Sanitary Design

Question
I have an application where a client is interested in a sanitary design for a USP water washing application. Specifically the client requested that we provide a sanitary version of spray gun that could be connected via hose to a USP drop (1"). Apparently, the type of equipment being washed does not lend itself to conventional methods of cleaning.

Answer
The word "sanitary" can sometimes lead to confusion. Items may be called sanitary which are not, and items that we normally don't think of as sanitary may work just fine in some applications. When something is called "sanitary" it usually means that it is constructed from materials that will not contaminate the process fluid and that it will not trap moisture that could lead to microbial growth. Stainless steel is used in place of other metals because it does not corrode significantly in most applications yet it is still reasonably inexpensive.

Any applications involving high chloride concentrations, however, may need something other than stainless steel, which can corrode significantly under these conditions. In this case, a part made of stainless steel would not be "sanitary", since the corrosion products could contaminate the process. Better choices would be Teflon or Hastelloy. Contamination can also come from hoses or elastomers used for diaphragms and gaskets. That is why we specify FDA grade materials for these components.

Most people understand the corrosion issue. The confusion stems more often from the concept of not trapping moisture. Another way of saying this is that the items must be completely drainable. Generally, this is a good target to shoot for. However, items that are not drainable can work in sanitary systems provided they can be properly sanitized. "Drainability" stems from the older concept of sterilizing items with steam. In steam sterilization, any undrainable pocket will collect condensate and could lead to a cool spot that is not properly sterilized. However, items that cannot be drained can be sanitized provided the sanitizing agent has access to all locations. Sanitizing agents can be chemicals, ozone, or more commonly, heat. Remember there is a difference between sterilization, which is the removal of all microbial life (to a certain level of assurance), and sanitization, which merely knocks the viable population down.