Pipe layout design of seamless hydraulic tubes

The installation of seamless hydraulic tubes is a major project in the installation of hydraulic equipment. The quality of pipeline installation is one of the keys to the normal performance of the hydraulic system.

1. When designing and piping, a comprehensive consideration should be given to the components, hydraulic components, pipe joints and flanges to be connected according to the hydraulic schematic diagram.

2. The arrangement and direction of pipeline laying should be neat and consistent, with clear layers. Try to use horizontal or vertical pipe layout, the non-parallelism of horizontal pipes should be ≤2/1000; the non-perpendicularity of vertical pipes should be ≤2/400. Check with a level.

3. There should be a gap of more than 10mm between parallel or intersecting piping systems.

4. The configuration of the pipeline must make it easy to install, disassemble and maintain the pipeline, hydraulic valve and other components. Any section of pipeline or component in the system should be able to be disassembled as much as possible without affecting other components.

5. When matching long hydraulic steel pipes, the pipes must have certain rigidity and anti-vibration ability. Pipe supports and pipe clamps should be properly configured. Bending pipes should be provided with brackets or pipe clamps near the starting point. Pipes shall not be directly welded to brackets or pipe clamps.

6. The weight of the pipeline should not be borne by valves, pumps and other hydraulic components and accessories; nor should the weight of heavier components be supported by the pipeline.

7. For longer pipes, effective measures must be taken to prevent the stress caused by the expansion and contraction of the pipe due to temperature changes.

8. The pipe material used must have a clear original basis material, and pipes with unknown materials are not allowed to be used.

9. Hydraulic system pipes with a diameter below 50mm can be cut with a grinding wheel cutting machine. Pipes with a diameter of more than 50mm should generally be cut by mechanical processing. If gas cutting is used, mechanical processing methods must be used to remove the part of the structure change caused by gas cutting, and at the same time, the welding groove can be turned. Except for the oil return pipe, the pressure pipes are not allowed to be cut with a roller squeeze cutter. The cutting surface of the pipe must be flat, and the burr, scale, slag, etc. should be removed. The cut surface shall be perpendicular to the pipe axis.

10. When a pipeline is composed of multiple pipe sections and supporting parts, it should be connected one by one in sequence. After one section is completed and assembled, the subsequent section should be configured to avoid cumulative errors caused by one-time welding.

11. In order to reduce local pressure loss, each section of the pipeline should avoid local sharp expansion or contraction and sharp bending of the section.

12. The pipe connected to the pipe joint or flange must be a straight pipe, that is, the axis of this pipe should be parallel and coincident with the axis of the pipe joint and flange. The length of this straight line segment must be greater than or equal to 2 times the pipe diameter.

13. Pipes with outer diameter less than 30mm can adopt cold bending method. When the outer diameter of the pipe is 30-50mm, cold bending or hot bending can be used. When the outer diameter of the pipe is greater than 50mm, the hot bending method is generally used.

14. Welders who weld hydraulic pipelines should hold valid high-pressure pipeline welding certificates.

15. Selection of welding process: Acetylene gas welding is mainly used for pipes with a general carbon steel pipe wall thickness less than or equal to 2mm. Arc welding is mainly used for pipes with a carbon steel pipe wall thickness greater than 2mm. The welding of the pipe is preferably argon arc welding. For pipes with a wall thickness greater than 5mm, argon arc welding should be used for priming and arc welding for filling. If necessary, the method of filling the tube hole with protective gas should be used for welding.

16. Welding rods and fluxes should match the pipes to be welded, and their grades must have clear reference materials, product qualification certificates, and be within the effective period of use. Welding rods and fluxes should be dried according to their product instructions before use, kept dry during use, and used on the same day. The electrode coating should be free from shedding and obvious cracks.

17. Butt welding should be used for welding of Changben hydraulic steel pipes. Before welding, the dirt, oil stains, water and rust spots on the surface of the groove and its vicinity with a width of 10-20 mm should be cleaned.

18. Butt welding flanges should be used for the welding of pipes and flanges, and plug-in flanges are not allowed.

19. The welding of pipes and pipe joints should be butt welding instead of plug-in.

20. Butt welding should be used for pipe-to-pipe welding, and plug-in welding is not allowed.

21. When the hydraulic pipeline adopts butt welding, the inner wall of the weld must be 0.3-0.5mm higher than the pipeline. Indentation of the inner wall is not allowed. After welding, use a file or a portable grinding wheel to smooth out the raised weld in the inner wall. Remove welding slag and burrs to achieve a smooth finish.

22. The section of the butt weld should be perpendicular to the center line of the pipe.

23. The weld section is not allowed at the corner, and should also be avoided between the two elbows of the pipeline.

24. When welding the piping, it must be positioned according to the spot welding at the installation position, then dismantled and welded, and then assembled and reshaped after welding.

25. During the whole welding process, wind, rain and snow should be prevented. After the pipe is welded, the weld with a wall thickness less than or equal to 5mm should be cooled naturally at room temperature, and forced cooling by strong wind or water is not allowed.

26. The weld seam should be penetrated and the surface should be even and smooth. Welds of pressure piping shall be sampled for flaw detection.

27. After the pipes are welded, all pipes should be pre-installed once according to their positions. Connect hydraulic components, valve blocks, valve frames and pump stations. Each interface should be naturally attached and centered, and cannot be connected by force. When loosening pipe joints or flange screws, there must be no large misalignment, separation or swaying angle relative to the center line of the joint surface. If this happens, it can be eliminated by fire roasting and shaping. (Guangzhou Changben)

28. After all the piping is completed, the pipe clamp and the frame can be welded firmly, or it can be carried out hand-in-hand as required.

29. After piping, welding, and pre-installation, the pipeline is disassembled again for pickling and phosphating treatment. After pickling and phosphating, hot air is passed into the pipeline for rapid drying. After drying, if it is reassembled into a system within a few days, and the long-ben hydraulic steel pipe oil is passed into the pipe, it is generally not necessary to perform anti-rust treatment, but it should be kept properly. If it needs to be shelved for a long time and anti-rust paint is required, it must be painted after 48 hours of phosphating treatment. It should be noted that the anti-rust coating must be compatible with the cleaning fluid or hydraulic oil used for subsequent pipeline cleaning.

30. The inner wall of each pipe needs to be pre-cleaned once before it is installed again after pickling, phosphating and drying. After the pre-cleaning is completed, it should be reassembled into a system as soon as possible, and the overall cycle purification treatment of the system should be carried out until the cleanliness level required by the system design is reached.

31. The application of the hose is limited to the following occasions:

――― Between moving parts of equipment

―――Easy to replace replacement parts

————Suppressing the transmission of mechanical vibration or noise

32. The installation of the hose must be careful not to cause additional stress, twisting, sharp bending, friction and other adverse working conditions on the hose and joints.

33. Before the hose is loaded into the system, the inner cavity and joints should also be cleaned.