The Minimum You Should Know About Valve Standards

Suppose one wants to build a new refinery. For that among other things, pressure vessels, piping, and valves are required. In the United States, most States have laws that dictate that pressure vessels must be designed, built, and installed according to the ASME BPVC. For piping, a refinery needs another code; the one most used is the ASME B31.3 (Process Piping). These codes specify the minimum engineering requirements deemed necessary for safe design and construction of pressure vessels and pressure piping. And what about valves?

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One can think of codes as mandatory design guidelines, a set of instructions to be used when dealing with a &#;system&#; such as pressure vessels or piping. &#;System&#;, in this instance, means that the final product is the sum of many parts. For example, both pressure vessels and piping require, among other things, flanges and gaskets. Codes do not detail everything that goes into the final &#;system&#;; any industrial product that is required for a system is referred to in a related standard. So, a standard is a document referred in a code that contains instructions on design, fabrication quality control, and testing of a particular item. By using standards, the code gets simplified and ensures that all items used in the &#;system&#; are &#;standard&#; (uniform in design and fabrication), preventing incompatibility issues and limiting the number of variations for a single item.

Looking again at the refinery example, future piping will follow the ASME B31.3. This code references several valve standards that can be used. For ball valves, for example, one can select API 608 (Metal Ball Valves-Flanged, Threaded, and Welding End) or API 6D (Specification for Pipeline and Piping Valves). For gate valves there is API 600 (Steel Gate Valves&#;Flanged and Butt-welding Ends, Bolted Bonnets), for butterfly there is API 609 (Butterfly Valves: Double-flanged, Lug- and Wafer-type), and so on.

When people talk about specifications, they can be referring to one of two things. One is a datasheet, that is, the technical requirements of an equipment. For example, annex &#;O&#; of the edition of the API 6D is named &#;Purchasing Guidelines&#;. On this annex there is a proposed table for a valve datasheet and API 6D states that this table &#;can be used to assist with the specification of valves for ordering&#;.

The second possibility of the term &#;specification&#; is related to materials. Equipment covered by ASME codes rely on a limited choice of materials. As a rule, pressure vessels, piping, and valves must be made using materials that have mechanical and chemical properties listed on the related ASME code.

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Basically, every material listed on an ASME code has an ASTM specification such as ASTM A216/A216M-21 (Standard Specification for Steel Castings, Carbon, Suitable for Fusion Welding, for High-Temperature Service) or ASTM A182/A182M-21 (Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service). These specifications contain requirements for chemical and mechanical properties, heat treatment, manufacture, heat and product analyses, and methods of testing. Figure 1 provides examples of codes, standards, and materials specifications for an American refinery.

It is also worth mentioning that standards and materials specifications might be amended by the end user. For example, more stringent rules might be forced by contract upon the supplier via supplementary requirements. The S-562 (Supplementary Requirements to API Specification 6D Ball Valves) is a publication from the IOGP with a set of supplementary requirements for the specification for procurement of trunnion mounted ball valves (only) to API Specification 6D Twenty-Fourth Edition, . Ball valves complying with the S-562 have, among other things, more specific design rules and more extensive testing.

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