Compressed Air – a hidden contamination risk

Lubrication is required for running a air compressor smooth and efficient. However, contact is possible between compressed air and lubricant, so that oil mist can come in the air. Replacement by oil-free compressors can be avoided by switching to food grade lubricant specially developed for compressors. As a result, it is possible, in the event of contact, to stay within the FDA standards, while the operation of the compressor can even improve.

The presence of air compressor lubricant in compressed air can be a major area of concern for food & beverage manufacturers. Commonly used in food processing plants, compressed air is used to mix liquids and provide safe power delivery for critical tasks in areas such as material transport, filling lines, spray applications and drying. However, as the majority of air compressors are oil lubricated, food safety can be quickly compromised by the use of non-food grade compressor oils.

Essential to the smooth and efficient running of air compressors, lubricating oils help to reduce metal-to-metal contact between the compressor’s rotor or helicoidal screws and the cylinder housing. This helps to minimise expensive component wear and damage, reducing unplanned downtime and enabling operators to realise the low maintenance and reliable performance benefits of compressors. As compressors operate in close proximity to food stuffs, there is a realistic threat of accidental oil contact, which is why Shell lubricants companies have developed a new food grade compressor oil.

Oil Mist Risks

Oil mist can form in compressed air as a result of high operating temperatures and can be difficult to detect. This increases the threat of the oil mist coming into direct contact with food; a problem that can easily go unnoticed until detected by the consumer. By this time though, it can be too late, as consumer health and welfare has been jeopardised. This can bring the company under public scrutiny, which can severely impact on long-term market performance and survival.

The amount of oil in compressed air depends on a number of factors, including the condition of the machine and how regularly it is maintained, the condition of the coalescer and filters and whether parts that have been fitted have been recommended by the original equipment manufacturer. Other risk factors include the age of the compressor oil, whether the correct oil is being used and whether secondary filters have been fitted. Failure to maintain and regularly replace filters will also increase the risk of contamination.

As Figure 1 shows, even when using multi-stage filtration, there is still a risk of contamination with food as oil particles remain in the compressed air. While a multi-filter system can reduce oil mist concentration to as low as 0.1 parts per million (ppm), it is impossible (under normal conditions) to remove 100 per cent of oil mist for an end result of 0.0ppm – the maximum tolerance of non-food grade lubricant contamination with food and beverages allowed by the US Food and Drug Administration (FDA).

Shell / Lubritech
Diagram of oil and air flow around compressor

Fig. 1. It’s impossible to remove 100% of oil mist

Reducing Contamination

While it is possible to avoid the presence of an oil mist by using an oil-free compressor, this is an expensive option requiring replacement of existing non-oil free compressors. A much more cost-effective solution for operators is the use of food grade compressor oils. Specifically developed for use in air compressors, high quality, synthetic, H1 approved, food grade compressor oils such as Shell Cassida ® Fluid CR 46 have been formulated using approved additives and base fluids. This composition means that Shell Cassida Fluid CR 46 is tasteless, colourless and odourless and will not contaminate food in quantities less than the US FDA’s maximum permitted level for H1 lubricants of 10 parts per million.

Fully registered by the NSF as H1 for incidental food contact, Shell Cassida Fluid CR 46 is a fully synthetic oil that can increase food safety and compressor performance. Cassida Fluid CR 46 has excellent high temperature resistance to oxidisation, which reduces gum and lacquer deposits on the coalescer, reducing filter saturation and the risk of oil mist. As well as improving air quality, the reduction in deposits enables better fluid circulation and lubrication of the compressor, improving efficiency and lowering maintenance costs.

Cassida CR 46 – Food Grade Performance
Atlas Copco oil-flooded GA 37 screw compressor, after 5,756 hours

Shell / Lubritech
Clean Coalescer

Clean Coalescer will remove oil mist efficiently

Shell / Lubritech
Oil filter mounting

Oil Filter Mounting Plate: no sign of oil oxidation

This compressor was running on a competitor fluid, which showed deposits before the oil change at 4,000 hours. It was flushed and filled with Shell Cassida Fluid CR 46. After 5,756 hours on Shell Cassida Fluid CR 46, the coalescer and oil filter were inspected with the following results:

  • Both were found clean and free from deposits
  • Seals were in excellent condition
  • Oil Analysis showed oil still in excellent condition
    (oil should be analysed periodically)

Shell Cassida CR 46 has been used in these compressors:
Atlas Copco, Berko Compressors, Compair Hydrovane, Gardner Denver, Grassair, Hitachi Compressors, Ingersoll Rand, Rietschle, Vemag Maschinenbau GmbH.

Food Grade Benefits

Although the risk of compressed air contamination is difficult to detect, the consequences are much more visible…. especially on the bottom line. Excessive costs can be incurred as whole batches of contaminated food are destroyed and unadulterated products recalled. Furthermore, production lines may have to be completely stopped as the contamination incident is rectified and compressors cleaned.

High quality, synthetic, food grade lubricants such as Shell Cassida CR 46 can help operators to maintain cleaner air and improve food safety levels, reducing the adverse impact of oil mist contamination. These safety benefits are supported further with excellent compressor oil performance, which can lead to extended oil drain intervals, meaning that operators do not have to make a choice between performance and safety.


2006/42/EC Machine directive: Supplementary essential requirements

2.1. Foodstuffs machinery and machinery for cosmetics or pharmaceutical products

2.1.1. General

Machinery intended for use with foodstuffs or with cosmetics or pharmaceutical products must be designed and constructed in such a way as to avoid any risk of infection, sickness or contagion. The following requirements must be observed:

  • a) materials in contact with, or intended to come into contact with, foodstuffs or cosmetics or pharmaceutical products must satisfy the conditions set down in the relevant Directives. The machinery must be designed and constructed in such a way that these materials can be cleaned before each use. Where this is not possible disposable parts must be used;

  • b) all surfaces in contact with foodstuffs or cosmetics or pharmaceutical products, other than surfaces of disposable parts, must:

    — be smooth and have neither ridges nor crevices which could harbour organic materials. The same applies to their joinings,

    — be designed and constructed in such a way as to reduce the projections, edges and recesses of assemblies to a minimum,

    — be easily cleaned and disinfected, where necessary after removing easily dismantled parts; the inside surfaces must have curves with a radius sufficient to allow thorough cleaning;

  • c) it must be possible for liquids, gases and aerosols deriving from foodstuffs, cosmetics or pharmaceutical products as well as from cleaning, disinfecting and rinsing fluids to be completely discharged from the machinery (if possible, in a ‘cleaning’ position);

  • d) machinery must be designed and constructed in such a way as to prevent any substances or living creatures, in particular insects, from entering, or any organic matter from accumulating in, areas that cannot be cleaned;

  • e) machinery must be designed and constructed in such a way that no ancillary substances hazardous to health, including the lubricants used, can come into contact with foodstuffs, cosmetics or pharmaceutical products. Where necessary, machinery must be designed and constructed in such a way that continuing compliance with this requirement can be checked.

2.1.2. Instructions

The instructions for foodstuffs machinery and machinery for use with cosmetics or pharmaceutical products must indicate recommended products and methods for cleaning, disinfecting and rinsing, not only for easily accessible areas but also for areas to which access is impossible or inadvisable.

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