Bearings are critical to the operation of food processing lines, but can act as traps for bacteria, so must be designed so as not to cause contamination. Phil Burge, marketing and communications manager at SKF UK, explains.
Possibly the worst nightmare for the manager of a food processing factory is a product recall and there is approximately one incident every day in the UK. Many recalls are down to mislabelling, but a significant number are caused by bacterial contamination. Since the start of 2019, there have been separate incidents of salmonella in Polish sausage, tahini and mayonnaise, and one of listeria in cheese.
To avoid these types of incident, food manufacturers follow the principles of hygienic design, which insists that plant and machinery is easy to clean, does not harbour germs, and reduces the risk of cross-contamination (such as by cleaning fluids or other contaminants).
One guiding principle of hygienic design is cleanability, which is why many preparation surfaces are flat and made of stainless steel. However, the rule is often broken at the component level.
Despite their small size in relation to an entire food processing line, bearing units can be a major centre of contamination. For instance, bearing housings can act as tiny incubators for bacteria.
The crevices within a bearing housing are notoriously difficult to clean and can house a variety of food particles, where bacteria can multiply. Once at this stage, an otherwise-rigorous cleaning regime can actually make the problem worse. High-pressure washing can dislodge the bacteria and carry them into the air in the form of aerosols. Once they settle on the floor, they can be spread around the factory. The key task is to stop the bacteria at source.
Food safety is also compromised by the lubrication process. A common problem is over greasing: contaminants that have worked their way into bearings are often removed using grease flushing. However, this has many downsides, including reliability issues, high costs, reduced asset availability and environmental issues.
Relubrication is another problem. Bearings must be lubricated in order to work efficiently, but this raises the risk of contaminating the product with lubricant. Although food grade lubricants are available, they can contain allergens.
The rigorous washdowns used in the food industry can also affect lubricants: the high temperature and pressure of the cleaning water, combined with harsh detergents, can penetrate bearing seals. This is often solved with grease flushing or relubrication and both have already been shown to cause problems.
Upgrading to food safe
The challenge is to redesign food grade bearing units (which can be used in food-contact applications) into food safe bearing units. With rigorous hygienic design principles elevating them to a higher level by the addition of elements such as extra sealability and cleanability, and the use of allergen-free, non-toxic materials.
A prime example of a food safe product is SKF Food Line ball bearing units – Blue Range, which follow the rules of hygienic design. They combine smooth, inert surfaces with a self-draining geometry, superior sealing and a relubrication-free design. These features ensure that microbes cannot penetrate the bearing, while lubricant cannot escape.
Materials are an important factor. The housing is moulded from polypropylene (PP), a highly inert material with high chemical resistance. Inclusion of 40% long glass fibres helps to enhance mechanical properties. The housing is co-injected with a rubber seal, sealing the interface between frame and housing to avoid crevices and empty spaces for bacterial growth. At the same time, the bearing grease used is allergen-free.
The sealed design also ensures that relubrication is not necessary. One example is in the back seal, which stops contamination entering through the shaft inside the bearing unit by providing both static sealing (against the housing) and dynamic sealing (against the shaft).
Another innovative feature is the gutter concept, which boosts cleanability by protecting against detergent ingress. Detergents are designed to pass through anything, so blocking this process is almost impossible. SKF’s gutter concept allows detergent through but guides it towards non-hazardous areas. If water enters the top lip of the seal during washdown, it is guided around and out of the other side by either gravity or centrifugal force, if the bearing is active.
In addition, components are coloured blue for easy optical detectability, while the sealed nature of the bearings means there is no need for relubrication.
One food industry user of the Blue Range bearing units said recently: “Not having to relubricate, and clean excess lubricant from units, is of vital importance to us. In both the appearance of the conveyor lines and the safety around them.”
More carefully designed products usually come with a premium. However, the concept of hygienic design actually saves money for customers through factors such as extended bearing life, reduced need for cleaning and the reduction in re-greasing costs, including the grease itself, and the time taken to apply it.
For instance, a large food industry conveyor system with 200 bearing units may need re-greasing 50 times per year. The cost of grease may be £40/kg, that of labour around £20/hour. Removing these costs can save more than £12,000/year. The labour could be redeployed onto continuous improvement activities.
