ASTM G131-96(2023)e1

Standard Practice for Cleaning of Materials and Components by Ultrasonic Techniques

SIGNIFICANCE AND USE
5.1 This practice is suitable for the removal of contaminants found on materials, parts, and components used in systems requiring a high level of cleanliness, such as oxygen. Parts shall have been precleaned to remove visible contaminants prior to using this procedure. Softgoods such as seals and valve seats may be cleaned without precleaning.  
5.2 This procedure may also be used as the cleanliness verification technique for coupons used during cleaning effectiveness tests as in Test Method G122.  
5.3 The cleaning efficiency has been shown to vary with the frequency and power density of the ultrasonic unit. Low frequencies in the 20 kHz to 25 kHz range have been found to damage soft metals such as aluminum and silver. Therefore, the specifications of the unit and the frequencies available must be considered in order to optimize the cleaning conditions without damaging the parts.
SCOPE
1.1 This practice covers a procedure for the cleaning of materials and components used in systems requiring a high level of cleanliness, such as oxygen, by ultrasonic techniques.  
1.2 This practice may be used for cleaning small parts, components, softgoods, etc.  
1.3 The values stated in SI units are 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. Specific precautionary statements are given in Note 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-Jun-2023
• ICS: 03.080.10 - Maintenance services. Facilities management
• Technical Committee: G04 - Compatibility and Sensitivity of Materials in Oxygen Enriched Atmospheres
• Drafting Committee: G04.02 - Recommended Practices

Relations

• Refers: ASTM F331-13(2020) - Standard Test Method for Nonvolatile Residue of Solvent Extract from Aerospace Components (Using Flash Evaporator)
• Effective Date: 01-Apr-2020
• Refers: ASTM E1235-12(2020) - Standard Test Method for Gravimetric Determination of Nonvolatile Residue (NVR) in Environmentally Controlled Areas for Spacecraft
• Effective Date: 01-Apr-2020
• Refers: ASTM F311-08(2020) - Standard Practice for Processing Aerospace Liquid Samples for Particulate Contamination Analysis Using Membrane Filters
• Effective Date: 01-Apr-2020
• Refers: ASTM E1235-12(2020)e1 - Standard Test Method for Gravimetric Determination of Nonvolatile Residue (NVR) in Environmentally Controlled Areas for Spacecraft
• Effective Date: 01-Apr-2020
• Refers: ASTM G121-18 - Standard Practice for Preparation of Contaminated Test Coupons for the Evaluation of Cleaning Agents
• Effective Date: 01-Dec-2018
• Refers: ASTM F311-08(2013) - Standard Practice for Processing Aerospace Liquid Samples for Particulate Contamination Analysis Using Membrane Filters
• Effective Date: 01-Nov-2013
• Refers: ASTM F331-13 - Standard Test Method for Nonvolatile Residue of Solvent Extract from Aerospace Components (Using Flash Evaporator)
• Effective Date: 01-Jun-2013
• Refers: ASTM E1235-12 - Standard Test Method for Gravimetric Determination of Nonvolatile Residue (NVR) in Environmentally Controlled Areas for Spacecraft
• Effective Date: 01-Nov-2012
• Refers: ASTM G122-96(2008) - Standard Test Method for Evaluating the Effectiveness of Cleaning Agents
• Effective Date: 01-Sep-2008
• Refers: ASTM E1235-08 - Standard Test Method for Gravimetric Determination of Nonvolatile Residue (NVR) in Environmentally Controlled Areas for Spacecraft
• Effective Date: 01-May-2008
• Refers: ASTM F311-08 - Standard Practice for Processing Aerospace Liquid Samples for Particulate Contamination Analysis Using Membrane Filters
• Effective Date: 01-May-2008
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM F331-05 - Standard Test Method for Nonvolatile Residue of Solvent Extract from Aerospace Components (Using Flash Evaporator)
• Effective Date: 01-Nov-2005
• Refers: ASTM G121-98(2015)e1 - Standard Practice for Preparation of Contaminated Test Coupons for the Evaluation of Cleaning Agents
• Effective Date: 01-Sep-2004
• Refers: ASTM G121-98(2010)e1 - Standard Practice for Preparation of Contaminated Test Coupons for the Evaluation of Cleaning Agents
• Effective Date: 01-Sep-2004

Overview

ASTM G131-96(2023)e1 is an international standard developed by ASTM International for the cleaning of materials and components using ultrasonic techniques. This practice is especially important in applications where a high level of cleanliness is critical, such as in oxygen systems and other sensitive environments. The document provides guidance on procedures, apparatus, and verification techniques to ensure the effective removal of contaminants from a wide range of materials, including small parts, components, and softgoods.

