ASTM D4898-23

Standard Test Method for Insoluble Contamination of Hydraulic Fluids by Gravimetric Analysis

SIGNIFICANCE AND USE
5.1 This test method indicates and measures the amount of insoluble contamination of hydraulic fluids. Minimizing the levels of insoluble contamination of hydraulic fluids is essential for the satisfactory performance and long life of the equipment. Insoluble contamination can not only plug filters but can damage functional system components resulting in wear and eventual system failure.
SCOPE
1.1 This test method covers the determination of insoluble contamination in hydraulic fluids by gravimetric analysis. The contamination determined includes both particulate and gel-like matter, organic and inorganic, which is retained on a membrane filter disk of pore diameter as required by applicable specifications (usually 0.45 μm or 0.80 μm).  
1.2 To indicate the nature and distribution of the particulate contamination, the gravimetric method should be supplemented by occasional particle counts of typical samples in accordance with Test Method F312.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 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. For a specific warning statement, see 7.1.  
1.5 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.

General Information

• Status: Published
• Publication Date: 30-Nov-2023
• ICS: 75.120 - Hydraulic fluids
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.N0 - Hydraulic Fluids

Relations

• Replaces: ASTM D4898-16 - Standard Test Method for Insoluble Contamination of Hydraulic Fluids by Gravimetric Analysis
• Effective Date: 01-Dec-2023
• Refers: ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 15-Dec-2023
• Refers: ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Jul-2023
• Referred By: ASTM D7843-21 - Standard Test Method for Measurement of Lubricant Generated Insoluble Color Bodies in In-Service Turbine Oils using Membrane Patch Colorimetry
• Effective Date: 01-Dec-2023
• Referred By: ASTM F302-09(2021) - Standard Practice for Field Sampling of Aerospace Fluids in Containers
• Effective Date: 01-Dec-2023
• Referred By: ASTM D6439-23 - Standard Guide for Cleaning, Flushing, and Purification of Steam, Gas, and Hydroelectric Turbine Lubrication Systems
• Effective Date: 01-Dec-2023
• Referred By: ASTM D4378-22 - Standard Practice for In-Service Monitoring of Mineral Turbine Oils for Steam, Gas, and Combined Cycle Turbines
• Effective Date: 01-Dec-2023
• Referred By: ASTM D8323-20 - Standard Guide for Management of In-Service Phosphate Ester-based Fluids for Steam Turbine Electro-Hydraulic Control (EHC) Systems
• Effective Date: 01-Dec-2023
• Referred By: ASTM D8506-23 - Standard Guide for Microbial Contamination and Biodeterioration in Turbine Oils and Turbine Oil Systems
• Effective Date: 01-Dec-2023

Overview

ASTM D4898-23: Standard Test Method for Insoluble Contamination of Hydraulic Fluids by Gravimetric Analysis establishes a systematic approach for measuring insoluble contamination in hydraulic fluids. Using gravimetric analysis, this standard identifies and quantifies both particulate and gel-like, organic and inorganic contaminants retained on a membrane filter, typically with pore sizes of 0.45 μm or 0.80 μm. Maintaining low levels of insoluble contamination is critical to ensure satisfactory performance, prolong equipment life, prevent filter blockages, and avoid potential system failures in hydraulic systems. This test method is recognized internationally and is approved for use by various agencies, including the U.S. Department of Defense.

Key Topics

• Gravimetric Analysis: The procedure determines contamination by filtering a specified volume of hydraulic fluid through a defined-pore membrane and weighing the increase in filter mass.
• Type of Contamination: Measures insoluble contaminants, such as particulate and gel-like matter, covering both organic and inorganic substances.
• Sampling and Filtration: Calls for careful sampling methods and the use of clean, contamination-free apparatus to ensure accurate test results.
• Apparatus Requirements: Specifies key equipment, including microbalances, vacuum sources, membrane filters, filtration funnels, and microscopes.
• Supplemental Analysis: Recommends periodic microscopic examination and particle counting (e.g., using ASTM F312) to further characterize the contamination.
• Result Calculations: Provides a standardized approach for recording and reporting contamination in mg/100 mL, ensuring clarity and comparability.
• Precision and Bias: Addresses repeatability of results and notes the absence of a suitable reference material for evaluating analytical bias.

