Whether you’re sitting down at breakfast with a glass of cold orange juice, having a bowl of hot soup for lunch, or enjoying a hot fudge sundae for dessert after dinner, you’re consuming products that most likely are made possible by compressed air. You might think, “Hey, it’s just air.” Maybe it is just air, but there may be substances in that air — and your dessert — that aren’t on the menu.

All-too-common shortcomings
Our company has performed compressed air system audits throughout the United States in dairies, frozen food plants, canning facilities, and dry foods packaging plants. In a typical food processing plant, air compressors are located in the facility’s engine room. There, we frequently find 55-gal drums of lubricant available for use in the compressors. This is not food grade, but synthetic compressor lubricant. The synthetic oil does not necessarily get into the product because filters are in use that remove the oil contamination from the air would be required with any type of oil-flooded or oil lubricated compressors.

Figure 1. Areas housing compressors often are not maintained at the same high cleanliness standards as those found in the production areas of a food processing plant.As we look over the air filtration in the engine room, Figure 1, we find that the filters are the same type as those found in many other industries — not those designed for the food and beverage processing industry. In addition, it is not unusual for filters to be three months overdue for service or replacement. Moving out onto the production floor, we hope to find adequate filtration used on the actual process machinery. Unfortunately, examining much of the equipment reveals that the point-of-use filtration often is inadequate. Even more disturbing, the compressed air is making incidental — or even direct — contact with the food products or their containers.

Why do we, as compressed air system auditors, notice a few drums of synthetic compressor lubricant? We see synthetic oil all of the time, but we shouldn’t see it in the food processing industry if there is any contact, either direct, or indirect, with the food or beverage product or the containers for holding that product. However, we frequently encounter synthetic compressor oil in food and beverage processing plants all over the United States. In many cases, we find facilities using compressed air containing unacceptable levels of synthetic lubricant to perform tasks such as aerating ice cream, manufacturing beverage containers, and drying the inside of bottles and jars, prior to filling.

Unfortunately, the scenario at the beginning of this article is all too common. We often see the same conditions in plant after plant. Why do they occur, especially since there are regulations concerning compressed air use in the food and beverage industry? How can food and beverage companies correct the problems, when, and if, they become aware of them?

To find answers to these questions, we must take a close look at the food and beverage processing industry’s concerns, needs, and to some extent, its motivations. We also must examine Food and Drug Administration (FDA) regulations, as well as other standards organizations guidelines, concerning compressed air in the industry.

FDA regulations for compressed air
The FDA established clear parameters for compressed air use in Title 21 — Food and Drugs, Chapter 1, Part 110, Section 110.40. Paragraph g. Page 212 reads, “Compressed air or other gases mechanically introduced into food or used to clean food-contact surfaces or equipment shall be treated in such a way that food is not contaminated with unlawful indirect food additives.” Title 21 is updated annually in early summer, but more demanding guidelines have been developed by organizations such as The Dairy Committee and The U. S. Public Health Service.

The International Association of Milk, Food, and Environmental Sanitarians, United States Public Health Service, and The Dairy Industry Committee formulated 3-A Accepted Practices for Supplying Air Under Pressure in Contact with Milk, Milk Products and Product Contact Surfaces, Number 604-04.3-A-604-04 addresses compressed air in seven sections and 29 sub-sections that cover everything from the supply of compressed air, piping, and filtration, to special requirements for handling the air at the point of use.

Contamination — invisible and ignored
Oil contamination in compressed air used in the food and beverage industry occurs largely due to lack of awareness and limited knowledge concerning existing regulations and standards. Most plant managers and engineers at food and beverage plants are unaware of the potential for compressor oil contamination in their facilities because compressed air is, essentially, invisible. This out-of-sight, out-of-mind philosophy is as prevalent throughout the food processing industry as it is among most others. Most people tend to think of compressed air the same way that they think of the air they breathe, not realizing or understanding the process by which compressed air is produced.

Even though many maintenance managers, plant managers, and plant engineers realize that they spend a significant amount of money on compressor lubricants every year, they may never consider the end result of improper application, management, and use of those lubricants in regard to the compressed air supplied to their processes and their products. Too many plants have not updated their processes, integrated new technologies, or kept up-to-date on the latest regulations and standards regarding compressed air supply, distribution, and use. This is the primary causing of compressor oil contaminating the food being processed.

The source: oil-flooded compressors
Many compressed air systems, especially those outside the food processing industry, are supplied by oil-flooded rotary screw type compressors. The oil in these compressors provides a seal when the air is compressed between the rotors and helps cool the rotors and bearings. The rotary screw air end (the rotor pair and bearing assembly that turns inside the housing) discharges air containing a substantial amount of oil.

Figure 2. This filter-regulator assembly shows signs of contamination from synthetic compressor lubricant. The impact of this undesirable condition is magnified by the the fact that it occurred in a food processing plant. This air and oil mixture is separated by a filter (sometimes called a de-mister) prior to leaving the compressor. However, even the best rotary-screw compressor, with the most effective and reliable oil separator system, will still pass as much as 4 ppm of compressor oil downstream. This small amount may seem insignificant, but when a compressor is generating 1000 cfm or more of flow, that small amount of oil adds up very quickly.

We audited a midwest dairy that uses a popular synthetic compressor lubricant in all of their oil-flooded rotary- screw compressors. The compressors in this particular facility have an average oil carry-over of 3 to 5 ppm. During our point-of-use analysis, we identified several processes using compressed air where both incidental and direct contact with oil occurred routinely.

Compressed air was used for blow-molding quart and half-gallon milk and juice containers — an example of incidental contact. It was also used to aerate ice cream during packaging (direct contact), and the packaging process for small fruit juice containers supplied to public school systems (both incidental and direct contact). In most areas where compressed air was vented regularly or leaked from the system, discoloration from the compressed air lubricant was easily visible on the contact surfaces, Figure 2.

One might assume that people at this plant were unconcerned with the problem. However, we’ve found that many plants are concerned; they are just not aware of any problem. In a food processing facility we audited for energy savings (as opposed to air quality), we mentioned in passing that they used synthetic compressor lubricant even though processes in their facility brought the compressed air into both direct and incidental contact with products. After a single comment concerning the compressed air quality, and their air’s contact with the product, they immediately changed their system over to food-grade compressor lubricant. In this case, the plant personnel rushed to find an immediate solution, without waiting for our report and recommendations. This demonstrated their willingness and commitment to correcting a problem once they became aware of it.