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Hydraulic Fluid

Hydraulic fluid particle testing standards are published by SAE, ASTM, and ISO. SAE standards cover aerospace fluid power and system sampling solid particle contamination. ASTM standards cover automatic particle counting using dilution to eliminate the contribution of water and interfering soft particles by light extinction. ISO standards cover calibration of automatic particle counters, particulate contamination level using light extinction and optical microscope, coding level of contamination, system sampling and measurement, and reporting analysis data.

SAE AS 4059F-2013 (SAE AS4059F-2013)

Aerospace Fluid Power - Contamination Classification for Hydraulic Fluids

This SAE Aerospace Standard (AS) defines contamination classes and levels for particulate contamination of hydraulic fluids and includes methods of reporting related data (Appendix A). The contamination levels selected are based on the widely accepted NAS 1638 cleanliness classes. The conversion from NAS 1638 cleanliness class specifications to AS4059 class specifications is defined. The comparison of the NAS 1638 classes to AS4059 classes and levels is provided and are defined and the differences explained (Appendix B). NAS 1638 classes based on weight of particles are not applicable to these classes and are not included. A contamination code has been added to describe the contamination levels of the fluid at the specified particle size ranges.

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SAE ARP 5376C-2021

Methods, Locations and Criteria for System Sampling and Measuring the Solid Particle Contamination of Hydraulic Fluids

This Aerospace Recommended Practice (ARP) provides: Recommended methods for cleaning sample bottles, when used, and the solvents to be applied and how these solvents should be prepared. Recommendations for three measuring methods for determining the level of solid particle contamination of hydraulic fluids used in aerospace hydraulics. Recommendations for the selection of the sampling point, sampling method, and the sampling frequency.

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ASTM D7647-10(2018)

Standard Test Method for Automatic Particle Counting of Lubricating and Hydraulic Fluids Using Dilution Techniques to Eliminate the Contribution of Water and Interfering Soft Particles by Light Extinction

1.1 This test method covers the determination of particle concentration and particle size distribution in new and in-service oils used for lubrication and hydraulic purposes. 1.2 Particles considered are in the range from 4 m (c) to 200 m (c) with the upper limit being dependent on the specific automatic particle counter being used. Note 1: For the purpose of this test method, water droplets not masked by the diluent procedure are detected as particles, and agglomerated particles are detected and reported as a single larger particle. Note 2: The subscript (c) is used to denote that the apparatus has been calibrated in accordance with ISO 11171. This subscript (c) strictly only applies to particles up to 50 m. 1.3 Lubricants that can be analyzed by this test method are categorized as petroleum products or synthetic based products, such as: polyalpha olefin, polyalkylene glycol, or phosphate ester. Applicable viscosity range is up to 1000 mm 2 /s at 40 C. This procedure may be appropriate for other petroleum and synthetic based lubricants not included in the precision statement. 1.4 Samples containing visible particles may not be suitable for analysis using this test method. 1.5 Samples that are opaque after dilution are not suitable for analysis using this test method. 1.6 The test method is specific to automatic particle counters that use the light extinction principle and are calibrated according to the latest revision of ISO 11171. 1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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ASTM D6595-17

Standard Test Method for Determination of Wear Metals and Contaminants in Used Lubricating Oils or Used Hydraulic Fluids by Rotating Disc Electrode Atomic Emission Spectrometry

1.1 This test method covers the determination of wear metals and contaminants in used lubricating oils and used hydraulic fluids by rotating disc electrode atomic emission spectroscopy (RDE-AES). 1.2 This test method provides a quick indication for abnormal wear and the presence of contamination in new or used lubricants and hydraulic fluids. 1.3 This test method uses oil-soluble metals for calibration and does not purport to relate quantitatively the values determined as insoluble particles to the dissolved metals. Analytical results are particle size dependent and low results may be obtained for those elements present in used oil samples as large particles. 1.4 The test method is capable of detecting and quantifying elements resulting from wear and contamination ranging from dissolved materials to particles approximately 10 m in size. 1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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ISO 11171:2020

