High-performance hydraulic fluid. Improved viscosity-temperature behaviour of hydraulic oil for more efficiency and less energy consumption

Modern hydraulic systems pose ever increasing demands on hydraulic fluids. Some years ago hydraulic oils of type HLP used to be standard; nowadays advanced products with improved temperature as well as friction behaviour and sometimes detergent properties are applied more and more often. (Hans-Jürgen Scholz)
Efficiency and compactness of modern hydraulic plants are increasing. Because of reduced tolerances and improved surface qualities larger operating pressures and more precise components are possible. At the same time machines of increased efficiency are supposed to require less energy and to provide a reliable performance also under heavy operating conditions. This in turn means increased requirements on the hydraulic fluids as well.

More compact plants usually use smaller oil volumes which reduces the residence time of the hydraulic fluid in the oil tank and thus also the time available for cooling down. Operating temperatures of hydraulic oils in modern mobile plants increase and amount to about 80 °C on average, at peaks to more than 100 °C, pressures are between 275 and 425 bar.

Ageing processes
Smaller oil volumes, higher pressures and rising operating temperatures are extreme operating conditions requiring more than conventional hydraulic fluids. These conditions accelerate oil ageing which in modern fluids is inhibited by anti-oxidants. However, these additives degrade with longer operating times, as do anti-wear-components.

Furthermore, all oils, also fresh oil, contain air in dissolved from; this share increases with increasing age. From a certain saturation oxygen reacts with hydrocarbons of the oil which causes minor, explosion-like reactions similar to spontaneous ignitions in diesel engines. Often however, these air bubbles do not contain enough oxygen for an entire combustion process and therefore soot particles develop making oil ageing visible by giving the oil a black colour.

Oil ageing means a decrease of performance and an increase of viscosity which has direct effects on the efficiency of the pump and thus on energy consumption.

Maximum efficiency
HV Eco Fluid, the pressure fluid developed by ADDINOL, German expert for high-performance lubricants, is supposed to exceed the performance of conventional hydraulic fluids. It is based on mineral oils and a new additive technology and meets DIN 51524/3 (HVLP), DIN EN ISO 6743-4 (HV) as well as requirements of all leading OEM. The optimum viscosity-temperature behaviour guarantees maximum system efficiency at both relatively high and low temperatures. Compared to conventional HVLP, HV Eco Fluid achieves a higher efficiency of the hydraulic altogether which means: higher power under full load, faster reaction of the system and decreased fuel consumption.
Here the optimum viscosity-temperature behaviour is highly important. The viscosity of the hydraulic fluid affects the pump’s efficiency: its hydraulic efficiency depends on the mechanical and volumetric component. For lowly viscous oils inner friction decreases and the mechanical efficiency is improved. On the other hand the volumetric efficiency benefits from a higher viscosity. ADDINOL HV Eco Fluid ensures an adjusted viscosity for starting and under heavy conditions at full load, as high pressures and temperatures. This means, it improves the overall efficiency and contributes to a reduced energy consumption; optimum operating range is extended considerably.

Calculated cost reduction
The efficiency of ADDINOL HV Eco Fluid was assessed in field tests and compared to conventional HLP hydraulic oils. For example, one Caterpillar mobile excavator 318 filled with 255 litres hydraulic oil and equipped with a diesel engine of type 3066 was tested under normal operating conditions. According to test records fuel consumption at 100 % full load was decreased by 13.8 % and at 90 % load by 8.6 % compared to a hydraulic oil of type HLP after 10 days. At a diesel fuel consumption of 23.5 l/operating hour the total savings achieved are quite high.
In addition, HV Eco Fluid was compared to conventional hydraulic oils of type HLP and HVLP, to mono-grade engine oil SAE 10W and to ATF: it achieved significantly better results here as well:
- 5-10 % increased hydraulic power under full load
- 5-10 % higher flow velocities at temperature peaks
- 5-10 % faster reaction of the system
- 5-7 % energy saving
- 5-10 % reduction of fuel consumption at equal work.

The innovative ADDINOL HV Eco Fluid is available in viscosity grades ISO VG 32, 46 and 68. Expected savings for a plant are determined by ADDINOL by the help of a cost calculator taking into account individual parameters and assuming a 6 % reduction of fuel consumption.

German article published in Mobile Maschinen 3/2010 (view German article here)


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