Hydraulic hose is an important part in concrete pump, excavators, loaders and other construction machinery. It is often not paid great attention by people. There are other two causes of hydraulic hose failure.
- Failures in the reinforcement layer
(1) The hose is broken and the braided steel wire near the break is rusted. And inspected that the outer adhesive layer is stripped. It is found that the braided steel wire near the break is rusted.
This is mainly due to the layer by the action of moisture or corrosive substances, weaken the strength of the hose, resulting in high pressure rupture.
This kind of situation, usually accompanied by the outer adhesive layer fracture, abrasion or serious deterioration of the phenomenon, so that the outer layer lost to strengthen the protective effect of the layer.
In this regard, we must first check and eliminate the mechanical damage, chemical corrosion, high temperature baking and other adverse factors of the external adhesive layer, and then replace the hydraulic hose.
But there are also good external adhesive layer still appears the strengthening layer rust and rupture, and the rupture is usually in the distance from the hose to the top 200mm range, the reason is most of the joint unqualified, moisture into the inner edge of the coat, so that the strengthening layer absorb moisture, resulting in rust caused by the compression strength of the hose is reduced and rupture.
(2) The hose strengthening layer is not rusty, but the strengthening layer appears irregular broken wire.
When the hose is broken and the outer adhesive layer is stripped, and not found in the reinforcing layer, but the irregular broken wire appears in the length direction of the reinforcing layer. The main reason is that the hose is affected by the high-frequency impact force.
There are many intersections between the steel wire and the braided strengthening layer. When the pressure in the pipe changes greatly, these intersections also move with the change of the pipe diameter, and the steel wire frictions with each other.
If the hose is subjected to high frequency impact pressure, frequent friction occurs at the intersection, resulting in wire fracture.
For the hose which is often subjected to high frequency impact, the steel wire winding skeleton should be used as the reinforcing layer.
- The fault manifested at the rupture
(1) One or more of the hoses are broken, the cracks are neat, and the other parts are kept in good condition.
The main reason for this phenomenon is that the system pressure is too high, which exceeds the pressure capacity of the hose.
If the system pressure meets the requirements, the actual pressure resistance capacity of the hose used should be checked to see if it meets the design requirements.
(2) Torsion occurs at the rupture of the hose. The reason for this phenomenon is that the hose is excessively twisted during installation or use.
After the torsion of the hose, the structure of the strengthening layer changes, and the gap of the braided steel wire increases, which reduces the compressive strength of the hose, and the hose is easy to break under the action of high pressure.
Therefore, in the process of using or keeping the hose, do not make the hose bear torsion moment. When installing the hose, try to make the axis of the two connecting heads in the motion plane, so as not to twist the hose in motion.
(3) The steel wire at the rupture of the hose is curled, and there is an obvious neck contraction phenomenon near the fracture. The reason for this phenomenon is that the hose is subjected to excessive tensile deformation, and the layers are separated, which reduces the compressive strength.
The hose will shrink or elongate in the direction of length under the action of high pressure, and the general telescopic amount is + 2% ~ 4% of normal.
If the hose is selected too short during installation, it will be subjected to great tensile action during work, and serious failure such as rupture or loosening will occur.
In addition, the hose span is too large, the weight of the hose and the weight of the oil will also give the hose a large tensile force, serious will also occur in the above failure.
Solution: If the installation is too tight, it should be replaced with a lengthened new hydraulic hose. If the span is too large, the middle supporting clip should be added.