How to choose, process, and install hydraulic tubes properly, in order to make the hydraulic line system work more energy-efficient, reliable, and have a longer life? This has become an important issue for hydraulic technologies. As one of the leading China hydraulic tube manufacturer and supplier, our company Younglee Metal specializes in manufacturing stainless steel hydraulic tubing and carbon steel hydraulic tubing for many years, and has many years experience of hydraulic tube related technology and research, we solved the hydraulic tube related technical issues for many customers, and provided production and technical services to them.

This article will briefly describe the hydraulic pipe selection, processing, installation, etc., with hope to help the customers in the hydraulic system industry who are in need.

Choose the right material and size of hydraulic tubes

The hydraulic tubes should be selected according to the system pressure, flow and application environment. Must pay attention to the strength of the tubing whether is enough, whether the pipe diameter and the wall thickness meet the system requirements, and the inner wall of the selected steel pipe must be smooth, non-corrosive, non-oxidized skin, no clips and other defects. If any of the following problems is found on the hydraulic tube, it cannot be used:

1. the inner and outer walls of the hydraulic pipe have been heavily rusted;
2. the scratch depth of the pipe body is more than 10% of the wall thickness;
3. the surface of the pipe body is recessed to more than 20% of the pipe diameter;
4. the wall thickness of the pipe section is uneven and the ellipticity is obvious.

In applications of medium and high pressure hydraulic systems, the seamless steel tubes are generally used, because they have the advantages as high strength, low price, and easy leak-free connection, it is widely used in hydraulic systems.

Ordinary hydraulic systems often use cold drawn low carbon steel tubes, because carbon steel hydraulic tubing can be reliably welded to various standard pipe fittings. And for applications where there is corrosion resistance is required, such as Hydraulic servo system, often use ordinary stainless steel seamless pipe, stainless hydraulic tubes are with corrosion resistance, smooth inner and outer surfaces, accurate size.

Regarding how to choose the right outside diameter and the wall thickness of the hydraulic tubes, we will talk in another blog article later.

Hydraulic Tubes processing, like Cutting, bending, welding

The processing of pipes mainly includes cutting, bending, welding and so on. The quality of the pipe processing has a great influence on the parameters of the pipeline system, and it is related to the reliable operation of the hydraulic system. Therefore, scientific and reasonable processing methods must be used to ensure the quality of processing.

— Cutting of hydraulic tubing

Pipes of hydraulic systems with a diameter of less than 50mm can be cut with a wheel cutter. Pipes with a diameter of more than 50mm can be mechanically cut, such as special cutting machine tools. Manual welding and oxygen cutting methods are strictly prohibited. After cutting, the end face of the pipe and the axial centerline should be kept as perpendicular as possible. The cutting surface of the pipe must be flat. The pipe must be free from burrs, oxide scales, and slag.

— bending of hydraulic tubes

The bending of the pipe is preferably carried out on a mechanical or hydraulic pipe bender. General 38mm and below pipelines are cold-formed and bended in a cold state with a bender to avoid oxide scale and affect tube quality. The bends are not allowed to be bent during the production of the bends, and can be replaced by stamping elbows and other pipe fittings because deformations, wall thinning, and oxide scales are easily generated during hot bending.

The bending radius of the pipe should be considered. When the bending radius is too small, stress concentration in the pipeline can be caused and the strength of the pipeline can be reduced.The bend radius should not be less than 3 times the pipe diameter. The higher the working pressure of the pipeline, the greater its bending radius should be. The ellipticity after bending pipe production should not exceed 8%, and the bending angle deviation should not exceed ±1.5mm/m.

Some some wonderful hydraulic tube bender on youtubes:

— Welding of hydraulic tubes

Welding of hydraulic pipes is generally carried out in three steps:

Step1: weld bevel processing

Before welding, the hydraulic pipe must be grooved at the end of the pipe. When the weld bevel is too small, it will cause the pipe wall to be incompletely welded, resulting in insufficient welding strength of the pipe. When the groove is too large, it will cause defects such as cracks, slag and weld defects. The bevel angle should be implemented in accordance with the type of national standard that is most conducive to welding. Grooves are best machined by beveling machines. Machining bevels using mechanical cutting methods is economical, efficient, and easy to operate. It also guarantees machining quality and avoids the use of ordinary grinding wheels for cutting and beveling.

