Whether the fiber layer at the joint of a PPR tube with fiber needs to be removed during welding depends crucially on the distribution of the fiber layer, the pipe structure, and the sealing principle of the hot-melt connection. The ultimate goal is to ensure that the melted PPR material is fully integrated, preventing the fiber layer from becoming a "barrier" at the joint surface and affecting sealing. The inherent sealing reliability of PPR hot-melt connections relies on the integrated bond formed by the PPR base material of the pipe and fitting after melting at high temperatures. Only when the PPR molecules on both contact surfaces fully penetrate and tightly bond after cooling can a seamless seal be formed. The presence of a fiber layer (commonly a reinforcement layer such as glass fiber or polyester fiber) disrupts this "pure PPR melt fusion" condition. Therefore, in most cases, the fiber layer at the joint requires treatment.
The fiber layer of a PPR tube with fiber typically serves as an intermediate reinforcement layer, sandwiched between the inner and outer PPR base layers. Its function is to enhance the pipe's impact resistance, creep resistance, and overall strength, rather than participating in the hot-melt connection. During hot-melt welding, if the fiber layer at the joint is untreated, the fibers themselves will not melt along with the PPR base material during heating. Instead, they will become trapped between the pipe and fitting, acting as "foreign matter." The molten PPR cannot form a continuous fusion layer on both sides of the fiber layer. After cooling, tiny gaps will form between the fiber and PPR. These gaps, under the influence of water pressure, can easily become a leak hazard. Especially in environments with long-term alternating hot and cold weather, the difference in thermal expansion coefficients between the fiber and PPR will further widen the gap, leading to a continuous deterioration in sealing performance.
However, not all PPR tube and fiber joint treatment methods are identical; the specific structure of the pipe must be considered. Some manufacturers optimize pipe designs for welding requirements. For example, they reserve a certain length of "fiber-free zone" at the pipe end—remaining pure PPR at the end, with the fiber layer set back a certain distance from the end. This design eliminates the need to remove the fiber layer during welding and allows for the standard hot-melt welding process for PPR pipes, as the weld surface remains a fusion of pure PPR base material. However, this type of pipe is a specialized design and not a standard industry standard. Therefore, before installation, it is crucial to check the product manual to confirm whether the pipe has this provision to avoid misjudging and skipping any necessary steps.
For PPR pipe with fiber that does not have a fiber-free area, the fiber layer at the joint must be removed using specialized tools before welding. A common method is to use a scraper or specialized circular cutting tool to gently scrape away the surface material along the circumference of the pipe joint until the pure PPR base material is exposed. Care must be taken to control the scraping depth, ensuring that the fiber layer is completely removed without excessive scraping, which would significantly reduce the pipe wall thickness. Excessive wall thinning reduces the pipe's pressure-bearing capacity and poses a structural safety hazard. After scraping, use a clean rag to clean any debris from the joint to prevent impurities from adhering to the molten surface and further compromising the sealing effect.
It's important to note that if the fiber layer is only present in the middle layer of the pipe and the weld depth doesn't reach it, theoretically no treatment is necessary. However, in practice, precise control of weld depth is difficult, especially for novice operators, who can easily expose the weld surface to the fiber layer. Therefore, to avoid risks, even if the fiber layer appears to be unexposed, it is recommended to perform a light treatment on the joint to ensure the purity of the PPR substrate in the weld area. Furthermore, the treated joint should be heat-fused as soon as possible to avoid prolonged exposure to dust and oil, which can impair the fusion bond quality.
Whether to remove the fiber layer at the joint when welding PPR tube with fiber depends on ensuring that the heat-fused joint is fully integrated with the pure PPR material. In most cases, the fiber layer will hinder the melt penetration of the PPR molecules, so it is necessary to use a tool to remove the fiber layer at the joint. If the pipe has a special pre-removed design, this step can be omitted, but the product specifications should be consulted for details. In all cases, the core goal is to eliminate the impact of the fiber layer on sealing performance, ensuring reliable sealing and long-term stability of the welded pipe system.
