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This SAE Aerospace Information Report (AIR) identifies and explains the meaning of various ratings and terms used to describe the physical characteristics of liquid filter elements. The significance of various filter parameters is discussed. In addition, a number of filter test methods are briefly described. This AIR and the data presented are only applicable where the system liquid wets the filter elements.

This SAE Aerospace Information Report (AIR) provides technical information to assist the development of specific cleaning methods for those filter elements which are designated as "cleanable" and cannot be cleaned by simple and obvious procedures.

This SAE Aerospace Recommended Practice (ARP) describes a procedure for determining the insoluble contamination level of the downstream side of filter elements. Results of this procedure represent the particulate released from the tested filter element under the prevailing conditions of the test. The results may be used for comparative evaluation of the effectiveness of various cleaning methods or the cleanliness of elements after cleaning or as received from manufacturers.

The purpose of this document is to present test methods that can be utilized to evaluate the filtration and operating characteristics of filters that will be utilized in a cryogenic system. The methods presented herein are intended to supplement standard filter testing specifications to allow evaluation of filter performance characteristics in areas that could be affected by extreme low temperatures.

This SAE Aerospace Recommended Practice (ARP) describes a method for evaluating the performance of filter elements designed for Aerospace hydraulic systems. The performance is measured and reported in terms of filtration ratios and stabilized contamination level while testing with cyclic flow.

This SAE Aerospace Information Report (AIR) presents data on hydraulic fluids which are of interest to detail designers of hydraulic systems and components for aerospace flight vehicles. The data pertains to fluids conforming to the following specifications: MIL-PRF-5606 MIL-H-8446 MIL-PRF-27601 (canceled) MIL-PRF-27601 has been canceled without replacement and the data presented herein is for information purposes only. MIL-PRF-83282 MIL-H-53119 MIL-PRF-87257 AS1241 Type IV, Classes 1 and 2, and Type V

This SAE Aerospace Information Report (AIR) presents data on hydraulic fluids which are of interest to detail designers of hydraulic systems and components for aerospace flight vehicles. The data pertains to fluids conforming to the following specifications: MIL-PRF-5606 MIL-H-8446 MIL-PRF-27601 (canceled) MIL-PRF-27601 has been canceled without replacement and the data presented herein is for information purposes only. MIL-PRF-83282 MIL-H-53119 MIL-PRF-87257 AS1241 Type IV, Classes 1 and 2, and Type V

This procedure will be generally applicable to three classes of hydraulic components as listed below:

This SAE Aerospace Information Report (AIR) provides technical information to assist the development of specific cleaning methods for filter elements. Consideration is limited to filter elements which are designated as "cleanable" (not "disposable"), but which cannot be cleaned by simple and obvious procedures. Cleaning methods developed according to this report should be evaluated by the methods of ARP725. Satisfactory cleaning methods can be developed for most "cleanable" filter elements. Technical or economic feasibility of the cleaning method may be limited, however, by incompatibility of filter-element construction materials, by mechanical weakness or lack of corrosion resistance to withstand repeated or continued cleaning, or by the presence of unusually tenacious contamination. These factors must be considered when selecting approaches to the development of specific methods.

This SAE Aerospace Information Report (AIR) describes a mathematical model that can be used to analyze particle count data. Particle counts that fit the model can be graphically displayed, converted from one counting size-frequency range to another, and extrapolated to estimate counts beyond the measured range. Derivation, applications, and calculations are described.

The purpose of this document is to present test methods that can be utilized to evaluate the filtration and operating characteristics of filters that will be utilized in a cryogenic system. The methods presented herein are intended to supplement standard filter testing specifications to allow evaluation of filter performance characteristics in areas that could be affected by extreme low temperatures. The test methods can be utilized to evaluate filters for particle sizes equal to or greater than 5.0 μm and flows up to and including 60 gpm (230 L/min) capacity. If higher flow rate filters are to be evaluated in accordance with the test methods presented herein, it will be necessary to increase the system flow capacity and the size of effluent sampling system from those recommended in this document.

