Hydraulic hose is an important part in concrete pump, excavators, loaders and other construction machinery. It is often not paid great attention by people. However, when the hose seepage, crack, fracture or loose, most people just replace hose but not to analyze what cause the problem. So, the hose will appear same problem again. The loosening or rupture of hydraulic hose not only wastes oil, pollutes the environment, but also affects work efficiency, and even endangers safety of people and machine. The failure of hydraulic hose may be caused by improper use, unreasonable system design and unqualified hose manufacturing. This will be discussed in detail below.
First of all, the characteristics of the hose are analyzed. The hose is divided into rubber hose and plastic hose. Plastic hose is cheap and easy to install, but the bearing capacity is poor and easy to aging, only applicable to the return or drain hose. The rubber hose is divided into high pressure hose and low pressure hose. The high pressure hose is generally composed of four parts: the outer rubber layer, the steel wire strengthening layer, the middle rubber layer and the inner rubber layer. The inner rubber layer is directly in contact with the hydraulic oil and is made of synthetic rubber.
The bearing capacity of the hose depends on the reinforcing layer, which is the skeleton of the hose, usually woven or wound with steel wire. Most of the medium and high pressure steel wire braided skeleton, high pressure, ultra-high pressure steel wire winding skeleton.
The outer rubber layer is generally made of wear-resistant and corrosion-resistant rubber to ensure that the strengthening layer is not subjected to mechanical damage, chemical corrosion and damp rust. The low-pressure rubber hose is made of woven cotton and hemp instead of woven steel wire, which is generally used in low-pressure oil return pipeline.
Hose failure is generally manifested in the following four aspects: the fault of the outer rubber layer, the fault of the inner rubber layer, the fault of the reinforcing layer and the fault of the rupture. Next, I will explain two of these reasons.
- Failure of the outer adhesive layer
(1) Cracks appear on the surface of the hose
The main reason for the external crack of the hose is that the hose is bent in the cold environment.
If it is found that there are cracks on the surface of the hose, it is necessary to observe whether there are cracks in the hose glue and decide whether to replace the hose immediately.
Therefore, do not move the hose or dismantle and repair the hydraulic system at will in the cold environment. If necessary, it should be carried out indoors.
If you need to work in a cold environment for a long time, you should change to a cold hose.
(2) Bubbling on the outer surface of the hose The reason for bubbling on the outer surface of the hose is that the hose is not qualified in production quality, or it is used improperly at work.
If the bubble appears in the middle section of the hose, it is mostly the hose production quality problem, and the qualified hose should be replaced in time.
If bubbles appear at the joint of the hose, it is likely to be caused by improper fitting of the joint.
The hose is often connected to the top of the removable type, withholding type two.
The detachable hose joint is made into a hexagonal shape on the coat and the top core, which is easy to disassemble and install the hose frequently.
Withholding type hose joint is composed of joint jacket and joint core. During assembly, the outer adhesive layer must be peeled off, and then the hose is withheld on special equipment to obtain a certain amount of compression.
(3) The hose did not break but there was a lot of oil leakage. The reason is that the hose was washed and scratched when the high-pressure fluid flow passed through the hose, until the steel wire layer leaked out in a large area, leading to a lot of oil leakage.
This fault generally occurs at the bend of the pipe. The hose should be checked and replaced to ensure that the bending radius of the hose in use meets the technical requirements.
(4) The outer adhesive layer of the hose is seriously deteriorated and the surface is micro-cracked, which is the manifestation of natural aging of the hose.
Due to aging and deterioration, the outer layer is constantly oxidized so that its surface is covered with a layer of ozone, which is thickened with time. As long as the hose is slightly bent in use, it will produce tiny cracks. In this case, replace the hose.
- Failure of inner adhesive layer
(1) the hose inside the adhesive layer is hard, and there are cracks: the main reason is that the rubber products due to the addition of plasticizer, so that the hose is flexible and plastic.
But the hose overheating, will make the plasticizer overflow.
In addition, when the superheated oil passes through the cylinder, valve or other components in the system, if a large pressure drop is generated, the oil will decompose, resulting in the oxidation and hardening of the adhesive layer in the hose.
In this case, you should first check whether the working temperature of the system is normal, the throttle of the valve, the suction channel of the pump is smooth, etc., and replace the hose after excluding all the factors that cause the oil temperature to be too high and make the oil decomposable.
If it is only in the hose below the rupture of the inner glue is hard, and the top is kept good, this is because the hose at the rupture of too flattening, bending too fast or torsion and other phenomena lead to oil heating and accelerated oxidation, causing the inner glue hard.
(2) The hose inner rubber layer is seriously deteriorated and obviously swollen: the hose inner rubber layer is seriously deteriorated. The obvious reason for the swelling is that the hose inner rubber material is incompatible with the hydraulic system oil, and the hose is deteriorated by chemical action.
If this happens, check the oil tank, because it is possible to find broken rubber pieces at the oil return port.
This should check the system oil and hose glue material compatibility and working temperature is in line with the standard.