ASTM E3265-21

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Designation: E3265 − 20 E3265 − 21
Standard Guide for
Evaluating Water-Miscible Metalworking Fluid Foaming
Tendency
This standard is issued under the fixed designation E3265; 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.
1. Scope Scope*
1.1 This guide provides an overview of foaming tendency evaluation protocols and their appropriate use.
1.2 ASTM Test Methods D3519 and D3601 were withdrawn in 2018.2013. Although each method had some utility, neither
method reliably predicted in-use foaming tendency. Since Test Methods D3519 and D3601 were first adopted, several more
predictive test protocols have been developed. However, it is also common knowledge that no single protocol is universally
suitable for predicting water-miscible metalworking fluid (MWF) foaming tendency.
1.3 Moreover, there are no generally recognized reference standard fluids (either MWF or foam-control additive). Instead it is
important to include a relevant reference sample in all testing.
1.4 The age of the reference and test fluid concentrates can be an important factor in their foaming behavior. Ideally, freshly
prepared concentrates should be held at laboratory room temperature for at least one week before diluting for foam testing. This
ensures that any neutralization reactions have reached equilibrium and enables microemulsions to reach particle size equilibrium.
During screening tests, it is also advisable to test fluids after the concentrates have been heat aged and subjected to freeze/thaw
treatment.
1.5 The dilution water quality can have a major impact on foaming properties. In general, fluid concentrates diluted with hard
water will foam less than those diluted with soft, deionized, or reverse osmosis water. Screening tests using the expected range
of dilution water quality are highly recommended.
1.6 The temperature of the tested fluids can have a major impact on foaming properties. In general, test fluids should be held and
tested at temperatures that closely mimic the real-world application and process.
1.7 Cleanliness of test apparatus is critical during foam evaluation testing. Traces of residue on labware can significantly impact
the observed foaming tendency of a test fluid. Best practice is to clean any glassware or other vessels using some version of a
chemical cleaner that will alleviate any risk of cross contamination.
1.8 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this
standard.
This guide is under the jurisdiction of ASTM Committee E34 on Occupational Health and Safety and is the direct responsibility of Subcommittee E34.50 on Health and
Safety Standards for Metal Working Fluids.
Current edition approved Nov. 1, 2020April 1, 2021. Published December 2020April 2021. Originally approved in 2020. Last previous edition approved in 2020 as
E3265 – 20. DOI: 10.1520/E3265-20.10.1520/E3265-21.
*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
E3265 − 21
1.9 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.
1.10 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:
D2881 Classification for Metalworking Fluids and Related Materials
D3519 Test Method for Foam in Aqueous Media (Blender Test) (Withdrawn 2013)
D3601 Test Method for Foam In Aqueous Media (Bottle Test) (Withdrawn 2013)
D7049 Test Method for Metalworking Fluid Aerosol in Workplace Atmospheres
E2523 Terminology for Metalworking Fluids and Operations
E2889 Practice for Control of Respiratory Hazards in the Metal Removal Fluid Environment
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this method, refer to Terminology E2523.
3.1.2 foam, n—in liquids, a collection of bubbles formed in or on the surface of a liquid in which the air or gas is the major
component on a volumetric basis.
3.1.3 foam break, n—in foaming tendency testing, the change in total volume occupied by bubbles during a specified test period.
3.1.3.1 Discussion—
The total bubble volume is a function of individual bubble size and the number of bubbles present. Consequently, foam break can
reflect reduction of the volume of individual bubbles, decrease in the number of bubbles present, or a combination of both.
3.1.4 foam stability, n—in foam testing, the amount of static foam remaining at specified times following the disconnecting of the
air supply.
3.1.5 foaming tendency, n—in foam testing, the amount of static foam immediately before the cessation of air flow.
3.1.6 shear stress, n—the motivating force per unit area for fluid flow.
3.1.7 sparge, v—a process of delivering a chemically inert gas through fluids to displace materials for the purpose of mixing.
3.1.7.1 Discussion—
In MWF foam testing, most commonly the inert gas is filtered or unfiltered air from a laboratory or building compressor, or from
a vendor-supplied compressed gas cylinder.
4. Significance and Use
4.1 The process of recirculating MWFs entrains air bubbles which can accumulate, forming foam.
4.2 Optimally, air bubbles burst open quickly after they are created. However, air bubble persistence is affected by MWF
chemistry and the mechanisms by which energy is introduced into recirculating MWFs.
