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Permissible tensile force for the pulling-in of HD-PE and PP pipelines . (Table: Maximum permissible tensile forces for pipes made of PE 80) |
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The maximum tensile force (Z) is exhibited at the bursting head (1), but without a bending moment. With the weld factor αw, the net cross section AQ,n (after deduction of the screw holes) and Ez≥ Edis the tensile stress calculated: Equation 5: (Formula: Ermittlung der maximalen Zugspannung σZ) (→ Table: Equation variables) of mathematical variables (Image: Inside view of the pulling head with bolt connections) (Image: Pulling head with bolt connections … |
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At the old pipe (2) the determination of the σZ is based on the tensile force (Z), area of the cross section of the new pipe, the bending moments and the moment of resistance of the cross-section of the new pipe: Equation 6: (Formula: Ermittlung der maximalen Zugspannung σZ Am Altrohr) with (Formula: Wq) With full wall systems (Formula: Wq bei vollwandsystemen)(Table: Equation variables) |
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The tensile force Z [kN] produces a tensile stress σZ in the pipeline, which must be less than the allowable tensile stress. (Formula: Rohr Zugspannung σZ) The allowable stress is dependent on
Only winches capable of measuring and recording the pulling force should be used. |
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The compressive stress at the old pipe (2) is calculated as follows: Equation 7: (Formula: Die Druckspannung am Altrohr) (Table: Equation variables) |
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The tensile stress from equation 5 and equation 6 is used to calculate the expansion, and the compressive stress from equation 7 is used for the compression. Equation 8: (Formula: Berechnung der Stauchung εz) Equation 9: (Formula: Berechnung der Stauchung εd) (Table: Equation variables) |
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(Image: Tabellenicon) Taking into account any later occurring axial expansion due to internal pressure in non-pressure pipes or bending strains in curved pipelines, the expansion εzshould not exceed a value of 2.0 % during the pulling-in. If an expansion of 2 % is allowed during the pulling-in, the expansion in the bends is also to be a further 1 to 2 %. |
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The new pipeline is fed through a support bracket located at the top edge of the insertion pit into the old host pipe with sufficient clearance (due to the expansion). In general, it is recommended to shorten the insertion pit by utilising additional roller supports, at a distance I3 from the edge of the trench, to increase the clearance Δh3 [mm] above ground level. Equation 10: (Formula: minlG) For PE pipes SDR 33, 26, 21 and 17 without additional … |
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The minimum insertion pit dimensions are determined using the following parameters [DWA-A 143-2:2015] :
(Image: Pipeline and insertion pit parameters (sufficient … |
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Basis for the calculation model The required insertion pit length lG is determined for a unrestrained pipeline, i.e. freely stored at the top edge of the pit, insertion with clearance between expansion and the new pipeline (i.e. Ᾱ1 = 0). lGresults from the following conditions:
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Interpolation between the curves is allowed. (Formula: minlG) (→ Table: Equation variables) of mathematical variables (Image: Diagram for the required pit length lG for PE pipes SDR 21 (SN 8) during the insertion into the old pipeline (clearance Δh / dL,a)) |
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Diagrams for the determination of the pit length for PE pipes SDR 33, 26, 21 and 17 (Image: Required insertion pit length lG for PE pipes SDR 33 (SN 2) pulled into a host pipe (clearance Δh / dL,a) [DWA-M 143-2 draft]) (Image: Required insertion pit length lG for PE pipes SDR 26 (SN 4) pulled into a host pipe (clearance Δh / dL,a) [DWA-M 143-2 draft]) (Image: Required insertion pit length lG for PE pipes SDR 21 (SN 8) pulled into a host pipe (clearance … |
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If the insertion pit is excavated along its entire length, pipelines can be pulled in two directions. (Image: Insertion pit for the pulling in of two pipelines) |
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The maximum strain of σ = 21 N/mm2 (Short Term) applies to PE pipelines before buckling damage occurs, which is limited to (γ = 1.4) max σ ≅ 15 N/mm2 during installation. This strain includes the short-term module Eσ=15 = 500 N/mm2 and the elongation max ε = 3 % according to the DVS 2205-1 guideline. In order to prevent the buckling of the pipeline during the pulling-in procedure, the radius of curvature is to be determined as per equation 11: Equation … |
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To the max. RKbelongs the maximum allowable strain εK, with: Equation 12: (Formula: die maximal zulässige Dehnung εK) Due to the buckling danger, the strain max σKmust be reduced accordingly (see table on the next slide). The associated modulus of elasticity can be approximated by interpolation: Equation 13: (Formula: E-Modul) (Table: Equation variables) |
