Sanitary fittings normally have mechanically polished interior surfaces and often polished exteriors as well
No single article could explain the entire world of process piping and fittings. It is a huge matrix of pipe schedules, ID dimensions, OD dimensions and materials of construction, not to mention the various flange and threaded end options. This post will try to come to grips with the world of sanitary process piping. Sanitary process piping and fittings (also known as hygienic piping or high purity piping) is used almost exclusively in the food, beverage, biopharmaceutical and personal care industries.
Sanitary fittings and tubing (catagorized also as hygienic fittings and tubing) were developed and are used because they are cleanable; either by dismantling a system and manually cleaning it or using a CIP (clean in place) process. They limit entrapment areas where bacteria could form or harbor. They are also corrosion resistant.
Listed below are the common characteristics of sanitary piping.
- All sanitary piping is measured in tube OD. If you are holding a sanitary fitting in your hand, measure the outside diameter of the tube section of the fitting. That is the correct size, not what the face of the end fittings measures.
- You can buy fittings and tubing in sizes ranging from ½ through 12”. ½”-4” are the most commonly available sizes.
- The wall thickness of sizes ½”-3” is 0.065” (16Ga)
- The wall thickness of 4” is 0.083” (14Ga)
- The wall thickness of 6” is 0.109” (12Ga)
- The wall thickness of sizes 10” and 12” is 0.120”
- Most sanitary fittings are either 304 or 316L stainless steel. More noble alloys such as AL6XN, Titanium and Hastelloy are available in limited quantities and sizes.
- The quality of the surface finish is categorized by its Ra. Ra is determined by taking the average distance between the peaks and valleys on the metal surface. It is normally measured in micro inches. The minimum Ra measurement needed to render a fitting as “sanitary” is 32. Many industries such as the biopharmaceutical industry require tubing to be the 15-20Ra range.
- Sanitary fittings do not have any pockets, threads, or tight radii. The radii of sanitary elbows has been standardized. The radius of a sanitary elbow is 1 ½ time the OD of the tube. Thus a 1” elbow has a 1 ½” radius, a 2” elbow has a 3” radius, etc.
- The most prevalent sanitary fitting end connection offerings are buttweld and sanitary clamp. A sanitary clamp joint consists of two, gender neutral fittings with a sanitary gasket in between, all head together by a clamp. There is a host of other lesser known sanitary connection systems including, bevel seat, John Perry, I Line and Q Line. You can see pictures and or drawings of the various sanitary fittings types on our website.
The main suppliers of sanitary tubing in the US are RathGibson and United Industries. Both manufacture domestically. The main suppliers of sanitary fittings are Alfa Laval, Waukesha Cherry Burrell and VNE. Alfa Laval and Waukesha source their fittings primarily in China. Most VNE fittings are manufactured in Israel.
We will go into more detail on the various connection systems, surface finishes and tubing options in future blog posts.
Holland Applied Technologies