Compressed Air Contamination
Contaminants originate from three general sources.
Contaminants in the surrounding ambient are drawn into the air system through the intake of the air compressor. Ingested contaminants appear in the form of water vapour, hydrocarbon vapours, natural particles and airborne particulates.
As result of the mechanical compression process, additional impurities may be introduced into the air system. Generated contaminants include compressor lubricant, wear particles and vaporized lubricant.
A compressed air system will contain in-built contamination. Piping distribution and air storage tanks, more prevalent in older systems, will have contaminant in the form of rust, pipe scale, mineral deposits and bacteria.
Water vapour enters the system through the intake of the air compressor. In total volume, condensed water vapour represents the majority of liquid contamination in a compressed air system. On a typical summer day of 80(F (21(C) and 70% relative humidity, approximately 19.5 gallons (73.8 litres) of water enters a 100 scfm (170 nm3/hr) system in a 24 hour period. This moisture will spoil food products, cause pneumatic machinery failure and promote bacterial growth in the compressed air piping. Compressed air systems serving the food processing industry must maintain dry, moisture free conditions mitigating the risk of micro-organism growth.
Since compressed air used in food processing operations may come in direct contact with the food, a compressed air dryer producing a sub-zero pressure dew point is required. Dew point, specified as temperature, is the point at which the water vapour held in the compressed air is equal to the compressed air’s capacity to hold water vapour. Desiccant dryers- using activated alumina- will adsorb water vapour from the air most effectively, delivering ISO 8573.1 Quality Class 2 (-40( F/-40( C) pressure dew point), ideal for the food processing industry. At this level of dryness, bacteria will cease to grow.
The next time you sit down for dinner, take a good look at your food. There’s a very good chance compressed air or nitrogen played an
essential role in preparing your meal for consumption.
Q. So what standard does your air or nitrogen have to be or comply with in Australia to be safe?
A. Currently there is no universal standard set down by law in Australia governing the quality of compressed air or nitrogen in the food industry.
Sounds crazy, but this is the case. There is a recognised standard that should be achieved to ensure best quality and safety to the consumer.
So what do we do? The issue is addressed with the following;
Air & Nitrogen Quality Standards for compressed air used in the food industry
Once hazards are identified, measures must be put in place to remove the hazards or reduce them to acceptable levels. So what level of compressed air contamination is deemed acceptable in the food industry.
Unlike compressed air that is used for breathing or medical purposes, NO standards or laws exist that define a minimum acceptable level of cleanliness (quality) when the compressed air is used for food manufacture. As food manufacturers have a duty of care to protect the consumer and compressed air systems are known to carry large quantities of contamination, what actions should be taken?
If a hazard is identified such as poor quality air or lack of maintenance or even equipment not suitable for the job then the manufacturer MUST REMOVE the hazard.
Introducing the Food Grade Compressed Air Code of Practice
In the United Kingdom, the British Compressed Air Society (BCAS) who are the governing body for compressed air and the British Retail Consortium (BRC) who represent the retail industry, have jointly developed a Code of Practice for Food Grade Compressed Air in order to assist food manufacturers . This Code of Practice evolved because of the absence of compressed air quality standards or legislation specific to the food manufacturing industries. The Code of Practice gives minimum purity (quality) standards for compressed air and defines allowable levels for dirt, water and oil, in line with air quality levels specified in ISO8573-1 the International Standard for compressed air quality. In Australia we also follow these guidelines.
HOW CAN CPS (HIre) Help?
1. We only recommend installation of the best equipment to ensure risk of failure is limited.
2. We recommend the use of 100% Oil Free Class zero air to eliminate the risk.
3. We can set a maintenance plan to ensure your system operates as designed. If any changes are needed we can advise.
4. An air quality test to verify the quality of your compressed air and nitrogen is recommended every 6-months.
Air Quality (Purity) Requirements of the Code of Practice
To comply with food hygiene legislation, the food manufacturer is required to follow the principles of HACCP (Hazard Analysis and Critical Control Point) and a risk analysis must be carried out on the entire manufacturing process.
