1. Characteristics of pressure conditions
The cooling circuit is mostly low-pressure, high flow, with a working pressure of generally 1-6 MPa, and there are oil return shocks and pressure pulses, rather than static constant pressure; It must have the ability to resist instantaneous impact and prevent joint leakage and pipe bursting.
2. Outstanding temperature resistance performance
The long-term working temperature of hydraulic oil is 60-95 ℃, and the short-term peak can reach 110-120 ℃.
The rubber inside the hose is made of nitrile NBR/hydrogenated nitrile HNBR, which is resistant to mineral hydraulic oil, high temperature and heat aging, and avoids rubber swelling, hardening and cracking under high temperature.
Steel pipes have good heat dissipation effect and are suitable for fixed layout in high-temperature areas of the engine room; The hose should avoid prolonged contact with the engine exhaust pipe heat source to prevent accelerated aging and failure of the outer skin.
3. Strong medium compatibility
Highly compatible with mineral hydraulic oil, the inner rubber layer is oil resistant, not easily swollen or precipitated, and prevents oil contamination; Reliable sealing to prevent oil leakage.
4. Anti vibration and anti fatigue characteristics (core requirements for construction machinery)
Continuous vibration during the operation of the whole machine, shaking of the frame, and displacement of the radiator will occur.
Rubber hose section: absorbs vibration, compensates for installation misalignment, buffers pipeline stress, and avoids fatigue cracking at hard pipe welding positions.
Hard pipe part: using cold drawn seamless steel pipes, with reliable pipe clamps to reduce resonance; Hard pipes and flexible pipes are alternately matched, and rigid steel pipes cannot be used entirely.
5. Environmental protection capability
Construction machinery operating outdoors, facing impacts from sand and gravel, exposure to ultraviolet radiation, mud and water, and salt alkali dust:
The outer rubber of the hose is wear-resistant, weather resistant, UV resistant, resistant to sand and gravel scratches, and delays aging and cracking;
Acid pickling, phosphating, painting/electrophoresis on the surface of steel pipes for rust and corrosion prevention;
Add protective sleeves to some areas that are prone to friction.
6. Flow channel and structural characteristics (exclusive to cooling system)
Large diameter and low resistance: High flow hydraulic oil flows through, and the selection of pipeline diameter is too large to reduce resistance along the way and avoid high back pressure affecting the efficiency of the radiator.
Smooth inner wall, reducing hydraulic pressure drop; The pipeline layout should minimize sharp bends to prevent local throttling and oil temperature rise.
The pipeline routing facilitates exhaust, reduces system air accumulation, and ensures smooth cooling circulation.
7. Assembly and reliability characteristics
Combination arrangement of hard and soft pipes: seamless steel pipes are used to fix the frame parts; Rubber hoses are used to transition the displacement and vibration positions at both ends of the radiator.
The joint has high sealing performance and is commonly used with sleeve type and buckle type joints, which are not easy to loosen and leak oil under vibration conditions.
The hose strictly ensures the minimum bending radius and does not allow twisting or deformation to extend its service life.
8. Applicable material differentiation
Rubber hoses: fiber-reinforced low-pressure hoses, steel wire braided low-pressure hoses; Used for the vibration displacement position at both ends of the oil cooler.
Seamless steel pipe: Cold drawn precision seamless steel pipe, used for fixing the pipeline section of the frame.
Plastic pipes are rarely used, and the strength and temperature resistance of construction machinery are insufficient under harsh working conditions.
