Facilitating Efficient Equipment Cleaning

Equipment design and cleaning procedures both play a role in thorough sterilization and cleaning.
May 02, 2012
Volume 36, Issue 5

Per-Åke Ohlsson
Sterilization or sanitization is usually applied to kill bacteria in a system. In addition, equipment is cleaned to remove residues from the previous batch of product, and subsequently flushed to remove the cleaning liquids. To ensure that sterilization and cleaning are efficient and safe, it is not enough to develop the appropriate procedures. Selecting the right manufacturing equipment further improves cost efficiency, as well as patient safety.

Considerations in equipment selection

The chosen equipment must minimize the risk of contamination due to inappropriate product-contact surfaces. Machines should not introduce airborne particles and dust into the environment, nor should they entail the risk that oil or other substances required for their operation will contaminate the product. If an operator cannot contact all equipment surfaces adequately, he or she simply cannot clean them. To facilitate efficient cleaning, equipment must be designed with this principle in mind.

Figure 1: The time, action, chemistry, and temperature circle. (ALL FIGURES ARE COURTESY OF THE AUTHOR)
The time, action, chemicals, and temperature (TACT) circle originally developed by Sinner in 1960 shows the cleaning effects that these parameters generate on the equipment surface (see Figure 1). The circle shows the extent to which time, plus at least one more parameter, clean residues from a surface. If one parameter is increased, the others may be reduced.

For example, if one dips one's greasy hands in water, they will not become clean. If one puts them into a soap bath, they will become clean, but only after a long time. If one raises the temperature of the soap bath, however, one's hands will become clean more quickly. But if one also rubs one's hands together, they will become clean even more quickly.

The residue and the product-contact surface determine the size, or the impact, needed for the cleaning process. The most suitable type of chemicals and the appropriate temperature are decided according to the residue. High surface action enables the chemicals and temperature to work more efficiently, which makes it possible to reduce both of these parameters, as well as the cleaning time. Because the action is often built into the equipment design, selecting the right equipment can reduce the cost and increase the cleanability of a system.

Cleaning action on the equipment surface is achieved by generating high velocity or flow of cleaning fluids on all product-contact surfaces. This technique distributes the chemicals and temperature better than low velocity does. Increased velocity also generates high turbulence and shear force on the surface, which ensures that the chemicals and temperatures reach deep into the residues and dissolve or detach them safely and efficiently.

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