FEATURE COMPRESSED AIR
ISO8573 – WHEN COMPRESSED AIR QUALITY COUNTS
air purity (quality) requirements for the application. To achieve the degree of air purity (quality) specified by ISO8573- 1, a careful approach to system design, commissioning and operation must be adopted. Best practice is to treat compressed air prior to entry into the distribution system and at critical usage points and application, to ensure that contamination already in the distribution system is removed. Purification equipment should ideally be installed where the air is at the lowest possible temperature, i.e., downstream of air receivers, but also protected from freezing. Point-of-use purification equipment should be installed as close as possible to the application. To allow correct sizing and selection of purification equipment, operators should have the following operating parameters to hand:
Roy Brooks, Technical Development Officer for the British Compressed Air Society (BCAS) outlines the basic principles of ISO 8573, the international standard for air purity
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s many as 90 per cent of all industrial manufacturing sites rely on compressed air for some part of their operations, so ensuring a high-quality source of air at all times is vital for uptime and productivity. Compressed air is not clean! In fact, it can contain up to ten different contaminants, which need to be treated correctly. They are combined into three distinct categories: particles (including viable and non-viable microbiological organisms), water and oil. ISO 8573-1 refers to the main contaminants in this format. When selecting purification equipment, it is important to note that contaminants will be in one of three different phases (states of matter). For example, water and oil in a compressed air system will be found in liquid form, as an aerosol (fine mist) and in a vapour (gaseous) phase and a different purification technology will be required depending upon the phase of the contaminant.
STANDARDS Depending on the application, there are several compressed-air standards and best-practice guidelines that can be used to assist, of which the most commonly-used is the ISO8573 (excluding breathing air or
18 APRIL 2021 | IRISH MANUFACTURING
medical air). It is made up of nine separate parts. Part 1 refers to air purity (quality), whereas parts two to nine provide details on the equipment and methodology to be used to measure for different contaminants in a compressed air system (and meet the air purity (quality) classifications shown in part one). ISO8573-1 – International Standard
Relating to Compressed Air Purity (Quality) ISO8573-1 provides guidance on specifying the air purity (quality) required for the entire compressed-air system and/or for individual usage points, based on the application requirements. In addition, there are also specific requirements for compressed air that comes in direct or indirect contact with food or beverage products as well as the HTM02-1 purity recommendation for medical and surgical air and HTM2022 for dental air. Finally, BS EN 12021:2014 is the specified standard for breathable air, indicating maximum permitted contaminant levels both in the UK and the EU.
SPECIFICATION Whether designing new systems or reviewing existing ones, the first step should be to define the precise compressed
• The maximum compressed air flow rate into the filters/dryer.
• The maximum operating temperature into the filters/dryer. • The maximum ambient air temperature where the equipment is to be installed (required for some dryer technologies). • The required dewpoint (dryers). Individually, each of the primary operating parameters can influence product sizing, however collectively they can have a major impact on product sizing and performance. Many manufacturing plants only need a proportion of the compressed air to be treated to a very high purity (quality). In these cases, excellent savings are achievable by treating all the generated air to the minimum acceptable level and improving the purity (quality) to the desired level at the usage point. The specification of the most appropriate air treatment can be a complex task and this article only illustrates the basic principles. BCAS now offers an ISO8573 blended learning workshop. The course is aimed at typical industrial compressed air applications operating at low pressure, with a range between 7 bar g to 20 bar g and provides guidance on the differences between indicative testing and air quality verification. Use this link to learn more about the course:
https://bit.ly/BCAS- ISO8573. In addition, detailed guidance can be found in the ‘Filtration and Drying of Compressed Air - Best Practice Guide 104 at
www.bcas.org.uk/airtreatment.
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