Oil pollution is the main cause of hydraulic system failure and premature wear or damage of hydraulic components, and the resulting loss accounts for about 70%-80% of the total failure loss of hydraulic system. So hydraulic oil and lubricating oil are the same kind of oil? What are the hazards of oil pollution?
The damage of pollution to the hydraulic system is mainly reflected in the following three aspects:
1) Oil pollution particles enter the matching gap of hydraulic components, which will aggravate the wear of the sliding surface, resulting in the reduction of the sensitivity of the components or the confusion of the operation cycle, and shorten the service life of the components.
2) The pollutants in the oil will block the damping holes and slot control valves of the hydraulic components, so that the hydraulic components can not work normally.
3) Oil pollution will change the viscosity of the oil, reduce the physical and chemical properties of the oil such as emulsification resistance, lubricity and defoaming, resulting in premature aging failure of the oil, and cause various hydraulic system failures. Hydraulic fluids with good cleaning properties can effectively reduce system deposits and sludge, helping to extend equipment life, reduce maintenance and improve overall system performance.
How to choose hydraulic oil reasonably? The frequent failure of the hydraulic system is painful, and I believe that many companies have spent a lot of resources on the replacement and treatment of hydraulic oil. The poor cleaning and maintenance performance of hydraulic oil will lead to sludge deposition in the system, which will affect the operation of the system and cause failure. So the reasonable selection of hydraulic oil is very important. In general, the selection of hydraulic oil should follow the following principles: excellent performance, economic and reasonable, reliable quality, easy to manage.
1 General construction machinery manufacturers in the equipment manual or manual specified the equipment hydraulic system to use the hydraulic oil variety, brand and viscosity level, the user should first choose hydraulic oil according to the equipment manufacturer's recommendation.
2. Choose hydraulic oil according to the ambient temperature of the hydraulic system. High ambient temperature, the selection of high viscosity hydraulic oil; On the contrary, low viscosity hydraulic oil is used.
3, according to the working pressure and speed of the hydraulic system to choose hydraulic oil. System pressure is high, the selection of high viscosity hydraulic oil; On the contrary, low viscosity hydraulic oil is used.
4. Choose hydraulic oil according to the structural characteristics of hydraulic components of the hydraulic system. The hydraulic system contains a variety of hydraulic components, but the hydraulic pump speed is high, the pressure is large, the working temperature is high, the working conditions are harsh, and the hydraulic oil is generally selected according to the requirements of the pump.
5. Choose hydraulic oil according to fire risk. In the equipment with fire risk, flame resistant hydraulic oil should be selected.
How to improve the service life of hydraulic media? At present, many large and medium-sized construction machinery adopts hydraulic transmission system, due to the influence factors such as oil leakage and oil temperature change, the correct selection of hydraulic oil, rational use and maintenance are the key to play the mechanical efficiency. The following measures can effectively improve the hydraulic system.
Prevent contamination and water from mixing
1) Strengthen the management of safety and cleaning work of oil depots, oil drums, oil filters, oil funnels, oil pipes, etc., so as to be dedicated, keep clean before and after use, and no pollutants are mixed.
2) When the site uses a simple method to identify the degree of pollution, the hydraulic oil must be replaced in the following cases:
a, the particle size is greater than 40UM, that is, when it is visible or when the used oil in the test tube is black and has a foul smell;
b. When the heated oil drops have residual black spots on the filter paper; 3. When a drop of used oil is dropped on an iron plate heated to 250 degrees Celsius, there is an explosion (containing water).
c, there is often water at the bottom of the oil drum, and the air in the system contains water vapor that will condense into water, which should be excluded.
2. Prevent air from entering
1) Keep enough oil (height) in the tank, and the suction pipe and return pipe are kept below the oil level.
2) Use seals with good performance, pipe joints and screws on each joint surface should be tightened.
3) Prevent the pressure everywhere in the system from being lower than atmospheric pressure or local vacuum.
4) Open the cylinder exhaust valve before starting or replacing the new oil, and move several times within the travel range of the cylinder to remove air.
The leakage of the hydraulic system can be divided into external leakage and internal leakage. External leakage is mainly leakage to the outside, such as pipe leakage and cylinder leakage. Internal leakage from the high pressure chamber to the low pressure chamber in the component directly affects the performance of the component.
1) The weldment of the casting should ensure the quality. When conditions are available, the hydraulic parts should be subjected to pressure test before assembly, and the pressure of the pressure test should reach 150% -200% of the working pressure.
2) When installing various joints, be sure to make the fastening nut fit properly with the thread on the joint. Especially when installing, remove burrs, otherwise, hard tightening with burrs will squeeze the thread and leave a problem. When installing the joint, you can first tighten the sealing surface contact by hand, and the hand cannot be screwed. Indicates that the sealing surface is in contact, and then tighten with a wrench.
3) Choose the right viscosity of hydraulic oil, has good viscosivity temperature performance.
4) Various sealing rings, especially in the type 0 sealing ring specifications are many, and the diameter difference between adjacent sizes is not large, and it is difficult to distinguish by sight. Therefore, the sealing ring sizes of various specifications are indicated and stored separately to avoid mixing sizes. When changing, it is easy to choose according to the specified size, and it can not be replaced by small or large. Do not use tools with edges during installation to prevent scratching seals. The O-ring can not be twisted after being installed. U, V, Y and other directional seals, pay attention to the direction when installing, do not install reverse. The replaced old sealing ring should be put aside in time, and the new and old can not be confused, so as to avoid rework caused by mistake during installation.
5) Regularly check whether the clearance of moving parts in the pump, valve cylinder and other components is too large.
6) To ensure the quality of oil seals and seals, material, geometry and accuracy to meet the design requirements.
