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Hydraulic pipeline installation is a major task in the installation of hydraulic equipment. The quality of pipeline installation is one of the key factors determining whether the hydraulic system operates properly. 1. Both in pipe layout design and piping, it is necessary to first consider comprehensively the components to be connected, hydraulic elements, pipe fittings, and flanges based on the hydraulic schematic diagram. 2. The layout and direction of the pipes should be neat and orderly, with clear layers. Try to use horizontal or vertical piping; the misalignment of horizontal pipes should be ≤2/1000 ； The out-of-plumbness of vertical pipes shall be ≤ 2/400. Check with a level. 3. There should be a gap of more than 10 mm between parallel or intersecting piping systems. 4. The piping layout must facilitate the installation, removal, and maintenance of pipes, hydraulic valves, and other components. Any section of pipe or component in the system should be able to be removed and installed freely as much as possible without affecting other components. 5. When installing pipes, it is necessary to ensure that they have a certain degree of stiffness and vibration resistance. Pipeline supports and clamps should be properly installed. Bent pipes should be fitted with brackets or pipe clamps near the bend point. Pipes must not be welded directly to brackets or pipe clamps. 6. The weight of the pipeline should not be borne by valves, pumps, and other hydraulic components and accessories ； Pipes should also not bear the weight of heavy components. 7. For longer pipes, effective measures must be considered to prevent stress caused by the expansion and contraction of the pipes due to temperature changes. 8. The material used for pipes must have clear original documentation; pipes of unknown material are not permitted to be used. 9. Tubing with a diameter of 50 mm or less in hydraulic systems can be cut using a grinder. Tubes with a diameter of 50 mm or more should generally be cut using mechanical processing methods. If gas cutting is used, the areas affected by the structural changes resulting from gas cutting must be removed by machining, and the welding groove can also be machined at the same time. Except for the return oil pipe, pressure pipes must not be cut using a roller-type cutting tool. The cut surface of the pipe must be smooth, with burrs, scale, slag, and the like removed. The surface of the cut should be perpendicular to the axis of the tube. 10. When a pipeline is composed of multiple pipe segments and associated components, the pipes should be connected segment by segment in sequence; after one segment is connected and assembled, the next segment is then attached, in order to avoid cumulative errors that could occur if all connections were made at once. 11. To reduce local pressure losses, sections of the pipeline should avoid sudden local expansions or contractions in cross-section as well as sharp bends. 12. The pipe connected to the pipe fitting or flange must be a straight section; that is, the axis of this pipe should be parallel to and coincide with the axis of the pipe fitting or flange. The length of this straight segment must be greater than or equal to 2 times the pipe diameter. 13. Tubes with an outer diameter of less than 30 mm can be bent using the cold bending method. When the outer diameter of the tube is between 30 and 50 mm, cold bending or hot bending methods can be used. When the outer diameter of the pipe is greater than 50 mm, the hot bending method is generally used. 14. Welders working on welding hydraulic pipelines must hold a valid certification for welding high-pressure pipelines. 15. Selection of welding process: Acetylene welding is mainly used for pipes with a general carbon steel wall thickness of 2 mm or less. Arc welding is mainly used for pipes with a carbon steel wall thickness of more than 2 mm. Tube welding is best done using TIG welding. For pipes with a wall thickness greater than 5 mm, TIG welding should be used for the root pass, followed by MIG welding for the fill pass. Welding should be carried out by filling the pipe holes with a protective gas when necessary. 16. Welding rods and fluxes must be compatible with the pipes to be welded; their grades must be supported by proper documentation, they must come with product certificates, and they must be within their valid usage period. Welding rods and fluxes should be dried in accordance with the instructions provided in their product manuals before use, and kept dry during use, to be used on the same day. The flux coating of the welding rod should have no peeling or significant cracks. 17. Butt welding should be used for all hydraulic pipeline welds. Before welding, the surface contaminants, oil stains, moisture, and rust spots within a width of 10–20 mm around the groove must be thoroughly removed. 18. Butt welding should be used for the welding of pipes and flanges; plug flanges shall not be used. 19. Welding of pipes and pipe fittings shall be carried out by butt welding; plug welding shall not be used. 20. Welding of pipes together should be carried out using butt welding; plug welding is not permitted. 21. When butt welding is used for hydraulic pipes, the inner wall of the weld must be 0.3–0.5 mm higher than the pipe surface. There should be no indentation on the inner wall. After welding, use a file or a hand-held grinder to smooth out any protruding welds on the inner wall. Remove slag and burrs to achieve a smooth surface. 22. The cross-section of the butt weld seam shall be perpendicular to the pipe’s centerline. 23. The weld cross-section shall not be located at corners, nor should it be placed between two bends in the pipe. 24. When welding piping, it is necessary to first spot-weld it in place according to the installation location, then remove it for welding, and finally reassemble and shape it after welding. 25. Throughout the welding process, protection from wind, rain, and snow should be ensured. After pipeline welding, for welds with a wall thickness of 5 mm or less, they should be allowed to cool naturally at room temperature; forced cooling using strong winds or water spraying is not permitted. 26. The welds should be fully penetrated, and the surface should be even and smooth. The welds of pressure pipelines shall be inspected by sampling for flaw detection. 27. After the piping is welded, all pipes should be pre-installed according to their locations. Connect the various hydraulic components, valve blocks, valve frames, and pump stations together. All interfaces should fit together naturally and be aligned; forced connections are not allowed. When loosening the pipe joint or flange screws, there must be no significant misalignment, gaps, or tilting relative to the center line of the mating surfaces. If this occurs, it can be corrected by heating and reshaping. 28. The pipe clamps can be welded firmly to the frame after all piping is completed, or they can be installed as required. 29. After piping, welding, and pre-installation, the pipeline is disassembled again for pickling and phosphating treatment. After acid washing and phosphating, hot air is blown into the pipes for rapid drying. After drying, if it is reinstalled in the system within a few days and hydraulic oil is filled into the pipes, rust prevention treatment is generally not necessary, but it should be stored properly. If long-term storage is required and anti-rust coating is needed, it must be applied 48 hours after phosphating. It should be noted that the anti-rust coating must be compatible with the cleaning solution used during subsequent pipeline cleaning or the hydraulic oil employed. 30. Before the pipes are reinstalled after acid washing, phosphating, and drying, each pipe’s inner wall must first be pre-cleaned. After pre-cleaning is completed, the system should be reassembled as soon as possible to undergo a full-cycle purification process, until the cleanliness level required by the system’s design is achieved. 31. Hoses should be used only in the following situations: – Between movable components of equipment; – In areas where it is easy to replace parts; – To prevent the transmission of mechanical vibrations or noise. 32. When installing hoses, care must be taken to avoid subjecting them and their connectors to additional stresses, twisting, sharp bends, friction, or other harmful conditions. 33. Before installing the hose in the system, its interior cavity and connectors should also be cleaned thoroughly.