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Technical Paper

Investigation of Premature Water Pump Seal Failures

Automotive water pump seals which have failed prematurely during in-service use have been characterized using a variety of analytical methods. Nearly one hundred failed seals collected over the past several years from local automotive dealerships, major automotive manufacturers, coolant related fleet tests, and pump seal manufacturers have been examined as part of this study. This has enabled us to determine the chemical composition and morphology of surface deposits on failed seals and classify their failure mode. The main failure mode found for domestic in-service automobiles is filming, a term used to describe a failure type in which deposits form between the sealing surfaces resulting in a leak path. This paper reports on the composition, morphology and possible causes of in-service filming failures. In addition, the results of this study will be contrasted with those reported in other studies which found film transfer as the main type of failure.
Technical Paper

Water-Glycol Hydraulic Fluid Evaluation by ASTM D 2882: Significant Contributors to Erroneous Results

One of the most commonly used tests to evaluate the antiwear properties of a hydraulic fluid is ASTM D 2882 which is based on a Vicker's V-104 vane pump. Although this is a commonly used test, the results are subject to numerous potential problems in both testing procedure and pump hardware. In this paper, the particular focus will be placed on potential problems that may be encountered with testing of water-glycol hydraulic fluids which may lead to erroneous and non-reproducible results.
Technical Paper

Performance Map Characterization of Hydraulic Fluids

There is increasing interest in the development of bench tests to characterize the performance of hydraulic fluids in order to minimize the cost of testing and the volumes of fluid currently required for pump testing. One method which permits comprehensive characterization of the boundary, mixed EHD and EHD wear regimes encountered in pump lubrication is to develop a performance map. This paper discusses the use of this testing method to characterize the performance of two experimental hydraulic fluid formulations.
Technical Paper

Effect of Low Molecular Weight Carboxylic Acids on Hydraulic Pump Wear

All types of hydraulic fluids may encounter thermal excursions at some point during their lifetime in use. When this occurs, there is the potential for the formation of degradation by-products. For most hydraulic fluids, including water-glycols, these degradation by-products include various low molecular weight carboxylic acids, e.g. formic acid and acetic acid. This paper describes the potential formation of these acids and the impact of their presence on wear and corrosion of hydraulic systems.
Technical Paper

Water-Glycol Hydraulic Fluid Performance Monitoring: Fluid Performance and Analysis Strategy

Hydraulic fluid performance, including water-glycols (W/G), is dependent on the chemical composition of the fluid and cleanliness. An overview of W/G fluid chemistry on pump wear is provided here. Also provided, is a brief overview of the impact of fluid cleanliness on the potential wear properties of various components. Finally, an overview of recommended analytical procedures to assure adequate long-term fluid hydraulic and lubrication performance is provided. If these procedures are followed, substantial improvements in hydraulic pump longevity and performance will be realized.
Technical Paper

Evaluation of Hydraulic Fluid Performance: Correlation of Water-Glycol Fluid Performance by ASTM D2882 Vane Pump and Various Bench Tests

The antiwear results of a series of hydraulic fluids were determined using various bench wear tests including: Shell 4-Ball, Pin-on-V-Block Falex Wear Test, SRV Ball-on-Disk, Timken Block-on-Ring and a recently developed cyclic contact stress (3-vane-on-ring) test and the ASTM D-2882 Sperry-Vickers V-104 vane pump test. These bench tests were selected since they are used in the fluid power industry for fluid selection, qualification and performance troubleshooting. The results of this work showed that none of the bench tests evaluated provided any correlation with the wear rates obtained with the ASTM D-2882 pump test. Comparison of these results relative to fundamental lubrication principles and published literature on similar problems showed that bench wear test correlations are possible only if the conditions of the wear test, such as wear contact geometry, loading, speeds, and materials reasonably model the specific wear contact of interest in the hydraulic pump.
Technical Paper

