Ask Control Engineering
The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control and embedded systems. Control Engineering answers questions from readers of Control Engineering's print and online magazines, newsletters and other publications. To comment on any blog posting, click on the post's highlighted question and scroll to the "Post a Comment" box at the bottom. Submit questions as comments to any existing post.
What is a "sanitary" device?
Dear Control Engineering: One of the things I see regularly in your new product listings are devices that are designated as “sanitary,” for use in food and pharmaceutical applications. What does that mean?
Manufacturing plants that produce food and pharmaceutical products are concerned about bad things growing in a manufacturing environment that could make it into the final product and cause contamination. Such things can make consumers sick or even dead, so we should all be glad such concerns exist. There are many organizations that oversee food and pharmaceutical manufacturing, depending on the specific segment. For example, there is the U.S. FDA, various departments of agriculture, and local health departments.
These groups use standards for hardware configuration and production practices that describe in extraordinary detail exactly what the equipment should look like and materials of construction. One such group is the International Association of Food Industry Suppliers (IAFIS), which is connected to the 3-A Sanitary Standards organization. These standards describe how equipment is to be made such that it can be adequately sanitized in cleaning processes, and not provide a breeding ground for bacteria and other bugs that can contaminate products. The standards touch on many key points:
• Appropriate materials, e.g., stainless steel and various plastics;
• Cleanable surface finishes;
• Absence of internal cracks, crevices, threads, and pockets;
• Welding specifications, and so forth.
These standards and practices came out of the dairy industry originally, but have now been adopted for many applications with similar concerns.
Devices, such as temperature transmitters or pressure sensors, that are made to be inserted into process piping or tanks, normally use the same kinds of fittings as the pipes themselves. This tri-clamp system uses a pair of tapered flanges on the end of the pipe or device that mate with a gasket and external clamp. This approach ensures an effective seal, but one that can be disassembled easily and minimizes any possibility of breeding contamination.
In the photo, the device on the left is designed for sanitary insertion and built in compliance with the relevant 3-A requirements. If you looked at the underside of the flange, you would see that it has a very fine surface finish, the point where the probe joins the flange has a smooth fillet, and an appropriate grade of stainless steel is used. The key point is that the device cannot become a source of contamination.
--Peter Welander, pwelander(at)cfemedia.com