Recently, many truck-mounted crane owners have been extremely confused and frequently ask when the hydraulic oil of the crane should be changed. Some might mistakenly assume that it is similar to private cars and should be changed only after it is completely used up. In reality, this is a significant misunderstanding. For the hydraulic oil of a crane, determining whether to change it is not based on simply waiting for it to be depleted but rather by identifying its viscosity. Today, the author will thoroughly teach you how to judge when hydraulic oil should be changed. Here are the detailed judgment steps:
Inverting hydraulic oil: Take out a portion of the hydraulic oil from the fuel tank and place it in two transparent glass bottles of the same size as the brand-new hydraulic oil respectively. Ensure that the bottle caps are tightly secured. Mark the two small bottles clearly and place them side by side. Then, invert them. This process is crucial for observing the behavior of the hydraulic oil. If the bubbles exhibited by the tested hydraulic oil in the bottle rise faster than those of the standard oil in the bottle, it indicates that the viscosity of the hydraulic oil is lower than that of the standard hydraulic oil. On the contrary, if the bubbles rise more slowly, it indicates that the viscosity of the hydraulic oil is higher. If the bubble rising speeds in the two bottles are close, it suggests that the viscosities are similar and there is no need to dilute or change the hydraulic oil at this time.
Let’s delve deeper into this step. The inversion of the bottles allows for a visual comparison of the bubble movement. The speed at which the bubbles rise is directly related to the viscosity of the oil. A lower viscosity oil will allow the bubbles to rise more quickly as it is less resistant to flow. This can be an indication of degradation or contamination of the hydraulic oil. On the other hand, a higher viscosity oil will cause the bubbles to rise more slowly as it is thicker and more resistant to flow. By comparing the bubble movement to that of a standard, new hydraulic oil, one can get a good indication of the condition of the used oil.
Glass plate inclination method: Take a clean glass plate and place it horizontally on a flat surface. Carefully drop a drop of the hydraulic oil taken from the fuel tank on one side of the glass. At the same time, drop a drop of standard hydraulic oil on the other side. After this preparation, start to incline the glass plate gently. 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, it indicates that its viscosity is lower than that of the standard hydraulic oil. Conversely, if the flow rate and flow distance are smaller, the viscosity is higher.
This method provides another way to assess the viscosity of the hydraulic oil. As the glass plate is inclined, the oil will start to flow down due to gravity. The rate and distance of flow are influenced by the viscosity of the oil. A lower viscosity oil will flow more quickly and cover a greater distance, while a higher viscosity oil will flow more slowly and cover a shorter distance. By comparing the behavior of the tested oil to that of the standard oil, one can further confirm the condition of the hydraulic oil.
It should be noted that normally, when a crane works for about two to three years, which is approximately 2,000 working hours, the hydraulic oil needs to be changed. However, this is only a general guideline. In theory, the oil change standard depends on several factors such as the viscosity and aging degree of the oil, as well as whether it is clean. In actual daily use, the decision to change the hydraulic oil is often determined based on actual working conditions and experience.
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. Additionally, regular inspections of the hydraulic system can help detect signs of oil degradation such as discoloration, increased acidity, or the presence of contaminants. These signs can indicate the need for an earlier oil change.
After determining that the hydraulic oil needs to be changed, the next step is to carry out the oil change process.
First, drain the hydraulic oil in the hydraulic tank. This is a crucial step as it removes the old, degraded oil from the system. Carefully remove the drain plug or use a suitable pumping device to drain the oil completely. After draining the oil, 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.
Remove the main loop pipe. This step allows for the flushing of the hydraulic system. Start the engine and let it idle to make the oil pump work. The oil pump will circulate the new oil through the system and help remove any remaining old oil.
Operate each mechanism respectively. This step ensures that the new oil reaches all parts of the hydraulic system. Manually operate each hydraulic mechanism such as the boom, winch, and outriggers. 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 process may need to be repeated several times to ensure that all the old oil is replaced.
The last step is to connect the main return pipe to the fuel tank and add new hydraulic oil to the specified position in the fuel tank. Check the oil level carefully and make sure it is within the recommended range. Once the oil change is complete, run the crane for a short period to check for any leaks or abnormal operation.
The above is the normal process of changing hydraulic oil. Have you learned it? Changing the hydraulic oil of a truck-mounted crane is an important part of maintenance. Regular oil changes can help ensure the proper functioning of the hydraulic system, prolong the life of the crane, and reduce the risk of breakdowns and costly repairs. By following the correct procedures and paying attention to the signs of oil degradation, crane owners can keep their equipment in good condition and ensure safe and efficient operation.
