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Technical Paper Series I00-1.9
Biodegradable, Fire-Resistant, High-Performance Water-Glycol Hydraulic Fluids Dr. George E. Totten, Union Carbide Corporation Roland J. Bishop, Jr., Union Carbide Corporation Jacques Cerf, Union Carbide Canada Inc.
Presented at the International Exposition for Power Transmission and Technical Conference 4-6 April 2000
LEGEND Sample Identification Number: I00-3.2 I 00 3 2
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Volume number (only one volume) 2000, year of the conference Conference Session Number Second paper in the Session’s presentation order
All papers presented at the 2000 International Exposition for Power Transmission and Technical Conference are available in one volume, Proceedings of the 48th National Conference on Fluid Power.
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BIODEGRADABLE, FIRE-RESISTANT, HIGH-PERFORMANCE WATER-GLYCOL HYDRAULIC FLUIDS George E. Totten and Roland J. Bishop, Jr., Union Carbide Corp., Tarrytown N.Y. Jacques Cerf, Union Carbide Canada Inc., Anjou, Quebec Canada Although the final Blue Angle label requirements are being developed, an approved hydraulic fluid will probably require greater than 80% biodegradability in 21 days by the CEC-33-A93 test or greater than 70% biodegradation by the Modified Sturm Test. All components must be non-polluting as evidenced by a Water Hazard Class 0 or 1. In addition to the base stock, a hydraulic fluid typically contains additives. The additives are used to enhance the fluid properties which include antioxidant, anti-wear, reduced foaming and improved air release properties. The presence of these additives are integrally dependent on the overall biodegradation and toxicology properties of the hydraulic fluid. [8,9,10,11] Additive selection is of paramount importance because their presence may significantly affect the net biodegradability properties of a hydraulic fluid.  Thus far, the most commonly cited base stocks used for the formulation of "environmentally friendly" hydraulic fluids are either a vegetable oil or a synthetic ester [7,13,14]. The most common vegetable oils that have been identified for hydraulic fluid formulations are soybean oil, [15,16,17] rapeseed oil , and high oleic sunflower oi1. Work by Rhee, et.al, have shown that synthetic esters exhibit a number of advantages over vegetable oils such as a broader range of operational temperature, typically, -40°C 150°C versus to vegetable oil derived fluids which typically exhibit operational temperatures of -10°C 90°C.[20This range of operational temperature of vegetable oils often renders them unsuitable for cold-weather applications. Other workers have reported that in addition to a broader operational temperature range, synthetic esters provide substantial improvement in the thermal/oxidative stability than many vegetable oil based fluids. [21,22] A number of workers have published results of use of various vegetable oil derived hydraulic fluids. [18,23-26] Typically, either a vane or piston pumps were used for performance testing. Although the antiwear results were generally good, these tests showed that vegetable oils exhibit poorer oxidative stability than mineral oil based hydraulic fluids. In view of the significant market pressures for the availability of "environmentally friendly" hydraulic fluids, most hydraulic pump manufacturers and many equipment suppliers have developed guidelines for the selection and use of these fluids. [ 27-30] Due to the
ABSTRACT Like all industries, the fluid power industry is under increasing pressure to identify and use hydraulic fluids that offer higher performance, improved fire safety, and exhibit improved environmental and toxicological behavior. Recently a novel hydrolube composition has been developed that is capable of being used in hydraulic pum.ps at pressures of 34.4 MPa (5000 psi) and greater. In addition to being a Group 1 Fire Resistant Hydraulic Fluid according to the new Factory Mutual Research Corporation's testing methodology, this high-performance hydrolube also exhibits excellent biodegradability and toxicology properties. The objective of this paper is to discuss pump performance, fire resistance, and environmental and toxicology properties of this fluid..
INTRODUCTION Although mineral oils have traditionally been the most commonly used hydraulic fluids in the fluid power industry, they are being subjected everincreasing controls particularly due to the increasingly stringent governmental regulations regarding their use. Routine disposal and inadvertent leakage of used oils into the soil where it may leach into drinking water aquifers is becoming increasingly regulated by the EPA.  Improper disposal, even if it is incidental, may be the source of large penalties or even litigation.  European studies have identified hydraulic fluid leakage as one of the primary sources of ground water contamination. This has been followed by a worldwide effort to identify hydraulic fluids which will exhibit reduced environmental and toxicological impact upon incidental contact with the environment. [4,5] Additional impetus has been provided by the use of national environmental labeling criteria. One of the first and most stringent environmental labeling procedures is the German "Blue Angel" label. Another program currently in development is the Environmental Choice Program of Canada. .
This fluid is d e s i g n a t e d as U C O N ® H P - 5 0 4 6 and is a v a i l a b l e from U n i o n C a r b i d e Corp., Danbury, CT.
In a more recent study, using the ASTM D 2882 Vickers vane pump test, conducted for 100 hours at 13.7 MPa (2000 psi) and 1200 rpm, it was shown that a high performance hydrolube  exhibited lower wear rates than achievable with mineral oil. The wear rate data is shown in Table 2.
variability of the performance of some of the vegetable oil based hydraulic fluids that are currently available, some manufacturers appear to have developed their own privately labeled fluids to provide greater quality assurance. Because of their favorable low temperature properties (pour point of -63°C), water solubility and fire resistance, hydrolube compositions provide a potential alternative to vegetable oils and synthetic esters as biodegradable hydraulic fluids.  Unfortunately, although there are numerous references describing various biodegradability properties of vegetable oils and to a lesser extent synthetic esters, there are considerably fewer analogous references describing recently obtained biodegradation and toxicological results for hydrolube compositions obtained using OECD GLP Principles (OECD, 1992a). In some cases, it is not clear either how the reported data was obtained or if it was previously published in other sources. One of the objectives of this paper is to provide recently published biological and toxicological data for a newly developed high-performance hydrolube composition.
Table 2 Comparison of ASTM D 2882 Vane Pump Test Results for Various Fire-Resistant Hydraulic Fluids and Mineral Oil Fluid Wear Rate (mg/hr) 1 Conventional Hydrolube 0.63 Phosphate Ester 0.05 Polyol Ester 0.10 High. Performance 0.10 Hydrolube Anti-wear Oil 0.24 1. These test were conducted for 100 hours at 13.7 MPa (2000 psi) and 1200 rpm using a SperryVickers V-104 vane pump according to ASTM D 2882. The pump was equipped with a 30 I/min (8 gpm) ring. The "pass" criteria is 1.0 mg./hr.
DISCUSSION What is a "High-Performance" Hydrolube?
In addition to exhibiting low wear rates, these high performance hydrolubes may be used at high pressures (>34 MPa, 5000 psi), previously unattainable with other more conventional hydrolube compositions. In a number of recent cases, this fluid has been used in some vane pumps not only at high pressures but also under non-derated conditions. Therefore, a high-performance hydrolube is an aqueous hydraulic fluid that can be used at pump pressures approaching those normally reserved for mineral oils, often under non-derated operating conditions.
There have been progressive improvements in the performance of hydrolubes since their initial introduction in 1947.  Table 1 illustrates that wear rates have continuously decreased from 1955-1974 approaching those exhibited by mineral oils when tested according to DIN 51,389 (Vickers V-104 vane pump for 250 hours at 10 MPa (1500 psi) and 1500 rpm.
Table 1 Historical Wear Rates of Hydrolubes (19551974) Total Wear (mg) 1 Year 1955-1965 1300-2800 1965-1970 4700-15100 1970-1974 300-1100 after 1974 approx. 100 (Mineral Oil)