Q&A: Considering Sanitary Requirements

Feb. 28, 2008

Lyle Hamilton Lyle Hamilton is a project engineer for Richards Industries, where he is currently responsible for the design and support of the Steriflow line of sanitary products, including

Lyle Hamilton

Lyle Hamilton is a project engineer for Richards Industries, where he is currently responsible for the design and support of the Steriflow line of sanitary products, including the company’s new Sanitary Control Valve. He is also responsible for product certification by the 3A Symbol Council and ASME BPE compliance, as well as ongoing monitoring of manufacturing processes, quality assurance, and assembly/testing procedures. Mr. Hamilton can be reached at [email protected] or 513 533-5604.

Q: How do sanitary requirements differ from industry to industry. For example, how are sanitary requirements for pharmaceutical applications different than they are for food and beverage, biotech, and/or cosmetics applications?

A: First, and most obvious, sanitary valves are almost always made from 316L stainless steel and will have a surface finish of 25 Ra or better. Some pharmaceutical-use valves will have finishes better than 8Ra. All soft goods and lubricants (if applicable) are approved for use by some or all of the following: Food and Drug Administration (FDA, www.fda.gov), 3A Symbol Council (Milk Products), United States Phamacopeia (USP, www.usp.org), and the National Sanitary Foundation (NSF, www.nsf.org).

Q: What are the key sanitary standards governing process environments in the pharmaceutical, food and beverage, biotech, and cosmetics industries? How do these standards influence the design of process equipment for use in such environments?

A: For pharmaceutical, cosmetics, and biotech, use the ASME’s Bio Processing Equipment (BPE) standard and the United States Phamacopeia standards. For food and beverage, the 3A Symbol Council and the National Sanitary Foundation (NSF) are the major players.

Q: What are some best practices users can employ when designing a sanitary system to ensure it meets long-term cleanliness and purity requirements?

A: First and foremost is design for good surface finishes — 4Ra or better — and observe minimum radii requirements to prevent "dirt traps" and crevices where bacteria can embed and flourish. Next is the elimination of stagnant zones. This means elimination of dead space or any space where the flowing media can swirl or eddy and remain in the valve body instead of flowing in and out. Last, but not least, drainability or holdup. When the process is shut down at the end of a batch or because of a breakdown, the valve must be able to fully drain once all process pressure has been removed.

Q: What are some common pitfalls users encounter when designing sanitary systems that may ultimately compromise the purity of the application?

A: Tough areas are clamping surfaces, such as the joint where the body clamps hold the diaphragm in a pressure regulator. To make the diaphragm last, some sort of a radius is required to prevent a sharp holding edge from cutting the diaphragm like a cookie cutter cuts dough. At the same time, the configuration must not create a stagnant zone or dirt pocket. O-ring seals are another tough area, because an o-ring gland that produces an effective seal may not be the most sanitary design. The oft-conflicting requirements of seal integrity and cleanliness must be carefully weighed and considered. This is a particular area that requires not only design expertise, but also design expertise within regulatory constraints.

Q: How has sanitary process equipment evolved over the past 10-15 years? How is today’s sanitary equipment better suited to enable the purity of applications than the sanitary solutions of yesteryear?

A: The ever-increasing selection of suitable soft goods for use as seals and diaphragms has been a big gain for both manufacturer and end-user. New computer-controlled welding robots are another area that has greatly improved the product by preventing delta ferrite precipitation, which is of great importance to the pharmaceutical user. Welding lathes and clamp-on orbital welders are some examples that manufacturers and contractors now use.

Q: Where do you see sanitary processes going from here? In your opinion, what are some of the obstacles that still need to be overcome in sanitary environments to better ensure the purity of end products?

A: The trend is moving toward tighter requirements on surface finish, specifically the elimination of small pits and scratches, which can accumulate during the multi-step fabricating processes now used. Better tooling, fixturing, and packaging techniques are helping to improve this aspect of the product. Better inspection tools like profilometers and handheld ferro-magnetometers that interface with a computer provide better quality control and record keeping. Improved soft goods, such as elastomers with higher temperature capabilities and perfluoroelastomers with wide chemical compatibility, are among the most obvious resources in the never-ending drive for higher purity. Lastly, the selection of new metallurgy and the use of super austenitic alloys like AL-6XN® are being employed more often to minimize the possibility of rouging, corrosion, and pitting, which can occur with stainless under some process conditions.


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