With any oil change, the aim should be to remove as much of the old fluid as possible. There are some simple steps that can be taken to maximize the amount of oil coming out of the system.
Healthy hydraulics recommends:
1. The first thing is to ensure that the machine is parked on stable level ground with the excavator end folded to close the hydraulic cylinders. The engine should be off and the hydraulics isolated.
2. Oil will drain better if the machine and oil is warm/hot. Do not drain oil immediately after hard work as the heat soak could damage components causing sticking.
3. Depending upon the hydraulic system’s complexity, there may be more than one drain port from which to drain oil. The main hydraulic oil tank should have the largest drain port, which will allow the oil to be safely removed for proper disposal or recycling. However, some components may have individual drains to remove fluid from them or other low areas of the circuit.
4. Another good way to drain the system is to remove 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.
5. When draining a machine air must be allowed into the circuit which allows the oil to drain fully. Ideally all breather ports should be fitted with a desiccating breather which reduces the moisture in the air and helps reduce contaminant ingression.
6. Most mobile equipment manufacturers will have their own procedures for the oil change process. While they may vary from brand to brand and model to model, the same basic elements 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 and ensure a healthy machine.
7. Always follow the manufacturer’s recommendation regarding the grade and quantity of hydraulic oil. Do not mix brands or grades of oil. If a biodegradable hydraulic oil is being used extra care needs to be taken as these are oils are very sensitive to water ingress.
8. Portable filter carts can be used not only to filter incoming oil but also to pull out old oil.
9. If you are concerned about the quality of the new oil or if the machine has suffered from oil contamination prior to the oil change it is a good idea to filter the new hydraulic oil before filling the machine. A range of ‘off-line’ filter carts are available for this purpose. Most are fitted with twin filters that remove water and contaminants. Hydrotechnik (www.hydrotechnik.co.uk) supply filter carts with in-built particle counters that give a read-out of oil cleanliness in real time.
10. Most modern excavators, and other types of earthmoving equipment, with high pressure servo controlled hydraulic systems require oil with an ISO cleanliness code of 16/14/11 or better and a water content of 100-400ppm.
11. Oil sampling and analysis is a good way to ‘plot’ the cleanliness level of hydraulic oil between changes. Off-line filtration can be used at any time to bring oil back to an acceptable cleanliness level safeguarding a machine’s reliability and performance.