Causes of damage to high pressure hoses

1. Poor manufacturing quality

(1) The inner and outer layers of the high-pressure hose wall are made of oil-resistant rubber, and the middle is (2 to 4 layers) cross braided steel wire or winding steel wire. Poor quality hoses will appear: uneven wall thickness of the hose; too tight or loose steel wire braiding or too few steel wire layers; large deformation (elongation, shortening or bending deformation) of the hose after pressure; outer rubber poor air-tightness leads to steel wire corrosion; poor sealing of the inner layer glue makes high-pressure oil easily enter the steel wire layer; insufficient adhesion between the glue layer and the steel wire layer. The above conditions will reduce the bearing capacity of the hose, and eventually burst at the weak point of the tube wall.

(2) The improper selection of the crimping pressure and crimping speed during the assembly of the hose and the joint, or the unreasonable selection of the structure, material, and size of the joint, can cause the pressure of the hose and the joint to be too tight or too loose, causing early damage to the joint .

When assembling, if the crimping pressure is too small, that is, when the pressure between the joint and the hose is too loose, the hose may come out of the joint at the beginning of use under the action of oil pressure; if the crimping pressure is too large, the joint and the hose will be compressed. Too tight, it is easy to cause partial damage to the inner layer of the hose, causing cracks. The high-pressure oil will directly enter the steel wire layer from the rupture, and then run along the gap between the steel wires to the end of the outer jacket and spray out, or it can be accumulated along the steel wire layer somewhere, make the outer layer of glue bulge or even break.

When assembling the hose and the joint, if the crimping speed is too fast, it will easily cause damage to the inner rubber and breakage of the steel wire layer, which will cause the hose to be damaged prematurely during use.

In addition, unreasonable joint design and poor processing quality will also cause damage to the inner rubber; if the joint material is not properly selected, it is easy to deform during the crimping process, which will affect the crimping quality and shorten the life of the hose.

2. Improper use

Under the premise of quality assurance, improper use will greatly shorten the service life of the hose. In actual work, most of the damage to the high-pressure hose is caused by improper use.

(1) Subject to frequent and severe pressure shocks. The burst of the high-pressure hose is generally not caused by too much static pressure, but is related to the severity and number of pressure shocks. When construction machinery is in operation, the oil pressure in the oil pipe will repeatedly rise or drop, which will cause frequent pressure shocks on the oil pipe, resulting in increased damage to the oil seal of each part, blistering and rupture of the rubber pipe, loosening and leakage of pipe joints. Therefore, during operation, the valve stem should not be pulled too hard and must be gentle.

(2) The use temperature of the oil is too high. When construction machinery is working, the hydraulic system heats up the oil due to power loss, and the influence of outside air temperature (especially in summer) can make the oil temperature rise sharply. The higher the temperature of the oil is, the more easily the rubber will age, the elasticity will deteriorate, the strength and sealing performance will decrease, and the hose will burst quickly. Therefore, during operation, when the hydraulic system temperature rises too high or too fast, the cause should be found out in time and eliminated; during summer operations, especially continuous operations, necessary cooling measures should be taken.

(3) Unreasonable selection and installation of hoses. When replacing the high-pressure hose, the length of the selected hose, the number of steel wires, the shape and size of the joint should be reasonable, and the degree of bending of the hose should be minimized; when tightening the joint nut, do not make the hose twisted, excessive bending and twisting will greatly reduce the service life of the hose; protective measures should be taken for some parts prone to friction to prevent the hose from bursting due to wear.