This test method describes a procedure for determining the insoluble contamination level of the downstream side of filter elements. Results of this procedure represent the particulate release rate of the tested filter element under the prevailing conditions of the test and may be used for comparative evaluation of the effectiveness of various cleaning methods or cleanliness of elements as received from manufacturers. Because of the variety of conditions which may exist even under the provisions of this procedure, it is difficult to correlate data from one testing agency to another. The data obtained by this procedure do not necessarily indicate qualitatively or quantitatively, the contamination which may be released by a filter element into the operating fluid during service. When properly conducted, however, the procedure will show marked differences between various cleanliness levels of filter elements.

This report discusses the characteristics of hydraulic fluids and evaluates their importance, not only from the standpoint of fluid formulation, but also in their effect on aero-space hydraulic system design and the materials used in the components of the system. In some cases numerical parameter limits are suggested, but, in general, the effect of a parameter is the basic consideration. Not only must the characteristics of the fluid be considered in the design of a hydraulic system in which it is to be used, but also the characteristics of the system will affect the extent of the importance of the various characteristics of the fluid. In each individual system, as it employs a fluid, the characteristics of the fluid must be assessed with their immediate import and weighed in considering their effects on the system design requirements based upon the variables of system environment, function and basic design.

This AIR identifies and explains the meaning of various ratings and terms used to describe the physical characteristics of liquid filter elements. The significance of various filter parameters are discussed. In addition, a number of filter test methods are briefly described. This AIR and the data presented are only applicable to filters in which the system liquid wets the filter elements.

This SAE Aerospace Information Report (AIR) presents data on hydraulic fluids which are of interest to detail designers of hydraulic systems and components for aerospace flight vehicles. The data pertain to fluids conforming to specifications MIL-H-5606, MIL-H-8446, MIL-PRF-27601, MIL-PRF-83282, MIL-H-53119, MIL-PRF-87257, Aerospace Standard 1241 Type IV, Classes 1 and 2, and Type V. The relative merits of hydraulic fluid properties in relation to the fluid formulation, aerospace hydraulic system design and the related materials compatibility are discussed in AIR81, Hydraulic Fluid Properties. This document is essentially a metric document with English units available in the data charts for convenience. There is a treatment of conversions between ISO and English units in AIR1657.

This SAE Aerospace Recommended Practice (ARP) describes a method for evaluating the performance of filter elements designed for Aerospace hydraulic systems. The performance is measured and reported in terms of filtration ratios and stabilized contamination level while testing with cyclic flow.

This SAE Aerospace Information Report (AIR) describes a mathematical model that can be used to analyze particle count data. Particle counts that fit the model can be graphically displayed, converted from one counting size-frequency range to another, and extrapolated to estimate counts beyond the measured range. Derivation, applications, and calculations are described.

The purpose of this test procedure is to present test methods that can be utilized to evaluate the filtration and operating characteristics of filters that will be utilized in a cryogenic system. The methods presented herein are intended to supplement standard filter testing specifications to allow evaluation of filter performance characteristics in areas that could be affected by extreme low temperatures. The test methods can be utilized to evaluate filters up to and including 60 gpm (230 lpm) capacity. If higher flow rate filters are to be evaluated in accordance with the test methods presented herein, it will be necessary to increase the system flow capacity and the size of effluent sampling system.

This document discusses the relative merits of the properties of hydrocarbon-based hydraulic fluid in relation to the fluid formulation, aerospace hydraulic system design and the related materials compatibility. In some cases, numerical limits are suggested, but, in general, the effect of a property is noted qualitatively. The properties of the fluid must be considered in the design of a hydraulic system, but it is possible to design a system to be less sensitive, or more robust, to a particular fluid property. For this reason, the property of the hydraulic fluid must be weighed for each individual hydraulic system, taking into account the system's basic design, function and environment, as well as the fluid toxicity and disposal issues. Besides the hydraulic system itself, ground handling and servicing needs of the system must also be considered. The only absolute characteristic of a hydraulic fluid is that it be a liquid throughout the range of use.