As compressed air is seen as a utility, it is often missed as a potential source of contamination. To be fully compliant, the compressed air system must be included as part of the hazard analysis and anywhere compressed air is used, classified as a Critical Control Point and subject to the air purity (quality) recommendations highlighted in section 6 of the Code of Practice.
Section 6 states:
The outlet compressed air must be designated as one of the following:
• Air that comes into direct contact with the food (Contact).
• Air that will never come into contact with the food (Non-Contact).
• Where the HACCP Hazard Analysis shows a potential risk of the Non-Contact air indirectly contacting food or entering the food manufacturing area then the air shall be defined as Non-Contact High Risk.
Air that comes into direct contact with ingredients, finished food, packaging materials, storage vessels or the manufacturing machinery.
Air that will never come into contact with ingredients, finished food, packaging materials, storage vessels or the manufacturing machinery.
Non-Contact High Risk
Air that is not supposed to come into contact with ingredients, finished food, packaging materials, storagevessels or the manufacturing machinery, but may
inadvertently do so.
New Food & Beverage Best Practices Guideline from BCAS
New best practice guideline BPG 102 for food and beverage processors on the safe and efficient use of compressed air has been unveiled by the British Compressed Air Society (BCAS). This is Australia not Britain but it is this standard or guideline that we use as a basis for our industry.
Following this best practice guideline in association with the food/beverage industry requirements to apply the pre-requisite programme and where applicable HACCP process will ensure that the compressed air system will not only meet current industry best practice but also contribute to customer confidence in food supplied to market.
The guideline expands and clarifies the compressed air requirements identified in existing food/beverage safety standards, guidelines and in some areas legislation.
The best practice guideline is intended to provide an encouragement to the food and beverage industry to improve their compressed air provision rather than demand immediate and possibly costly expense.
This best practice guideline identifies the requirements for compressed air systems, operating at a pressure greater than 0,5 bar, as pre-requisites in the production and processing including packaging and transportation for safe food and beverage production.
It also identifies the air purity requirements for compressed air for both direct and indirect product contact.
Installation practices are provided as guidance for both existing installations and new installations.
Measurement and testing procedures are identified to verify the purity of the compressed air.
Maintenance activities are identified to retain continued performance of the compressed air system.
Importantly all food/beverage sites will be subject to auditing processes. The guideline provides specific advice to auditors on what should be reviewed and verified to ensure that the compressed air system complies with the set standards.
The guideline has been produced to be applicable anywhere that a food and beverage plant is located. Copies of the best practice guideline are available as hardcopy or pdf from the BCAS, visit www.bcas.org.uk
Compressed air is a vital energy source and is utilized in multiple operations in a food processing facility. When properly treated, compressed air is regarded as a safe, clean utility, as compared to other energy sources. Compressed provides the energy source for pneumatic conveyers that transport liquids, powders and moisture sensitive product throughout the plant. It provides power for pneumatically operated tools and equipment that renders meat products, aerates liquids and mixes granular ingredients. It is ultimately used to package, wrap, seal, palletize and label food products prior to storage or shipment.
Of the primary utilities employed in the food-manufacturing environment, compressed air is the only utility generated by the end-user. This means the end-user directly influences the quality of this energy source. High quality compressed air is critical for providing food products that are not only cost effective to process but also safe to eat. Therefore, it’s in all our best interests for food processors to select the proper compressed air equipment. The ISO 8573 air quality standards and ISO 12500 compressed air filter standards make the basis for air treatment product selection much easier.
Compressed Air & Nitrogen in the Food Industry (Australia)
Liquid Oil and Oil Vapour
The most scrutinized and often discussed contaminant classified by ISO 8573.1 is oil. Compressed air “free from oil” is a requirement in a food processing environment.
End users are given the choice of selecting from several air compressor technologies, some of which require lubrication in the compression chamber for cooling and sealing purposes, and others that operate less lubricant in the compression chamber. The end user determines which compressor design best meets the desired requirements. The purpose of this discussion is not to tip the scale toward either technology, but to address air treatment requirements in food processing applications.
