In the food industry, comprehensive cleaning regimes are commonplace as companies look to meet stringent sector requirements on hygiene. However, such practices can prove detrimental to production line components, not least the bearings that provide motion in critical machinery, equipment and systems. Here, spraying with hot steam, high-pressure water jets or very strong cleaning agents can cause two principal problems: foreign objects entering the bearings; and lubricant being washed out of the bearings. For these reasons, NSK offers a comprehensive range of Molded-Oil bearings that is purpose-designed to deliver extended operating life in harsh food industry environments.
The lubricant within Molded-Oil bearings is durably incorporated inside a stable carrier medium, namely an oil-impregnated polyofin resin. This type of lubricant cannot be washed away by steam or liquids, and prevents contamination from entering the bearing. Moreover, as the carrier only releases the lubricant slowly, sufficient lubrication is maintained over a long operating period.
A wide range of Molded-Oil bearings is available, including deep groove ball bearings, spherical roller bearings and tapered roller bearings, in several product series and in special forms such as housed bearing units. The range also includes Molded-Oil bearings made of stainless steel.
These advanced products are suited to a broad range of food industry applications, where many manufacturers of machines and systems install Molded-Oil bearings as part of the original equipment. However, they are also suitable for retrofit applications.
A case in point can be seen at a British food manufacturer, where the standard deep groove ball bearings in a seven-track conveyor system were only lasting for a period of 4 months. The reason was water penetration within the bearings during daily washouts, which resulted in costly maintenance work and damage to the conveyor belts. Each time there was a failure, the company had to endure downtime of 24 hours, creating a considerable dip in productivity.
After inspecting the bearings, NSK recommended using stainless steel bearings with Molded-Oil lubrication and DU seals on both sides. Subsequently, bearing operating life increased three-fold, to 12 months, while bearing-related maintenance costs (including downtime) were reduced by more than EUR52,000 annually.
Prolonged operating life
The story was similar at a manufacturer of frozen pizzas, where failures were being experienced every 4 weeks on the belt tensioner serving one of the company’s food conveyors. Regular cleaning of the production line with water had led to corrosion. Moreover, the grease lubricant had been washed out of the bearings, and the seals were damaged. NSK inspected the application and again recommended the use of Molded-Oil bearings made from stainless steel. This resulted in a significantly prolonged operating life, plus annual cost savings of approximately EUR15,700.
Elsewhere, the bearings of belt pulleys within the cake-cutting machines at a large bakery were failing on a constant basis. Each year, approximately 20 sets of bearings had to be replaced due to failures every 4 to 6 weeks. After analysis by NSK, it emerged that the primary cause was water and dust infiltrating the bearings. NSK therefore recommended replacement with Molded-Oil bearings. A test was run and the operating life of the bearings increased to 26 weeks. This significantly boosted the productivity of the manufacturing line, helping the user to save approximately EUR9,400 annually in maintenance and downtime costs.
In a final example, a vegetable processing company had installed a biogas plant in order to ferment organic waste from production and transform the resulting methane into electricity and heat for self-consumption. However, problems had been found with the rotary screen, which filters out coarse and non-fermenting material prior to the fermentation stage. Failures were occurring repeatedly in the bearings of the rotary screen and disrupting the overall operation of the biogas plant. Every 6 weeks on average, the deep groove ball bearings with contact seals had to be replaced. Each rotor has two bearings and there are two rotors per rotary screen. Replacement time was 1 hour each.
Experts from NSK found that the breakdowns were caused by contamination penetrating the bearing raceways. The customer subsequently followed NSK’s recommendation to install Molded-Oil deep groove ball bearings made of stainless steel with DU seals on both sides, a move that has led to far fewer replacements.
This yet again confirms one of NSK’s “rules of thumb”: in applications where the environment is contaminated by moisture and dust, the service life of Molded-Oil bearings in stainless steel is more than twice that of bearings with conventional grease lubrication. Go to www.nskeurope.com for further information.