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Eliminating Lubricant Contamination From Food Processing Machinery

​Contamination poses serious problems for food and beverage producers. As production becomes more and more reliant upon automated machines, there is yet another source of potential contaminants: spilt or leaking lubricants. Phil Burge, Marketing and Communications Manager at SKF describes how food and beverage manufacturers can avoid this problem.

Phil Burge, SKF

Phil Burge, SKF

Food and beverage is a major contributor to the UK economy. Early in 2017, the Food and Drink Federation commissioned the global professional services network operator, Grant Thornton, to undertake a study into the UK food and beverage manufacturing sector.

Among its findings, the sector manufacturing gross value added (GVA) grew by 27% between 1997 and 2015 (compared with 13% for manufacturing as a whole over this period).

In 2017, it accounted for 16% of total manufacturing GVA, making it the largest manufacturing sub-sector in terms of GVA contribution.

Food safety continues to be a major concern for the sector. In common with other large economic contributors such as the automotive industry, product recalls can have serious business consequences.

For food and beverage producers, product recalls arising from contamination events pose a serious threat to profitability, and as the sector grows its investment in automation and high-end processing machinery, so too does the risk of contamination from essential machine lubricants.

The food and beverage industry estimates that between 15 and 25% of its entire maintenance budget is spent as a result of poor lubrication practices. Indeed, as much as 40% of all premature bearing failures in this industry can be tracked down to lubrication problems.

While the food and beverage industry has any number of lubrication methods to choose from, not all are recognised under current hazard analysis and critical control points (HACCP) certification scheme, which is widely adopted throughout the industry.

Implementing HACCP compliant lubrication management techniques that are primarily designed to eliminate contamination risk is therefore imperative for any food and beverage manufacturers.

Several technologies have emerged to support HACCP compliant lubrication practices for food and beverage processing machinery containing bearings or transmission chain driven and flat top conveyor systems.

This includes re-lubrication-free bearings, fully automated lubrication systems and NSF H1 certified lubricants. In general, the industry adopts three main approaches to avoiding lubricant contamination: the use of ‘food- grade’ lubricants; the use of sealed bearings or a move away from grease lubrication altogether, towards alternative ‘dry’ or ‘solid’ forms of lubricant technology.

Food-grade lubricants are widely used, and are certified for food production punishing, inducing lubricant leakage from bearings and water ingress, both of which will shorten the life of a bearing. Even if a lubricant is food-grade, leakage into a food product is wholly undesirable, so efficiently sealed bearings are commonly used.

Bearings that are required to tolerate frequent wash-downs, such as those used in a poultry processing application, for example, are usually contained within corrosion- resistant composite housings, have stainless steel bearing inserts and a special multi-lip seal that prevents both grease displacement and water ingress.

A poultry processing firm that was advised by SKF to use this type of bearing as a replacement for previously installed nickel-plated cast iron bearings, has seen bearing service life effectively quadrupled, with substantial savings made on maintenance and lubricant consumption as a result of the change.

So-called ‘dry’ methods of lubrication have proved particularly beneficial to the smooth running of conveyors in baking ovens operating at temperatures of 180°C or higher.

Solid oil - Food Processing Machinery Contamination

Bearings within ovens require frequent re-lubrication, because the high temperatures can degrade grease very quickly. A solution is to replace traditional grease lubricated bearings in these applications with like-for-like versions that use graphite cages.

Here, tiny graphite particles are eroded from the cage and deposited as a thin layer onto the surface of the steel balls. Graphite is a very effective lubricant, and this thin, protective layer is enough to prevent the direct metal-to-metal contact that ultimately shortens bearing life. Although the cage is wearing away gradually, the effect is very slow and will usually last for the life of the bearing.

Reducing the frequency of re-lubrication or eliminating the need for lubrication altogether, and having effective seals that protect against lubricant loss and damaging ingress of contaminants, will go a long way to achieving food safety.

A good example is our Solid Oil encapsulated lubricant technology, which can be applied to virtually any bearing. This uses a polymer matrix saturated with lubricant that completely fills the internal space, encapsulating the cage and rolling elements and ensuring that food particles are kept out and chemicals and are virtually maintenance- free.

This approach has been successfully applied on a bottle filling station, where previously used stainless steel deep groove ball bearings, although sealed and greased for life, were leaking grease and admitting water during the frequent washdown operations.

Replacement our bearings with Solid Oil lubrication had a huge positive effect: bearing service life was extended from 12 weeks to two years, while maintenance costs were slashed and leakage almost completely eliminated.

High temperature bearings - Food Processing Machinery Contamination

Manual or automatic lubrication for food and beverage production?

Manual lubrication in the food and beverage sector raises a number of issues. It is labour-intensive and time-consuming, and imprecise manual metering may lead to over- or under-lubrication which will have an impact on machine reliability and the cleanliness of the production environment.

Under-lubrication is likely to cause leakage of excess grease into the processing environment as bearing seals are compromised and, of course, poor lubrication will ultimately result in the premature wear of bearing rolling elements.

Manual lubrication in food and beverage processing environments will also come up against a number of restrictions due to the nature of the operations and the products being processed.

Certainly, there will be strict controls concerning access for personnel during production for reasons of safety and hygiene; the process equipment is also likely to be complex and not all lubrication points will be easy to access, leaving often vital parts of machines poorly lubricated or missed out altogether.

An alternative approach is to automate the process of lubrication such that all points receive the marketing correct amount of lubricant, at the appropriate time while avoiding the intervention of maintenance staff.

In essence, an automated lubrication system comprises easily accessible and refillable central reservoirs from where lubricant, oils or greases, are pumped in precisely metered quantities via a system of pipes directly to a machine’s lubrication points.

Chain lube nozzles sensor - Food Processing Machinery Contamination

Automated centralised lubrication systems can be installed at the time of machine installation or retrofitted to existing machines. Examples include our SYSTEM 24 and MultiPoint lubrication systems, which can be mounted for just one or many lubrication points to deliver the right amount of an appropriate lubricant 24 hours a day, seven days a week.

The quantities and timing of automated lubricant deliveries will depend on the severity of duty and/or environmental conditions in the plant, and might follow an existing maintenance schedule that reflects these needs.

In more advanced configurations, the lubrication cycle might be based on statistical machine data (such as the number of revolutions or other machine ‘events’), on data from real time condition-based monitoring systems or on the results of lubricant analysis.

While lubrication is absolutely essential to efficient bearing operation, the food processing industry must make every effort to minimise, at best eliminate, the risk of product contamination from bearing lubricants. This means that processors are increasingly looking at alternatives to traditional food-grade grease lubricated sealed bearings, which have proved to mitigate such risks.

Process Industry Informer

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