ISO/TC 118/SC 4 - Compressed air treatment technology

This document provides a method for sampling compressed air and a guide for choosing suitable measuring equipment to determine its particle size and concentration by number (to be referenced as "concentration" throughout this document). It also describes the limitations of the various measurement methods and describes the evaluation and uncertainty considerations. This document will report the particle size and concentration of all types of particle combined and does not aim to be able to segregate the separate solid and liquid particle fractions. When it is required that the concentration of a specific fraction is to be determined then recourse to the relevant standard method from the ISO 8573 series is recommended. NOTE 1 The test methods described in this document are those suitable for determining the purity classes given in ISO 8573‑1. NOTE 2 Particle content determined as concentration by mass is dealt with in ISO 8573‑8. NOTE 3 This document does not address instances where non-isothermal conditions exist, and separate arrangements should be made where particles may be formed by vapour condensation or lost through evaporation.

ISO 8573-2:2018 specifies test methods for the sampling and quantitative analysis of liquid oil and oil aerosols that can typically be present in compressed air. Test methods for oil vapour are excluded from this document as they are covered by ISO 8573‑5. Two different methods are described, Method A and Method B. Method B is subdivided into two parts to clearly distinguish between procedures for obtaining the quantity of oil for analysis. Method A describes an oil collection technique using inline coalescing filters whereas Method B utilizes sampling discs in a holder from which the collected oil is extracted with a solvent and analysed by infrared spectrometry or gas chromatography with flame ionization detection. ISO 8573-2:2018 also includes descriptions of alternative oil aerosol detection by the use of indicator type devices, see Annex E.

ISO 3857-4:2012 identifies the terms and provides the definitions for the vocabulary used in the air-treatment field.

ISO 8573-1:2010 specifies purity classes of compressed air with respect to particles, water and oil independent of the location in the compressed air system at which the air is specified or measured. ISO 8573-1:2010 provides general information about contaminants in compressed-air systems as well as links to the other parts of ISO 8573, either for the measurement of compressed air purity or the specification of compressed-air purity requirements. In addition to the above-mentioned contaminants of particles, water and oil, ISO 8573-1:2010 also identifies gaseous and microbiological contaminants. Guidance is given in Annex A on the application of ISO 8573-1:2010.

The test method described in ISO 12500-4:2009 is designed to determine the water-removal efficiency and operational pressure drop of any device designed for water removal from compressed air described as wall flow in accordance with ISO 8573-2.

ISO 12500-3:2009 provides a guide for choosing an appropriate method of determining the solid particulate removal efficiency rating by particle size of filters used in compressed air systems. ISO 12500-3:2009 specifies the layouts and procedures for testing these filters. Measurement methods are recommended based on the size range of the particulates that the filter being tested has been designed to remove. The test is performed as a “type-test” on filters as being representative of a range. The following two particle diameter size ranges are identified in ISO 12500-3:2009: a fine filter range, 0,01

ISO 7183:2007 specifies the performance data that are necessary to state and applicable test methods for different types of compressed air dryers. It is applicable to compressed air dryers working with an effective (gauge) pressure of more than 50 kPa (0,5 bar), but less than or equal to 1 600 kPa (16 bar) and include the following: adsorption dryers, membrane dryers, refrigeration dryers (including drying by cooling) or a combination of these. A description is given of the principles of operation of the dryers within the scope of ISO 7183:2007. ISO 7183:2007 identifies test methods for measuring dryer parameters that include the following: pressure dew point, flow rate, pressure drop, compressed-air loss, power consumption and noise emission. ISO 7183:2007 also provides partial-load tests for determining the performance of energy saving devices or measures and describes the mounting, operating and loading conditions of dryers for the measurement of noise. ISO 7183:2007 is not applicable to the following types of dryers or drying processes: absorption dryers, drying by over-compression and integral dryers.

ISO 12500-2:2007 specifies the test layout and test procedures required for testing hydrocarbon vapour adsorbent filters used in compressed air systems to determine their effectiveness in removing hydrocarbon vapours. The performance characteristics to be identified are the adsorptive capacity and the pressure drop. ISO 12500-2:2007 defines one method of presenting filter performance as hydrocarbon-vapour capacity, expressed in milligrams, from results obtained under test conditions.

