Although hydraulic hoses are often regarded as ordinary components, they have to withstand complex working conditions – a wide range of pressures, thousands of machine cycles, frequent pressure fluctuations, and large ranges of motion. Once a failure occurs, it may lead to high downtime costs, equipment damage, and even casualties. Therefore, scientific management of the entire process from design to installation is the core to ensure its reliability, maintenance convenience, and safety.
1. Core factors affecting the life of hydraulic hoses
(1) Environmental erosion:
Long-term exposure to high temperature and ultraviolet light will accelerate aging; on-site collisions and continuous wear will directly damage the outer sheath and reinforcement layer.
(2) Installation defects:
Even if environmental problems are solved, all protective efforts will be ineffective if the installation and layout are improper. For example, failure to consider the expansion and contraction characteristics of the hose, excessive bending or twisting will directly lead to a sharp reduction in life.
2. Structure and core identification of hydraulic hoses
The three-layer structure of hydraulic hoses determines their performance, similar to the design logic of automobile tires:
(1) Inner tube:
directly transports the medium and needs to adapt to the medium characteristics (such as oil, water-based fluid, etc.).
(2) Reinforcement layer:
bears the pressure bearing function and is the core of the hose’s explosion resistance and strength.
(3) Outer sheath:
protects the reinforcement layer from external damage such as wear and ultraviolet rays.
The printed line on the outer sheath has two key functions:
(1) Information carrier: mark core parameters such as product code, inner diameter (ID), working pressure, etc.
(2) Installation indicator: if twisting occurs during installation, the printed line will appear irregularly wound, and installation defects can be intuitively judged.
3. Key principles for installation and layout
(1) Reserve expansion margin
Hydraulic hoses will expand when pressurized (up to 2%) and may shrink after depressurization (up to 4%). If this expansion is rigidly constrained, it will exert excessive tension on the reinforcement layer and joints, significantly shortening the life. Therefore, when cutting the hose, it is necessary to reserve an appropriate length to provide space for expansion.
(2) Strictly control the bending radius and twisting
① Minimum bending radius:
The manufacturer clearly specifies the minimum bending radius of different hoses. Exceeding this range will cause stress concentration in the outer reinforcement layer, which may cause bulging or even rupture under the outer sheath. Note: Highly wear-resistant hoses are often less flexible, and the bending radius must be more strictly followed.
② Avoid multi-plane bending:
The hose should only be bent in a single plane to prevent the reinforcement layer wire from twisting. Data shows that a 5% twist can reduce the life by 60%-70%, and a 7%-8% twist can cause a sudden reduction in life by 90%.
(3) Solution:
If it cannot be avoided, adjust the direction of the hose, use a swivel joint, or install a hose clamp between the bends (sufficient length must be reserved on both sides of the clamp to relieve the stress of the reinforcement layer. The specific length depends on the inner diameter, reinforcement layer type and minimum bending radius).
4. Targeted anti-wear design
Abrasion is a common cause of hose failure and needs to be prevented through multiple measures:
(1) Reasonable use of clamps:
fix the hose to avoid friction with hard objects and sharp corners. The size of the clamp must match the outer diameter (OD) of the hose – it must prevent movement, but not be too tight to damage the outer sheath; at the same time, reserve the slack required for expansion and contraction.
(2) Add a protective sleeve:
select the appropriate type according to the working conditions:
(3) Nylon sleeve:
highly versatile, suitable for various friction scenarios, and provides basic wear protection.
(4) Plastic spiral wrapping:
economical and affordable, can be wrapped after the connector is installed, suitable for single or bundled hoses.
(5) Galvanized steel wire protective sleeve:
used with springs, suitable for harsh working conditions, can disperse bending stress and reduce the risk of knotting.
(6) Correct selection of swivel joints:
distinguish between “compression swivel joints” and “movable swivel joints”: the former is mostly used to eliminate kinks during installation and is not suitable for continuous rotation (such as high-pressure cleaning machines); the latter can rotate for a long time and is suitable for scenarios that require dynamic angle adjustment. Note: The hose end is a rigid section and cannot be used as a flexible section.
5. Optimization principles for system design
(1) Keep wiring neat
①Neat wiring not only reduces the risk of twisting and wear, but also reduces maintenance costs – hoses are clearly marked and easy to disassemble and assemble, reducing the probability of misoperation.
(2) Reduce connection points and optimize connectors
①Preferably use hose connectors with angles (45°, 90°) rather than multiple adapter combinations, because each connection point is a potential source of leakage.
②For connectors with angles at both ends, pay attention to “clock positioning”: for example, when both ends are 90° connectors, ensure that the relative angles match (in a straight line or at a specific angle) to avoid forced twisting.
