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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.

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.

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.

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.

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.

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.

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.

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.

There has been an ongoing interest in replacing mineral oil with more biodegradable and/or fire-resistant hydraulic fluids in many mobile equipment applications. Although many alternative fluids may be more biodegradable, or fire-resistant, or both than mineral oil, they often suffer from other limitations such as poorer wear, oxidative stability, and yellow metal corrosion which inhibit their performance in high-pressure hydraulic systems, particularly high pressure piston pump applications. From the fluid supplier's viewpoint, the development of a definitive test, or series of tests, that provides sufficient information to determine how a given fluid would perform with various hydraulic components would be of interest because it would minimize extensive testing. This is often too slow or prohibitively expensive. Furthermore, from OEM's (original equipment manufacturer's) point of view, it would be advantageous to develop a more effective, industry accepted fluid analysis screening.

Reaction Injection Molding is rapidly becoming accepted as a viable industrial process for preparing large intricate parts using reactive urethane intermediates. High modulus polymers are among the newest systems capable of being prepared using the RIM process. Proper balance of the many features of urethane chemistry and technology allows preparation of high modulus material with excellent properties, including impact resistance. Fillers can be added to these high modulus polymers to increase their moduli even further. Studies have shown that milled fiberglass added to certain polymers can result in a composite with a flexural modulus in excess of 320M psi (2206MPa).

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.