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Getting the quality right

20 March 2017

Mark Ranger discusses the issues surrounding product contamination from a compressed air system. 

The food and beverage industry has witnessed several recent incidents that have led companies to recall their products. Insurance company, Lockton, has reported that the number of food recalls by the Food Standards Agency (FSA) in 2015 grew by 78%, compared with the previous year. The presence of bacteria was responsible for 15% of recalls. Of those recalls, half were due to salmonella, and 12% were because of a foreign object or body – the most common being metal. 

So, the source of contamination in the food and drink industry varies. However, the financial, reputational and legal implications are almost always damaging. In seeking to reduce the risk it is important to look at many factors, including compressed air. 

Compressed air is an almost silent, invisible form of energy used at many stages of food and drinks processing and manufacturing - including food filling machines, packaging, transporting and mixing.  It is considered that air in its pure state has no moisture or contaminants. However, in reality, this is not the case. To control and reduce contamination, it is recommended that companies follow a six-stage optimisation process to meet the key considerations that help ensure good air quality; as stated in the BCAS Food and Beverage Grade Compressed Air Best Practice Guideline 102 (2014). 

Guideline recommendations
The Guidelines recommend that food and beverage manufacturers define and know their air demand profile. This can be achieved by conducting an ISO 11011 energy audit on the compressed air system and distribution network. This is a detailed and objective compressed air audit that can be carried out after the first stage of the optimisation process. It requires a site visit by a compressed air service engineer to estimate the potential energy savings at stake and to ensure that the right type of compressor is being used. For any process where compressed air comes into direct contact with end products on a production line, the use of oil-free compressors is recommended. These are proven to be the only way to 100% avoid compromising product quality through dirt or compressor oil carry-over. In applications where compressed air does not come into contact with the product then oil-injected compressors, with filtration, can be considered. 

The compressed air audit should specify potential savings, based on an accurate measurement of current status using tools that quantify flow, pressure, electrical current input, ambient conditions, air quality, pressure dewpoint and leakages. Air leaks are the biggest source of energy waste in compressed air systems, with a leakage point as small as 3mm costing an estimated £3,260 in wasted energy over the course of a year. In addition, this second step allows manufacturers to identify the air quality that the process requires. In the food and beverage industry, there are two considerations when it comes to compressed air. The first is direct contact, defined as the process whereby compressed air is in contact as part of the production and processing including packaging and transportation of safe food production. Secondly there is indirect contact, whereby compressed air is exhausted into the local atmosphere during food preparation, production, processing, packaging or storage. 

Direct contact
For direct contact, the Food and Beverage Grade Compressed Air Guideline recommends a Compressed Air Purity Designation ISO8573.1 (2010) class 2:2:1. This means that the amount of dust must be < 1 micron, the pressure dewpoint should be -40oC and the oil content <0.01 mg/m3. Meanwhile the suggestion for indirect contact is ISO8573.1 (2010) class 2:4:1 where levels of dust should be < 1 micron, the pressure dewpoint should be +3oC and the oil content <0.1 mg/m3. 

The third step of the optimisation process will deliver a detailed report recommending system improvements to achieve the advised air quality needed in production. In applications where the required air quality is in the direct contact category, it is advised to use a 100% oil-free compressor. 

Atlas Copco’s oil free solutions meet the latest ISO 8573-1 and ISO 22000 standards. Also, when combined with VSD technology they offer low total cost of ownership: by avoiding filter replacements, eliminating the costs of lubricants, cutting maintenance costs and that of treating oil-laden condensate, and importantly, avoiding the costs of extra energy needed to combat filter-induced pressure drop. The identified enhancements should then be carried out under step four of the process. 

Step five seeks to maintain optimised performance over the long term. With the introduction of a compressor monitoring system energy performance can be continuously measured and assessed. Monitoring the system also helps ensure that the air quality meets the recommended levels.

Finally, the sixth stage of the optimisation cycle involves repeating the original audit at regular intervals to ensure that air quality is kept at optimal levels and that new saving opportunities can be identified and acted upon. By following these six steps in a coordinated manner, compressed air users in the food and beverage industry can implement a pattern of good practice that can ensure the purity of compressed air and deliver calculable and ongoing financial and sustainability benefits.  

Mark Ranger is business line manager, Oil-Free Air Division, at Atlas Copco Compressors UK.

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