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?
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.
NTN-SNR makes food-processing the flavour of the month
NTN-SNR, a leader in precision mechanics, is pressing ahead with food safety. The company plans to invest in its solutions for the food-processing industry as a way to optimise and strengthen its short-term range. The goal is to achieve optimal production with no risk to the user. This is necessary investment for a sector with increasingly stringent standards…
The average cost worldwide for product recalls in the food-processing industry was €7.92 million between 2012-2017. In 75% of cases, the causes were contamination with bacteria or allergens, or the presence of a foreign body. Despite strict standards, the food-processing market is the French industry leader, with a turnover of € 180 billion in 2017. It also ranks second among industrial sectors most affected by product recalls and withdrawals (16%), after the automotive industry. This presents a risk both to consumers’ health and to companies’ reputations, which are suffering considerable losses.
With this in mind, NTN-SNR, with its 30-year market presence, is pooling its strengths and developing its dedicated teams with a view to making the food-processing business its new battleground. The company’s repositioning brings fresh challenges, including rethinking and reintegrating all of the sector’s constraints, and reidentifying the various segments and ranges to meet each need as accurately as possible, while remaining accessible to all market participants.
A highly constrained environment
With its high-pressure washing, cleaning agents, humidity, fine particles, hygiene standards, high production rates, etc., the food-processing industry is a highly constrained environment.
NTN-SNR relies on its expertise to ensure that health standards-compliant, sustainable production is tailored to each sector of activity.
As of this year, the company is focusing on developing its existing ranges, with Germany and Italy as the main European targets for machine manufacture and France and Spain for maintenance.
NTN-SNR’s short-term food-processing market goals are to eliminate incident risks, reduce maintenance times to increase profitability, and to ensure peace of mind.
Fully suited solutions
To this end, the company offers a wide range of bearings, lubrication solutions, linear guides and stainless steel or thermoplastic self-aligning bearings. NTN-SNR has chosen to offer all-stainless steel bearings, where some market players only offer it for the insert, in combination with an anti-corrosion coated housing. The inserts are equipped with an elastomer seal protected by a shield to counter any impact or mechanical stress. As for the additional protective caps, they are provided with a radial or double-lip seal, offering additional resistance to high-pressure washes, even when in direct contact. These systems are true shields against moisture and dirt.
For added convenience, NTN-SNR inserts are available with Lubsolid® solid food grease. Fifty-five percent of premature bearing failures result from improper lubrication – a fact that led the company to design its flawless lubricant. The polymer matrix containing a large amount of oil completely fills the free space inside the bearing. As a result, neither pollutants nor water can enter.
The grease’s solid state means that it cannot flow, ensuring the cleanliness of your environment.
These properties increase the duration life of the bearing by up to 20 times compared to a part lubricated using a standard high-performance grease.
The appeal of this technology and growing user demand are behind the company’s plans to invest in its solid food grease. The goal is to secure production while increasing its manufacturing capabilities.
3 questions to Kévin Gay, NTN-SNR Market Manager
Why has NTN-SNR decided that this is the time to strengthen its presence in the food-processing industry?
It’s a gigantic market. The food-processing industry is the largest European manufacturing market. Market constraints mean that innovation is a constant, necessary feature.
NTN-SNR is one of the world’s leading bearings manufacturers. It is known in particular for its presence in the automotive, industry and aerospace markets. The company is also a player – albeit a more cautious one – in the food-processing market. Now, however, it seems vital that we emphasise our solutions and further develop our ranges to put forward options that are increasingly adapted to the many demands encountered by today’s manufacturers.
What is NTN-SNR’s added value compared to the competition?
Every experienced market player has high levels of technical skill and specific expertise (bearings, ball bearings, etc.). That being said, while designing reliable, innovative and qualitative products is essential to protect against bacterial growth, you can’t ignore the cost. Certain premium-quality ranges on the market have a rather high price tag. However, of the 300,000 companies making up the European market, 99% are SMEs with sometimes limited maintenance resources. As a result, they are forced to turn to lower cost solutions. For NTN-SNR, guaranteeing the accessibility of quality products in terms of cost to all food-processing stakeholders offers peace of mind.
What do you mean by “peace of mind”?
“Peace of mind” is one of the cornerstones and drivers for how we respond to the constraints of the food-processing business. It has several aspects.
First, there is health-related peace of mind – of the consumer, of course, but also of the manufacturer. On the business side, economic peace of mind is also a key point. With quality equipment, the maintenance manager can increase his operating intervals, thus increasing production. Peace of mind thus equates to saving time, productivity and profitability.
A wide range
- Topline ball bearings
- Thermoplastic mounted units
- Stainless steel mounted units
- Stainless steel ball bearings
- Linear axis and ball bushings
- Lubsolid®, solid food grease
- Lubrication solutions
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