I can think of no term found in specifications for cleaning machines that causes more controversy and confusion than the term “Sanitary Plumbing.” This term, frequently found in specifications for cleaning and processing systems destined for the semiconductor, medical, food processing and a growing number of other markets is vague and means different things to different industries and, in fact, to different companies in the same industry and even to individuals within the same company. In the pharmaceutical and medical industries, the goal of “sanitary plumbing” is usually to prevent harmful bacteria and other “bugs” from establishing a presence in processing equipment thereby contaminating the product. This, of course, is in direct alignment of the meaning of the word “sanitary.” In the semiconductor and other industries the intent may be to prevent contamination of one process liquid with another. In any case, “sanitary plumbing” indicates plumbing that doesn’t harbor contaminants or allow mixing of one process liquid with another. Although this sounds like a simple task it’s often not as simple as one would think.
Beyond the obvious fact that plumbing should be constructed using materials that don’t contaminate process liquids, there seem to be two main schools of thought on sanitary plumbing. The first embraces the use of pipe or tube, fittings and devices such as valves that not only prevent contamination of the liquids being processed but also prevent a place for bacteria and other contaminants to “hide” during normal operation of the equipment. The second takes the remedial approach that all surfaces that come into contact with the process liquid be accessible for periodic cleaning. “Accessible” may mean anything from simple flushing to actual dis-assembly of a plumbing system for mechanical cleaning and inspection of all surfaces both inside and out.
Note – The FDA (a frequently referenced source of regulations regarding sanitary plumbing) does not address specifics regarding choices of materials, components or plumbing protocol. What the FDA has to say about sanitary plumbing can be found here. For the most part, the FDA addresses sanitary plumbing as it applies to washroom and kitchen applications in either domestic or public facility settings. Clearly, the FDA requirements are far less stringent than those imposed by most users demanding a contamination-free liquid processing system.
Since there is no universal code defining “sanitary” plumbing, many manufacturing facilities producing a product that must be free of contamination have developed their own internal practices which, although they may be defined by internal documentation, are frequently open to interpretation on a case by case basis. Unfortunately, the documents defining the meaning of “sanitary” in a cleaning system are seldom included in a machine specification which can lead to a number of “surprises” down the road.
To start our discussion of sanitary plumbing, let’s look at a couple of examples of things that may come under scrutiny in the design of a system with “sanitary” plumbing.
Material of Construction –
In a majority of cases, “sanitary” means stainless steel with series 304 and 316L being the most common choices. In some cases, plastic of one sort or another is an option as far as compatibility and contamination goes but fails due to the lack of suitable “sanitary” fitting designs for plastics. Glass, although it has the proper credentials for compatibility, is a very difficult material to work with because of its fragility and, again, suitable fitting designs. I am not aware, for example, that I’ve ever seen a pump fabricated of glass. Selection of an appropriate material of construction is often the first consideration in the design of a “sanitary” system but, as will be revealed in upcoming blogs is far from the last.
– FJF –