Compressed air is an often overlooked yet vital component in the air quality of production lines within the UK’s manufacturing, food processing, pharmaceuticals, and engineering sectors. Many businesses see compressed air as an on/off utility. However, because contaminated compressed air is a leading cause of defective products, equipment failure, and costly downtimes, failing to have an adequate understanding of the ISO 8573-1 standard is the fatal flaw of any procurement or facilities manager.
ISO 8573-1 splits the purity of compressed air into three contaminants: solids, water, and oil, where each is rated from 1 to 6. For example, an air point of use classification of 1:4:1 indicates an engineer or auditor a specific level of cleanliness. The air class requirement for a food packaging line is more stringent than that of a workshop, and air tool use for tyre inflation and nail driving. In either case, costs associated with over-specifying filtration requirements for energy and capital waste, or under-specification leading to product contamination, corroded pneumatic parts, and disputes with equipment suppliers are significant.
The Importance of Oil Carryover
If the correct filtration system is not in place, most industrial compressors will allow a small amount of oil to pass downstream. For industries like pharmaceuticals and electronics assembly, just a tiny amount of oil can ruin a batch or cause expensive defects in coatings. Several facility managers think that the coalescing filter that is installed at the time of installation will take care of this, but filter elements become worn and require a scheduled replacement, usually between 6 and 12 months, depending on the duty cycle. A compressed air audit measuring actual output against the specified ISO 8573-1 class will catch this before it becomes a quality control issue.
Moisture is the other silent issue. Water vapour condenses in the pipework as the compressed air cools. If this is left unmanaged it will cause rust in receivers and pipes, water hammer in pneumatic cylinders, and ice build up in outdoor lines during the winter. An appropriately sized refrigerant or desiccant dryer and automatic condensate drains will keep the dew point low enough that condensation will not accumulate in the distribution system. For sites using compressed air that is run outside or in unheated storage areas, it is generally better to use a desiccant dryer that can achieve a pressure dew point well below the expected ambient temperature.
Particulate contamination is the third element of the standard and is usually the simplest to control with properly rated inline filters. However, it often gets overlooked because blocked filters restrict airflow gradually instead of failing completely. Each filter’s housing comes with a differential pressure gauge to warn you before the filter element releases its grip on the system and causes the compressors to work harder than they should, which requires an expensive and unnecessary energy expenditure.
When considering a new compressed air system, businesses should ask suppliers to specify the ISO 8573-1 class they anticipate the filtration and drying system will achieve for their proposed filtration and drying packages, instead of just providing a value for flow rate and pressure. This converts an ambiguous specification into one that is quantifiable and auditable, and which can be verified at commissioning and at every service interval thereafter. For facilities that already have a compressed air system, periodic air quality testing can be one of the most cost-effective ways to protect product quality and prevent unnecessary wear on the compressor. It is especially valuable when conducted by an independent engineer, rather than relying on outdated assumptions.
Air quality in compressed air systems is not a one-time decision made at the time of installation. To meet existing production requirements, use ISO 8573-1 to evaluate filtration periodically in order to maintain quality and minimize unplanned downtime.