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In addition, the variability of stresses and thus the effective modulus of elasticity Em [N/mm2] of the pipeline over the pit length lG , and the pipe diameter are taken into account as follows: Equation 14: (Formula: E Modul Em N mm2) (Formula: a von EModul Em Gleichung) If the pulling in of the pipeline takes place in temperatures other than 20 ° C, the pit length can be corrected as follows: Equation 15: (Formula: Ermittlung des maximalen Krümmungsradius … |
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With a longer interruption of the insertion process, the pipeline in the insertion pit must be secured so that the maximum permissible bending radii are not exceeded. |
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Congratulations! You have successfully finished this lesson. Next you will have the opportunity to review the newly acquired knowledge with an interactive questionnaire. You can of course still navigate back to any point in the lessons if you wish to review a specific point or subject. Stay curious! |
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Dec 20, 2013 This module focuses on the parameters that must be considered when pulling in the pipe string for gas, water and wastewater pipelines. In addition to a basic description of the replacement procedure, the importance of tensile forces, bending radii and the dimensioning of the excavation pit is therefore the focus of attention. After completing this module, you will have a sound knowledge of:
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Jun 27, 2019 Animation Replacement of a damaged pipeline over the length of two sections, consisting of DN 300 concrete pipes, in trenchless construction using the dynamic bursting method with simultaneous insertion of a DN 300 HDPE pipe string with an outside diameter of 350 mm.
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May 21, 2014 Course This course includes tutorial services and a final examination.
Replacement refers to the installation of new sewers and drains in place of existing pipelines, where the new pipeline takes over the functions of the old sewer or drain. The replacement process is subdivided into three methods: "open cut method", "semi open cut method" and "trenchless method". The focus of this module is the trenchless replacement method of pipelines by the means of pipe bursting, gallery techniques, and pipe extraction.
In addition to the replacement method and process description this module discusses the areas of application and limits, the advantages and disadvantages as well as possible rehabilitation errors and options for quality assurance.
The course consists of 7 modules:
1. Pipe bursting basics
2. Pipe bursting
3. The welding of plastic pipes
4. Pullback of pipelines
5. Gallery techniques
6. Pipe extraction
7. Geotechnical and hydrogeological principles
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Nov 16, 2015 Course This course includes tutorial services and a final examination. Replacement refers to the installation of new water, wastewater and gaspipelines in place of existing pipelines, where the new pipeline takes over the functions of the old water, wastewater and gaspipelines. The replacement process is subdivided into three methods: "open cut method", "semi open cut method" and "trenchless method". The focus of this module is the trenchless replacement method of pipelines by the means of pipe bursting, gallery techniques, and pipe extraction. In addition to the replacement method and process description this module discusses the areas of application and limits, the advantages and disadvantages as well as possible rehabilitation errors and options for quality assurance. The course presents this knowledge in 7 modules: 1. Pipe bursting basics |
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Nov 28, 2016 Course This course includes tutorial services and a final examination.
Replacement refers to the installation of new water, wastewater and gaspipelines in place of existing pipelines, where the new pipeline takes over the functions of the old water, wastewater and gas pipelines. The replacement process is subdivided into three methods: "open cut method", "semi open cut method" and "trenchless method". The focus of this module is the trenchless replacement method of pipelines by the means of pipe bursting, gallery techniques, and pipe extraction.
In addition to the replacement method and process description, this module discusses the areas of application and limits, the advantages and disadvantages as well as possible rehabilitation errors and options for quality assurance.
The course presents this knowledge in 6 modules:
1. Pipe Bursting Basics
2. Pipe Bursting
3. The Welding of Plastic Pipes
4. Pullback of Pipelines
5. Gallery Techniques
6. Pipe Extraction
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May 12, 2020 NA-08 - Replacement: Pulling-In the Pipe String during the Pipe Bursting Process (Demo) For this module, it is important to be familiar with certain pipe bursting terms:
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May 12, 2020 NA-08 - Replacement: Pulling-In the Pipe String during the Pipe Bursting Process (Demo) The insertion of a new pipe using the bursting process can be performed by pulling in a continuous pipe or by pulling in or pushing in segmental pipes. The former option requires the excavation of access pits and design calculations from an engineer. Therefore, the pulling-in of continuous pipelines will be discussed in greater detail. Pulling-in of a continuous pipe Pulling-in of discrete pipes with a smooth outer surface Pushing-in of discrete pipes … |
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