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原文传递 Have you noticed lower trial weld strengths in polyethylene seams?

题名：	Have you noticed lower trial weld strengths in polyethylene seams?
正文语种：	eng
作者：	George R. Koerner
作者单位：	Geosynthetic Institute in Folsom Pa
摘要：	Polyethylene (PE) seaming techniques are used in the field to fabricate rolls of geo-membranes into liner systems. There are two predominant methods used: hot wedge "fusion" welding and "extrusion" seaming. Over the past year, installers have noticed lower trial weld strength than in years past. This makes for much discussion on the jobsite between certified quality auditor (CQA) personnel and installers. No one wants to be below the GRI-GM19 specification for seam strength at the start of a job. This article presents one rational for lower peel and shear strength as a result of reduced thickness of a welding edge. Specification thinning in the area to be bonded can compromise seam strength. Obviously, this needs to be checked and reconciled prior to job commencement. The hot wedge method of seaming PE consists of a hot electrically heated element in the shape of a wedge that is passed between the two sheets to be bonded. Contacting the two heated surfaces together causes a fusion of fresh material to create a weld. Immediately following the melting, roller pressure brings the molten surfaces together to form a homogeneous fused bond. Single hot wedge and dual hot wedge systems are both available. The dual hot wedge weld forms a continuous air channel between two welds. The air channel can be used as a means of testing the bond continuity when air pressure is injected into it. Fusion welding parameters include speed rate, temperature and roller pressure. Most modern welders can continuously control, monitor and record these parameters. Adjustments are made according to environmental conditions such as ambient temperatures and relative humidity.
出版年：	2023
期刊名称：	Geosynthetics
卷：	41
期：	5
页码：	40-41