The different ways to clean machines after processing dry substances

When dry materials, such as powder are handled hygienically, it affects aromas, colors, flavors and chemical, physical and biological activities. Good cleaning is therefore crucial in order not to lose these desired properties. Cleaning can take place dry or wet. In addition, the cleaning procedure can take place manually, semi-automatically or fully automatically. When cleaning with water, the contact surfaces should be slightly inclined so that the cleaning agents can easily rinse away. In order to also ensure that material does not accumulate, sharp corners (radius ≤ 6mm) and cavities in the machine must be avoided as much as possible.

Dry cleaning can be applied in places where:

• one or more dust layers of the dry material remain behind and these do not pose a risk to the material that is subsequently processed in the same machine,
• any cross-contamination of residual and new material is no problem,
• the remaining material cannot provide microbial growth due to moisture and temperature,
• the dry material is not hygroscopic or tacky.
• With manual dry cleaning, the largest deposits and dust layers are removed with a vacuum cleaner. Other residues are manually swept up or scraped off with brushes or scrapers. This should not cause too much dust formation. For that reason, cleaning with compressed air is also not a good option, because it creates dust clouds that spread the dust and dirt.

Semi-automatic dry cleaning uses built-in air blowers and retractable nozzles. Air blowers blow the remaining material into a collection area, so that it can still be processed. A precondition for this is that the surfaces must not be contaminated and the air is of process quality and filtered. In addition, vacuum cleaners can also be used and hard particles such as rice or plastic balls serve as an abrasive for the pipe system.

Wet cleaning can be applied in places where:

• the dry material remaining behind poses a risk to the dry material that is subsequently processed,
• no cross-contamination between residual and new material may occur,
• the residual material can cause microbial growth due to moisture and temperature,
• the dry material is hygroscopic or has a low softening point, which can cause deposits to form and remain in the machine.
• The manual wet cleaning procedure starts with removing the deposits through a dry cleaning procedure. The contact surfaces are then soaked with water and cleaned with brushes, scrapers or water hoses. After manual cleaning, the machine must be dried immediately and thoroughly with warm air before a new product can be processed.

The semi-automatic wet cleaning method is called Washing-In-Place (WIP). Sprinklers are lowered into the pipe system or into the silos that clean the dirty surfaces with water and cleaning agents. The machine is then rinsed with water and must be dried thoroughly with warm air immediately. The cleaning fluids are collected and recirculated through the cleaning system. Separate storage tanks are used for cleaning water, cleaning agents or special liquids.

The automatic wet cleaning method is called Cleaning-In-Place (CIP). This is a fully automated cleaning procedure that does not require disassembling parts to install nozzles. These cleaning systems contain permanently mounted nozzles that are connected to the recirculation pumps and storage tanks for cleaning fluid. Afterwards, the equipment is immediately automatically dried with warm air.

Hygiene is paramount when cleaning the machines, but safety should not be forgotten either. Some cleaning methods, such as manual wet and dry cleaning, sometimes require the machines to be taken apart. This must be done in a safe manner. No special tools or hoists should be required for this. In addition, the cleaning equipment may not be used on other materials or for other purposes. The cleaning equipment must be cleaned and maintained regularly. The equipment must be stored in a clean environment. Broken tools should not be used as they can leave broken parts in the machine and cause contamination.