Key Topics

High-Cleanliness Cleaning Procedures

• Suitable for removing both molecular and particulate contaminants from materials where cleanliness is essential (e.g., aerospace, medical, oxygen systems).
• Parts should be precleaned to remove visible contaminants, with softgoods like seals and valve seats exempt from this requirement.

Ultrasonic Cleaning Methodology

• Utilizes ultrasonic cleaners with controlled frequency (25 - 90 kHz) and power density to optimize cleaning effectiveness while minimizing potential damage.
• Low frequencies (20 - 25 kHz) can harm soft metals like aluminum and silver, so care must be taken in selecting cleaning parameters.

Verification of Cleanliness

• Defines cleanliness verification using witness (control) coupons, frequently evaluated following ASTM Test Method G122.
• Cleanliness metrics such as nonvolatile residue (NVR) and particulate matter are quantified using referenced ASTM methods.

Best Practices & Safety

• Emphasizes selection of suitable cleaning agents, including water and various solvents, and highlights the importance of high-purity reagents and water.
• Addresses safety, health, and environmental considerations, instructing users to determine applicable regulations and safe handling practices, as some solvents may have low threshold limits or compatibility concerns (especially with oxygen).

Applications

Critical System Maintenance

• Ensures components in oxygen-enriched and high-purity systems remain free from contaminants that could affect system integrity or performance.
• Widely adopted in aerospace, pharmaceutical, medical device, and process industries where trace contamination can result in critical failures.

Small Parts and Delicate Components

• Ideal for cleaning small, complex, or delicate items, including those with intricate geometries or internal surfaces.

Softgoods and Elastomers

• Effective for cleaning seals, valve seats, and similar softgoods without pre-cleaning, saving time and reducing handling.

Cleanliness Testing and Quality Control

• Serves as an integral protocol for verifying cleaning agent/process effectiveness and compliance with industry cleanliness standards.
• Used to prepare parts for additional analysis (e.g., verifying contamination levels, NVR) or qualification in regulated environments.

Related Standards

• ASTM G121 - Preparation of contaminated test coupons for cleaning agent evaluations.
• ASTM G122 - Evaluation of cleaning agents and processes.
• ASTM D1193 - Specifications for reagent water.
• ASTM E1235, F324, F331 - Test methods for quantifying nonvolatile residue.
• ASTM F311 - Practices for analyzing particulate contamination.

Practical Value

By following ASTM G131, organizations can:

• Achieve documented high cleanliness required for oxygen-sensitive and contamination-sensitive systems.
• Systematically select and validate ultrasonic cleaning parameters to improve process reliability and product safety.
• Reduce risk of component failure stemming from residual contamination.
• Support compliance with regulatory and industry cleanliness requirements.

This standard helps ensure that the cleaning process is consistent, reliable, and validated-delivering confidence in component readiness for critical applications. For entities dealing with high-purity, safety-sensitive, or regulated environments, adopting ASTM G131 for ultrasonic cleaning is a practical necessity.

