ISO 16232 Road Vehicles - Cleanliness of Fluid Circuit Components

The “ISO 16232 Road vehicles - Cleanliness of fluid circuit components” standard published by the International Standards Organization (ISO) consists of a number of sub-standards published under the same title. Namely,

• In the “ISO 16232-1 Part 1: Vocabulary” standard, defines the vocabulary used in the characterization and measurement of particulate contamination of parts, components, subassemblies and assemblies constituting the fluid circuits of internal combustion engines of road vehicles. This standard applies to all components that may come into contact with a liquid (e.g. oil, fuel, air conditioning refrigerant, coolant), a solid lubricant or a gas (intake air). Unless otherwise stated, this standard deals only with particulate cleanliness. Therefore, it does not cover defects in appearance or contamination with liquid or gaseous materials. This standard covers the quantity and nature of residual particulate contaminants arising from all manufacturing processes and the environment.
• The standard “ISO 16232-2 Part 2: Method for removal of contaminants by shaking” describes the principles for removing contaminants from a component by shaking. This standard applies to components that are preferably hollow and suitable for shaking by an operator or a suitable mechanical device. This shaking method can be used alone or in combination with other removal methods described in the ISO 16232 series. Unless otherwise stated, this standard deals only with particulate contamination. Therefore, it does not cover defects in appearance or contamination with liquid or gaseous materials. It covers the quantity and nature of residual particles originating from manufacturing processes and the environment. In principle, contaminants are removed by partially filling the component with a known volume of test liquid, closing its openings and shaking it to remove particles from controlled surfaces and to suspend them in the extraction liquid for subsequent analysis.
• The standard “ISO 16232-3 Part 3: Method for removing contaminants by pressure rinsing” describes the principles for removing contaminants from a component by pressure rinsing. This standard is preferably applied to components where the surface to be examined can be reached by a test liquid jet. This method can be used alone or in combination with other removal methods described in the ISO 16232 series. Unless otherwise stated, this standard deals only with particulate contamination. Therefore, it does not cover defects in appearance or contamination with liquid or gaseous materials. It covers the quantity and nature of residual particles originating from manufacturing processes and the environment. In principle, contaminants are removed from the controlled surface of the component by pressure rinsing with a test liquid jet, which removes the particles for subsequent analysis.
• The standard “ISO 16232-4 Part 4: Method for the removal of contaminants by ultrasonic techniques” describes the principles for the removal of contaminants from a component by immersion in an ultrasonic bath or by direct ultrasonic vibrations via sonotrodes. This standard is preferably applied to small and medium-sized components with various geometries where both internal and external surfaces must be examined (e.g. joint seals, gears, etc.). It can also be applied to small parts to be analyzed in groups. This method can be used alone or in combination with other extraction methods described in the ISO 16232 series. The suitability of this method for complex geometries (e.g. small holes or large cavities with small openings) is decided on a case-by-case basis. Depending on the shape of the components, this method can also be used for groups containing more than one layer of components, as long as there is no obstacle to the removal of contaminants from the surface and their subsequent transfer to the test liquid. A large number of small compact parts are cleaned in a single layer. Unless otherwise stated, this standard only deals with particulate contamination. It therefore does not cover defects in appearance or contamination from liquid or gaseous substances. It covers the quantity and nature of residual particles originating from production processes and the environment. In principle, contaminants are removed from the surface of the component by ultrasound. The cleaning effect is due to cavitation, which implodes in the vicinity of the particles and creates microbubbles that are then ejected and transferred to the extraction liquid for subsequent analysis. In the case of an active component, particles are removed from the entire controlled surface of the component by passing through the liquid. Several operating parameters, such as power density, operating time and environment, the placement and orientation of the component with respect to the ultrasonic source, and the material from which the component is made, affect the extraction efficiency.
• The standard “ISO 16232-5 Part 5: Method for removing contaminants on a functional test bench” describes the principles for removing contaminants by testing on a laboratory functional test bench, where the test fluid flows under pressure or under vacuum. This standard applies to both active and passive components through which the fluid can flow easily. Unless otherwise stated, this standard deals only with particulate contamination. Therefore, it does not cover defects in appearance or contamination originating from liquid or gaseous materials. It covers the quantity and nature of residual particles originating from manufacturing processes and the environment. In principle, the component should be mounted on a validated test bench that simulates the functional operation of the component. The movement of the fluid under known conditions separates contaminants from controlled surfaces and transfers them to the test fluid for subsequent analysis. The movement of the test fluid is provided by pressure or vacuum. In the case of an active component, the component is operated by an external device or moving fluid, depending on the principle of function.
