The inner rubber layer of the high-pressure hose is hard and cracked: This is due to the plasticizer added to the rubber products, which makes the hose flexible and moldable. When the hose operates under high temperature and pressure, overheating can cause the plasticizer to leak out. Additionally, when overheated oil passes through cylinders, valves, or other components in the system, significant pressure drops can lead to oil decomposition, resulting in the oxidation and hardening of the rubber layer inside the hose.

In such cases, first check if the hydraulic system's operating temperature is normal, and whether the valve throttle and the pump's suction channel are unobstructed. After eliminating all factors that could cause the oil temperature to rise and the oil to degrade, replace the hoses. If only the inner rubber below the crack is hard while the upper part remains good, it indicates that excessive compression, sharp bending, or twisting at the crack has caused the oil to heat up and oxidize rapidly, leading to the hardening of the inner rubber.

The inner rubber layer of the high-pressure hose has severely deteriorated and visibly swelled: The severe deterioration and visible swelling of the inner rubber layer in the hose is due to the use of hydraulic oil beyond its expiration date or the presence of oxidized, degraded contaminants within the hydraulic system. The hose undergoes chemical degradation, and fragments of rubber can be found at the return port. If this occurs, inspect the physical and chemical properties of the hydraulic oil, verify the compatibility between the system oil and the hose's rubber material, and ensure the working temperature meets standards.