Several commonly used oils for loaders and their selection

The oil products frequently used in loaders mainly include engine oil, engine diesel, torque converter/transmission oil (hydraulic transmission oil), drive axle oil, hydraulic oil used in the hydraulic system, and grease used in each hinge pin. The correct selection and use of these oil products are of great significance for maintaining the normal operation of each system, reducing wear, and extending the service life of the machine.

1. Engine oil

Viscosity grade and quality grade

Currently, the widely adopted viscosity classification for engine oil internationally is the SAE (Society of Automotive Engineers) classification standard, such as SAE5W / 40 or SAE EL5W / 40. The "W" stands for winter (winter), and the smaller the number in front of it, the thinner the viscosity of the engine oil, the better its fluidity, and the better its protective effect on the engine during cold starts. The number following the "W" indicates the high-temperature resistance of the engine oil. The higher the value, the better the protective performance of the engine oil at high temperatures. Engine oil with higher viscosity also offers relatively higher resistance to the movement system, not only consuming more power and increasing fuel consumption, but also being prone to oxidation, which affects the protection during cold starts.

Generally, the API (American Petroleum Institute) grade is used to represent the classification of engine oil quality. It uses simple codes to describe the working capacity of engine oil. For diesel engines widely used in construction machinery such as loaders, the oil quality grades range from "SA" to "SL". The later the letter, the higher the quality grade. With each additional letter, The performance of engine oil is superior to the previous one, and it contains more additives that protect the engine.

The Chinese standard for viscosity grades and quality grades of diesel engine oil (GB11122-1997) is equivalent to the above-mentioned standard.

(2) Selection of diesel engine oil

For diesel engines used in loaders with harsh working conditions and heavy workloads, it is recommended to use CD grade engine oil. For the south, CD-grade SAE20W / 40 is recommended. For the north, CD-grade SAE5W / 30 or 10W / 30 is suggested. Some imported engines require the use of CE, CF or higher grade engine oil. For example, Cummins engines require CF-4 or higher grade engine oil.

2 Engine diesel

Generally, diesel with a sulfur content of less than 0.5% is used. If the sulfur content is high, the oil change cycle will be shortened. For general loaders, light diesel oil as specified in GB252-1994 is adopted. It is suitable for high-speed diesel engines with a full-load speed of over 1000r/min. The general principles for its selection can be referred to the following table:

3 Torque converter/transmission oil (hydraulic transmission oil)

(1) The function of hydraulic transmission oil

Hydraulic transmission oil serves as the medium for energy transmission in hydraulic torque converters.

② As lubricating oil for the gears and bearings of the gearbox.

③ As hydraulic oil for the friction clutch of the transmission.

④ As coolant for torque converters and gearboxes.

(2) Selection of hydraulic transmission oil

The normal working temperature of hydraulic transmission oil is between 82 and 95℃, and sometimes it can reach around 120℃. Due to the special requirements for the oil used in hydraulic transmission, there are currently no national standards stipulating its quality grade and viscosity requirements. Generally, No. 6 hydraulic transmission oil and No. 8 hydraulic transmission oil are used in loaders.

4 Drive axle oil

Gear oil

The quality classification standard for vehicle gear oil in China, GB7631.7 to 95, is based on the quality grade classification of API and is divided into three types: CLC, CLD, and CLE. Among them, CLE is equivalent to grades GL to 5 in the APl classification. It is generally recommended to use CLE grade gear oil for the drive axle of a loader.

(2) Drive axle brake fluid (brake fluid

The brake fluid for the drive axle of a loader (non-full hydraulic braking) generally uses HZY3 synthetic brake fluid as specified in GB12981□91, which is equivalent to SAEl703C oil as specified in API.

5 Hydraulic oil

Viscosity is an important performance index of hydraulic oil, as the lower the viscosity, the smaller the power loss and the higher the mechanical efficiency. When the viscosity is low, the volumetric efficiency also decreases. Therefore, the optimal viscosity should meet the requirement of minimizing wear on bearings and hydraulic pumps, and low-temperature performance should also be taken into consideration. Domestic hydraulic oil generally selects the mineral oil type and synthetic hydrocarbon type hydraulic oil as specified in GB11118.1 □94. Due to the harsh working conditions and heavy workload of the loader, as well as the high temperature of the hydraulic oil, high-grade anti-wear hydraulic oils L□HM32 and L□HM46 are generally used. In low-temperature conditions, low pour point hydraulic oils L□HV32 and L□HV46 are recommended.

6 Grease

The oil used abroad is a multi-purpose grease, containing 1% to 5% molybdenum disulfide, and it is also a suitable anti-corrosion agent. This grease is suitable for various hinge pins, spherical plain bearings, swing frame bearings, transmission shafts, etc., and has a very wide range of applications. This grease must be of high-grade lithium-based and E.P. The mixture of additives, throughout the entire working range, features stable chemical properties, no hardening, no leakage or no dripping. Generally, No. 1 or No. 2 grease specified by NLGI (American Grease Institute) is used. It has a wide applicable temperature range and is suitable for very low-temperature applications.

Domestic loaders commonly use No. 3 or No. 4 calcium-based grease. However, this type of grease can no longer meet the requirements of loaders operating in various climates (such as high or low temperatures, high humidity and excessive water, etc.). Due to the many excellent properties of lithium-based grease, its oil change cycle is about twice as long as that of calcium-based grease. Therefore, lithium-based grease is now frequently used in loaders.