What are Motor Graders?

Earthmoving machine using a scraper to level the ground. The scraper is installed between the front and rear wheel axles of the machine, which can lift, tilt, rotate and extend. Flexible and accurate movements, easy to operate, high leveling accuracy, suitable for subgrade and pavement construction, slope construction, excavation of side ditch, can also mix road surface mixtures, remove snow, push loose materials, and carry out soil roads and Maintenance work on gravel road.

Graders are the main machinery used in shaping and leveling operations in earthworks, and are widely used in road and airport large-scale ground leveling operations. The reason why the grader has a wide range of auxiliary operations is that its scraper can complete 6 degrees of motion in space. They can be performed individually or in combination. The grader can provide sufficient strength and stability for the roadbed during the construction of the roadbed. Its main methods in subgrade construction include leveling operations, brushing operations, and embankment filling. The grader is a high-speed, high-efficiency, high-precision and multi-purpose earthmoving engineering machine. It can complete the large-scale ground leveling and trenching, slope scraping, bulldozing, snow removal, loosening, compaction, distribution, mixing, assisting and land reclamation of important areas such as highways and farmland. Yes

The original grader dates back to the United States at the end of the 19th century. Since the 1920s, in the nearly 80 years of development, graders have experienced low speed to high speed, small to large, mechanical operation to hydraulic operation, mechanical shift to power shift, mechanical steering to hydraulic power steering, and then The development process of full hydraulic steering and whole frame to shovel frame. The reliability, durability, safety and comfort of the whole machine have been greatly improved. With the development of technology, the development and application of machinery manufacturing and hydraulic technology. Has been applied to construction machinery products in combination with them, and high-tech represented by modern microelectronic technology is more and more commonly used to transform construction machinery products.

The development and expansion of grader products not only need to meet the working adaptability of different working conditions, but also must maintain the maximum part commonality (or interchangeability) with the basic model, which brings the majority of users with maintenance. Great convenience. The crawler grader is mainly composed of engine, transmission system, working equipment, electrical parts, cab and hood. Among them, machinery and

Graders use mechanical transmission or hydraulic mechanical transmission systems with torque converters, and a few use hydraulic transmission systems.

1.Requirements on hydraulic oil performance

In hydraulic transmission, hydraulic oil is both a medium for transmitting power and a lubricant, and it also acts as a seal in some components. The heat in the system is also diffused through the oil, so it plays a role of heat dissipation. Therefore, in order to ensure that the hydraulic system works reliably, efficiently and economically, the hydraulic oil must guarantee the following requirements: 1) proper viscosity. Viscosity is a measure of the frictional resistance between molecules when oil flows. When the viscosity is too large, the resistance when the oil flows is large, the energy loss is large, and the system efficiency is reduced. In addition, the main engine has increased no-load loss, fast temperature rise and high operating temperature, and it is easy to cause "cavitation" phenomenon at the suction end of the main pump. If the viscosity is too small, good lubrication conditions of the hydraulic components cannot be guaranteed, which will increase the wear of the components, increase leakage, and reduce the efficiency of the hydraulic system. 2) Good viscosity-temperature characteristics. The viscosity-temperature characteristic refers to the degree to which the viscosity change of an oil changes with temperature, and is usually expressed by a viscosity index. The larger the viscosity index, the smaller the oil viscosity decreases with the temperature increase during the hydraulic system operation, so that the internal leakage of the hydraulic system will not be too large. The viscosity index should generally not be lower than 90. 3) Good abrasion resistance and lubricity. The purpose is to reduce mechanical friction and ensure sufficient oil film strength under different conditions of pressure, speed and temperature. 4) High chemical reaction stability, not easy to oxidize and deteriorate. Practice has proved that the chemical reaction speed doubles for every 10 ° C increase in oil temperature. Hydraulic oil with good anti-oxidation stability is not prone to oxidative deterioration for a long time, which can ensure the normal circulation of hydraulic oil. 5) The quality should be pure, and the content of mechanical impurities, moisture and dust should be minimized. 6) The influence on the seal is small. 7) Anti-emulsification is better, it is not easy to cause foam. Anti-emulsification refers to the ability of oil to be mixed with water and not become an emulsion after stirring, and water is separated from it. Anti-foaming refers to the ability of oil to be mixed with air and not stirred to form an emulsion, and the air bubbles to be separated from the oil. After mixing with water or air, the volume modulus of the hydraulic oil is reduced, the compressibility is increased, the hydraulic components act slowly, and they are prone to shock and vibration. 8) Good anti-rust performance. Hydraulic oil covers the surface of the part to prevent it from being oxidized and rusted. 9) Good shear stability. In order to improve the viscosity index of oil, high-molecular polymers such as polymethacrylate and polyisobutylene are often added to the oil. These substances have long molecular chains, and the oil is greatly sheared when it passes through the slits of hydraulic components. As a result, the molecular chain is often broken, and the viscosity-temperature characteristic of the oil is reduced. 10) The flash point and flash point should meet the ambient temperature, and the volatility should be small to ensure the safe use of hydraulic oil. ^[1]

