13. Tagung Zahnriemengetriebe am Institut für Feinwerktechnik und Elektronik-Design der TU Dresden

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1 am Institut für Feinwerktechnik und Elektronik-Design der TU Dresden Gerhard Fickenwirth (Gates Mectrol, Inc., Salem, NH, USA) PosiClean Belt - The Conveyor Belt with Timing Belt Technology 1. Introduction 2. Geometry and Positive Drive 3. Jacket Material 4. Tensile Members 5. Conclusion 6. Acknowledgements

2 Gerhard Fickenwirth: PosiClean Belt-The Conveyor Belt with Timing Belt Technology (Seite 1) 1. Introduction Consumption of processed foods is increasing globally. The challenge for food processors is to meet this increased demand and decrease operating costs while maintaining stringent sanitation requirements. International food processors are demanding that equipment manufacturers design machines that are easily sanitized and inhibit microbial growth. Trade associations in North America such as NSF International, 3A Standard, Inc. and American Meat Institute have published design guidelines for food processing equipment and conveyors. These design guidelines extend to the conveyor belts themselves. In particular, belts for conveying food products should be free of crevices that become habitats for microbes and are difficult to clean to a microbiological level. Gates Mectrol has developed and recently launched a direct food contact belt that meets these new guidelines: the PosiClean belt. (Figure 1). PosiClean is USDA accepted for meat, poultry and dairy processing. Figure 1: PosiClean Belt - USDA Accepted Food Conveyor Belt PosiClean

3 Gerhard Fickenwirth: PosiClean Belt-The Conveyor Belt with Timing Belt Technology (Seite 2) The design requirements for the PosiClean belt were drawn up by merging the new sanitation demands placed on food conveyor belts with our timing belt expertise. The main requirements were as follows: Surface and geometry that is easily cleaned Positive drive or synchronous drive for good torque transmission even when food materials are trapped between pulleys and belt Cover or jacket material that is FDA approved and resistant to cleaning and sanitation chemicals Tensile members to minimize belt stretch and to provide belt and splice strength; in addition, tensile members need to be sealed to prevent ingress of microbes 2. Geometry and Positive Drive Historically, food processors have had a choice between two belt types lightweight flat belts, typically with a woven polyester tensile member, or plastic modular belts. In past decades, despite being more expensive, the plastic modular belts have taken over many applications that had traditionally been lightweight flat belt applications. In demanding applications, the modular belts have longer belt life, are easier to repair, do not slip on the sprockets and are self-tracking. However, in direct food contact applications, it has been shown that modular belts are more difficult to clean. One simple reason why a modular belt is more difficult to clean is that by design it has more surface area than other belt types. A typical modular belt has at least 70% more surface area as compared to a PosiClean belt. This is primarily due to its hinges. See Figure 2. Figure 2: Left: PosiClean Belt Surface Area = 115 cm 2. Right: Plastic Modular Belt Surface Area = 202 cm 2.

4 Gerhard Fickenwirth: PosiClean Belt-The Conveyor Belt with Timing Belt Technology (Seite 3) Dr. Nelson Slavik of Environmental Health Management Systems, Inc. (EHMS) conducted a formal cleaning study on Gates Mectrol s behalf in July of The study compared the cleanability and disinfecting effectiveness of the PosiClean belt to polyethylene modular belt commonly used in the food industry. The typical meat industry cleaning/sanitation protocol begins with the large food residues being removed by a mechanical means such as scraping. Then the conveyor is sprayed with high pressure water (often as high as 100 bar/1450 psi, 60 C/140 F) to further remove food soils. Next a cleaning detergent, that is usually an alkaline/surfactant combination, is applied to the belt and followed by hot water (60 C/140 F) again to rinse off greases, remaining soils and the detergent. Lastly, a sanitizer (a germicide), is applied to the belt to ensure that the number of microorganisms is reduced to a safe level. Sometimes, depending on the toxicity level of the sanitizer, the belt is rinsed with water once more. The EHMS study was a series of bench top tests that used a simplified representation of the above described protocol. The purpose of the study was not to validate the typical cleaning protocol but to make a comparison of the ease of cleaning of the PosiClean belt versus a commonly used plastic modular belt. The steps of the bench top tests were as follows. 1. Raw sausage meat was applied to all the belt samples (No attempt was made to force meat between belt segments), see Figure After 20 minutes, a one-step degreaser and disinfectant was sprayed onto the meatcovered samples (approximately 2 ml). The degreaser/disinfectant was Metaquat TM a quateternary ammonium chloride containing surfactants. 3. Immediately the samples were wiped using a paper towel. 4. A second spray application of Metaquat (approximately 2 ml) was made onto the samples and allowed to sit for 10 minutes without wiping. 5. The samples were then sprayed with warm water (30ºC/86ºF, approximately 3 ml) and allowed to dry. 6. Then culture swabs were taken from various locations on each sample; cultures were grown in 3M TM -Petrifilm TM plates and a bacterial count done for each swab.