Historical Overview of the Development of Water-Glycol Hydraulic Fluids

Because of on-board fire problems during World War II, the us Navy initiated a program to develop hydraulic fluids that were more fire-resistant than the mineral oils that were in use at that time. Water-glycol hydraulic fluids were subsequently developed and first commercialized in 1947 which offered vastly improved fire resistance relative to mineral oils. Since 1947, in addition to formulation changes, there is significantly greater understanding of the impact of these changes on pump wear performance. This paper will present a selected overview of water-glycol formulation chemistry, some of the fluid formulation issues that have been encountered and the evolutionary improvement of hydraulic pump wear performance.
Technical Paper

Performance Map and Film Thickness Characterization of Hydraulic Fluids

A new approach is presented for the evaluation of hydraulic fluids for pump wear performance. The approach uses performance maps developed in terms of rolling and sliding velocities to establish lubrication and failure regimes for test fluids. Testing pathways within the performance map can determine the fluid attributes for wear, scuffing and traction (friction). The measurement of oil film thickness with optical interferometry is used as part of a comprehensive approach for fluid evaluation. These measurements allow the lubricated contact itself to provide the viscous film forming properties of the fluid. An “effective” pressure-viscosity coefficient is determined for a range of fluid types. Performance mapping, together with film thickness measurements, provide an insight into the fundamental chemical and physical attributes of the fluid. The new approach provides an alternative to the limited reliability of bench tests and the time consuming and expensive hydraulic pump tests.
Technical Paper

Hydraulic Pump Testing Procedures to Evaluate Lubrication Performance of Hydraulic Fluids

Although the selection and role of hydraulic fluids as energy transfer agents is relatively well understood, there is no consensus on the appropriate procedures to evaluate lubrication properties on a laboratory scale. Because the use of bench tests such as the Shell 4-ball has traditionally produced poor pump wear correlations, it has been necessary to develop various hydraulic pump tests for this purpose. Since hydraulic fluid lubrication is being modeled, it is necessary to view these hydraulic pump tests as tribological tests. The objective of this paper is to provide an overview of various vane, piston and gear pump tests that have been reported as tribological tests.
Technical Paper

Recent Results of Biodegradability and Toxicology Studies of Water-Glycol Hydraulic Fluids

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 pumps 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..
Technical Paper

Review of ASTM D-2882 Hardware Problems and Suggested Solutions

The ASTM test method D-2882 (Standard Test Method for Indicating the Wear Characteristics of Petroleum and Non-Petroleum Hydraulic Fluids in a Constant Volume Vane Pump) is widely used to evaluate hydraulic fluids. Performing this method can be difficult due to problems with the pump hardware and the written procedure. This paper discusses the problems and suggests possible remedies.
Technical Paper

Polyalkylene Glycol Refrigeration Lubricants - Current Status and Retrofit Applications

Polyalkylene glycol (PAG) lubricants have been chosen for use with refrigerant HFC-134a by the mobile air conditioning industry. As this industry gears up to use PAG lubricants, several issues have surfaced regarding the handling of these products. Information will be presented regarding the hygroscopicity and elastomer compatibility of PAG lubricants. Polyalkylene glycols are being evaluated by the automotive industry as retrofit lubricants. PAG lubricants exhibit good stability in the presence of residual CFC-12. Data from retrofit tests performed on compressor test stands will be summarized. This paper will also describe the retrofitting of CFC-12 vehicles to HFC-134a and PAG lubricants.
Technical Paper

Advanced High-Temperature Test Methods for Gasket Materials, 1989

Testing of nonasbestos gasket facing materials using high-temperature creep, high-pressure sealability, and an elevated pressure thermal conductance apparatus is presented. A discussion of the composition of nonasbestos facing suggests that thermal gravimetric analysis yields little useful information to the designer and that high-performance testing under thermal and/or compressive load are required. Materials are ranked in order of service temperature from cellulose fiber reinforced to homogenous flexible graphite. The data lead to the conclusion that the changes occurring in a gasket facing from ten percent thermally induced compressive creep can result in orders of magnitude change in sealability.