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In 1999, three new ground-breaking hydraulic filter test standards were adopted: ISO 11171 provides NIST (National Institute of Standards and Technology) traceable calibration of automatic particle counters (APCs); ISO 11943 establishes procedures for calibrating on-line particle counters; and ISO 16889 updates the multi-pass filter test method. Together, these standards ensure the generation of meaningful, reproducible multi-pass filter data and, for the first time, provide NIST traceability for particle size data obtained using APCs. In the global marketplace where data may be generated by different laboratories, personnel and/or equipment, companies face special challenges in obtaining consistent, quality filter test results. This paper addresses three questions: (1) what are significant differences in filter performance data, (2) what are the sources of inter-laboratory variability, and (3) what can be done to reduce variability.

To meet stringent emission regulations, particulate filters will be required for diesel engines. Effective filters should reduce both the mass and number concentrations of particulate matter. For this reason, the performance of diesel particulate filters (DPFs) should be evaluated by measuring both gravimetric and fractional efficiency. This paper reports on a method developed for measuring particulate emissions on a mass and number basis. A two-stage dilution process was used in which the entire engine exhaust gas is directed into a primary dilution tunnel with a critical flow venturi. This constant volume system maintains proportional sampling throughout temperature excursions. A portion of the diluted exhaust gas is directed to a secondary dilution tunnel, for further dilution and determination of particle size distribution using a scanning mobility particle sizer. The engine was run at ISO 8178 modes.

Liquid automatic optical particle counters (APCs) are used to monitor contamination levels in hydraulic and engine oil, to establish component and assembly cleanliness level specifications, and to determine filter efficiencies and size ratings. As a result of the recent revisions to ISO particle counter calibration, multi-pass filter test, and on-line particle counter calibration standards, it is anticipated that the quality and reliability of particle count and filter test data will improve, increasing their usefulness to the hydraulics, automotive and aerospace industries. However, the resultant redefinition of particle sizes affects how contamination levels and filter performance are reported and interpreted. The impact of these changes is discussed in this report.

Economic, regulatory and environmental concerns are forcing vehicle operators to reevaluate oil filtration practices. Operators can choose from options, including conventional disposable filters, sieves, centrifugal separators and in-place cleanable oil (IPCO) filters. To guide decisions about filtration practices, this paper compares the performance, serviceability, economics and environmental impact of these options. A laboratory evaluation of representative products was conducted. Additional field tests of disposable and IPCO filters for on- and off-road applications were also conducted Disposable and IPCO filters are similar in terms of serviceability and contamination control, but IPCO filters offer environmental and economic advantages

Environmental concerns over disposable oil filters impact engine oil filter selection for over-the-road trucks and buses. Fleets are extending oil drain intervals and considering alternatives to traditional spin-on filters in an attempt to reduce the costs associated with filter service and disposal. Alternatives to spin-ons, such as screen type separators, are inadequate in terms of particle removal efficiency and contaminant holding capacity. Further, these alternatives typically cost 20 to 40 times more than spin-on filters and are difficult to service. This paper discusses a new line of cleanable, high performance spin-on oil filters. Laboratory tests show that these reusable filters meet or exceed efficiency and capacity specifications set by engine manufacturers. These filters can be cleaned at the normally scheduled service interval without special tools and without removing the filter from the engine.

Environmental concerns over the use and service of traditional disposable oil filters are becoming important in filter selection for off-road equipment. This is particularly true on job sites where “zero” equipment oil leakage is demanded. However, many alternatives to traditional filters do not meet original equipment manufacturers specifications for particle removal efficiency and contaminant holding capacity. This paper discusses the operating features and performance of a new line of oil filters that can be cleaned in-place, on equipment. These new filters meet or exceed the capacity and contaminant removal efficiency of typical high performance synthetic or cellulose disposable filters. Laboratory test results of filtration performance and long term structural integrity are presented. Results of extensive, successful field testing on several types of off-road equipment will also be presented.

The lube oil filtration system for diesel engines is becoming increasingly important. Oil filtration systems typically consist of full-flow and bypass filters. A well-designed system will reduce engine wear and oil usage and may play a role in controlling engine emissions. Thus, both economic and environmental benefits are realized. Past work has dealt with the benefits of using finer full-flow filters and with the use of bypass filters; however, the critical issue of optimization of the entire system has largely been ignored. This is the subject of this paper. The removal and dust-holding capacity characteristics of a variety of commercially available and prototype filters, including cellulose, synthetic and “centrifugal” filters, were determined in the laboratory. The performance of these filters in various full-flow/bypass combinations were further evaluated in the field on city buses.

Past work suggests that finer filtration of engine lubricating oil reduces wear caused by abrasive particles. However, field data confirming this is limited. Filters were tested in the laboratory to establish micron ratings and in the field to relate filtration and wear. Field tests were conducted on city buses powered by Detroit Diesel 6V92 engines. Oil analysis was used as an indicator of engine wear and as the basis for comparing different filtration systems. Used oil was analyzed for particle size distribution, wear metal concentration and oxidation. Lower particle concentrations resulted when finer full-flow oil filters were used. Further reductions in particle concentrations resulted from the addition of bypass filters to the filtration systems. Corresponding decreases in engine wear metals accompanied reductions in particle concentrations.

Oil analysis programs are used to monitor the condition of diesel engines. From the standpoint of engine protection, the size and concentration of oil contaminants are as important as their chemical composition. Wear rates are related to the contaminant size distribution in the oil and degree of filtration. Spectroscopic analysis does not provide particle size information and is incapable of measuring the particularly damaging particles larger than 10 μm. Particle size analysis, when used to complement the spectroscopic analysis, provides a better description of the condition of lubricating and transmission oil. Particle size data can be obtained by particle counters, though in the past it was difficult to obtain reliable data. Recent developments overcome many of these difficulties and permit reliable interpretations of particle size data. This allows better decisions to be made concerning the engine and oil conditions and the filtration requirements of the system.