The thermal expansion coefficient of PPR pure plastic pipe is relatively high, which means that when the temperature changes, the pipe will expand and contract significantly. This characteristic puts forward detailed requirements for the expansion and contraction treatment during pipe installation to avoid damage to the pipe or loose connection due to improper expansion and contraction.
In the path planning stage before laying the pipe, it is necessary to fully consider the influence of thermal expansion and contraction. During installation, it is necessary to avoid fixing the pipe in a completely rigid structure and reserve a certain amount of expansion and contraction space for the pipe. For example, when grooving the wall or the ground, the length of the groove should be slightly longer than the pipe itself, so that the pipe has enough room for expansion and contraction when the temperature changes, and will not produce excessive internal stress due to limited space. At the same time, the direction of the pipe should try to avoid sharp bends or right-angle turns to reduce the resistance during expansion and contraction, make the expansion and contraction process smoother, and reduce the risk of cracking of the pipe due to excessive force on the bending part.
The fixing method of the pipe needs to be specially designed according to the thermal expansion coefficient. The fixing bracket cannot completely lock the pipe, but uses a fixing with a certain elasticity to allow the pipe to move slightly in the axial direction. When laying a long pipeline in a straight line, the spacing of the fixed brackets needs to be arranged reasonably to ensure that the pipeline will not sag due to its own weight and to allow enough expansion space in the middle section. For the fixation near key parts such as valves and joints, it needs to be more stable to prevent these connection points from loosening due to force during expansion and contraction. Through differentiated treatment of the fixing method, the stability and expansion requirements of the pipeline can be balanced.
The installation of expansion compensation devices is an important measure to deal with thermal expansion and contraction. In long straight pipe sections or areas with large temperature differences, special expansion joints or compensators need to be installed. These devices have movable structures inside that can extend or shorten accordingly when the pipeline expands and contracts to absorb the expansion and contraction of the pipeline. For example, when the pipeline expands due to rising temperature, the expansion joint will expand accordingly to accommodate the additional length; when the temperature drops and the pipeline contracts, the expansion joint will contract to prevent the pipeline from breaking due to excessive stretching. The installation location of this device needs to be determined according to the length of the pipeline and the ambient temperature difference to ensure that the effects of expansion and contraction can be effectively offset.
The treatment of the pipeline connection parts is also critical to the expansion and contraction treatment. PPR pure plastic pipe is often connected by hot melt. This connection method can ensure the sealing of the interface, but when it is expanded and contracted, the interface is prone to become a stress concentration point. Therefore, it is necessary to ensure the firmness of the hot melt interface during connection, and avoid additional tension or pressure on the interface. For the connection at the bend of the pipeline, an elbow with an arc should be used to allow the stress caused by expansion and contraction to be partially released through the deformation of the elbow, reduce the force at the interface, and prevent leakage due to long-term stress.
Flexible connection methods are required for the connection parts with other pipelines or equipment. When PPR pure plastic pipe is connected to rigid equipment such as metal pipes and water pumps, direct rigid connection will limit the expansion and contraction of the pipeline, resulting in stress concentration at the connection point. At this time, flexible joints or corrugated pipes should be used. These parts can bend or expand within a certain range, buffer the displacement of PPR pipes caused by thermal expansion and contraction, avoid damage to the connection point due to excessive force, and ensure the sealing of the connection to prevent water leakage.
In the part where the pipeline passes through the wall or floor, expansion and contraction treatment should not be ignored. Pipes that pass through walls or floors need to be installed with sleeves, with a gap between the sleeve and the pipe, and the gap is filled with flexible sealing materials. This design not only ensures that the expansion and contraction of the pipe is not hindered by the wall or floor, but also prevents leakage or moisture from appearing due to gaps during expansion and contraction through sealing materials. The length of the sleeve should be slightly longer than the thickness of the wall or floor, so that the pipe has enough expansion and contraction space at the crossing point to avoid affecting the overall expansion and contraction due to the constraints at the crossing point.
Testing and adjustment after installation are also important links to meet the expansion and contraction processing requirements. Before the pipeline is put into use, a temperature change simulation test is required. By artificially changing the ambient temperature, the expansion and contraction of the pipeline and the stress state of each part are observed, and the fixed bracket and expansion and contraction device are checked to see if they can work properly. If a part is found to be abnormally deformed or overstressed during expansion and contraction, the fixing method needs to be adjusted in time or a compensation device needs to be added to ensure that in actual use, the pipeline can be safely expanded and contracted under various temperature conditions and will not fail due to the influence of the thermal expansion coefficient.
