Maintenance of Hydraulic Hoses for Construction Machinery in the Application of Crimping Machines

The operating characteristics of hydraulic pipelines in construction machinery are as follows: the pipelines have small bending radii, narrow passages that easily lead to mutual friction and compression, significant impact loads, and frequent bending movements.

Shanghai Fender’s specific operational recommendations for hydraulic pipelines in construction machinery:

　　1. For hoses with the same pressure and inner diameter, selecting a high-pressure hose with a smaller bending radius can ensure that the carcass layer remains undamaged.

　　2. An additional protective spring is added to the body of the high-pressure hose to prevent friction between hoses, thereby avoiding damage to the outer rubber layer of the hose.

　　3. When selecting the hose pressure, take into account the presence of impact loads; the maximum working pressure of the hose should be 4 times greater than the maximum working pressure of the construction machinery. 4. Use “steel wire wrapping.”

"around the high-pressure hose," because when the hose is bent, the braiding process—compared to the winding process—causes greater wear and friction between the steel wires, leading to premature damage of the steel wire carcass layer!

Problems with Hydraulic Pipelines in Construction Machinery and Optimization Solutions

　The hydraulic piping system of construction machinery—including the hydraulic oil tank, hose assemblies, steel pipe assemblies, and connecting fittings—is the power transmission system of the machinery’s main unit; it can be described as the “lifeline” of the entire machine. However, currently, China’s construction machinery hydraulic piping systems suffer from serious quality problems, primarily manifested in oil leaks, oil seepage, failure to meet cleanliness standards, substandard product quality, technical barriers, and an inability to support high-pressure models.

　　For medium-pressure models (with system operating pressures below 20 MPa), since the pressure is relatively low, many OEMs choose from a wide variety of suppliers. Some OEMs even assemble and manufacture these components themselves, leading to a higher number of issues. The three-guarantee claim rate for such models typically ranges from 2% to 5%. As for high-pressure models (with system operating pressures above 20 MPa), the supply mainly relies on imports or assembly and distribution through agents of foreign brands, resulting in relatively high prices. Moreover, there isn't yet a single specialized, high-quality domestic manufacturer that OEMs can confidently select. This is precisely the area where we need to focus our efforts.

　　Based on years of experience accumulated in the research and production of hydraulic piping systems, we have identified the following issues:

　　1. Causes of hydraulic hose assembly failures

　　(1) When crimping the hydraulic hose assembly onto the fitting, if the crimping force is too great, the inner rubber layer of the hose may be damaged, leading to oil leakage.

　　(2) When crimping the hydraulic hose assembly onto the fitting, insufficient crimping force can lead to oil leakage, seepage, and fitting pull-out.

　　(3) Under repeated pulse pressure, the outer sleeve rebounds, reducing the clamping force and leading to oil leakage, oil seepage, and pull-out.

　　(4) The joint machining accuracy fails to meet the standard, resulting in oil leakage and seepage at the joint.

　　(5) Improper usage methods lead to a reduced service life.

　　Optimization plan:

　　(1) During the machining process of the connector’s inner core and outer jacket, strict dimensional control is required, and the machining tolerances must be kept within 0.05 mm.

　　(2) Use a pipe-crimping machine with excellent performance, and keep the crimping pressure and dimension control within 0.1 mm.

　　(3) Provide the OEM with the correct usage and design solutions.

　　(4) It is recommended to use a turning center for machining the joint connection areas, as it offers excellent stability and machining accuracy.