Applications

The ASTM D4898-23 test method is vital for a range of practical applications in industries using hydraulic systems, such as aerospace, manufacturing, and heavy equipment operation. Its uses include:

• Routine Maintenance: Enables laboratories and maintenance teams to routinely monitor hydraulic fluid cleanliness, thus preventing unexpected equipment outages and reducing maintenance costs.
• Quality Control: Assists manufacturers and suppliers in verifying that new or in-service hydraulic fluids meet contamination specifications, supporting equipment reliability and warranty compliance.
• Failure Analysis: Provides forensic data for troubleshooting system malfunctions due to contamination and for evaluating the effectiveness of filtration practices.
• Regulatory and Contractual Compliance: Ensures hydraulic fluids conform to client and regulatory cleanliness requirements, including those set by defense and aerospace agencies.

Related Standards

Several other ASTM standards complement or are referenced by ASTM D4898-23, offering broader tools for contamination analysis and sampling in hydraulic and aerospace fluids:

• ASTM F312 - Test Methods for Microscopical Sizing and Counting Particles from Aerospace Fluids on Membrane Filters
• ASTM D4175 - Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• ASTM F302 - Practice for Field Sampling of Aerospace Fluids in Containers
• ASTM F303 - Practices for Sampling for Particles in Aerospace Fluids and Components
• MIL-C-81302C - Cleaning Compound, Solvent, Trichlorotrifluoroethane (referenced for reagents)
• ASTM D1836 - Specification for Commercial Hexanes (referenced for cleaning and analysis)

Organizations implementing ASTM D4898-23 should consult these and other related standards to establish comprehensive contamination monitoring and control programs for hydraulic fluids, safeguarding system performance and longevity.

By following this gravimetric method, industries ensure the reliability of hydraulic equipment, maintain compliance with international standards, and uphold best practices for fluid cleanliness.

Standards Content (Sample)