Step2:  proper selection of welding methods

The selection of welding methods is the most critical step in the quality of pipeline construction and must be highly valued. At present, manual arc welding and argon arc welding are widely used. Among them, argon arc welding is the most suitable method for hydraulic pipe welding. It has a good weld quality, a smooth and beautiful weld surface, no welding slag, no weld oxidation, and welding efficiency. High advantage. Another welding method can easily cause welding slag to enter the tube, or produce a large amount of oxide scale on the inner wall of the weld, which is difficult to remove. In cases where the construction period is short and the number of TIG welders is small, the first layer (base layer) of argon arc welding may be considered, and the second layer may be started with electric welding. This will not only ensure the quality but also increase the construction efficiency.

Step3: Carefully checking after welding

The quality of the welds must be checked after welding. Items to be inspected include: presence of cracks, inclusions, porosity, excessive biting, splashing, etc;  to check whether the weld bead is neat, misaligned, whether the internal and external surfaces are protruding, and whether the external surface is damaged or weakened during processing.

Installation of steel hydraulic line tubing

The installation of hydraulic pipelines is generally performed after the connected equipment and hydraulic components are installed. Before laying the pipelines, they should be familiar with the piping scheme, clarify the sequence, spacing and orientation of the pipelines, and determine the positions of the valves, joints, flanges, and pipe clamps. Then marking and positioning it. To install the hydraulic pipes and tubes, people usually need to use pipe clamps to fasten the hydraulic pipes and tubes.

— Installation of tube clamps

The bottom plates of the pipe clamps is usually welded to the structural parts directly or through brackets such as angle steel, or fixed on the concrete wall or the side bracket with expansion bolts. The distance between pipe clamps should be appropriate. Too small will cause waste of clamps.  Too large will cause vibration. In the right-angled turn, there should be one pipe clamp on each side. The recommended clamp distance is shown in Table 1.

— principle of steel hydraulic line tubing laying

The general principle of hydraulic tube laying follows:

(1) The hydraulic pipes should be arranged horizontally or vertically as far as possible, pay attention to orderliness and consistency, avoid pipeline crossing, and must maintain a certain distance between two parallel or intersecting pipes;

(2) Large-diameter hydraulic pipes or pipes near the inside of the pipe support should be considered for priority.

(3) The hydraulic pipe connected to the pipe joint or flange must be a straight pipe. The shaft line of this pipe should be coincident with the axial line of the pipe joint or flange, and the length should be greater than or equal to 2 times the diameter;

(4) The distance between the outer edge of the hydraulic pipe and the edge of the pipe between adjacent pipes shall not be less than 10mm, and the flange or joint of the same row of pipes shall be staggered by more than 100mm; the joint position of the pipe passing through the wall shall be more than 0.8m from the wall;

(5) When laying a set of pipelines, 90° and 45° are generally used in the turning;

(6) The entire pipeline is required to be as short as possible, with few turns, smooth transitions, and reduced upward and downward bends to ensure appropriate thermal expansion and contraction of the pipeline. The length of the pipeline should be able to ensure the free disassembly and assembly of joints and accessories without affecting other Pipeline

(7) Pipeline laying position or pipe fitting installation position should be convenient for pipe connection and inspection. Pipeline should be close to the equipment, so as to fix the pipe clamp; the pipe should not be directly welded on the bracket;

(8) During the intermittent installation of the hydraulic pipe, the pipes shall be tightly sealed. When piping systems are installed, no sand, iron oxide skin, iron filings or other contaminants shall enter the pipe; all pipeline protection shall not be cleared in advance before installation. Otherwise it will pollute the pipeline.

Author by Fang Tao, Hydraulic equipment engineer of YOUNGLEE METAL.