Abstract: With the continuous development of hydraulic technology, how to correctly select, process and install hydraulic steel Pipes to ensure the energy-efficient, reliable and long-life operation of the hydraulic system has become an important issue for hydraulic system designers. This article discusses in detail the selection, processing and installation of hydraulic steel pipes.

With the progress of hydraulic technology, the correct selection, processing and arrangement of hydraulic steel pipes to make the hydraulic system more energy-efficient, reliable and have a longer service life has become the focus of hydraulic system designers. This article aims to explore the related issues of the selection, processing and installation of hydraulic steel pipes.

II. Pipe Selection:

The selection of pipes should be based on factors such as system pressure, flow rate and application scenarios. The steel pipes selected should have sufficient strength, and the diameter and wall thickness should meet the system requirements. At the same time, the inner wall of the steel pipe should be smooth, without rust, oxide scale and clad layer. In medium and high pressure systems, seamless steel pipes are widely used due to their high strength, low price and easy realization of leak-free connection. For ordinary hydraulic systems, cold-rolled low-carbon steel pipes No. 10, 15 and 20 are usually used. In hydraulic servo systems, stainless steel pipes are often selected, which have the advantages of corrosion resistance, smooth inner and outer surfaces, and accurate dimensions, but the price is relatively high.

III. Pipe Processing:

Pipe processing includes pipe cutting, bending and welding. Pipe cutting can be done with a grinding wheel cutter, and for pipes with diameters greater than 50mm, mechanical methods such as special machine tools are preferred. It is strictly forbidden to use manual arc welding, oxygen cutting and other methods.无条件 cases allow the use of manual saw cutting. After cutting, the end face of the pipe should be as perpendicular as possible to the axial centerline of the pipe, and the cut surface of the pipe should be smooth to remove burrs, oxide scale and slag.
The bending of the pipe should be carried out on a mechanical or hydraulic bending machine. In general, pipes with a diameter of 38mm and below are bent in a cold state using a bending machine, which can avoid the production of oxide scale and affect the quality of the pipe. When bending, attention should be paid to the bending radius. Too small a bending radius can cause stress concentration in the pipeline and reduce the strength of the pipeline. The bending angle deviation should not exceed ±1.5mm/m.

Pipe welding generally consists of three steps
  • Before welding, the ends of the pipes must be grooved. The angle of the groove should be carried out according to the type of welding that is beneficial to welding in national standards. Too small a groove can lead to poor welding penetration and reduce the welding strength; too large a groove can easily cause cracks, slag inclusion and uneven welds.
  • The choice of welding method is the key to the construction quality of the pipeline and must be highly valued. At present, manual arc welding and argon arc welding are widely used, among which argon arc welding is suitable for welding of hydraulic pipelines. It has the advantages of good weld quality, smooth weld surface, beautiful appearance, no welding slag, no oxidation of the weld and high welding efficiency. When the construction period is tight and there are few argon arc welders, it is possible to consider using argon arc welding for the first layer (backing), and then electric welding for the second layer to ensure quality and improve construction efficiency.
  • After the welding of the pipeline, the quality of the weld should be checked. Inspection items include the presence of cracks, inclusions, pores and excessive咬肉, and spatter around the weld; whether the weld is straight, whether there is misalignment; whether there are protrusions on the inner and outer surfaces, and whether there are damage or weakening of the pipe wall strength on the outer surface during the processing.
  • IV. Pipe Installation:

    The installation of hydraulic pipelines is usually carried out after the connection equipment and hydraulic components are installed. Before laying the pipeline, the piping plan should be studied carefully to clarify the arrangement sequence, spacing and direction of each pipeline, and to determine the positions of valves, joints, flanges and pipe clamps.
    Installation of pipe clamps: The spacers of the pipe clamps are generally directly or through angle steel brackets welded to the structural components, or expansion bolts are used to fix on concrete walls or wall brackets. The distance between pipe clamps should be appropriate, too small will cause waste, too large will cause vibration.

    Pipe laying: The laying of pipelines should follow the following principles:

    1. The pipes should be arranged as horizontally or vertically as possible, paying attention to being neat and consistent, avoiding pipeline intersections.
    2. The distance between the pipe walls of two parallel or intersecting pipes must be maintained to a certain extent.
    3. Large diameter pipes or pipes near the piping bracket should be given priority.
    4. The pipes connected to pipe fittings or flanges must be straight pipes, and the axis of the straight pipe should coincide with the axis of the pipe fitting or flange, and the length should be greater than or equal to 2 times the diameter.
    5. The distance between the outer wall of the pipe and the adjacent pipe, and the edge of the fitting should not be less than 10mm; the flanges or hose connections of adjacent pipes on the same row should be staggered by more than 100mm; the joints of pipelines should be more than 0.8m away from the wall.
    6. When laying a group of pipelines, a 90° or 45° bend is generally used at the corner.
    7. The entire pipeline should be as short as possible, with fewer bends and smooth transitions to reduce up and down bends and ensure that the pipeline has appropriate thermal expansion and contraction space. At the same time, the length of the pipeline should allow free removal and installation of fittings and accessories without affecting other pipelines.
    8. The position or installation of piping and fittings should facilitate the connection and maintenance of pipes, and piping should not be directly welded to supports.
    9. Before piping installation, all piping protection should not be removed in advance, otherwise it will contaminate the piping.


    The hydraulic system is composed of various hydraulic components connected through pipelines, pipe fittings and Oil passages blocks. In the transformation of hydraulic equipment, the selection, processing and installation of hydraulic steel pipes are very important links. Correctly mastering these methods will help to stabilize the operation of the hydraulic system.

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