1. Type of leakage
There are two main types of leakage in the hydraulic system of the loader. One is the leakage of the fixed part (ie, the static joint surface, such as the joint between the cylinder head and the cylinder); the second is the sliding part (ie, the moving joint surface, such as The leakage of the seal between the hydraulic cylinder piston and the inner wall of the cylinder tube, the piston rod and the cylinder head guide sleeve can also be divided into internal leakage and external leakage. Internal leakage mainly occurs in hydraulic valves, hydraulic pumps (hydraulic motors) and hydraulic cylinders. The oil flows from the high pressure chamber to the low pressure chamber; the external leakage mainly occurs in the hydraulic system hydraulic lines, hydraulic valves, hydraulic cylinders and hydraulic pumps (hydraulic motors). The outside of the part, that is, leaking to the outside of the component. Specifically, the oil leakage caused by the pipe joint, the seal, the component joint surface, the casing and the system itself.
2. Reasons for leakage
Leakage in hydraulic systems is typically generated after a period of use. From the surface phenomenon, most of the seal failure, damage, Bad, extruded, or the surface of the seal is pulled or the like. The main reasons are: oil contamination, improper sealing surface roughness, unqualified sealing groove, loose pipe joints, increased clearance of fittings, high oil temperature, deterioration of sealing rings or poor assembly.
(1) The leakage of the pipe joint is related to the processing accuracy, fastening strength and whether the burr is removed at the joint. The main performance is that the type of pipe joint is not in accordance with the conditions of use; the structural design of the pipe joint is unreasonable; the processing quality of the pipe joint is poor, and the sealing effect is not achieved; the pressure pulsation causes the pipe joint to loosen, and the bolt creep is not tightened in time; The joint tightening torque is too large or not enough.
(2) Leakage caused by the seal is related to damage or failure of the seal. The main performance is that the material or structure type of the seal does not match the conditions of use; seal failure, insufficient compression, aging, damage, unqualified geometric accuracy, poor processing quality, irregular products; hardness, pressure rating, deformation of the seal Indicators such as rate and strength range are not required; seals are improperly installed, surfaces are worn or hardened, and life is expired but not replaced in time.
(3) Leakage caused by component bonding surfaces is related to design, processing, and installation. The main performance is that the design of the seal does not meet the requirements of the specification, the size of the sealing groove is unreasonable, the sealing precision is low, the matching gap is out of tolerance; the sealing surface roughness and flatness error are too large, the processing quality is poor; the sealing structure is improperly selected, resulting in Deformation, the joint surface can not be in full contact; the assembly is not careful, the joint surface has sand dust or large plastic deformation due to damage.
(4) The leakage of the casing mainly occurs on the defects of the casting and the welded parts, and gradually expands under the action of the pressure pulsation or impact vibration of the hydraulic system.
(5) The main reason for the system's own leakage is that the system is rough, lacks vibration and vibration isolation measures; the system is overpressured; the system is not properly inspected and disposed according to regulations; the life of the consumables expires but is not replaced in time.