"When changing out hydraulic oil in mobile hydraulic equipment such as an excavator, what is the best way or process to remove all or as much oil as possible? Are there any published processes for this?"
With any oil change-out, the goal is to remove as much of the old fluid as possible. There are some steps you can take to maximize the amount of oil coming out of the system.
One thing you can do is to ensure all of the hydraulic cylinders are in the closed position. When they are closed, little oil is left in the components. The same is true for any other expansion component located within the hydraulic circuit.
Depending upon the hydraulic system’s complexity, there may be more than one drain port from which to drain oil. The main reservoir should have the largest drain port, which will facilitate the quickest draining of the system. However, some components may have individual drains to remove fluid from them or other low areas of the circuit.
Another good way to drain the system is to pull any return-line filters. These filters can hold a significant amount of oil, and by removing them, you also open the return lines for additional draining.
Whenever a drain is performed, air must be allowed into the circuit to permit any oil to drain. All breather ports should be outfitted with breathers to strip incoming air of moisture or particulate debris. A good desiccating breather is a must to help reduce contaminant ingression.
Different mobile equipment manufacturers will have their own procedures for the oil change process. While they may vary from model to model, the same basic elements will exist. Remove the drain plug, replace the filters and refill with new oil. Gravity will do the majority of the work in draining the oil, but there are other options to help expedite the process.
Portable filter carts can be used not only to filter incoming oil but also to pull out old oil. By utilizing a filter cart to drain the oil, you can reduce the time it takes to remove the oil as well as fill the system without having to open the reservoir to the environment for as long a period. If using a filter cart to drain the oil, be sure to bypass the filters. Finally, don’t forget to save the filters for topping up or refilling the compartment.