Extending the life of Bosch Rexroth Hydraulics: Best Maintenance Practices
The smooth operation of regular processes is a major objective of every operations department. Bosch Rexroth, known for its reliable hydraulics lineup, remain pivotal in achieving that. Its hydraulic systems have a remarkable uptime and are an integral part of many industries around the world. While Bosch Rexroth brings reliability, proper maintenance practices are still required for long-term, error-free life of its products.
Covering the bases: a hydraulic system
Before diving deeper in hydraulic lineup maintenance, let’s revise our knowledge of hydraulic systems. A hydraulic system [1] consists of plumbing comprising, but not limited to, a reservoir (tank), pump, filters, and valves and hydraulic fluid flowing through the preceding as seen in Figure 1. Using the components of plumbing, the fluid is propagated to transfer force in a uniform and lossless manner. Ensuring that the pump provides the required pressure, the filters remove the contaminants, and the temperature remains in the operating range is the prime concern for the successful operation of a hydraulic system.
Standard Recommendations
For maintenance of hydraulics lineup, Brandon Wronski recommends three simple procedures in National Driller Magazine. Firstly, one must maintain a clean and sufficient hydraulic fluid having the required type and viscosity as recommended by the manufacturer. Secondly, filters and strainers should be inspected and cleaned at regular intervals. Lastly, all the connections in the hydraulic system must be tightened, but not to the point of distortion, to prevent aeration.
Keep an eye out for oil
It is recommended to analyze oil samples at regular intervals. If lacking in equipment or capacity for outsourcing, check the oil by looking at its colour. Poor oil can be:
- Dark and smell burnt
- Yellow or milky, indicating the presence of air or water.
Let’s go practical
While it’s true that a hydraulic system will work best when it is clean and isolated from the outside environment, how will we ensure that? Let’s discuss the maintenance procedures for Bosch Rexroth hydraulic lineup in practical terms.
Fluid Maintenance
To ensure an excellent service life of the hydraulic fluid, we need to ensure the following:
- Controlling the temperature — As the fluid is forced through the tubing, it heats up. At high temperatures, the oxidation of the oil can occur resulting in the formation of varnish and sludge [2]. On the other hand, low temperatures can cause condensation, and thus pump cavitation. To ensure an optimum temperature, keep the reservoir clean and clear the surrounding area from obstructions for heat exchange.
- Keeping the plumbing clean — Prevent contaminants from entering the plumbing around the reservoir cover, openings for suction and drain lines, and through leaks in pump suction lines.
- Keeping the fluid clean — Hydraulic fluid needs to be clean for the long life of a hydraulic system. To ensure that, regularly inspect filters for clogging or pressure drops and prevent the system from entering bypass mode.
- Using an oil analysis program — While Bosch Rexroth recommends that the oil in its hydraulic lineup should be changed after every 2000 to 4000 operating hours [3], a better alternative is to use an oil analysis program. It will allow you to increase the interval of change. You can refer to the “Rexroth Oil Cleanliness Booklet” [4] for further details.
System Maintenance
While the hydraulic fluid is the soul of the system, the system itself also provides many cues for inspection and diagnosis. Employing those in maintenance pave way for a longer life of hydraulic lineup. A 10-point checklist [2] for weekly inspection is as follows:
1) Check fluid levels and add oil (of the same oil brand and viscosity) if needed.
2) Check filter clogging indicator or pressure gauges.
3) Check system temperature.
4) Inspect breather cap and filter.
5) Perform visual inspection on all pipes, pipe connectors, and system hoses for leaks.
6) Inspect the inside of the reservoir using the fill hole.
7) Inspect a small sample of hydraulic fluid for colour and smell.
8) Use an infrared thermometer to scan the electric motor for hot spots.
9) Listen to the pump for any signs of cavitation.
10) Scan servo valve with an infrared thermometer. High valve temperature, about 150 °F, indicate that valve is sticking.
References
[1] Deparment of the Army, Hydraulics. Washington, DC, 2017.
[2] Exxon, “Hydraulic System Care and Maintenance,” 2009.
[3] B. Rexroth, “Installation, Commissioning and Maintenance of Hydraulic systems,” Manual.
[4] Rexroth Bosch Group, “Rexroth Oil Cleanliness Booklet,” 2011.