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Savings potential for hydraulic plants

In a long-term test in a 6,500-kN-machine new hydraulic oil reduces energy consumption by 5 percent

Hydraulic systems of modern injection moulding machines 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 are applied more and more often. Now ADDINOL Lube Oil GmbH, Leuna, offers HV Eco Fluid – a hydraulic fluid which increases the efficiency of hydraulic systems and decreases the energy consumption of plants. In a long-term test in an injection moulding machine of a company supplying parts for auto industry the operator could prove savings of up to 5 % together with ADDINOL.

Efficiency and compactness of hydraulic systems in injection moulding machines are increasing. Because of reduced tolerances and improved surface qualities larger operating pressures are possible for increased clamping force and a more precise operation of components. At the same time machines of increased efficiency are supposed to require less energy and to be available all the time. This in turn means increased requirements on the hydraulic fluids as well which transmit forces, lubricate and protect. Hydraulic systems in injection moulding machines usually use smaller oil volumes – this 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 increase.

Smaller oil volumes, higher pressures and rising operating temperatures are extreme operating conditions requiring more than conventional hydraulic fluids. Furthermore, all lubricants and hydraulic fluids are subject to ageing during their application which means they react with oxygen. High temperatures, long operating lives, high pressures and sometimes also wear particles accelerate this process. In order to slow it down the fluids contain anti-oxidants. However, these additives degrade with longer operating times, as do anti-wear-components. In combination with heavy operating conditions these speed up the oil ageing further.

Oil ageing means a decrease of performance and an increase of viscosity which has direct effects on the efficiency of the pump. Pressure build-up necessary for the operation of the injection moulding machine is not effected as required, the hydraulic fluid needs to be changed and shorter operating intervals increase the costs.

In elaborate tests with rotary vane pumps, gear pumps and reciprocating piston pumps the viscosity’s influence on pump efficiency has been proven several times. Its hydraulic efficiency depends on the oil’s viscosity at the pump inlet, pump speed and pressure. Therefore, the viscosity of the fluid does not only influence the overall efficiency of the pump but also energy consumption. Thus stable viscosities over the whole operating period are expected.

Taking these complex relations into account ADDINOL, expert for high-performance lubricants, has developed the innovative hydraulic oil ADDINOL HV Eco Fluid. It is based on high-grade mineral oils and an additive technology especially developed for these conditions. HV Eco Fluid meets DIN 51524/3 (HVLP), DIN EN ISO 6743-4 (HV), ISO 11158 (HV), AFNOR NFE 48603 (HV), CETOP RP 91 H (HV) as well as requirements of all leading OEM. The product can be delivered in the viscosity grades ISO VG 32, 46 and 68. 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 energy consumption.

In order to prove the performance and the reduced energy consumption under practical conditions ADDINOL documented the application of HV Eco Fluid 46 in an injection moulding machine. The plant of type Krauss-Maffei 650 (6.500 kN clamping force) is operated by a well-known company in the plastics industry producing parts for auto industry such as handle bars and covers for engine compartments. Operating hours per year amount to roughly 7,500 hours; oil filling is 1,500 litres. Before, conventional hydraulic oil HLP 46 (DIN 51524-2, DIN EN ISO 6743-4 HM) had been used. The system required no flushing before the change as the new fluid can be mixed with standard hydraulic oils according to DIN without any problems.

During application the operator of the injection moulding machine measured and documented energy consumption. Before and after the oil change the same kinds of injection moulding parts were produced by the machine. For both parts energy consumption under constant conditions (same cycle times etc.) was determined and calculated for every piece moulded. In the time monitored the same number of parts was manufactured. Therefore the energy consumption per injection moulding part could be determined very exactly.

Ten months after the start the notes were analysed for the first time. For the operation with ADDINOL HV Eco Fluid 46 energy consumption was reduced by 4.8%. In concrete figures this means:
  • In the first year of operation with ADDINOL HV Eco Fluid costs declined by about 500 EUR. This calculation already takes the extra costs for the higher-quality oil into consideration.
  • Provided the oil is not changed in the meantime total savings amount to ca. 3,000 EUR after three years.
  • If further injection moulding machines of the plant are changed over to the new fluid this will cut total costs accordingly.

In addition to measuring and calculating the energy consumption, ADDINOL had a sample analysed by an independent laboratory after the first six months with positive results: the sample did not show any irregularities. In order to guarantee maximum safety and to collect further information on the performance and power of the product the application is accompanied by oil sample analyses once a year. The fluid has been applied since February 2009 in the machine sketched out above without any failures or problems. Energy consumption is still measured to make statements on the product’s sustainability over longer periods.