How good that there are alternatives to conventional hydraulic oil. In applications with a high risk of loss and contamination, an oil must be used that has the lowest possible impact on the environment in the event of leakage. Bio-based hydraulic oils have gained acceptance here. However, the technical advantages of these oils are also penetrating other areas. What is there to consider here and how do GIEBEL Adsorbers® help to save costs?

Rapidly biodegradable oils

Environmentally compatible hydraulic oils are classified according to ISO 15380 / ISO 6743-4 are divided into the following groups:

  • HETG / Triglycerides (vegetable oils)
  • HEES / synthetic esters
  • HEPG / Polyglycols
  • HEPR / Polyalphaolefins and other hydrocarbons

The synthetic esters are particularly interesting because they can potentially be produced from renewable raw materials instead of petroleum. The advantages of rapidly biodegradable oils are:

  • a lower risk of contamination,
  • excellent lubricating properties
  • a good viscosity index and
  • a service life that can even exceed that of comparable mineral oils.

Notes on maintenance

The enemies of hydraulic oil are solid contaminants, undissolved air, temperature, an unauthorized mixture, and water. Bio-oils are extremely sensitive to hydrolysis and decompose when exposed to water. Therefore, when using these fluids, special care must be taken to prevent moisture from entering the tank. The water content should be less than 0.1% for bio-oils.

Consequences of lack of maintenance

The water content in the fluid is negatively affected by the relative humidity in the free part of the tank. There are various reasons for the entry of humidity. One frequently neglected source of error is the breather filter. Due to oil level fluctuations, fresh, moist air is drawn in with each cycle, contaminating the oil. Water can really decompose HEES fluids. It is therefore advisable to regularly analyze the pressurized fluid and effectively protect it from water.

Protection by aeration dryer

By using an aeration dryer instead of an aeration filter, the incoming air is almost completely dried. As a result, the water content in the air is less than 2 g/m³, with a dew point averaging below -12.5 °C.

Adsorbers can be retrofitted very easily, which makes sense at the time of oil changeover to bio-oil. But also during the new installation or after a deteriorated laboratory result of the oil, the use of a filter adsorbing the humidity in the air is a simple and very effective protective measure.

Examples of use

From an ecological point of view, bio-oils are advisable where rapid biodegradability is required. In addition, there are fields of application where these operating fluids have advantages over conventional products due to their specific properties. These include, for example:

Hydraulics of a lift bridge

Hydraulics in the hydropower plant

Hydraulics on a cruise ship

Hydraulics on a lock

Excavator hydraulics

Hydraulics of a tunnel boring machine


The use of an adsorber ensures that rapidly degradable hydraulic fluids can show their advantages over conventional fluids. A longer maintenance interval can be combined with ecological use and sustainability. GIEBEL Adsorbers® help to protect oil from its enemies and to save costs.