5 Gerhard Fickenwirth: PosiClean Belt-The Conveyor Belt with Timing Belt Technology (Seite 5) Table 1: Comparison of colony forming units (CFU) per cm 2 of area cleaned and disinfected. * TMTC = Too Many To Count CFU/cm 2 PosiClean Belt 0.13 Modular Belt Flat Areas 0.53 Modular Belt Hinge Rings TMTC* Figure 5: Cleaning/Disinfectant Test - Bacterial Count. Left: PosiClean Center: Modular Belt Right: Modular Belt Hinge Section The PosiClean belt was disinfected with a very simple cleaning/disinfection process. This same simple process will not disinfect the hinge area of modular belt. A more elaborate process is required to disinfect this area of a modular belt. 3. Jacket Material The environmental conditions, in which a typical food conveyor belt runs, necessitated that the PosiClean belt cover or jacket be a FDA approved polymer, resistant to hydrolysis, as well as, cleaning chemicals. The jacket material also needed to have good abrasion resistance and flexibility at low temperatures. As Gates Mectrol is a producer of polyurethane belts and therefore there was a leaning toward polyurethane early on in the development. Table 2 shows a comparison of typical abrasion resistance for various materials including TPU. Table 3 gives abrasion test results of the PosiClean jacket material and other TPUs under consideration for this product.

6 Gerhard Fickenwirth: PosiClean Belt-The Conveyor Belt with Timing Belt Technology (Seite 6) Table 2: Taber abrasion, CS17 wheel, 1000 gm weight, 5000 revolutions. Ref: Handbook of Thermoplastic Elastomers, Litton Educational Publishing, 1979 Material Weight Loss, (mg) TPU Nylon 6/10 16 Nitrile rubber 44 Nylon 6/6 58 Rigid PVC 122 Natural rubber 146 SBR 177 Platicized PVC 187 Butyl rubber 205 ABS 275 Neoprene (polychloroprene) 280 Table 3: M is the TPU selected for PosiClean. L is our TPU for our standard industrial belt. Testing per ASTM D with a 10.0 N normal force and 40.0 meter abrasion path length. Material Code Average Abrasion Loss (mm^3) St Dev Abrasion Loss (mm^3) L M H O DD N The final chemical resistance testing of the jacket material was done per 3-A Sanitary Standards for Multiple-Use Plastic Materials, Number This was a requirement of the USDA Dairy Branch for acceptance of the PosiClean belt. Many of the cleaning chemicals involved in this standard test for dairy equipment are also used in other food processing sectors. The test has 3 sections: 1. Cleanability Response: Samples are immersed in several cleaners and sanitizers. 2. Product Treatment Heavy Cream: Samples were soaked in heavy cream 168 hrs. 3. Product Treatment Lactic Acid: Samples were soaked in lactic acid for 168-hrs. Table 4 shows the results of this test.