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.
Designation: D4898 − 23
Standard Test Method for
Insoluble Contamination of Hydraulic Fluids by Gravimetric
Analysis
This standard is issued under the fixed designation D4898; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* Stainless Steel Wire and Wire Rods
D1836 Specification for Commercial Hexanes
1.1 This test method covers the determination of insoluble
D2021 Specification for Neutral Detergent, 40 Percent Al-
contamination in hydraulic fluids by gravimetric analysis. The
kylbenzene Sulfonate Type (Withdrawn 2000)
contamination determined includes both particulate and gel-
D4175 Terminology Relating to Petroleum Products, Liquid
like matter, organic and inorganic, which is retained on a
Fuels, and Lubricants
membrane filter disk of pore diameter as required by applicable
E319 Practice for the Evaluation of Single-Pan Mechanical
specifications (usually 0.45 μm or 0.80 μm).
Balances (Withdrawn 2021)
1.2 To indicate the nature and distribution of the particulate
F302 Practice for Field Sampling of Aerospace Fluids in
contamination, the gravimetric method should be supple-
Containers
mented by occasional particle counts of typical samples in
F303 Practices for Sampling for Particles in Aerospace
accordance with Test Method F312.
Fluids and Components
1.3 The values stated in SI units are to be regarded as
F312 Test Methods for Microscopical Sizing and Counting
standard. No other units of measurement are included in this
Particles from Aerospace Fluids on Membrane Filters
standard.
F314 Methods of Test for Identification of Metallic and
Fibrous Contaminants in Aerospace Fluids (Withdrawn
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 1990)
responsibility of the user of this standard to establish appro-
2.2 Military Standard:
priate safety, health, and environmental practices and deter-
MIL-C-81302C Cleaning Compound Solvent Trichlorotrif-
mine the applicability of regulatory limitations prior to use. 4
luoroethane
For a specific warning statement, see 7.1.
1.5 This international standard was developed in accor-
3. Terminology
dance with internationally recognized principles on standard-
3.1 Definitions:
ization established in the Decision on Principles for the
3.1.1 For definitions of terms used in this test method, refer
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical to Terminology D4175.
Barriers to Trade (TBT) Committee.
4. Summary of Test Method
2. Referenced Documents
4.1 The insoluble contamination is determined by passing a
2.1 ASTM Standards:
given quantity of a fluid sample through a membrane filter disk
A555/A555M Specification for General Requirements for
and measuring the resultant increase in the mass of the filter.
The fluid sample is drawn through the filter by a vacuum and
the insoluble contamination is collected on the surface of the
This test method is under the jurisdiction of ASTM Committee D02 on
filter. In addition, the filter disk is microscopically scanned for
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
excessively large particles, fibers, or other unusual conditions.
Subcommittee D02.N0 on Hydraulic Fluids.
Current edition approved Dec. 1, 2023. Published December 2023. Originally
approved in 1965. Test Method F313 was redesignated as D4898 in 1988. Last
previous edition approved in 2016 as D4898 – 16. DOI: 10.1520/D4898-23.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or The last approved version of this historical standard is referenced on
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM www.astm.org.
Standards volume information, refer to the standard’s Document Summary page on Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,
the ASTM website. Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4898 − 23
5. Significance and Use 7. Reagents
5.1 This test method indicates and measures the amount of 7.1 Commercial Hexane, conforming to Specifications
D1836. (Warning—Flammable. Harmful if inhaled. Skin irri-
insoluble contamination of hydraulic fluids. Minimizing the
levels of insoluble contamination of hydraulic fluids is essen- tant on repeated contact. Eye irritant. Aspiration hazard.)
tial for the satisfactory performance and long life of the
7.2 Detergent, free-rinsing. Material conforming to Specifi-
equipment. Insoluble contamination can not only plug filters
cation D2021.
but can damage functional system components resulting in
7.3 Isopropyl Alcohol, acetone-free. (Warning—
wear and eventual system failure.
Flammable. Harmful if inhaled. Skin irritant on repeated
contact. Eye irritant. Aspiration hazard.)
6. Apparatus
7.4 Refrigerant-113 (trichlorotrifluoroethane) conforming to
6.1 Microbalance, accurate to 0.005 mg, and the zero shall
U.S. Military Specification MIL-C-81302C. (Warning—
not drift more than 0.005 mg during the test period. The rated
Environmentally hazardous substance. Harmful if inhaled.
accuracy shall be obtainable by personnel actually making the
Skin irritant on repeated contact. Eye irritant. Aspiration
weighings, under actual conditions of use and shall be verified
hazard. Acute and chronic aquatic hazard.)
in accordance with Practice E319.
8. Sample
6.2 Membrane Filter Support, fritted glass, sintered metal,
or stainless steel screen, to support 25 mm or 47 mm to 51 mm
8.1 A 100 mL 6 1 mL fluid sample should be used for this
membrane filters. The support shall be designed to enable
method. Larger or smaller samples may be used, however, to
attachment of a vacuum flask.
meet problems of unusually high or low contamination levels.
6.3 Filtration Funnel, glass or stainless steel, minimum
NOTE 1—Methods for obtaining the fluid samples are not specified in
capacity 15 mL, designed to enable attachment to the mem-
this method. These methods should be established by the individual
agencies or laboratories in accordance with their requirements. However,
brane filter support by means of a suitable clamping device.
extreme care should be taken to ensure that the samples are representative
The filter funnel is calibrated to indicate volume.
and free of external contamination.
6.4 Vacuum Flask, with rubber stopper.
8.2 The following ASTM sampling test methods should be
6.5 Filtered Liquid Dispensers (2)—Washing bottles or used when applicable: Practices F302 and F303.
other dispensers capable of delivering liquid through a 0.45 μm
9. Preparation of Apparatus
in-line membrane filter.
9.1 The filtration funnel, petri dishes, graduated cylinders,
6.6 Air Ionizer, alpha emitter, 18.5 MBq, of polonium-210,
