Failure analysis of high pressure hose

1. Failure of the outer rubber layer:

(1) Cracks appear on the surface of the hose

The main reason for the cracks on the surface of the hose is that the hose is bent under cold conditions.

(2) bubbling on the outer surface of the hose

The reason for the bubbling on the outer surface of the hose is that the hose production quality is not qualified, or it is used improperly when working.

(3) The hose is not broken but a lot of oil seepage

A large amount of oil permeated the hose but no rupture was found, the reason is that when the high-pressure liquid flow in the hose, the inner adhesive was eroded and scraped until a large area of the steel wire layer leaked out resulting in a large amount of oil seepage.

(4) The outer rubber layer of the hose is seriously deteriorated, and the surface is slightly cracked, which is the performance of natural aging of the hose. Due to aging deterioration, the outer layer is constantly oxidized so that its surface is covered with a layer of ozone, which is prolonged with time.

When the hose is thickened, as long as it is slightly bent during use, it will produce tiny cracks. In this case, replace the hose.

2. Failure of the inner rubber layer:

(1) The rubber layer inside the hose is hard and cracked: the main reason is that due to the addition of plasticizer in the rubber products, the hose is flexible and plastic. But if the hose overheats, the plasticizer will overflow.

(2) The rubber layer inside the hose is seriously deteriorated and obviously swollen: the rubber layer inside the hose is seriously deteriorated, and the reason for the obvious expansion is that the rubber material inside the hose is incompatible with the oil of the hydraulic system, and the hose is changed by chemical action quality.

3. Failure in the reinforcement layer:

(1) The hose is broken, and the braided steel wire near the break is rusty. The hose is broken, and the outer rubber layer is peeled to check and the braided steel wire near the break is rusty. This is mainly due to the layer being subjected to damp or corrosive substances

It weakens the strength of the hose and leads to rupture under high pressure.

(2) The hose reinforcement layer is not rusted, but the reinforcement layer appears irregular broken wire phenomenon.

The hose was broken, the outer rubber layer was peeled and no rust was found in the reinforcing layer, but irregular broken wires appeared in the direction of the length of the reinforcing layer. The main reason is that the hose was subjected to high-frequency impact force.

4. Failure at the rupture:

(1) The hose is broken at one or more places, the cracks are neat, and other parts are maintained well.

The main reason for this phenomenon is that the system pressure is too high, exceeding the pressure resistance of the hose.

(2) Torsion occurs at the rupture of the hose

The reason for this phenomenon is that the hose is subjected to excessive torsion during installation or use.

5. In summary, through the above analysis, the following matters should be paid attention to when using hydraulic hoses in the future:

(1) The hose layout should be as far as possible to avoid heat sources and away from the performance of the engine exhaust pipe. If necessary, devices such as bushing or protective screen can be used to prevent the hose from deteriorating due to heat.

(2) Where the hose must be connected or where friction may occur with the mechanical surface during work, protective devices such as hose clamps or springs should be applied to avoid damage to the outer layer of the hose.

(3) When the hose must be bent, the bending radius should not be too small, and should be greater than 9 times the outer diameter. The joint of the hose and the joint shall have a straight line section greater than 2 times the outside diameter of the pipe.

(4) The hose installation should avoid being in a tension state, even if there is no relative movement at both ends of the hose, it is necessary to keep the hose loose, the tension hose will expand under pressure, and the strength will drop low.

(5) Do not twist the hose during installation. A slight twist on the hose may reduce its strength and loosen the joint, which should be tightened on the hose when assembling, not on the hose but on the joint.

(6) If the hose is configured on key components, it is recommended to check or replace it regularly.