Contamination

In powder and process technology, contamination is the unintended introduction of substances, particles or microorganisms into a product that are not part of the formulation. Whether contamination is critical depends on the product: in food, pharmaceutical and cosmetics manufacturing, even traces can render a batch unusable, whereas the chemical and building materials industries usually allow higher tolerances. Industrial mixers are a key point in this respect, because many components come together in them and the equipment is often used for changing products.

Types of contamination

Depending on the origin of the foreign substance, the following types are distinguished:

• Cross-contamination: Residues of another product or a previous batch enter the subsequent product, for example via residual quantities in the mixer, in pipes or in dosing units. An important special case is the carryover of allergens. See cross-contamination for details.
• Microbiological contamination: Germs, yeasts, moulds or biofilms settle in dead spaces, crevices or moist product deposits and pass into the product.
• Chemical contamination: Residues of cleaning agents and disinfectants, lubricants from bearings and shaft feedthroughs, or substances that pass from product-contact materials into the product (migration).
• Physical contamination: Foreign bodies and particles such as metal abrasion from mixing tools and the vessel wall, abrasion from seals or loose small parts.
• Contamination from the environment: Dust, moisture or airborne germs enter the mixing chamber during filling, sampling or via venting openings.

This must be distinguished from the opposite direction of action: containment is about protecting personnel and the environment from the product, for example with highly potent active ingredients or toxic powders. In practice, product protection and personnel protection are often designed together, because both require tight, closed process control.

Entry points in the mixer

Typical entry points are shaft seals and bearings, dead spaces and crevices, residual quantities after discharge, rough or poorly accessible surfaces and inadequately designed welds. Cleaning itself can also become a source if cleaning agents or residual moisture remain in the equipment.

Preventive measures

The most effective measures start with the design: a construction based on the principles of hygienic design, a high residual discharge rate, low surface roughness (see roughness parameter), suitable materials and a sealing concept that reliably separates the product chamber from the drive. In addition, there are organisational measures such as campaign planning of the product sequence, defined cleaning procedures such as CIP or WIP and their validation. In regulated industries, GMP requirements and the guidelines of the EHEDG set the framework.

How does amixon® solve this?

amixon® designs its mixers for almost complete discharge and easy cleanability. Mixing tools such as SinConcave®/SinConvex® and KoneSlid® guide the product flow in a targeted manner and minimise residues in the mixing chamber. For applications with personnel protection requirements, containment systems and docking stations can be integrated. amixon® works with the customer to determine which design is suitable in each individual case, with trials in the pilot plant on request.