Third-party tests have also shown that the cleaner state of the Blue Range bearing units means they require around one-third less water to clean them.
Overall, though, the largest saving could be that of creating the necessary conditions to cut the risk of food contamination, and subsequent product recalls, to a minimum – and what factory manager would say ‘no’ to that?
New Timken Hygienic Bearings for Food and Beverage Plants Are a Stronger Line of Defense
Meet Timken experts at IPPE 2020 and see a full line of corrosion-resistant options to improve uptime and safety.
The Timken Company a world leader in engineered bearings and power transmission products, is helping customers engineer a stronger line of defense in food processing plants where harsh chemicals and aggressive washdowns can spell equipment troubles. Already including corrosion-resistant and greaseless bearings, the Timken portfolio of solutions for food and beverage makers now features hygienic housed units to combat common safety hazards.
Safer by Design
Hygienic bearing design considers several factors unique to food processing such as chemical contamination related to lubricant leakage, oxidation and corrosion. It also accounts for physical contamination from foreign bodies or loose or broken machine parts. Preventing microbiological contamination from bacteria that develop in dead volumes is another point of emphasis.
Timken® hygienic housed unit bearings have been designed to comply with the most stringent industry requirements. New to the company’s line of safer solutions are:
- Timken® Hygienic Ball Bearing Housed Units that are interchangeable with standard mounted bearings from 20 to 50 mm (3/4 to 2 in.). These units feature smooth surfaces (having no reinforced bolt holes) and are available with food-grade Solid Lube that eliminates the need for re-greasing. Standard is a metal-detectable cage that significantly improves foreign particle detection probability, and customers have the option of an optically detectable blue thermoset housing that further increases the accuracy and resolution of contaminant detection. Ideal for: conveyors, mixers, metal detectors, check-weighers, tumblers, slicers and breaders.
- Timken® Hygienic Poly-Round® Housed Units that are engineered with a special polymer insert to prevent water ingress and corrosion (the most common failure mode for bearings in food processing plants). These plain bearing units are interchangeable with industry-standard designs from 20 to 50 mm (3/4 to 2 in.) and can outperform ball bearings where a stronger solution is needed. Optically and metal-detectable inserts are available, and an optional QuiKlean® housing helps avoid dead volume between the housing base and machinery, allowing washdown from all sides (perfect for HACCP/HARPC positions and meeting FDA food contact compliance). Ideal for: modular belt conveyors, dumper pivots, horizontal mixers, chillers and freezers.
Notable is that Timken hygienic housed units and Poly-Round inserts are certified according to ANSI/NSF/3-A SSI 14159-1-2014 requirements. These globally recognized standards help improve food safety by mandating the use of chemically resistant materials and by requiring that bearings are easy to clean (e.g., smooth surface, laser marked, minimal crevices). The housings and inserts are further certified as Accepted Equipment by the USDA under the Meat and Poultry Equipment Review Program.
More to See
At the upcoming International Production & Processing Expo, attendees can meet Timken experts in booth B8017 or booth A2863 to discuss a smoother operation built around more reliable bearings. In addition to hygienic designs, Timken offers corrosion-resistant ball bearings, corrosion-resistant plain bearing housed units and corrosion-resistant deep groove ball bearings that provide long-lasting performance in highly wet or contaminated environments.
At Timken.com, visitors will find approved friction management solutions for every part of the plant floor, from processing to packaging, including other power transmission products that keep food and beverage producers in motion. Customers looking to manage harsh conditions, improve machine uptime and meet the highest standards for food safety can get in touch with a local Timken representative to start the conversation.
The very best of NTN’s ball bearings, available in Europe
In step with a process launched last year, CM internal clearance is now spreading to the whole range of deep-groove ball bearings so that bore diameter codes 00 to 06 are also available in the coming months. Initially designed for applications with stringent requirements – electric motors in particular – NTN deep-groove ball bearings with CM internal clearance make up the brand’s new offer. They feature major improvements in terms of internal radial clearance and noise levels. These qualities are guaranteed by strict control procedures during the manufacturing process. With this range, NTN-SNR is offering higher-quality deep-groove ball bearings that can take the place of the standard references used in industry. By further enhancing its own standard, NTN-SNR has once again highlighted its determination to provide all its customers, distributors and end users with the very best of NTN Japanese design.
