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In order to receive real time data from the pulling head, a data cable must be inserted ahead of the new pipe and connected to a computer. Otherwise, the data can only be collected after the completion of the pulling-in of the new pipe. (Image: Tension sensor) |
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As a reference, the following table shows the allowable tensile forces for PE 100 pipes for a load duration of 30 minutes (according to the German DVGW working sheet GW 323: Trenchless replacement of gas and water supply pipelines with pipe bursting; Requirements, quality assurance and inspections / not available in English at present). (Table: Allowable tensile forces for PE 100 pipes under a 30 min load) |
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The rupture strength of HDPE pipes is 2.5 times the allowable tensile strength [DVGWGW323]. The cross sectional area of a pipe section used as overload protection may only amount to 40 % of the cross sectional area of the new pipe being pulled in. (Image: Overload protection in form of a predetermined breaking point by reduction of the wall thickness) (Table: Example calculation of an overload protection for HDPE 100 used in pipe bursting) |
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Illustrated example of the steps involved in the manufacturing of the overload protection in the form of a predetermined breaking point. (Image: Step 1: New pipeline) (Image: Step 2: Wall thickness reduction) (Image: Step 3: Welding on of the overload protection) (Image: Step 4: Removing the weld seam) |
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A cross section reduction is obtained by reducing the effective circumference of the pipe or the effective cross-sectional area. (Image: Overload protection in form of a predetermined breaking point by reduction of the effective pipe circumference) (Table: Overload protection) |
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Congratulations! You have successfully finished this module. Next you will have the opportunity to review the newly acquired knowledge with an interactive questionnaire. You can navigate back to any point in the lessons if you wish to review a specific point or subject. Stay curious! |
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Nov 03, 2016 This module is devoted to the pipe bursting as a special method of the replacement of pipelines. In addition, the module looks at the material and equipment requirements and the effects that pipe bursting has on the pipeline itself as well as its surrounding environment. Upon the successful completion of this module, you will be able to:
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This lecture deals with the theoretical background of the topic of welding of polyethylene pipes, as well as the practical steps and limiting conditions that have to be considered. The aim is to outline the requirements that must be met for quality assurance and the consequences of non-compliance. |
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Nov 04, 2016
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Nov 04, 2016 The image below presents the classification of plastic materials into groups and sub-groups, based on similar characteristics. (Image: Classification of plastics according to [Jürge05] [Image: S&P GmbH]) |
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Nov 04, 2016 Plastics can be grouped into three main categories, based on their arrangement of the chain molecules and their properties. These groups and their schematic view are presented in the image below. (Image: Schematic view of the arrangement of the chain molecules in plastics and their properties according to [Bos00] [Image: S&P GmbH]) |
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Nov 04, 2016 A schematic view of the structure of plastics van be visualized in the image below. (Image: Schematic view of the structure of plastics according to [Bos00] [Image: S&P GmbH]) |
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Nov 04, 2016
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Nov 04, 2016 The table below presents a general overview of the chemical resistance of various plastic materials. (Table: General chemical resistance of plastics according to [Bos00]) |
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Nov 04, 2016 The main plastics for pipe production are listed as follows:
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Polyethylene belongs to the thermoplastics, i.e. to the plastics that superficially fuse (plasticise) when heated and solidify when cooled. Structure of polyethylene Polyethylene (PE) consists of long chains (macromolecules) whose basic components (monomers) contain ethylene, which is extracted of mineral oil or natural gas. These chains are produced by so-called polymerisation. Polymerisation is a chemical reaction process in which molecules give up … |
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The below image differentiates between low and high pressure polyethylene. (Image: PE modification [Grondo95]) |
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This table presents the various properties of polyethylene, as well as advantages and limits of the different types of polyethylene.
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The quality of welded joints depends on the qualification of the welders, on the machines and devices used, as well as on the compliance with welding regulations. The welding seam can be examined by non-destructive and/or destructive testing. |
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