ISO 12500-1:2007 specifies the test layout and test procedures required for testing coalescing filters used in compressed-air systems to determine their effectiveness in removing oil aerosols. ISO 12500-1:2007 provides the means to indicate performance characteristics of the pressure drop and the capability of removing oil aerosols. ISO 12500-1:2007 defines one method of presenting filter performance as outlet oil aerosol concentration stated in milligrams per cubic metre from results obtained under standard rating parameters.

ISO 8573-8:2004 specifies test methods for determining the solid particle mass concentration in compressed air, expressed as the mass of solid particles with maximum particle size limits. The methods' limitations are also specified. One of a series of standards aimed at harmonizing air contamination methods, it identifies sampling techniques and also gives requirements for evaluation, uncertainty considerations and reporting for the air purity parameter solid particles by mass concentration. The test methods are suitable for determining the purity classes in accordance with ISO 8573-1. (Particle content based on counting particles is dealt with in ISO 8573-4.)

ISO 8573-9:2004 specifies test methods for determining the liquid water content in compressed air, expressed as the liquid water mass concentration. The methods' limitations are also specified. One of a series of standards aimed at harmonizing air contamination methods, it identifies sampling techniques, specifies measurement procedures and also gives requirements for evaluation, uncertainty considerations and reporting for the air purity parameter liquid water. The test methods are suitable for determining the purity classes in accordance with ISO 8573-1. (Water vapour content is dealt with in ISO 8573-3.)

ISO 8573-7:2003 specifies a test method for distinguishing viable, colony-forming, microbiological organisms (e.g. yeast, bacteria, endotoxins) from other solid particles which may be present in compressed air. One of a series of standards aimed at harmonizing air contamination measurements, it provides a means of sampling, incubating and determining the number of microbiological particles. The test method is suitable for determining purity classes in accordance with ISO 8573-1, and is intended to be used in conjunction with ISO 8573-4 when there is need to identify solid particles that are also viable, colony-forming units.

ISO 8573-6:2003 provides a selection of suitable test methods for the measurement of contamination gases in compressed air. It specifies sampling technique, measurement and evaluation, uncertainty considerations and reporting for the applicable gaseous contaminants carbon monoxide, carbon dioxide, sulphur dioxide, nitric oxide, nitrogen dioxide, and hydrocarbons in the range C1 to C5 (see ISO 8573-5 for C6 and above). The methods given are also suitable for other gases.

This part of ISO 8573 provides guidance on selection from the available suitable methods for measurement of humidity in compressed air and specifies the limitations of the various methods. It does not provide methods for measurement of water content in states other than vapour. This part of ISO 8573 specifies sampling techniques, measurement, evaluation, uncertainty considerations and reporting for the air contamination parameter humidity. It gives guidance for the conversion of humidity statements to the standard format.

ISO 8573-2:2007 specifies test methods for the sampling and quantitative analysis of oil aerosols and liquid oil that can typically be present in compressed air. Test methods for oil vapour are excluded from ISO 8573-2:2007 as they are covered by ISO 8573-5. Two different methods are described, method A and method B. Method B is subdivided into two parts to clearly distinguish between procedures for obtaining the quantity of oil for analysis.

Describes test methods for the sampling and quantitative analysis of aerosol oil content and liquid oil (excluding oil vapour) normally present in the air discharged from compressors and compressed air systems. Gives detailed instructions on the equipment to be used and the test methods to be employed for the measurement of oil content. Applies to compressed air systems up to 30 bar working pressure, but excluding systems intended for medical use or for direct breathing.

Provides general information to assist users and engineers in the selection of the type of compressed air dryer which will best serve their needs. Does not cover safety requirements.

Specifies reference conditions, acceptance test methods and the most important characteristic data of different dryers. Applicable to dryers working in the effective (gauge) pressure range of 0,16 to 40 MPa, but excluding: liquid absorption types; cooling with aftercooler; overcompression. A test report form is shown in annex A. Annex b includes a typical testing system for air dryers. Saturation pressure and density of pure water vapour is tabulated in annex C.