Per-Åke Ohlsson
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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)
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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.