• The purpose of the standard “ISO 16232-6 Part 6: Determination of particle mass by gravimetric analysis” is to determine the mass of particle contamination by gravimetric analysis. Contaminants are separated from the extraction liquid by filtration. This standard applies to automotive components in contact with a liquid. Unless otherwise stated, this standard deals only with particle cleanliness. Therefore, it does not cover defects in appearance or contamination originating from liquid or gaseous materials. It covers the amount of residual particulate contaminants originating from production processes and the environment. In principle, the total amount of extraction liquid used to remove particulate contaminants from components in accordance with ISO 16232-2, ISO 16232-3, ISO 16232-4 or ISO 16232-5 standards is filtered under vacuum or pressure through one or more membrane filters. The number of filters depends on the mass of the contaminants removed. The difference in mass on the membrane filter before and after the test is used to determine the mass of contaminants in the component.
• The standard “ISO 16232-7 Part 7: Particle sizing and counting by microscopic analysis” describes methods for determining the size and number of contaminant particles removed from components and deposited on the surface of a membrane filter, as determined using a light optical microscope or a scanning electron microscope. The result of this measurement is the particle size distribution on the membrane filter. Since the function of components and parts can be impaired by the presence of single or a few critical particles, a complete analysis of the total membrane filter surface is essential. These analyses can be performed manually or automatically using image analysis techniques, if the appropriate equipment is available. Manual complete surface counting is a difficult and tedious task associated with errors. Therefore, an automatic counting system is recommended if the membrane filter is properly prepared as described here. Counting and sizing results depend on many parameters, such as the type and model of microscope, magnification, illumination and other settings used. In principle, As described in the ISO 16232-2, ISO 16232-3, ISO 16232-4 and ISO 16232-5 standards, the entire volume of the extraction liquid used to remove particles from the test compound is filtered on a membrane filter and the separated particles are counted and sized using microscopic techniques. The longest dimension of a particle is used to determine particle size.
• In the standard “ISO 16232-8 Part 8: Determination of particle nature by microscopic analysis”, energy dispersive X-ray spectroscopy and scanning electron microscope A method for determining the nature of contaminant particles by determining their elemental chemical composition using a combination of the following is described. Contaminant particles are extracted from automotive parts or components and deposited on the surface of a membrane filter. In addition to the number and size of particles described in the ISO 16232-7 standard, this measurement gives the elemental composition of the analyzed particles. This information can be used to classify particles into possible material groups. This method cannot determine the nature of organic material. Analyses can be performed manually or fully automatically, provided the appropriate equipment is available. In principle, the entire volume of the extraction liquid used to extract particles from the test component is filtered and the separated particles are counted and sized using a scanning electron microscope in accordance with the 16232-7 standard.
• The method described in the standard “ISO 16232-9 Part 9: Particle sizing and counting by automatic light extinguishing particle counter” describes methods for determining the size distribution of particulate contaminants extracted from automotive parts using the techniques described in ISO 16232-3, ISO 16232-4 and ISO 16232-5 using automatic light extinguishing particle counter instruments. This method is only valid for the analysis of the entire volume of the extraction fluid. The size range of particles that can be measured by this technique is limited to u 70 µm(c) due to the calibration method used. However, the calibration can be extended to other sizes, provided that it is accepted and included in the inspection document. This technique is only valid for measuring particles present in clear, single-phase liquids. In principle, the extraction samples are passed through the detection volume of an automatic light extinguishing particle counter, where particles with defined properties are sized and counted according to the calibration of the instrument. The primary result obtained is the quantitative particle size distribution of the contaminants present in the analyzed sample, either differentially or cumulatively. The analysis procedure consists of the following basic steps: cleaning the analysis equipment, conditioning the extraction liquid, analysis of the extraction liquid and subsequent analysis of the rinse liquid and expression of the results.
• The standard "ISO 16232-10 Part 10: Expression of results" defines the rules and formats for expressing and presenting the results of the measurement of particulate cleanliness of components for the fluid circuits of motor vehicles. It also defines a cleanliness coding system to simplify the reporting and communication of particulate contamination data. This standard also defines the rules to be used to specify the cleanliness requirements, but does not concern the expression of particulate cleanliness of fluids.

In principle, particle contamination measured in the entire volume of the extraction fluid used in one of the extraction and analysis methods described in the ISO 16232 series of standards is measured as follows:

• Per component
• Wetted surface of a component to a reference surface of 1 000 cm2
• Wetted volume of a component to the reference volume of 100 cm3

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