and sample bottles shall be cleaned before each use by the
with a useful life of 1.5 years to a final value of 1.1 MBq.
following method:
6.7 Membrane Filters (2), 25 mm or 47 mm to 51 mm in
9.1.1 Thoroughly wash in a solution of detergent and hot
diameter, with pore diameter as required.
water.
6.8 Microscope, capable of 35× magnification. 9.1.2 Rinse with hot tap water
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4898 − 16 D4898 − 23
Standard Test Method for
Insoluble Contamination of Hydraulic Fluids by Gravimetric
Analysis
This standard is issued under the fixed designation D4898; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 This test method covers the determination of insoluble contamination in hydraulic fluids by gravimetric analysis. The
contamination determined includes both particulate and gel-like matter, organic and inorganic, which is retained on a membrane
filter disk of pore diameter as required by applicable specifications (usually 0.45 μm or 0.80 μm).
1.2 To indicate the nature and distribution of the particulate contamination, the gravimetric method should be supplemented by
occasional particle counts of typical samples in accordance with Test Method F312.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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 healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use. For a specific warning statement, see 6.17.1.
1.5 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.
2. Referenced Documents
2.1 ASTM Standards:
A555/A555M Specification for General Requirements for Stainless Steel Wire and Wire Rods
D1836 Specification for Commercial Hexanes
D2021 Specification for Neutral Detergent, 40 Percent Alkylbenzene Sulfonate Type (Withdrawn 2000)
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
E319 Practice for the Evaluation of Single-Pan Mechanical Balances (Withdrawn 2021)
F302 Practice for Field Sampling of Aerospace Fluids in Containers
F303 Practices for Sampling for Particles in Aerospace Fluids and Components
F312 Test Methods for Microscopical Sizing and Counting Particles from Aerospace Fluids on Membrane Filters
F314 Methods of Test for Identification of Metallic and Fibrous Contaminants in Aerospace Fluids (Withdrawn 1990)
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.N0 on Hydraulic Fluids.
Current edition approved Jan. 1, 2016Dec. 1, 2023. Published February 2016December 2023. Originally approved in 1965. Test Method F313 was redesignated as D4898
ɛ1
in 1988. Last previous edition approved in 20102016 as D4898 – 90 (2010)D4898 – 16. . DOI: 10.1520/D4898-16.10.1520/D4898-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4898 − 23
2.2 Military Standard:
MIL-C-81302C Cleaning Compound Solvent Trichlorotrifluoroethane
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this test method, refer to Terminology D4175.
4. Summary of Test Method
4.1 The insoluble contamination is determined by passing a given quantity of a fluid sample through a membrane filter disk and
measuring the resultant increase in the mass of the filter. The fluid sample is drawn through the filter by a vacuum and the insoluble
contamination is collected on the surface of the filter. In addition, the filter disk is microscopically scanned for excessively large
particles, fibers, or other unusual conditions.
5. Significance and Use
5.1 This test method indicates and measures the amount of insoluble contamination of hydraulic fluids. Minimizing the levels of
insoluble contamination of hydraulic fluids is essential for the satisfactory performance and long life of the equipment. Insoluble
contamination can not only plug filters but can damage functional system components resulting in wear and eventual system
failure.
6. Apparatus
6.1 Microbalance, accurate to 0.005 mg, and the zero shall not drift more than 0.005 mg during the test period. The rated accuracy
shall be obtainable by personnel actually making the weighings, under actual conditions of use and shall be verified in accordance
with Practice E319.
6.2 Membrane Filter Support, fritted glass, sintered metal, or stainless steel screen, to support 25 mm or 47 mm to 51 mm
membrane filters. The support shall be designed to enable attachment of a vacuum flask.
6.3 Filtration Funnel, glass or stainless steel, minimum capacity 15 mL, designed to enable attachment to the membrane filter
support by means of a suitable clamping device. The filter funnel is calibrated to indicate volume.
6.4 Vacuum Flask, with rubber stopper.
6.5 Filtered Liquid Dispensers (2)—Washing bottles or other dispensers capable of delivering liquid through a 0.45 μm in-line
membrane filter.
6.6 Air Ionizer, alpha emitter, 18.5 MBq, of polonium-210, with a useful life of 1.5 years to a final value of 1.1 MBq.
6.7 Membrane Filters (2), 25 mm or 47 mm to 51 mm in diameter, with pore diameter as required.
6.8 Microscope, capable of 35× magnification.
6.9 Vacuum Source, capable of pulling 550 mm Hg. An electrically driven vacuum pump must be explosion-proof.
6.10 Drying Oven, capable of maintaining a temperature of 80 °C.
6.11 Sample Bottles, with contamination-proof caps. Aluminum-foil wrapped stoppers or polyethylene liners between cap and
bottle have proved satisfactory.
Available from Standardization Documents Order Desk, DODSSP, Bldg. 4, Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098
May be obtained from any source approved by U.S. Nuclear Regulatory Commission.
D4898 − 23
6.12 Graduated Cylinder, 100 mL (May be replaced by volume-calibrated filter funnel.)
6.13 Petri Dishes, covered glass, 150 mm in diameter.
6.14 Forceps, with unserrated tips.
6.15 Calibration Weights, for microbalance, 10 mg and 20 mg, accurate to 0.005 mg and made from nonmagnetic material
conforming to Type 310 in Specification A555/A555M. The accuracy is traceable to the National Bureau of Standards as discussed
in their Technical Note 288.
7. Reagents
7.1 Commercial Hexane, conforming to Specifications D1836. (Warning—Flammable. Harmful if inhaled. Skin irritant on
repeated contact. Eye irritant. Aspiration hazard.)
7.2 Detergent, free-rinsing. Material conforming to Specification D2021.
7.3 Isopropyl Alcohol, acetone-free. (Warning—Flammable. Harmful if inhaled. Skin irritant on repeated contact. Eye irritant.
Aspiration hazard.)
7.4 Refrigerant-113 (trichlorotrifluoroethane) conforming to U.S. Military Specification MIL-C-81302C. (Warning—
Environmentally hazardous substance. Harmful if inhaled. Skin irritant on repeated contact. Eye irritant. Aspiration
...