7 Gerhard Fickenwirth: PosiClean Belt-The Conveyor Belt with Timing Belt Technology (Seite 7) Table 4: PosiClean 3A-Standard Number results Test Cleanability Response Product Treatment: Heavy Cream Product Treatment: Lactic Acid Total No. Of Samples Tested % Weight Gain 32 Samples: 0.42% % 13 Samples: 0.00% % 15 Samples: 0.23% % Max. Acceptable Weight Gain 1.22% 1.59 % 1.29% % Weight Loss 3 Samples: <0.01% % 1 Sample: 0.04% Max. Acceptable Weight Loss 0.05%.05% 4. Tensile Members The PosiClean design borrows from our timing belt technology in that it has the combination of integral teeth for positive drive and tensile members for torque transmission. The tensile members provide the belt and splice strength. Other belt manufacturers have developed polyurethane belts without tensile members that are positive drive and easier to clean than a modular belt. These are referred to as homogeneous belts. Figure 6 shows the load and elongation of the PosiClean belt versus homogeneous belts. Figure 7 shows the load and elongation of the belt weld splices of the PosiClean and the homogeneous belts. The higher PosiClean splice strength as well as the belt strength can be attributed to its tensile members. Open Ended Belt: Load vs. Elongation Load, N Percent Elongation Homogeneous TPU Belt 1 Homogeneous TPU Belt 2 PosiClean Figure 6: Belt Strengths of Open Ended Pieces of PosiClean and Positive Drive Homogeneous Belts. Note: initial sample dimensions were, 50 mm width, 150 mm length)

8 Gerhard Fickenwirth: PosiClean Belt-The Conveyor Belt with Timing Belt Technology (Seite 8) Belt Splices: Load vs. Elongation Load, N Percent Elongation Homogeneous TPU Belt 1 Homogeneous TPU Belt 2 PosiClean Short Finger Figure 7: Welded Splice Strengths of PosiClean and Positive Drive Homogeneous Belts. Note: initial sample dimensions were, 75 mm width, 300 mm length. We chose individual cords rather than a woven carcass for the tensile member because we wanted the tensile members to be sealed at the belt edges without the need for a secondary sealing operation, see Figure 8. Typically, a conveyor belt is produced at a master width. The final belt width that a customer receives is produced by slitting or cutting the master roll. If a woven carcass is used, cutting a master roll to a narrower width leads to the weft yarns being cut and exposed. Exposed yarns allow wicking of liquids and ingress of microbes into the belt, which in turn leads to an unsanitary condition on the conveyor. The cord spacing in the PosiClean belt is designed to allow slitting between cords without exposing them. Figure 8: PosiClean diagram illustrates cord spacing. The cords are completely encapsulated by the TPU jacket to prevent absorption of liquids. Designing the cord spacing to allow for slitting means that the number of cords is limited. Limiting the number of cords limits the belt strength. We therefore selected a high strength fiber for the cord to achieve good belt strength: aramid. The aramid cords, not the TPU, provide the majority of the tensile strength of the belt and reduce belt stretch over time.

9 Gerhard Fickenwirth: PosiClean Belt-The Conveyor Belt with Timing Belt Technology (Seite 9) Tensile members also help in achieving good tooth pitch accuracy during belt manufacturing. This in turn ensures that all teeth-in-mesh on the pulley contribute to the torque transmission from the drive pulley to the belt. 5. Conclusion Combining a food conveyor belt concept with timing belt technology gives PosiClean features that are important to the food processing industry. Continuous smooth surfaces allow easy cleaning Positive drive design for good torque transmission Jacket material that is resistant to hydrolysis and chemicals used for belt cleaning and sanitation Aramid tension members provide belt and splice strength as well as reduce belt stretch Sealed belt edges and tension members keep microbes out of the belt These features provide benefits to the food processor using PosiClean belt. Easy-to-clean surfaces improve the likelihood that surfaces are properly cleaned and sanitized. Easy-toclean surfaces also help in reducing cleaning and sanitation costs: water and chemical consumption is lower when surfaces make food soil removal easier. Sealing the tension members eliminates microbe habitats and promotes good sanitation. The chemical resistant jacket material along with the high strength and creep resistant tension member contribute to improved belt life. Improved belt life contributes to a reduction of unplanned equipment downtime and thereby contributing to improved throughput of the food processing line. Gates Mectrol incorporated these features into the PosiClean belt to help food processors meet their challenge of increasing throughput while holding operating costs down and maintaining stringent sanitation standards. 6. Acknowledgements Dr. Nelson Slavik is president of Environmental Health Management Systems, Inc., Niles Michigan, USA and holds a Ph.D. in Microbiology from the University of Illinois at Urbana- Champaign. Metaquat is product of Spartan Chemical Company, Inc., Maumee, Ohio, USA