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Trenchless Constructionfor District Heating networks

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+

Source: Weidlich

Combining Trenchless Technology andDistrict Heating

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Trenchless Technology: Installation problem.

District Heating pipelines: Operation problem.

Source: AGFW

Combining Trenchless Technology andDistrict Heating

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Source: Weidlich, BRUGG

Steel medium pipe

PUR insulation foamPE-coating

Characteristics of District Heating pipes

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Structural analysis is required, because of

Temperature up to 140

C,Pressure of 25 bar,

Pipe soil interaction.

Source: EN13941

Structural Analysis

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[DIN EN 13941:2007]

- friction forces f u (axial interaction)- bedding pressure p v (lateral interaction)

F

f u

uu u

p

pu

vu v

Source: AGFW

Characteristics of DH pipelines

[Foto: Weoidlich]

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)0(

MMtH EAN

)0(Ru

)0(MMt

GF

EA

l

2

l

EA

Fw

2G

)0(Ru

max

Normal stresses in the adhering section:

Length of the gliding section:

Maximum displacement:

z,w

x,u

+

0friction forces

adhering section gliding section

Distripipeli

Axial

Source: AGFW

Characteristics of DH pipelines

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D

H r

2

02* d

D F

r Ru

21

*2* k

D H m

m

Rohr Ru Gk

D H D F ''21*2****

Source: Weidlich

Characteristics of DH pipelines

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Contact pressure is not clearly understood.

Main influences: Acting earth pressure Use of bentonite suspensions Temperature Time / Durability of the pipe

Because of that, the use of trenchless technology in the DH sector is still seenwith caution. In Germany today ATV A 161 is used.

Source: Weidlich

Contact pressure

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30 years of service lead to cyclic loads.

Pipe type Equivalent full action cycles in30 years according to EN13941

Major pipelines 100

Main pipelines 250

House serviceconnections

1000

[DIN EN 13941:2007]

Cyclic interaction

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EN13941:2003 , Design and installation of preinsulated bonded pipe systemsfor district heating

EN253:2009 , District heating pipes Preinsulated bonded pipe systems fordirectly buried hot water networks Pipe assembly of steel service pipe,

polyurethane thermal insulation and outer casing of polyethylene

FW401:2007 , Laying and structural analysis of plastic jacket pipes for districtheating networks

ATV127:2000 , Statische Berechnung von Abwasserkanlen und -leitungen

FW420:2004 , Part 1 bis 5, Flexible district heating pipeline systems

EN489:2009 , District heating pipes - Preinsulated bonded pipe systems for directly buried hot water networks - Joint assembly for steel service pipes, polyurethane thermalinsulation and outer casing of polyethylene .

Source: Weidlich

Standard and technical rules

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Pipe quality requirements: PE-coatingStrong interaction between soil and pipe during installation

Source: BRUGG Pipesystems

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Strong interaction between soil and pipe during operation

Coarse soil environment will affect the pipe coating

and the joints due to cyclic loading.

Source: FFI

Pipe quality requirements: PE-coating

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Stress-strain coupling between the medium pipe,insulation foam and the PE-coating is necessary.

The allowed shear stress in the foam is t ax

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Pipe curving means additional bending and stress in the pipe

sDCR adesign

bzul

aelast 2

DER

Source: AGFW

Pipe quality requirements: Steel medium pipe

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Characteristics of trenchless technology

Use of bentonite slurries as a friction reducer.

Source: TRACTO TECHNIK

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Reduction of technological barriers

Temperature dependence of bentonite suspensions for drilling

Classification tests showed no influence of the temperature fortypical coating temperatures of 20 , 30 and 40 degrees.

Source: IGth

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In some tests a temperature dependent behaviour of bentonite-sand

mixture was observed.

Coefficient of friction for 40 C drying

0,29

0,33

0,37

0,42

0

0,05

0,1

0,15

0,2

0,25

0,3

0,35

0,4

0,45

PE + Sand + Bentonite(fresh)

PE + Sand + Bentonite(2d drying)

PE + Sand + Bentonite(10d drying)

PE + Sand

C o e

f f i c i e n

t o f

f r i c t i o n

Reduction of technological barriers

Source: IGth

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Outlook

Combining Trenchless Technology and District Heating is promising forpreinsulated bonded district heating pipes.

Combining Trenchless Technology and District Heating