An excavator remains an excavator for the time being. The similarities between a classic earthmoving excavator and a mining excavator cannot be overlooked. In the classic case, both are driven by a diesel engine. The work hydraulics together with the slewing gear take care of the excavation and a hydrostatic traction drive ensures freedom of movement. Incidentally, the trend towards e-mobility and automation has now also arrived here. Today, fully electric excavators are also ready for the market and in use. Big and smart are therefore by no means mutually exclusive.

In principle, similar assemblies are to be lubricated in an excavator, whether in the earthmoving or mining sector. If we look at the classic oil-lubricated components of an excavator, these are mainly the diesel engine, transfer case, slewing gear, traction drives and the hydraulic system (work hydraulics and hydrostatic traction drive). For the sake of simplicity, the different systems, e.g. of wheel loaders or tippers, should not be dealt with in detail at this point.

Table 1 shows an overview of the lubricating oils used in an excavator in the earthmoving sector and, by way of comparison, in a mining excavator, followed by explanations of the principal and operational characteristics.

Low-emission and consumption-optimised engines are currently used in both sectors (emission limit values of stages IV and V). Modern engines place high demands on the quality of the engine oil. Engine oils of insufficient quality are not suitable for the operation of the exhaust gas aftertreatment systems such as particulate filters, AdBlue injection, SCR catalytic converters, nor do they achieve the expected oil change intervals. Yesterday’s standard engine oils are clearly not up to the job and can lead to expensive damage.

The transmission oils used differ significantly depending on the type of transmission. In addition to the gear oils listed above, some manufacturers also use special gear oils of SAE classes 30 and 50 in their equipment, and special LS gear oils in the axles of wheel loaders.

Detergent oils are increasingly used as hydraulic fluids, which keep penetrating condensate in suspension in a finely distributed manner in order to prevent its contact with the metal surface and thus corrosion. However, this does not mean that increased water content in detergent oils cannot cause cavitation damage, for example, to axial piston pumps. Detergent hydraulic oils should therefore also not exceed a maximum water content of 0.1 percent during use.

In response to the fluctuating temperatures, multigrade oils are increasingly being used in the earthmoving sector in particular. Their optimised viscosity-temperature characteristics allow a wider temperature application range and at the same time offer energy-saving potential.

Environmentally friendly hydraulic fluids have been used in construction machines for several decades in addition to classic hydraulic oils. These hydraulic fluids, known simply as bio-oils, must fulfil special environmental requirements in addition to the technical ones, for example in terms of biodegradability, ecotoxicity and sustainability.

Whether construction site or quarry: Both places are dusty, depending on the weather conditions, wet, cold or hot. However, the extraction of raw materials often takes place in areas that are far from urban centres and at the same time have extreme climatic conditions.

One major difference between mining equipment and classic construction machinery (earthmoving), apart from the size and the loads to be moved, can be found in the operation: The daily duration of use.

While an earthmoving machine in Germany works around 1,000 hours per year, a mining machine can easily work eight times that! A typical mining excavator works 23 hours a day, followed by one hour of maintenance, seven days a week, all year round. This results in significantly different maintenance requirements, guaranteed machine availability and longer service life of the components and oils used.

Two examples illustrate this difference quickly and easily:

• If the hydraulic oil in an earthmoving machine is changed – quite realistically – after five years, this means 5,000 hours of oil usage. If the hydraulic oil in the mining excavator had been changed after the same number of operating hours, it would be less than a year and absolutely insufficient.
• The same applies to the service life of the components to be lubricated. In addition, both the costs for the components to be replaced and the downtime costs of the mining equipment are many times higher than those of the earthmoving equipment.

Sustainability is rightly on everyone’s lips today. It's about conserving our natural resources, which are ultimately finite. Both the resources that we take from the earth for construction etc. and the resources that we need to operate the plants.

In addition to the use of sustainable lubricants, professional condition monitoring of the lubricating oils and hydraulic fluids used is a proven way of reconciling sustainability and economic requirements when operating machines and systems. A method that is increasingly used in both the mining and earthmoving sector. The main focus is on three things:

• The oil condition,
• abnormal wear trends,
• the monitoring of impurities.

This means that oils are only changed when necessary. At the same time, professional oil monitoring provides early information on irregularities, such as dirt or water ingress or other malfunctions, which in turn can significantly shorten the service life of components or even lead to unplanned machine failures.

“Think big!” also means thinking outside the box. Acting truly sustainably works best when environmental protection and economic efficiency are equally in focus. In this way, sustainable action can practically pay for itself.