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Precautions for pipeline installation 1. Installation of compensators For pipelines equipped with compensator devices, the pipeline and its fixing brackets must not be fixedly connected before installing the compensators. L-shaped, Z-shaped, and II-shaped compensators are generally fabricated at the construction site, and high-quality seamless carbon steel pipes must be used for their production. Typically, a Type II compensator should be installed horizontally, with its parallel arms aligned with the slope and direction of the pipeline, while its vertical arm should remain horizontal. When a type II bend is installed with the upward orientation, an exhaust device should be installed at the highest point ； Otherwise, a drain device should be installed at the lowest point, provided that all parts of the entire compensator remain in the same plane. The maximum distance at which compensators can be installed in the straight sections, as well as the bending radius of the compensator elbows, must meet the design requirements. At both ends near the compensator, at least one guide support should be provided on each end. When the ambient temperature during installation is below the compensation zero point (1/2 of the difference between the designed maximum and minimum temperatures), the compensator should be pre-stretched, with the specific amount of stretching specified in the design documents. When installing a bellows compensator or packed compensator, the end with a weld or the end with a spigot on its inner sleeve must be oriented in the direction of the medium flow when installed horizontally ； When installed vertically, it should be placed at the top. When installing the compensator, it should be in line with the slope of the pipeline. Within 50 meters in front of the wave-shaped compensator or the packing-type compensator, the axis of the pipeline must align with the axis of the compensator; there should be no deviation. The exposed length of the core tube of the packed compensator, or the distance between its end and the retaining ring inside the sleeve, should be greater than the deformation amount specified in the design. When using a directly-buried compensator, its fixed section should be securely anchored, while its movable section should be able to deform freely. After the pipeline installation, pressure testing, and insulation are completed, the temporary fixing devices of the compensator should have their fasteners loosened to ensure that it can expand and contract freely during use. 2. Installation of pipe supports (brackets, hangers, pedestals, fixing pedestals, etc.) Apart from buried pipes, the fabrication and installation of pipe supports are the first step in pipe installation. The fixed supports must be installed strictly at the positions specified in the design, and the pipes should be firmly secured to these supports. When the scaffold is installed on precast concrete piers, the strength of the concrete must meet the design requirements ； The sliding surface of the sliding bracket should protrude 4–6 mm above the surface of the pier, and the deviation between the longitudinal center line of the pier and the center line of the pipeline should not exceed 5 mm. The position of the support should be correct, level, and secure, with a slope that complies with the design specifications. The elevation of the support surface for pipe supports can be adjusted by adding metal shims on top of it; however, no more than two layers of metal shims should be used. The shims must be welded to the embedded iron pieces or steel structures. Pipes with different displacement amounts shall not share the same hanger or slide support, unless there are specific design requirements to the contrary. The sliding support plate on the bracket that holds the slide support, the sliding surface of the slide support, and the working surface of the guiding bracket must be flat, smooth, and in good contact; there should be no tilting or sticking. When laying the duct trench, a support (hanging) frame should be installed 0.5 m from the entrance of the trench, and sliding supports must be provided at the entrances on both sides of the thermal chamber. The deviation of the center point of the bracket from the designed position shall comply with the standard specifications. o The hangers and suspension rods for pipes without thermal displacement should be installed perpendicular to the pipe axis ； For pipes with thermal displacement supports or hangers, the center of the hanger rod should be on the side opposite to the direction of pipe displacement, and the amount of displacement should be 1/2 of the value calculated based on design requirements. The installation height of the spring brackets and hangers should be adjusted in accordance with the design requirements, and the temporary fixing devices for the springs should be removed after the pipeline installation, pressure testing, and insulation work are completed. At the joints of directly buried heat pipelines and pipelines that are not allowed to deform under external forces, fixing piers should be installed at the positions and according to the requirements specified in the design, in order to ensure the stability of the pipeline system. When not required by the design, the mass of the fixing pier shall meet the following requirements: the strength grade of concrete fixing piers shall be no lower than C30 ； The diameter of the rebar should not be less than 8 mm, and its spacing should not exceed 250 mm ； Reinforcement bars shall be arranged in two layers, and the cover thickness shall not be less than 30 mm ； Where the pipeline passes through a fixed pier, reinforcement bars should be provided at the edge of the hole. The distance between the end of the sliding support and the circumferential weld of the pipe shall be not less than 0.15 m ； The distance between the end of the fixed bracket angle plate and the circumferential weld of the pipe shall be not less than 0.5 m. 3. Protection measures for pipes and fittings with pre-applied anti-corrosion and insulation layers. For pipes and fittings that have already been pre-coated with anti-corrosion layers and insulated, strict technical measures must be formulated to prevent damage to these layers and insulation prior to lifting and transportation; these measures must then be diligently implemented.