Hydraulic fluid power - Calibration of automatic particle counters for liquids

This document specifies procedures for the following: a) primary particle-sizing calibration for particle sizes 1 µm(c) and larger, sensor resolution and counting performance of liquid automatic particle counters that are capable of analysing bottle samples; b) secondary particle-sizing calibration using suspensions verified with a primary calibrated APC; c) establishing acceptable operation and performance limits; d) verifying particle sensor performance using a test dust; e) determining coincidence and flow rate limits. This document is applicable for use with hydraulic fluids, aviation and diesel fuels, engine oil and other petroleum-based fluids. This document is not applicable to particle-sizing calibration using NIST SRM 2806b primary calibration suspensions.

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ISO 11500:2008

Hydraulic fluid power - Determination of the particulate contamination level of a liquid sample by automatic particle counting using the light-extinction principle

ISO 11500:2008 specifies an automatic particle-counting procedure for determining the number and sizes of particles present in hydraulic-fluid bottle samples of clear, homogeneous, single-phase liquids using an automatic particle counter (APC) that works on the light-extinction principle. ISO 11500:2008 is applicable to the monitoring of the cleanliness level of fluids circulating in hydraulic systems, the progress of a flushing operation, the cleanliness level of support equipment and test rigs and the cleanliness level of packaged stock.

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ISO 4407:2002

Hydraulic fluid power - Fluid contamination - Determination of particulate contamination by the counting method using an optical microscope

This International Standard specifies methods for determining the level of particulate contamination in liquids used in hydraulic systems by counting the number of particles deposited on the surface of a membrane filter using an optical microscope. It includes particle counting by two manual methods and image analysis, using either transmitted or incident lighting systems. Particle sizes greater than or equal to 2 micrometres can be sized and counted by this method, but the resolution and accuracy of the results will depend upon the optical system used and the capabilities of the operator. All hydraulic fluids with a wide range of contamination levels can be analysed according to this International Standard. However, the counting uncertainty at the larger particle sizes increases if the volume filtered is reduced to allow smaller sized particles to be counted, where a fine precipitate or a high particle concentration is present.

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ISO/TR 16144:2002

Hydraulic fluid power - Calibration of liquid automatic particle counters - Procedures used to certify the standard reference material SRM 2806

ISO/TR 16144:2002 describes the procedures used by the United States National Institute of Standards and Technology (NIST) for the certification of the calibration material SRM 2806, which is used in the primary calibration of liquid automatic particle counters. SRM 2806 is a suspension of ISO MTD in hydraulic fluid with a number size distribution certified using a scanning electron microscope (SEM) and image analysis techniques.

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ISO 11943:2021

Hydraulic fluid power - Online automatic particle-counting systems for liquids - Methods of calibration and validation

This document establishes methods for: — validating equipment used to prepare secondary calibration suspensions for automatic particle counters; — performing online secondary calibration of automatic particle counters; — matching two or more online particle counters, i.e. to count the same number of particles at a given size by two APCs associated online; — validating online particle counting systems with and without online dilution as used, for example, to measure the filtration efficiency of a hydraulic filter as described in the multi-pass filter test in ISO 16889.

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ISO 4406:2021

Hydraulic fluid power - Fluids - Method for coding the level of contamination by solid particles

This document specifies the code to be used in defining the quantity of solid particles in the fluid used in a given hydraulic fluid power system.

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ISO 5884:2018

Aerospace series - Fluid systems and components - Methods for system sampling and measuring the solid particle contamination in hydraulic fluids

This document specifies best practice for sampling hydraulic fluid from aircraft hydraulic systems and other hydraulic systems associated with aerospace purposes.

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ISO 3938:1986

Hydraulic fluid power -- Contamination analysis -- Method for reporting analysis data

Specifies methods for reporting data relating to contamination levels of fluids used in industrial, mobile and marine applications for the following types of contamination analysis techniques: microscopic particle counting, automatic particle counter, gravimetric. Is intended to establish the minimum information required to allow valid comparison and interpretation of contamination level data. The figures show the data sheet of concern.

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