Drying is often neglected or under-estimated when planning contamination control strategies or cleaning processes. Adding drying to an established process incurs costs and complexities that could be avoided with appropriate up-front planning.
When planning the cleaning process, recognize that:
Particles from the surrounding air can alight onto wet components
Particles that dry onto a surface can be particularly difficult to remove
Controlling when, where, and how drying occurs minimizes contamination issues. Premature drying can result in adherent contamination. A mist spray can prevent flash drying during tank-to-tank transport. Placing cleaning and drying equipment in the cleanroom is often not a good use of costly real estate and may run counter to good contamination control practices.
Locate equipment to:
Insure that the product is sufficiently clean when it emerges from the process
Prevent the process from re-contaminating an already clean product or to compromise the cleanroom particle specification
A commonly recommended practice is to locate all but the final drying chamber (or final rinse and dry areas) outside the most stringently controlled area. Besides the benefit of reducing contamination in the cleanest area, the more costly real estate is saved for higher-value assembly processes. However, when product is transported from a less clean to a more clean area, it is important to assure that transport mechanisms (e.g., hoists, conveyor belts, and transport baskets) do not contribute to contamination