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.
´1
Designation: G131 − 96 (Reapproved 2023)
Standard Practice for
Cleaning of Materials and Components by Ultrasonic
Techniques
This standard is issued under the fixed designation G131; 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.
ε NOTE—Editorially updated formatting in 7.1 in July 2023.
1. Scope Cleaning Solvents Using the Solvent Purity Meter (With-
drawn 1987)
1.1 This practice covers a procedure for the cleaning of
F331 Test Method for Nonvolatile Residue of Solvent Ex-
materials and components used in systems requiring a high
tract from Aerospace Components (Using Flash Evapora-
level of cleanliness, such as oxygen, by ultrasonic techniques.
tor)
1.2 This practice may be used for cleaning small parts,
G121 Practice for Preparation of Contaminated Test Cou-
components, softgoods, etc.
pons for the Evaluation of Cleaning Agents
G122 Test Method for Evaluating the Effectiveness of
1.3 The values stated in SI units are standard.
Cleaning Agents and Processes
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3. Terminology
responsibility of the user of this standard to establish appro-
3.1 Definitions of Terms Specific to This Standard:
priate safety, health, and environmental practices and deter-
3.1.1 contaminant (contamination), n—unwanted molecular
mine the applicability of regulatory limitations prior to use.
and particulate matter that could affect or degrade the perfor-
Specific precautionary statements are given in Note 1.
mance of the components upon which they reside.
1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
3.1.2 contaminate, v—a process of applying a contaminant.
ization established in the Decision on Principles for the
3.1.3 control coupon (witness coupon), n—a coupon made
Development of International Standards, Guides and Recom-
from the same material and prepared in exactly the same way
mendations issued by the World Trade Organization Technical
as the test coupons, which is used to verify the validity of the
Barriers to Trade (TBT) Committee.
method or part thereof.
3.1.3.1 Discussion—In this practice, the control coupon will
2. Referenced Documents
be contaminated in the same manner as the test coupons and
2.1 ASTM Standards:
will be subjected to the identical cleaning procedure.
D1193 Specification for Reagent Water
3.1.4 degas, v—the process of removing gases from a liquid.
E1235 Test Method for Gravimetric Determination of Non-
3.1.5 nonvolatile residue (NVR), n—residual molecular and
volatile Residue (NVR) in Environmentally Controlled
particulate matter remaining following the filtration and con-
Areas for Spacecraft
trolled evaporation of a solvent containing contaminants.
F311 Practice for Processing Aerospace Liquid Samples for
Particulate Contamination Analysis Using Membrane Fil- 3.1.6 particle (particulate contaminant), n—a piece of mat-
ters ter in a solid state with observable length, width, and thickness.
F324 Test Method for Nonvolatile Residue of Volatile
3.1.6.1 Discussion—The size of a particle is usually defined
by its greatest dimension and is specified in micrometres.
This practice is under the jurisdiction of ASTM Committee G04 on Compat-
4. Summary of Practice
ibility and Sensitivity of Materials in Oxygen Enriched Atmospheres and is the
direct responsibility of Subcommittee G04.02 on Recommended Practices. 4.1 A part, material or component is placed in a container
Current edition approved July 1, 2023. Published July 2023. Originally approved
containing the cleaning agent. This container is then placed in
ɛ1
in 1995. Last previous edition approved in 2016 as G131 – 96 (2016) . DOI:
an ultrasonic cleaner and treated for a given period of time at
10.1520/G0131-96R23E01.
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 last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
G131 − 96 (2023)
the recommended temperature for the cleaning agent. This safe handling procedures, particularly in open tanks. Many
results in a solution if the contaminant is soluble in the test solvents are not considered to be compatible with oxygen and
fluid or a emulsion if the contaminant is not soluble in the test must be completely removed from cleaned components prior to
fluid. The cleaning solution combined with the rinse solutions the use of these components in oxygen systems. The preferred
may then be analyzed for particulate, NVR, or total carbon method of removal shall be determined by the user.
(TC).
7.2 Purity of Reagents—Reagent grade chemicals shall be
4.1.1 In the case of aqueous-based agents, the parts are
used in all tests. Unless otherwise indicated, it is intended that
rinsed after the removal from the cleaning bath and ultrasoni-
all reagents conform to the specifications of the Committee on
cally cleaned in reagent water to provide a solution for TC
Analytical Reagents of the American Chemical Society where
analysis using G TC.
such specifications are available. Other grades may be used,
4.1.2 In the case of solvent-based agents, the parts are rinsed
provided it is first ascertained that the reagent is of sufficiently
with fresh solvent, which is collected and combined with the
high purity to permit its use without lessening the accuracy of
solvent used in the cleaning process, and the NVR determined
the determination. Detergents used shall be identified by
using Test Method E1235, Test Method F324, or Test Method
manufacturer and name (registered trademark, if any).
F331, as appropriate.
