Home Health Food protection and security: preventing and mitigating contamination during food processing and production
Conveyor frames should have an open structure with a minimum of hidden areas/surfaces. But guards are required in places where a drive station, a pulley, rollers or the conveyor belt may cause injury. The guards, however, should be easy to dismount to allow for complete cleaning. Solid cross members as structural members are preferred over hollow section members. Open profile angle or channel sections must be installed in a manner such that horizontal ledges and crevices are absent. Where open profiles are used, the folding should be turned outward for easy cleaning (Fig. 6.42). Welding is preferred over fastening.
Conveying surfaces shall be supported by a minimum amount of carrying surface or bed (Fig. 6.44) as required. The use of solid plate that expands the whole top surface of the conveyor table to provide support to a belt is likely
FIGURE 6.42 The conveyor frame and subframe should have an open structure without horizontal surfaces and with a minimum of hidden areas/surfaces. At the outside, the framework consists of open profile members turned outward for easy cleaning. The conveyor frame is an all-welded construction with flat cross-members welded at the outside framework. The crossmembers not only act as structural frame members, but also as belt supports. The weld-on flat cross-members are provided with gaps to accommodate the freely located plastic wear strips that help to support the conveyor belt. No bolts, holes or nuts were used for fastening the ultra-high- molecular-weight (UHMW) polyethylene wear strips. The swivel-mounted roller permits release of the belt tension, hence providing improved access for cleaning the bottom side of the belt as well as the bearing strips. Courtesy of Interroll.
to increase contamination problems and cause excessive wear of the belt. Nonremovable bearing surfaces for belts cannot be cleaned easily. Rollers shall be used where practical, or line supports that are easily removable for cleaning. The conveyor belt should have minimal debris retention, and running under turned over sections of side cladding (overhanging belt edges) is not allowed because the whole surface of the belt cannot be cleaned, and the belt cannot be lifted up to allow cleaning and inspection of internal surfaces and support members (Fig. 6.2). But also pivoted covers can’t be cleaned easily if continuous hinges are used. In continuous hinges, food debris and microbial slime are strongly retained in the hinge segments (Fig. 6.43). Side guides used to contain product should be capable of being removed. So, pivoting guides using pin hinges with removable pins are acceptable. But removable guides also may cause problems because of the possibility of the fastening system working loose. The conveyor frame must be designed so that the sides of the belt are turned up to form an integral guide to the belt. Besides this guide, cladding can be made removable allowing for effective cleaning (Fig. 6.44).
The most common design of a drive station is placing the drive pulley between two bearings, one at each side of the conveyor. Open bearings have low Ingress Protection (IP), making them sensitive for the removal of lubricant during cleaning operations (Fig. 6.45). Because they require more frequent lubrication, the risk of overlubrication increases. Self-aligning pillow block bearings or flange bearings with covers and constructed from materials
FIGURE 6.43 The conveyor belt running under turned over section of side cladding (overhanging belt edges) is not allowed because the whole surface of the belt cannot be cleaned, and the belt cannot be lifted up to allow cleaning and inspection of internal surfaces and support members. In this example, the side guides serve both as belt and product guide. They may pivot to the outside due to the hinge segments. Pin hinges with removable pins are used, which allows for minimal debris retention and excludes the likeliness of microbial growth and concomitant slime production. Courtesy of PaxiomWeighPack Systems Inc.
FIGURE 6.44 The conveyor frame (1) must be designed so that the sides of the belt are turned up to form an integral guide (2) to the belt (3). Besides this guide, cladding can be made removable allowing for effective cleaning. The conveyor belt shall be supported by a minimum amount of carrying surface or bed (4) as required. Rods, slats, rollers, or like supports shall be used where practical (CFPRA, 1983; Hauser et al., 2004b).
approved for food contact may provide waterproof and corrosion-free designs. The higher IP rating prevents lubricant inside bearings being removed during cleaning operations, making overlubrication less likely. Lubricated bearings, including permanent sealed types, should be located outside the direct product contact surface area with adequate clearance open for inspection between the bearing and any product contact surface (Kold et al., 2016).
If the specification of the gear motor allows it, the bearing on the gear motor side of the conveyor can be omitted, using the output shaft of the gear as a bearing. In this case the gear motor has to be fixed to the side of the
FIGURE 6.45 Lubricated bearings should be located outside the direct product contact surface area with adequate clearance between the bearing and any product contact surface. Open bearings have low Ingress Protection (IP), making them sensitive to the removal of lubricant during cleaning operations. Because they require more frequent lubrication, the risk of overlubrication increases. Excessive lubricant and grease should be removed to prevent them from coming into contact with the product. Courtesy of John Butts, Land O’Frost.
FIGURE 6.46 Although the drive motor has a drip pan, the difficult-to-clean motor is located too close to the product flow, because the fan may blow dust and dustborne microbes around and onto the food. Frank Moerman, © 2016.
conveyor ( = direct drive motor). Drive motors should be located below the line of the product flow because the exposed motor may have a fan that will blow dust and dustborne microbes around (Fig. 6.46). It is also possible to place the gear motor away from the drive drum, driving it by means of a chain or toothed belt, for example. Such a design requires a guard around the chain or belt to avoid any contamination of food product, as well as for occupational safety reasons. However, a chain guard, when open, may provide a place where product may accumulate, allowing microbes to multiply in large numbers and so posing a contamination hazard for the food product on the belt (Fig. 6.47). Measures have to be taken to make the drive guard
FIGURE 6.47 The drive motor is located below the line of the product flow. Gears, chains (stainless steel or polyacetal), and motors of belt drives must be covered to avoid any contamination of product. However, a chain guard (essential from an occupational safety point of view), when open, may provide a place where product may accumulate, allowing microbes to multiply to large numbers and so posing a contamination risk for the food product on the belt. A transparent chain guard may allow detection of any product debris inside the chain guard. Courtesy of Dorner Mfg. Corp.
FIGURE 6.48 Drum motors make external gears and chains redundant. Courtesy of Interroll.
using a hygienic and easy-to-clean design (e.g., hermetically sealed housing). Furthermore, the guard must be designed in a way that the generated heat from the gear motor can be conducted away.
The drive motor is often of a type that cannot be washed with a high- pressure hose using water and cleaning agents. However, IP54/55/67 sealed wash-down or easy-clean motors which do not require ventilation or housings are available. There should be enough air space around the motor for cleaning and disinfection, maintenance and repair. Where possible, use drum motors (motorized pulleys) (Fig. 6.48) that are fully closed, nonventilated, conveyor belt drives where motor and gearwheels are at the inside, submerged in a bath of food-grade lubricant, providing at the same time lubrication and cooling. Drum motors make gears and chains redundant.
FIGURE 6.49 Rollers and pulleys shall not have hollow parts. Don Graham, Graham Sanitary Design Consulting LCC, © 2010.
FIGURE 6.50 Hollow rollers and pulleys shall not be used. Courtesy of General Mills.
Rollers and pulleys shall not have hollow parts (Fig. 6.49). The design of rollers, pulleys and sprockets shall be closed if hollow (Figs. 6.50 and 6.51) and shall be free of end recesses (Fig. 6.49). A welded construction should be preferred to a sealed design (Fig. 6.51).
Embedded reinforcements, as well as fabric backing materials in conveyor belts, must be covered to avoid contact with the product. Cut edges of belts which incorporate reinforcing materials must be sealed to prevent penetration by wicking (capillary action) of liquids into the interior (Fig. 6.52).
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