A noticeable reduction in sound level
NTN deep-groove ball bearings with CM internal clearance were originally designed specially for electric motor applications which require particularly quiet bearings. These CM bearings feature radial internal clearance that lies within the limits of normal internal clearance, but with reduced clearance tolerances (for example, for a bore diameter of 50 mm, a bearing with normal internal clearance would have clearance of 6 to 23 microns, whereas a product with CM internal clearance has one of 9 to 17 microns).
This innovative technical characteristic significantly reduces the bearing’s vibration levels and, therefore, the noise that it makes when in operation. Laboratory tests reveal a reduction of up to -3 dB: a noise level reduced by half when compared with conventional standard-clearance products.
CM clearance is obtained thanks to excellent control of the manufacturing process and NTN’s recognised know-how. Every part we manufacture is inspected to guarantee clearance and noise levels.
The range of NTN deep-groove ball bearings with CM internal clearance
249 references in individual boxes
- Bore diameters of 10 to 160 mm
Deep-groove ball bearings
- With deflectors, 5K grease
- With contact seals, 5K grease
- With non-contact seals, 5K grease
Easy implementation for the user: Fully interchangeable parts, regardless of the dimensions
These bearings with CM internal clearance feature assembly parameters that are identical to those of their counterparts with normal internal clearance and they are fully interchangeable. They have the same load capacities and identical performance levels as regards rotation speed. For the sealed references (deflectors and seals), the products are provided greased for life using a high-performance grease (suffix 5K).
To ensure customers can easily identify the upgrade, the bearing designation systematically includes the CM suffix. The initial parts are already on sale. Roll-out of this range of ball bearings will be completed soon.
NTN-SNR is the only actor on the European market to offer ball bearings of this quality, thus confirming its premium positioning and its determination to deploy “made by NTN” quality on its industrial markets.
New NSK deep groove ball bearings for electric motors boost energy efficiency
The low energy consumption of electric drives is an important target in many industrial applications, and rolling bearings can play a role in delivering this ambition. NSK demonstrates this effect with a new series of deep groove ball bearings that generates up to 80% less energy loss, a factor that has a positive effect on the energy efficiency of electric motors.
Before this development, NSK conducted an intensive investigation into the parameters influencing the energy loss of bearings, drawing a number of interesting conclusions. As a result, the new bearing series uses new grease that has been specially developed for friction reduction, while the grease filling level has also been optimised.
In comparison with a conventional deep groove ball bearing, the new NSK high-efficiency bearings demonstrate 60% less friction when using a steel cage. If a plastic cage is used, internal friction is reduced even further, by almost 80%. As a further benefit, service life with the new grease is increased by a factor of 2.7.
NSK Europe is the European organisation of the Tokyo-based bearing manufacturer NSK, which was founded in Japan in 1916 and today employs around 31,000 people in its worldwide operations. The products and solutions provided by the industrial and automotive supplier can be found wherever things move. In addition to nearly all types of rolling bearings, the company´s portfolio includes housed bearings, linear technology, wheel bearing units, transmission and engine bearings and steering systems. The company is oriented to perfection in all of its business activities. Its aim is quality leadership in its industry, which it strives for through a continuous process of improvement, excellent product development, optimised production processes and customer-oriented service processes.
Industrial Hardware and Machine Parts3 years ago
The necessity of bolted flange connection training
Gear drives2 years ago
Klingelnberg at control 2018: Tactile and optical measurement on one machine
Industrial Hardware and Machine Parts3 years ago
ABB and Formula E partner to write the future of e-mobility
Motors3 years ago
New generation of hollow shaft motors
Industrial Hardware and Machine Parts3 years ago
Rexnord adds to its Autogard Torque Limiters with the XG Series
Motors3 years ago
Get a first-class ticket to productivity
Motors3 years ago
ZF Technology on the Winners’ Podium of the Dakar Rally 2017
Motion control3 years ago
Rexnord to Acquire Centa Power Transmission