1. Selection basis
The correct choice of hydraulic hose relates to whether the entire hydraulic system can work properly and the cost of purchasing the company. The selection of hydraulic hose should be taken into consideration from factors such as its size, pressure, bending radius, temperature adaptation range, working medium, and moving space.
(1) Hose size
If the internal diameter of the hydraulic hose is too small, the flow rate of the medium in the tube will increase, which will cause the system to generate more heat and reduce the efficiency. It will also cause excessive pressure drop and affect the performance of the entire system. An excessive internal diameter will increase the purchase cost and affect the normal operation of the system. When the hose is fixed with a pipe clamp or the hose is passed through the steel plate, pay attention to the outer diameter size of the hose. Using the hose flow, internal diameter and flow rate diagrams, the appropriate hose diameter can be quickly selected as shown in the figure. For example: the flow rate of the hydraulic system is 75 L/min, the recommended flow rate of the pipeline is 6 m/s, and the two coordinate values are connected into one straight line, and the intersection point with the pipeline inner diameter column is 15.9 mm, which is the required internal diameter of the hose. .
(2) hose pressure
The more pressure resistant hydraulic hose, the higher the price. The maximum working pressure of the hose must be determined based on the pressure of the system. When selecting, it is necessary to consider not only ensuring the normal operation of the system, but also saving procurement costs. Due to the impact load in the hydraulic system, the maximum working pressure of the hose is generally greater than the maximum working pressure of the hydraulic system, and the burst pressure of the hose is generally 3 to 4 times the maximum working pressure.
(3) Temperature adaptation range
Hydraulic hose working environment temperature is too high or too low, it will affect the life and pressure capacity of the hose, so no matter how the working status of the hose changes, the ambient temperature must not exceed the temperature limit of the hose. Temperature lower or higher than the recommended temperature limit of the hose may reduce the performance of the hose, causing damage to the hose and causing the hose to leak. Therefore, when the hoses are arranged near the heat source, proper insulation measures must be taken.
(4) Working medium
According to the condition of the hydraulic medium, choose the suitable hose. The working medium of construction machinery is hydraulic oil. When hoses are selected, hoses compatible with the hydraulic oil used should be selected.
(5) Bend radius
When choosing a high-pressure hose, you should pay attention to the bending radius of the high-pressure hose. When calculating the bending radius, the buckle length of the front joint should be subtracted. If the bending radius of the hose used is less than the bend radius of the hose, the pressure bearing capacity and service life of the hose will be reduced. When the allowable pressure and the inner diameter of the hose are the same, the hose with the smaller bending radius should be preferentially selected so that the structural layer is not damaged.
(6) Activity space
The construction machinery has many hoses, and its space for activities is limited. When it is used, it is often in contact with or rubbing against hard objects. Therefore, a sheath must be installed outside the hose as appropriate.
After selecting the hose, you must also select the appropriate fitting. Pipe ends or fittings are usually determined by the interface of the equipment they are connected to, so consider whether there is a suitable fitting. For high-pressure pipelines, permanent pressure-type pipe fittings should be used.

2. Installation precautions
It is very important to install the hose correctly. If the hose is too long, it will not only affect the appearance, but also increase the cost; if the hose is too short, there is not enough room for expansion, and it is easily damaged during the use of construction machinery. When arranging the hoses, avoid the hoses from being damaged due to friction due to stretching, compression, twisting or sharp corners, so as to ensure the safety and service life. Before installation, the hose must be carefully inspected. The inspection items include the size, type, length, and cleanliness of the hose assembly, as well as any defects such as clogging, blistering, and delamination.
(1) Do not distort
When installing the hose, do not twist it, otherwise it will damage the hose or loosen the joint when the pressure is too high. If there is some distortion of the hose can not be avoided, the twist angle should not exceed 5 °.
(2) The length should have a margin
Pressure will lead to changes in the length of the hose, the change range up to -4% ~ +2%. In addition, many of the construction machinery hoses are moving with the machinery, so there should be a margin in the installation, otherwise long-term use will cause leakage at the joints, and even loose the joints. The hose should also leave enough free length. General free length L ≥ 1.5 D (D is the hose outer diameter).
(3) The bending radius should be sufficient
The hose should have enough bending radius. A sufficiently large bending radius (ie, a suitable length) can prevent hose damage and throttling; too small a bend radius can severely reduce the life of the hose and cause excessive pressure loss and reduce work efficiency. The bending radius generally takes R ≥ (8 ~ 10) D (D is the outer diameter of the hose).
(4) Select the right elbow and accessories
When the hydraulic piping of the construction machinery is more complex, suitable bends and accessories should be selected. This can reduce the amount of hose, and can reduce the curvature and distortion of the hose to avoid additional stress on the hose.
The correct use of the pipe clamps can ensure the stability of the pipeline arrangement, avoid damage to the surface of the hose and equipment due to contact, and can make the arrangement of the hose more beautiful, neat and reasonable.