2.Pollution causes and hazards of hydraulic oil

2.1 Sources of pollutants

1) Contaminants in new oil. Although hydraulic oil is refined under relatively clean environmental conditions, it is contaminated by pipes, oil drums and oil storage tanks during transportation and storage. Some dust, sand, rust, Moisture and other liquids. 2) Residual contaminants in components and systems. During the processing, assembly and cleaning of hydraulic components and hydraulic systems, some contaminants remain due to incomplete cleaning. 3) External intruding pollutants. During the work of hydraulic components and machinery, due to the imperfect seal of the fuel tank, damage to component seals and protective devices, some pollutants, such as dust, sand, moisture, etc., are invaded from the outside of the system. 4) Pollutants generated inside the hydraulic system. The hydraulic system itself generates some solid particulate pollutants during work, including metal particles or rubber powder generated by the wear and corrosion of hydraulic components, and pollutants generated by the oxidation of oil. ^[1]

2.2 Hazard of hydraulic oil pollution

1) Contaminants often block the throttle valve and pressure damping hole, and even jam the valve core, which causes the working pressure and speed of the hydraulic system to change from time to time, affecting its normal work. 2) Accelerate the wear of hydraulic pumps, motors, and valve groups, causing an increase in internal leakage. 3) The water mixed into the hydraulic oil corrodes the metal and accelerates the deterioration of the hydraulic oil. 4) Air mixed in hydraulic oil can cause noise, vibration, crawling, cavitation and impact phenomena, thereby deteriorating the working performance of the hydraulic system. ^[1]

3. Maintenance of hydraulic oil

3.1 Prevent oil pollution

Among the various pumps and valves used in graders, the matching clearances and working surfaces between the relative moving parts are small. There are also many damping holes and gap control valve ports in the hydraulic components. If the oil is mixed with dirt, Objects, blocking will occur, and even scratch the mating surface, increase leakage, and even jam the valve core, causing component failure. Therefore, keeping the oil clean is the key to maintaining the hydraulic system. 1) The hydraulic oil must be strictly filtered. When filling the hydraulic oil tank, it should pass through a 120-mesh oil filter. 2) Regularly check the cleanliness of the oil, and replace it regularly according to the working conditions. When replacing, drain out about 40L of oil in the hydraulic system memory as much as possible. Among them, the method using the outer loop of the system is more operable. The method is to first drain the waste oil in the fuel tank and radiator, and then fill with new oil. Remove the oil return pipe entering the fuel tank and start the engine, so that the waste oil can completely flow out of the oil return pipe. It is particularly emphasized that the oil level in the fuel tank should be observed in a timely manner, and the safe height of the oil level should be guaranteed. When replacing with new oil, the filter element of the filter should be replaced at the same time. 3) Do not disassemble the hydraulic components easily. If disassembly is necessary, clean the parts with kerosene or diesel and place them in a clean place to avoid contamination of impurities during reassembly. ^[1]