The influence of brake fluid on the braking performance of wheel loaders

I. Introduction

In recent years, the faults of the braking system of loaders have been on the rise, especially a series of problems such as brake failure, temperature rise of the braking system, and oil leakage from the vent holes of the brake pump. Currently, the service braking systems of domestic loaders almost all adopt air-top oil caliper disc brakes, and the selection of braking components is largely the same as that of automobiles. The causes and influencing factors of the failure of the braking system of a loader are multi-faceted, such as the damage of braking components leading to brake failure. In recent years, the braking system of loaders has shown an upward trend. The author believes that the decline in the quality of brake fluid and brake friction pads is also one of the influencing factors. The following is a brief introduction to the influence of brake fluid on the braking performance of wheel loaders.

Ii. Performance Requirements for Brake Fluid in Loaders

(1) Good viscosity-temperature performance and low-temperature performance

Loaders often operate in harsh working environments such as mountainous areas and mines. Therefore, the working mode of loaders requires them to frequently move forward and backward in each working cycle. The brake friction plates remain in a braking state for a long time. During the braking process, due to frictional heat generation, the temperature of the friction plates can reach up to 250℃. Part of its heat is transferred to the brake fluid, causing its working temperature to reach 70℃ to 90℃. In mountainous and other environments where frequent braking is required, its working temperature can reach 110℃, and sometimes even as high as 150℃. However, in winter in regions like Northeast and Northwest China, the temperature of the brake fluid can drop below -40℃. Therefore, the brake fluid is required to have good viscosity-temperature performance and low-temperature fluidity. Suitable high-temperature viscosity, low freezing point and low-temperature viscosity.

(2) Appropriate lubricity

To ensure that the brake cylinder and rubber bowl can slide well, the brake fluid is required to have appropriate lubricity.

(3) Ensure safe and reliable braking without air resistance

When a loader is in motion, frequent braking generates a large amount of frictional heat, causing the temperature of the braking system to rise. If brake fluid with a low boiling point and easy evaporation is used, at high temperatures, due to the evaporation of the brake fluid, the local braking system pipes will be filled with vapor, resulting in vapor lock and causing brake failure. Therefore, brake fluid is required to have a high boiling point and low volatility to avoid reducing the occurrence of vapor lock.

(4) Good corrosion resistance

Brake fluid should have good anti-corrosion properties for various metal parts of the brake.

(5) Good chemical stability

Brake fluid is used for a long time under the effect of high humidity, so it is required that the brake fluid does not undergo thermal decomposition and overlap, which would increase the viscosity of the oil, nor is it allowed to form sludge deposits.

(6) Good compatibility with rubber

In the braking system, there are many rubber seals and cups, etc., which are used to keep the braking system completely sealed. Therefore, the brake fluid should have good compatibility with rubber seals to prevent the rubber seals and cups from expanding and having their mechanical strength reduced due to incompatibility with the fluid.

Iii. Impact on the Braking Performance of Wheel Loaders

When the pipes of the braking system are filled with vapor and gas, due to the high compressibility of the gas, if the brake pedal feels soft and elastic when stepped on, it indicates that air has seeped into the brake fluid, which will deteriorate the braking effect, reduce safety and slow down the response speed of braking. Especially in mountainous and mountainous areas, frequent braking causes the temperature of the brake fluid to rise. If the boiling point of the brake fluid is low, it is more likely to cause cavitation in the braking system, thereby damaging the rubber sealing ring of the booster pump and the braking components. It causes the braking system to fail completely, posing a threat to personal safety. In addition, when there is gas in the brake fluid line of the braking system, when the brake pedal is released, due to the faster expansion rate of the gas than that of the brake fluid, sometimes oil will spray out from the brake fluid cup of the booster cylinder. Low-boiling-point brake fluid seriously affects the braking performance of wheel loaders. At present, most domestic wheel loaders use 719 synthetic brake fluid, which is equivalent to HZY3 in domestic GB12981-2003 and DOT3 in the international common standard. The dry boiling point of this type of brake fluid is 205℃. The dry boiling point refers to the boiling point right after being added to the braking system from a sealed container. However, some inferior brake fluids have a lower dry boiling point, which affects braking safety.

(2) Inferior brake fluid has a strong water absorption capacity. Water vapor in the air is absorbed by the brake fluid, and working in rainy weather causes water to enter the brake fluid. Once water enters the brake fluid, the boiling point of the brake fluid will drop, and thus the brake fluid's resistance to air lock will also be greatly reduced. When in use, if you find that a large amount of water has entered the brake fluid for some reason, you must replace it with new brake fluid in time. When renewing the brake fluid, be sure to dry the braking system thoroughly. It is strictly forbidden for water and other oils to mix in.

Iv. Simple Identification Methods and Usage Precautions for Brake Fluid

Pour a small amount of brake fluid onto your palm. Genuine brake fluid usually feels a bit cold at first, then a little warm after a while, and it doesn't evaporate easily. If you feel the brake fluid is abnormally cold without a warm sensation and it evaporates slowly, it is very likely to be fake brake fluid.

(2) Before changing the brake fluid, it is essential to thoroughly clean the oil stains, dirt and other contaminants from the brake system's fluid filling port, air release screw and other parts to prevent impurities from entering the brake system and contaminating the brake fluid. The braking system should be cleaned in accordance with the provisions of the maintenance manual. It is recommended to use the same type of brake fluid to clean each pipeline of the braking system. It is best not to use alcohol, cleaning agents or the like.

(3) Brake fluid is somewhat toxic and should not be inhaled with the mouth.

(4) Brake fluid has a destructive effect on the coating on the exterior of the vehicle body, which can cause the "paint biting phenomenon". Therefore, when replacing and refilling brake fluid, it is essential to strictly prevent the brake fluid from dripping onto the coating of the vehicle body and corroding the surface of the loader, causing rust on the machinery.

(5) It is strictly prohibited to mix with other brake fluids. Due to the different raw materials, additives and manufacturing processes used in various types of products, turbidity or sedimentation may occur after mixing. This not only significantly reduces the performance of the original brake fluid, but also the sediment particles can clog the pipelines, causing serious consequences such as brake failure. Even if brake fluids of the same type have good compatibility, they cannot be mixed if they are of different brands. Because of good compatibility, it only indicates that there will be no stratification, turbidity or sedimentation when mixed with other products. It does not mean that the performance remains unchanged after mixing. The additives added to each product are different and there is a relative balance among them. Once other substances are mixed in, this balance may be disrupted, thereby losing or reducing the due effect. Therefore, when changing brands, it is essential to clean the pipeline with the product to be added.

V. Conclusion

Brake fluid for wheel loaders is an important medium for transmitting power in the braking system of loaders and a major factor related to the braking safety of wheel loaders. Due to the influence of some counterfeit brake fluids in recent years, the braking performance of automobiles and wheel construction machinery has decreased, posing a threat to personal safety. This should be noted by users of wheel loaders.