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Sanitary valves are designed for hygienic applications where the primary concern is to ensure aseptic conditions without the introduction of harmful substances in the media flow. This is accomplished by valve material selection and machining processes. Sanitary valve bodies are usually made of stainless steel due to superior corrosion resistance. To minimize particle entrapment and possible bacterial growth, the wetted surfaces are polished to a greater degree than industrial valves. Sanitary gaskets and seals are made from chemically inert material such as PTFE, silicone or Viton. Seal material depends on the specifics of the application. The two most common types of sanitary valves are sanitary ball valves and sanitary butterfly valves. Sanitary ball valves usually have filler material behind the valve seats to minimize internal cavities. This is feature is called “encapsulated seats.” Like their industrial counterparts, sanitary ball valves can withstand high pressures and temperatures. Sanitary butterfly valves are simpler and lower cost but have lower pressure and temperature ratings. Some features that differentiate higher quality sanitary valves include 316 stainless construction (vs 304), highly polished internals (8-10 Ra), and encapsulated seats. Explosion proof actuators are for use in potentially flammable environments. They are specially designed so they will not act as an ignition source and are certified as such. In practice this means not only will an explosion proof actuator suppress any spark or ignition source, but the enclosure must also be able to contain an internal explosion with no flame or spark escaping. In the US the most common certification is the UL Class/Division standard, where Class refers to the type of explosion hazard (gaseous (Class I) or dust (Class II)) and Division refers to whether or not the hazard is normally present (Div I) or not normally present (Div II). The EU generally uses the ATEX standard which classifies application by environment (type G for gases and type D for dusts) and zones which roughly correspond to the UL system. In addition, there is a third standard, IECEx, which is intended to be for global use. It is an industry standard (as opposed to a government one) and is quite similar to ATEX. However, unlike ATEX, EU countries are not required to adopt it. Explosion proof design techniques include circular field joints to better withstand explosion pressures, long faying surfaces to suppress flame travel and internal compartmentalization to ensure explosion containment.
