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HYDRAULICS & PNEUMATICS
FEATURE
should be to define the precise compressed air purity (quality) requirements that the application requires. 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
ISO 8573 – WHEN QUALITY MATTERS
Roy Brooks, technical development officer at the British Compressed Air Society, outlines the basics of ISO 8573, the international standard for air purity (quality), and explains why all parts of a compressed air system should be considered during the specification process
s many as 90% of all industrial manufacturing sites rely on compressed air for some aspect of their operations, so ensuring a high-quality source of air is vital for uptime and productivity. However, compressed air is not clean – it can contain up to ten different contaminants, which need to be treated correctly. These tend to be combined into three
A
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,
remember 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.
WHICH STANDARD? Depending on the application, there are number of different compressed air standards and best practice guidelines which can assist. ISO8573 series is the most commonly used
standard for compressed air (excluding breathing air or medical air). It is made up of nine separate parts. Part 1 refers to air purity (quality), while 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 upon application requirements. There are also specific requirements
for compressed air that comes in to 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.
SPECIFYING CORRECTLY Whether designing new systems, or reviewing existing systems, the first step
BLENDED LEARNING WORKSHOP
BCAS offers an ISO8573 blended learning workshop to provide further training. The course is aimed at typical industrial compressed air applications operating at low pressure, with a range between 7bar g to 20bar g. Further information and bookings are available at:
https://elearning.bcas.org.uk/our-courses/blended-learning-courses/understanding-iso-8573-the- air-quality-standard/ Detailed guidance can be found in the ‘Filtration and Drying of Compressed Air - Best Practice Guide 104 at:
www.bcas.org.uk/airtreatment.
MARCH 2022 DESIGN SOLUTIONS 19
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: • 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. If most of the compressed air is needed at a high purity (quality), it can make sense to treat all the compressed air to the level required by the highest purity (quality) application.
BCAS
www.bcas.org.uk.
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