Lubricated compressors are typically less expensive to purchase and have a lower cost of ownership. Dependent on the age of the compressor and preventative maintenance programs performed, a lubricated rotary screw air compressor will introduced 2 to 10 ppm/w of oil into the air system. A well maintained 250 scfm lubricated air compressor, with a conservative 4 parts per million carry-over, will add up to 4.8 gallons (18.2 litres) of oil into the air system over an 8000 hour operation.
Lubricant free compressors generally have a higher initial cost and greater maintenance costs over the life cycle of the equipment. Lubricant is only required for the bearings and timing gears, which is segregated from the compression chamber. This compressor technology presents no risk of lubricant migrating into the process air.
Both air compressor technologies are subject to the inherent challenges presented by quality of the intake air. Ingested contamination in the form of water vapour, solid particulate and hydrocarbon vapour must be addressed regardless if the compressor is lubricated or free from lubricant. Depending on the location of the compressor intake, oil vapour levels in industrial areas may contain 20-30 ppm of airborne hydrocarbon aerosols. Hydrocarbon vapours, the primary component of fossil fuel combustion, will condense in a piping system when cooled forming a liquid contaminant.
Because compressed air may come in direct and indirect contact with food processing, an elevated level of filtration is required. A high efficiency coalescing filter capable of removing solids and liquids is recommended. It should be capable of removing solid and liquid aerosols 0.01 micron and larger. The remaining oil content should be 0.007 ppm, or less. An activated carbon filter, installed in series, is also recommended downstream of the coalescing filter. The adsorption filter will remove trace odours and oil vapour to 0.003 parts per million by weight. This filter combination will ensure specified filtration levels achieve ISO 8573.1 Class 1 for oil and vapour removal.
In a general industrial area, there are nearly 4,000,000 airborne particles per cubic foot of air. When this ambient air is compressed to 100 psig, the concentration of solid contamination will reach significant proportions. Most air compressor intake filters are rated to capture sold particles 4 to 10 microns in size and larger and are rated at 90-95% efficiency. Approximately 80% of airborne particles are 10 micron or less. Spores, pollen and bacteria are less than 2 micron in size. This may seem like a lot of particulate matter, but keep in mind, a solid particle 40 um in size is barely visible to the naked eye. Even a well maintained and routinely changed intake filter will allow solid particles to enter the air system.
Solid particulate must be removed from process air serving the food industry. In pneumatic control circuits, solids particles plug control valve orifices, affect accuracy of gauging and score air cylinders walls, causing leaks. Particles may restrict flow through air jet nozzles used to clean food preparation surfaces or adversely affect the consistency of spray coatings applied on food products.
To achieve the recommended ISO 8573.1 Class 2 classification for solid particulate removal, a 1.0 micron particulate filter is recommended. The particulate filter will also enhance the service life of high performance coalescing filters by minimizing solid loading.
A Very Good Start – ISO 8573.1
Food processors maintain a social responsibility for upholding the quality of their products and that accountability begins with the selection of compressed air system components. In most cases, end users select compressed air system components by comparing technical data from various air treatment manufactures. In 1991, the International Standards Organization (ISO) established the 8573 compressed air quality standard to facilitate compressed air system component selection, design and measurement.
ISO 8573 is a multi-part standard, with Part 1 classifying contaminant type and assigning air quality levels, and Parts 2 through 9, define testing methods to accurately measure a full range of contaminants within the end user’s facility.
ISO 8573.1 identifies three primary contaminant types as prevalent in a compressed air system. Solid particulates, water and oil (in both aerosol and vapor form) are recognized. Each is categorized and assigned a quality class ranging from class 0, the most stringent, to Class 9, the most relaxed. The end user-user is responsible for defining the air quality required for their particular application or process.
Air treatment manufacturers present technical data in reference to ISO 8573.1. An easy to understand ISO 8573.1: 2001 table defines the various air quality classes. The standard also determines that air quality shall be designated by the following nomenclature:
Compressed Air Purity Classes A, B, C:
A= solid particle class designation
B= humidity and liquid water class designation
C= oil class designation