Bearing up to the challenges of food plants
2013 October 01, 09:00 GMT
How food processing and packaging companies can make considerable improvements to production line efficiency by implementing robust components developed and designed with the application in mind.
Food processing and packaging companies understand more than most the vital need to protect production and optimise productivity, and ensure reliable, predictive and preventative machine maintenance programmes are in place to avoid delayed deliveries, wasted product and damaged reputations.
However, extreme temperatures, humidity and the presence of a wide range of contaminants combine to create a particularly tough operating environment for bearings and seals used in food and beverage processing equipment. The ensuing problems include reduced operating life, possible machine failure and downtime, and higher maintenance costs, plus the risk that minute particles from corroded or worn surfaces can find their way into the process where they threaten the safety of the product.
The good news is that an extensive range of bearings and seals has been developed with specialised features that meet these needs, enabling food and beverage manufacturers to maintain and increase efficiency.
For example, a range of seal materials have been developed for use in food industry applications that can both defend bearings from corrosion and prevent food from becoming contaminated by leaking lubricant. For example, PTFE is able to withstand extreme temperatures and lubricant-free installations, as it displays low friction levels and will not adhere to a bearing’s counter surface. PTFE seals can also effectively withstand particularly aggressive chemical cleaning, eliminating the problem of flaking and bacteria accumulation. PTFE seals are available in FDA (Food and Drug Administration) approved compounds, specially designed for reducing contamination in food processing applications.
Seals are also under considerable stress at the opposite end of the temperature scale. Standard seals are generally unable to cope with temperatures inside freezers, leading to equipment failure and downtime, while lubricants can also freeze, bringing production to a standstill. Seals are also damaged by severe changes in temperature, such as when low temperature equipment is cleaned during wash-downs; temperature can change dramatically, causing the air in a bearing first to expand as it heats up and then to contract as the temperature drops again, putting immense pressure on the seal to open up. These intense cleaning processes also present the risk of moisture entering a bearing cavity and corroding the component.
In proving ovens high pressure wash-downs and humid operating conditions also cause premature chain and bearing failure, an increased risk of product contamination and unnecessary maintenance and re-lubrication costs. Moisture, water and cleaning fluid will creep into existing bearings, resulting in drastically reduced lubrication. Bearing grease then absorbs the water and emulsifies, changing the consistency of the grease and allowing it to easily wash out and fail. Along with corrosion accelerated by the humid environment, this causes the guide wheel bearings of the proving oven conveyor to frequently fail.
An efficient solution is to upgrade the guide wheels to re-lubrication-free stainless steel deep groove ball bearings. For example, SKF stainless steel deep groove ball bearings filled with Solid Oil eradicate the problem of emulsification, as the Solid Oil matrix cannot be washed out of the bearing during hygienic wash-downs, while the stainless steel bearing material reduces corrosion, enabling reliable long-term, re-lubrication-free operation. Where temperatures do not exceed 95 ºC, Solid Oil bearings, which feature a solid form of lubricant that completely fills the free space within the bearing, minimise the risk of food contamination, as the components are able to withstand considerable centrifugal forces without leaking.
Where bearings and seals are continually subjected to extreme temperatures, exceeding 150 ºC in baking, frying and roasting equipment, SKF Y-bearing units have been developed to withstand an extremely wide range of operating temperatures between -150 ºC and +350 ºC and require little or no lubrication, enabling users to reduce both maintenance requirements and costs.
With today’s food manufacturers and processors under greater pressure than ever to maximise productivity and minimise costs, paying attention to seemingly commodity components such as bearings and seals can have a significant effect. The latest generation of bearings, seals and lubricants for the food industry have been designed to withstand aggressive environments where extreme temperatures and moisture are common. As a result, these specialised components can increase the performance, reliability and service life of machinery, while at the same time lowering operating costs dramatically.
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This article was published in the October 2013 edition of Drives and Controls magazine.