection leg in mm
d 1 = diameter pipe
∆l = Lenght change caused by expansion
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HDPE drainageInstallation guidelines
Pipe fixing system
Figuur 6.3.3 length deflection leg at operation temperature -40°C - 25°C
Figuur 6.3.2 length deflection leg at operating temperature 25°C - 100°C
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Installation guidelines
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HDPE drainage
Pipe fixing system
Remark:
If the calculated deflection leg is shorter than the available length there
will be no extra load on the pipe system. If this is not the case an additional
expansion socket needs to be installed (see paragraph 6.4).
Fixing system
Check: LB1 + LB2 ≤ Allowed L A
When the distance between both guide brackets is larger than the allowedbracket distance La the deflection leg needs additional support to prevent
sagging.
This extra bracket should not hinder the working of the deflection leg. This
can be done by a pendulum bracket. Bracket distance LA can be found in
table 8.2.3.
6.4 Installation in guide brackets
With compensation for axial movement of the pipe with
combination of 6.2 and 6.3
When possible a combination of a deflection leg with expansion sockets
is recommended. It uses the advantages of both systems and saves
expansion sockets. In illustration 6.4.1 you will find an example:
Working temperature : +15°C / +75°CPipe lengths L1 - L4 ≤ 5m
The expansion sockets take up the expansion of pipe sections L3 and L4.
Several guide brackets have to be installed. The deflection leg LB1 and LB2
compensates the length change of L1 and L2 from pipe section L1 and L2.
When the expansion is more than can be compensated in one expansion
socket a number of expansion sockets with anchor brackets need to be
used.
Illustration 6.3.4
Check fixing systemIllustration 6.4.1 Installation with deflection leg and expansion sockets
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HDPE drainageInstallation guidelines
Pipe fixing system
6.5 Rigid installation with anchor points
In some applications the Akatherm HDPE drainage systems can also be
installed using the rigid installation method. The HDPE pipe is not free to
expand and the forces cause by the expansion will be transferred com-
pletely to the brackets. Because of the forces and resulting tensions in
the pipe, the applications are limited.
Illustration 6.5.1
Anchor point load at ambient temperature -40°C - 25°C
Illustration 6.5.2
Anchor point load at ambient temperature >15°C
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Installation guidelines
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HDPE drainage
Pipe fixing system
When applying this installation method, the following aspects need to be
taken into account:
The force on the bracket depends on wall thickness and diameter of the
pipe. The length of the pipe is not part of the equation. When a the pipe
diameter is reduced an anchor point needs to be placed. (The occurring
force can be found in table 6.5.1 and 6.5.2). The guide brackets need to
be installed between anchor points to prevent the pipe from buckling
(snake effect). The bracket distances are in diagram 8.2.3. At higher
temperatures the bracket distance gets smaller (diagram 8.1.1). Small
diameters are recommended to be installed with support trays.
6.6 Embedding in concrete
By embedding the pipe system in concrete it acts as a rigid system. Short
pipe sections can be embedded without any problem. With long pipe
sections certain precautions have to be taken. There will be no connection
between the concrete and the HDPE. This means that the pipe can freely
contract and expand as a result of temperature changes when no precau-tions are taken.
To prevent the axial movement in long straight pipe sections, fittings like
the akafusion coupler can be installed to serve as an anchor point. As an
alternative for the installation of anchor points snap expansion sockets
can be used. They act as an anchor point on one side and absorb the
expansion on the other side of the socket. The snap-expansion socket
can accommodate the expansion and contraction of a 5 meter pipe.
All fittings installed in the pipe system act as an anchor point and are
subdued to the expansion force.
The following precautions have to be taken when installing 45° and
88,5° branches.
When the length change is smaller than the shrinkage of the concrete no
special precautions have to be taken (see illustration 6.6.1). This is very
rarely the case.
A branch is subdued to the expansion force Fvp. This force and a possible
deformation of the fitting can be counteracted by installing an akafusion
coupler (see illustration 6.6.2) or two snap-expansion sockets (see illu-
stration 6.6.3).
Illustration 6.6.2
Illustration 6.6.3
Illustration 6.6.1
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HDPE drainageInstallation guidelines
Pipe fixing system
Both the akafusion coupler and snap-expansion socket act as an anchor
point preventing the additional load to be transferred to the branch.
When the length of the branch is more than 2 meters special precautions
have to be taken there as well.
A fitting installed in a ceiling penetration acts as an anchor point as well.
In case branches are used in this place it is recommended to use an
akafusion coupler for the jointing and embed this coupler in the concrete
as well.
6.7 HDPE systems below ground
Due to its specific features like flexibility and temperature resistance
(frost) HDPE pipe systems are very suitable for underground use.
Necessary steps:
- The bedding (1) of the pipe needs to be free of stones and other
material that can damage the pipe. The bedding must be at least100 mm deep.
- The pipe must be fully supported by the bedding to prevent sagging
and point loads.
- The consolidation and protection layer (2) must get to at least
300 mm above the pipe.
- After the pipe has been laid with the correct slope it must be
underpinned before filling in the protection layer with sand.
The compacting needs to be done by hand.
- After filling the trench with the protection layer of sand the rest of the
excavated material can be filled in and mechanical compacting can be
used.
- The trench must be as narrow as possible (Pipe dimension + 400 mm)
to avoid additional load on the pipe.
- The pipes must be laid below the frost line.