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What are the Different ANSI Classes for Valves?

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What is ANSI Class?

ANSI refers to the  American National Standards Institute.  This organization is the voice of the U.S. standards and conformity assessment system.  In the valve industry, we often have to adhere to different ANSI classes for valves such as ANSI, ANSI 300, ANSI 600, ANSI 900, or even above.ansi-class-chart.png

ANSI Class in the Valve Industry

When buying  valves, it is imperative that the ANSI class meets the specifications laid out.  These different classes refer to standard conformities in pressure and temperature ratings/relationships.  Suppliers are often required to adhere to these standards to assure safety for the system and the operators.  These ratings are based on a valve material, such as cast iron, carbon steel, stainless steel, etc., as well as the way in which the body was cast.  Each material has limits for pressure and temperatures and therefore associated ANSI ratings.  This way, customers are assured that they are not only buying parts that fit, but that they are purchasing parts which will stand up to the conditions under which they will be placed.

On a measurement chart, standard ANSI ratings are identified by a three digit number, running between 100 and 900. Higher class ratings are in the 1000s and up. Examples of an ANSI class specification for valves will look something like this: “1 inch carbon steel  ball valve, 150# flanged valve, ANSI 150”.  This means the engineer is looking for a valve that is rated to the ANSI class 150, therefore, if his valve is at a temperature of 100F, it would be rated to 285 psig. The chart above displays a cross reference of pressure/temperature ratings.  For example: a cast iron housing with a 150 class rating will have a hydrostatic test pressure (psig) of 285.  A valve supplier or engineer can check specifications against this chart to insure safety standards are met. Another very important point for valve engineers to recognize is a “safety factor” with specifications.  Although the valve is rated for 285 psig at 100F, the valve should never meet that.  The general rule of thumb of a safety factor is 20% in the valve industry, so although the valve is rated at 285 psig, the safe engineering of that valve is 228 psig.

The American National Standards Institute, was founded in 1918 by a joint force of five industry groups including the  American Society of Civil Engineers, as well as three government agencies, including the U.S. Navy.  One of the very first goals of the ANSI was to establish standards in pipe threads--a big issue for pipe-fitters and valves manufacturers. Safety was, and continues, to be a motivational force behind ANSI.  To be in compliance with ANSI means that manufacturers, architects, suppliers, builders and workers, etc., all recognize and adhere to a set standard, ensuring everyone has the same understanding of terms, definitions, measurements, and that the characteristics of products are consistent.  ANSI also sets the standards for how parts are tested.  In other words, ANSI classes for valves guarantees that valves will fit, will not fail under certain pressures, and will be safe to use.

Today, the ANSI, a non-profit organization based in Washington, D.C., facilitates voluntary standards and conformity for countless American industries.  The organization's membership includes other organizations, government agencies, corporations, academics, international bodies, as well as individuals, and represents the interests of over 3 million people and over one hundred thousand companies.  These numbers are attributed to industry and technological advances. Since technology constantly evolves, and industries expand, there is a continuing need to set and/or create standards among trades--today ANSI is practically global, and works closely with international organizations (like the ISO) to promote and secure standards in world-wide trade.  This helps enable manufacturers in other countries to meet expected qualifications and produce parts for U.S. industries, thus boosting the global market.

Just Valves

While the ANSI does all this and more, it is primarily the ANSI classes for valves that concerns us.  The ValveMan  valve store appreciates the industry standards that the American National Standard Institute has established--making our job, and your job, much easier and safer.  When you need valves, call us and one of our trained engineers will be more than happy to help you. We're specialists in industrial valves, and we can help you navigate through the ANSI standards.  Just valves: it's simply what we do, it’ what we have always done, and we like to think we do it better than anyone else.