The hydraulic oil of a truck-mounted crane plays a crucial role in its operation. To ensure the proper functioning and longevity of the crane, it is essential to monitor the condition of the hydraulic oil and change it when necessary. One way to determine if it’s time to change the hydraulic oil is by identifying the viscosity of the oil.
Inverting the hydraulic oil in the vessel:
This method provides a visual way to compare the viscosity of the used hydraulic oil with that of a standard hydraulic oil. First, take out some hydraulic oil from the fuel tank of the truck-mounted crane. Place this oil in two transparent glass bottles that are the same size as bottles containing standard hydraulic oil. Make sure to plug the bottle mouths tightly. Then, place these two bottles side by side. Inverting the bottles allows us to observe the behavior of the bubbles in the oil.
If the bubbles in the tested hydraulic oil rise faster in the bottle than the bubbles of the standard oil, it indicates that the viscosity of the hydraulic oil is lower than that of the standard hydraulic oil. This could be a sign that the oil has degraded or become contaminated. On the other hand, if the bubbles rise more slowly in the tested oil than in the standard oil, it means the viscosity is higher. However, if the bubbles in the hydraulic oil in the two bottles rise at a similar speed, it indicates that the viscosities are similar and there is no need to dilute or change the oil at this time.
Let’s take a closer look at why bubble movement is related to viscosity. Viscosity is a measure of a fluid’s resistance to flow. A lower viscosity oil will allow bubbles to rise more quickly because it is less resistant to the movement of the bubbles. As the hydraulic oil in the crane is used over time, it can become contaminated with dirt, water, or other substances that can lower its viscosity. This can lead to reduced performance and potential damage to the hydraulic system.
For example, if the hydraulic oil has been contaminated with water, it can cause the viscosity to decrease. Water can enter the hydraulic system through leaks or condensation. When water mixes with the hydraulic oil, it can affect its lubricating properties and cause the oil to become less effective at transmitting power. By observing the bubble movement, we can get an indication of whether the oil has been contaminated and if it needs to be changed.
Glass plate inclination method:
This method provides another way to compare the viscosity of the tested hydraulic oil with that of a standard oil. Start by taking a clean glass plate and placing it horizontally on a flat surface. Then, drop a drop of the extracted hydraulic oil on the glass. At the same time, drop a drop of standard hydraulic oil next to it. After this, incline the glass plate gently. By doing this, we can observe the flow rate and flow distance of the two drops of oil.
If the flow rate and flow distance of the tested hydraulic oil are both larger than those of the standard hydraulic oil drop, it indicates that its viscosity is lower than that of the standard oil drop. Conversely, if the flow rate and flow distance are smaller for the tested oil, it means its viscosity is higher.
The principle behind this method is similar to the bubble inversion method. A lower viscosity oil will flow more quickly and cover a greater distance on the inclined glass plate. As the oil is used in the crane, its viscosity can change due to factors such as heat, pressure, and contamination. By comparing the flow behavior of the tested oil with that of a standard oil, we can determine if the viscosity has changed enough to warrant a change in the hydraulic oil.
Note: Generally speaking, the hydraulic oil of the crane needs to be changed after working for 2,000 hours, which is about two to three years. Theoretically, the oil change standard is to look at the viscosity and aging degree of the oil, such as whether it is clean, etc. In actual daily use, it is determined according to the working conditions and experience.
The working hours and time period mentioned are general guidelines for when to change the hydraulic oil. However, different operating conditions can affect the lifespan of the hydraulic oil. For example, if the crane is used in a harsh environment with high temperatures, heavy loads, and frequent operation, the hydraulic oil may degrade more quickly and need to be changed sooner. On the other hand, if the crane is used in a relatively mild environment with light loads and infrequent operation, the hydraulic oil may last longer.
The viscosity and aging degree of the oil are important factors to consider. As the oil ages, it can become thicker or thinner, depending on various factors. Contamination can also affect the viscosity and cleanliness of the oil. If the oil is dirty or contains particles, it can damage the hydraulic components and reduce the efficiency of the system.
In actual daily use, operators should pay attention to any signs of abnormal operation or decreased performance of the crane. These could be indications that the hydraulic oil needs to be changed. For example, if the crane is slower to respond, has reduced lifting capacity, or makes unusual noises, it may be time to check the hydraulic oil.
Correct steps for changing hydraulic oil:
First, drain the hydraulic oil in the hydraulic tank.
This is the first step in changing the hydraulic oil. Carefully remove the drain plug or use a suitable pumping device to drain the old hydraulic oil from the tank. After draining the oil, it is important to clean the tank thoroughly to remove any sediment, dirt, or contaminants that may have accumulated. This can be done using a clean cloth or a mild solvent. Once the tank is clean, add new hydraulic oil. Make sure to use the correct type and grade of oil as specified by the crane manufacturer.
For example, if the tank is not cleaned properly, any remaining contaminants can mix with the new oil and reduce its effectiveness. Additionally, using the wrong type of oil can cause compatibility issues and damage the hydraulic system.
Remove the main loop pipe.
Start the engine and let it idle to make the oil pump work. This step helps to circulate the new oil through the system and flush out any remaining old oil. By removing the main loop pipe, we can direct the flow of the oil and ensure that it passes through all the necessary components.
When the engine is idling, the oil pump creates pressure and forces the oil to flow through the hydraulic system. This helps to remove any air pockets and ensure that the system is properly lubricated.
Operate each mechanism respectively.
Use the hydraulic oil to discharge the old oil in the loop one by one until new oil flows out of the main return pipe. This step ensures that all the old oil is removed from the various hydraulic mechanisms of the crane. Manually operate each mechanism, such as the boom, winch, and outriggers, to force the old oil out and replace it with new oil.
For example, by operating the boom up and down, we can circulate the oil through the hydraulic cylinders and remove any old oil that may be trapped inside. Repeat this process for each mechanism until new oil is seen flowing out of the main return pipe.
Finally, connect the main return pipe to the fuel tank and add new hydraulic oil to the fuel tank to the specified position.
After all the old oil has been flushed out and new oil is flowing through the system, connect the main return pipe to the fuel tank. Then, add new hydraulic oil to the tank until it reaches the specified level. Make sure to check the oil level regularly to ensure that it remains within the proper range.
Explanation: Although this oil change is a bit slower and it also depends on the specific vehicle model and situation, at most half a day to one day is enough for doing this.
Changing the hydraulic oil of atruck-mounted crane can be a time-consuming process, but it is essential for maintaining the performance and reliability of the crane. The time required for the oil change can vary depending on the complexity of the hydraulic system and the experience of the person performing the task.
For some smaller cranes with simpler hydraulic systems, the oil change may take less time. However, for larger cranes with more complex systems, it may take longer. Additionally, if there are any issues or complications during the oil change, such as difficult-to-access components or stubborn old oil, it can further increase the time required.
In conclusion, draining the waste hydraulic oil and changing it with new oil is an important maintenance task for truck-mounted cranes. By following the correct methods and paying attention to the condition of the hydraulic oil, operators can ensure the proper functioning and longevity of their cranes. Regular oil changes can help prevent costly breakdowns and extend the life of the hydraulic system.
