Powder handling has long been one of the toughest issues for food and beverage companies. Powder is messy, intrusive, and sometimes abrasive, prone to leakage or spillage, and when it does, the powder usually covers the surface of the accessory and is difficult to remove.These challenges are doubly difficult when it comes to switching channels.
Many processors are required to quickly switch between different formulations. The nature of powder and bulk solid materials makes the problem particularly tricky, and equipment suppliers say their customers are increasingly facing such problems.
Mark Felts, Director of Sales for Powder Process-Solutions, said, "Cleaning is a constant concern for a large percentage of our customers. They are very aware of the need for cleaning between material transitions."
Robert Meirick, sales and marketing manager for material transfer and storage, agrees: "A lot of our customers have different materials to handle,when they switch from one material to another, they worry about cross-contamination."
Cleaning is the most important and challenging aspect of powder material conversion. They percolate like a liquid, but leave a solid residue that is difficult to remove.This is why cleaning methods are a fundamental problem for every processor that uses powdered materials, especially when cleaning is relatively frequent.
"There is no doubt that people need more sanitation all the time." "Said Nick Hayes, CEO of Volkmann USA.
The most basic decision is whether to clean in situ or off-site, that is, whether to remove and manually clean hoppers, mixers, and especially conveyors for handling powder. The latter is more thorough and is often the only option in viscous or hard-to-remove powder applications. As a hygiene measure, such applications usually require frequent cleaning of treatment equipment, even in the absence of product conversion.
If the powder handling equipment needs to be manually cleaned,then the device must be designed to be quickly disassembled and reassembled, preferably without tools.
David Kennedy, Business Development Manager, VAC-U-Max, said, "The removal can be done without tools and without any edges or ledges on the internal/product contact surfaces will provide the most effective cleanliness. We also recommend the use of removable gaskets (no adhesive) and eccentric clamps to secure the components. These fixtures are all fixed hardware, so they don't fall down during the process or get lost during cleaning."
Heavy duty static equipment can be designed for easy access during the cleaning process. Powder ProcessSolutions, for example, offers filters that are easy to remove and clean. For systems that require frequent, seamless cleaning, a rotary valve with a rotor on the slide is recommended.
Mark Felts estimates that wet cleaning of the interior of the rotor and rotary valves can take anywhere from 15 minutes to an hour, depending on the application, installation, product and cleaning level required.
Dry or wet cleaning?
Of course, some factories don't have that much time to make the switch. For these applications, cleaning in place is the only option.
In theory, in-place cleaning can be accomplished by either a "thousand" or a "wet" method. The thousand-way method involves blowing high pressure air through a conveyor belt or static equipment and removing residues, debris, or a mixture of both by physical impact.
For example, a disc conveyer made by Cablevey Conveyors transfers product to stainless steel pipes by a disc suspended from a cable. A common way to keep pipes clean is to use a flexible polyurethane disc slightly larger than the diameter of the pipe, which acts as an internal scraper to remove fine particles from the inner surface of the pipe.
Another option is the "brush box," which is a case with a rotating brush that can remove large particles from the magnetic disk.For a more thorough cleaning, insert a detergent soaked sponge into the cable to drag the disk across the pipe.
However, dry cleaning is often used more for ongoing hygiene needs than cleaning between transitions. The latter is usually done by "wet" cleaning with detergents and/or hygiene chemicals and water.
There are two basic methods of wet cleaning: (1) forcing the cleaning fluid through the system; (2) Use electrostatic devices (such as spray balls) for cleaning.
No matter how it's done, the biggest challenge with wet cleaning is getting everything ready to run again, in other words, waiting for the equipment to dry again.
"When you introduce wet cleaning, you also have to consider drying time," says Mark Felts.
Volkmann's Hayes agrees: "It's not about cleaning in place. We can use modern technology (nozzles) for in-situ cleaning, whatever in-situ cleaning you need. Your problem is to dry it in place." The biggest challenge, he says, is the filter, which is almost impossible to dry when installed. "The question becomes, can you dry them? The answer is no, you can't dry them while they're in the conveyor belt." The filter must be removed separately for drying, which makes the cleaning system a mix of in-place and off-site cleaning.
Conveying cleanliness
Other factors that influence the use of cleaning methods include the nature and size of the equipment to be cleaned. For example, there are a variety of alternative methods for conveying powder materials. By far, the type of powder transported and its handling characteristics will be the most important factor in determining the type of conveyor, but different types of conveyor will vary in terms of ease of cleaning.
"At a very high level, I think pneumatic (vacuum) conveyors are the cleanest, flexible (or centless) screw conveyors are second, and pneumatic mechanical conveyors are third," says VAC-U-Max's Kennedy. . He explained that the ease with which a pneumatic conveyor can be cleaned depends on the length of the segment: a shorter segment can be disassembled relatively easily, while a longer segment may need to be "cleaned" by running a cleaning module.
For the use of flexible screw conveyors, although they do not have many parts, but it still takes time to clean the screw structure and pipe inside. As for the third option, "if you change the product frequently, we generally do not recommend pneumatic mechanical conveyors unless there is a lot of time between runs and they are used for non-sanitary applications." He said.
Hayes also thinks that for conveyors, the longer the conveying line, the more difficult it is to clean. "This is where life becomes more difficult," he said. "It's easy to take the filter receiver apart and clean it, but what about 30, 40, 50, 100 feet of conveyor line with components?
Conveyors that physically push the product forward, such as garden plates or screw conveyors, can be designed as disks or screw conveyers that extend beyond the discharge point. This will squeeze out some residual powder.
"The driving force of the Flexi-Disc tubular wireline delivery system extends beyond the final discharge point to prevent material from coming into contact with seals or bearings," said David Boger, executive vice president, Flexicon Corp. "By evacuating material at the end of a production run, the delivery system eliminates waste and residual material, thereby minimizing downtime for cleaning and disinfection."
Conveyors face different conversion challenges, such as processing equipment such as mixers, mixers and bag unloaders.Like a few moving parts,this is an important aspect of the cleanliness of such equipment.
"The most important is, want to eliminate cross contamination at the same time reduce the conversion time of food processors, you should specify the lack of internal shaft and other moving parts of mixing and stirring device," Munson Machinery company's marketing manager, Steve Knauth said, "whether or not the shaft is fixed on the container or container internal mixer, contact with the shaft seal materials are inherent defects, it would increase the time and complexity, in some cases, increase the cleaning and disinfection of the uncertainty of the agreement.
Kauth noted that Munson's rotary intermittent V-cone mixers are ideal for dry powder mixers and offer the advantage of quick conversion because they have no internal moving parts and are internally barrier-free.
For the bag unloader, cleanliness is always a key concern and bags must be replaced periodically even if the contents remain the same. The powder in the bag goes into the transition hopper and is then released downstream, which must be easy to clean. Unloading machines made by Volkmann and others have hoppers that can be rolled out for cleaning.
"One of the biggest problems with bulk bags is not what happens to them when they're full, but what happens to them when they're empty," Hayes said. Remove the bag and fold it over to get rid of the remaining air inside as well as any remaining powder.Olkmann provides a vacuum cleaner, located on the side of the bulk bag unloading point, through which the main vacuum collects the ash produced by the powder stream. When the bag is unloaded, the vacuum is diverted to the bag itself to extract the remaining powder residue.
If it becomes too difficult to remove the powder from the equipment, processors may sometimes have to consider another option: avoiding the switch by dedicating separate production lines and equipment to different products.