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What is the consequence of inadequate joining pressure?
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What are some of the main causes of failure of the welding process? Sources of failure:
Thus, there must be a certain layer thickness of the residual cast after the welding procedure. It is assumed that the best strength values of the welding seam can be achieved with a melt displacement … |
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The image below presents the major causes of failure and their consequences if the required welding times are not followed. (Image: Influence of the welding times – sources of failure and consequences) |
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Nov 04, 2016 Below are shown the main factors that influence the welding quality:
(Image: Factors of influence on the welding quality) |
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Nov 04, 2016
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Nov 04, 2016
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Nov 04, 2016
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Nov 04, 2016
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Nov 04, 2016 The following preliminary tasks should be accomplished prior to starting the heating element butt welding process:
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Nov 04, 2016
(Image: Heating element butt welding device) (Image: Welding of the HD-PE long pipes into continuous pipes) (Image: Welding of the HD-PE long pipes into continuous pipes) |
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Nov 04, 2016 The joining areas are pressed against the heating element as long as the complete areas lie flat (coplanar) against the heating element. The alignment process is finished when the heights of beads have reached stipulated values along the whole perimeter or the whole top of the panel, respectively. The bead heights are indications that the joining areas lie evenly against the heating element. The adjusting pressure is maintained during the whole procedure. |
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Nov 04, 2016 In order to get heated, the joining areas have to lie flat against the heating element under low pressure. For this purpose, the pressure is reduced to almost zero (≤ 0.02 N/mm2). During the heating process, the heat enters into the areas to be welded. As a result, the required welding temperature is reached. (Image: Heating element butt welding ? adjusting the joining areas) (Image: Temperature sequence and pressure curve in the adjusting and heating-… |
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Nov 04, 2016 After heating-up, the joining areas are to be removed from the heating element. The heating element is to be taken out without damaging or soiling the heated joining areas. The joining areas are to be brought together quickly until they almost meet. The relocating time is to be kept as short as possible as otherwise the plastified areas cool down. This would have negative effects on the quality of the welding seam. (Image: Heating element butt welding - … |
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Nov 04, 2016 The areas to be welded are supposed to connect with a velocity of near zero. The necessary joining pressure is preferably applied in linear increase and is, for instance, 0.15 ± 0.01 N/mm2 for PE. Sudden use of full pressure would press the hot plastic material out of the welding zone which would result in an inadequate weld factor [Simona11]. The jointing pressure has to be maintained during the cooling-off period. (Image: Heating element butt welding - … |
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Nov 04, 2016 Reference values for the heating element butt welding of PE pipes and fittings are provided by the pipe manufacturers. These values are generally applicable at an external temperature of about 70°F (20 °C). (Table: Guidance values for the heating element butt welding of pipes, pipelines and sheets made of HDPE at an external temperature of about 70 °F (20°C) and moderate air flow) |
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Nov 04, 2016
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Nov 04, 2016 The following list of equipment is necessary for the heating element butt welding process:
(Image: Equipment for heating element butt welding [FI-Huern]) |
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