7.3 Purity of Water—The water used shall meet the require-
4.1.3 Particulate analyses may be performed by filtering the
ments of Specification D1193, Type II.
final cleaning solution. The particles captured by the filter are
then counted using Practice F311.
8. Procedure
5. Significance and Use
8.1 Sample Preparation:
8.1.1 If cleanliness verification is to be performed on control
5.1 This practice is suitable for the removal of contaminants
or test coupons, prepare the coupons in accordance with
found on materials, parts, and components used in systems
Practice G121.
requiring a high level of cleanliness, such as oxygen. Parts
8.1.2 If cleanliness verification is to be performed on small
shall have been precleaned to remove visible contaminants
parts, measure the total surface area (S) in square centimetres
prior to using this procedure. Softgoods such as seals and valve
or the mass in grams, or both, as applicable, to the nearest tenth
seats may be cleaned without precleaning.
of a milligram (M1). Record the surface area (S) and mass
5.2 This procedure may also be used as the cleanliness
(M1).
verification technique for coupons used during cleaning effec-
8.2 Preliminary Procedure:
tiveness tests as in Test Method G122.
8.2.1 If a cleaning agent is being used that requires dilution
5.3 The cleaning efficiency has been shown to vary with the
or special preparation, carefully follow the manufacturer’s
frequency and power density of the ultrasonic unit. Low
instructions. Use Type II water to prepare the aqueous cleaning
frequencies in the 20 kHz to 25 kHz range have been found to
agent solutions or as the actual cleaning agent.
damage soft metals such as aluminum and silver. Therefore, the
NOTE 2—It has been found that many common hydrocarbon based
specifications of the unit and the frequencies available must be
lubricants are effectively removed to acceptable levels using Type II water
considered in order to optimize the cleaning conditions without
at 50 °C to 55 °C. Contaminants more difficult to remove, such as
damaging the parts.
fluorinated or silicone based lubricants, have typically been found to
require the use of surface active agents. Use Test Method G122 to evaluate
6. Apparatus
the cleaning effectiveness of the proposed cleaning agent.
6.1 Ultrasonic Cleaner, with an operating frequency range
8.2.2 Fill the ultrasonic bath to the level specified by the
between 25 kHz and 90 kHz, a typical power range between
manufacturer with water. Place the support bracket in the
10 W ⁄L and 25 W ⁄L, and a temperature-controlled bath ca-
ultrasonic bath, heat the ultrasonic bath to the desired
pable of maintaining a temperature between ambient and 70 °C
temperature, and degas the water for 10 min.
with an accuracy of 2 °C.
8.2.3 Clean the stainless steel sample parts pan to be used.
Conduct the sampling procedure using the selected cleaning
6.2 Parts Pans, stainless steel container with volumes
agent without parts to verify the cleanliness of the parts pan.
between 1 L and 4 L.
Use the same sampling and analysis procedures that will be
6.3 Bracket, stainless steel device capable of supporting the
used on the actual parts. Determine the contamination level of
parts pans in the ultrasonic bath.
the parts pan, the blank value (B), which shall be less than the
NOTE 1—The bracket should be designed to hang in the ultrasonic bath allowable contamination level for the items being cleaned or
without contact with the bottom.
extracted. If the contamination level of the parts pan is greater
than that specified for the parts, reclean the parts pan until the
7. Reagents
7.1 Solvents such as the following may be used: tetrachlo-
roethylene (perchloroethylene), trichloroethylene, methylene
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Standard-Grade Reference Materials, American Chemical Society, Washington,
chloride, and perfluorinated carbon fluids. Warning—Solvents
DC. For suggestions on the testing of reagents not listed by the American Chemical
such as tetrachloroethylene (perchloroethylene),
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
trichloroethylene, and methylene chloride have relative low
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
threshold limit values and the user should refer to appropriate copeial Convention, Inc. (USPC), Rockville, MD.
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G131 − 96 (2023)
contamination level is less than the allowable contamination 8.4.4 Determine and record the mass (M ) of the nonvolatile
specified for the parts. residue in milligrams to the nearest tenth of a milligram using
Test Method E1235, Test Methods F324, or F331. Ensure that
8.3 Cleaning Procedure:
the reported NVR is adjusted to subtract the NVR of an
8.3.1 Place the material or part(s) being cleaned in the
equivalent volume of “blank” solvent.
stainless steel parts pan.
8.5 Sampling Procedure for Aqueous Cleaned Materials
8.3.2 Pour a measured amount of the cleaning agent into the
and Parts
stainless steel cleaning pan sufficient to cover the parts. Cover
8.5.1 Remove the parts pan from the ultrasonic bath and
the parts pan with aluminum foil or a stainless steel lid, place
remove the cover. Swirl the parts pan to mix the Type II water.
the parts pan in the bracket in the ultrasonic bath, adjust the
8.5.2 After swirling, quickly decant the Type II water from
water level in the bath such that it is above the cleaning agent
the parts pan.
level in the parts pan, an
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