4.2.1 The primary mechanisms imparting energy into recirculating MWFs are:
3 –1 –1
4.2.1.1 Turbulent Flow—The high velocity (typically >0.75 m min ; >200 gal min ).
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volume information, refer to the standard’s Document Summary page on the ASTM website.
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4.2.1.2 Impaction—Energy generated when MWF strikes the tool-workpiece zone.
4.2.1.3 Centrifugal Force—MWF moved by the force of rotating tools or work pieces.
4.3 When air bubbles persist, they tend to accumulate as foam. Persistent foam can:
4.3.1 Inhibit heat transfer;
4.3.2 Cause pump impeller cavitation;
4.3.3 Foul filters;
4.3.4 Overflow from MWF sumps; and
4.3.5 Prevent proper lubrication.lubrication;
4.3.6 Contribute to MWF mist formation, including bioaerosol dispersion; and
4.3.7 Contribute to safety and hygiene hazards in the plant.
4.4 To prevent the adverse effects of MWF foam accumulation, chemical agents are either formulated into MWF concentrate,
added tankside, or both.
4.5 Laboratory tests are used to predict MWF foaming characteristics in end-use applications. However, no individual test is
universally appropriate.
4.6 This guide reviews test protocols commonly in use to evaluate end-use diluted MWF foaming tendency and the impact of
foam-control agents on MWF foaming tendency.
5. Foam Formation Theory
5.1 Foam is a dispersion of a gas phase in a liquid system. Air is introduced into the system mechanically or chemically to create
the gas phase. Foam accumulation is related to stabilization of the thin film of liquid that outlines the gas bubble, also known as
the lamella.
5.2 In order for gas to escape, bubbles must coalesce, rise, drain, and burst at the surface. Foam is stabilized in the liquid via
several mechanisms dependent on the system and application type.
5.2.1 Surface Viscosity—Increased structure in a liquid slows drainage and causes higher foaming; the foam film breaks when film
thickness falls below a minimum value, dependent on the system.
5.2.2 Electrostatic Repulsion and Steric Hindrance—Occurs due to the nature of emulsifiers and surfactants present which contain
hydrophilic and hydrophobic groups. They tend to stabilize gas bubbles within the liquid and at the surface of the liquid causing
stable foam.
5.3 Specific viscosity properties and the use of surfactants and emulsifiers are essential to water-miscible metalworking fluids. In
order to reduce foam tendency, it is important to formulate with these components carefully as well as consider the use of
defoamers for high-foam systems.
6. Metalworking Fluid Foam Tendency Evaluation Protocols
6.1 Blender Test:
6.1.1 Concept—A blender test is a foam collapse test performed by exposing the sample to a very high amount of shear stress for
a short period of time.
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6.1.1.1 Foam control effectiveness is a function of the maximum foam volume and time required for the foam to disappear (break).
6.1.1.2 The most effective control is reflected in minimum initial foam volume and a short time for the foam to break completely.
NOTE 1—The terms “minimum” and “short” are subjective and situational. They depend on the application and user’s operational objectives.
Consequently, neither a volume nor time interval can be specified here.
6.1.2 Apparatus—Either a laboratory grade or kitchen blender and a timer.
6.1.2.1 Laboratory grade blenders are best suited for testing when there is a need to compare results taken at different points in
time (for example, for periodic quality control testing).
6.1.2.2 Typical kitchen blenders are typically less expensive than laboratory grade blenders but are sufficient for comparing the
foaming tendencies of multiple samples as a single test series.
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6.1.3 Protocol Summary:
6.1.3.1 An aqueous MWF dilution to be tested is dispensed into a blender vessel which is then sealed.
6.1.3.2 The blender is then run at a high speed for a specified time using a timer; a typical blending time is 60 s.
NOTE 2—Blender speeds vary among makes and models. Typically, high speed implies ≥1000 rpm.
NOTE 3—The setting used for speed can be adjusted based on the application and type of shear, for example liquefy or setting 8.
6.1.3.3 A timer is started immediately after blending is stopped. This is the rest period during which the sample is permitted to
stand undisturbed.
6.1.3.4 During the rest period the foam volume or height is recorded at specified time intervals, such as 30 s, 60 s, 120 s, etc.
NOTE 4—Some blenders are graduated and make volume measurements practical. Others are not. If the blender is not graduated, its contents may be
transferred to a graduated cylinder for volume measurement. Alternatively, a ruler may be used to observe foam column height.
6.1.3.5 The most effective control is reflected in minimum in
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