Valve Size Standards

Figure 1: Valve size standards ensure compatibility across different types of valves.

Understanding the various valve size standards is crucial for professionals in industries where precise fluid control is critical, as it ensures compatibility and efficiency across different systems and geographical regions. This article overviews various valve size standards, including those set by the International Organization for Standardization (ISO), Deutsches Institut für Normung (DIN), the American National Standards Institute (ANSI), and the British Standards (BS). Each of these standards plays a vital role in defining valves' dimensions, tolerances, and physical specifications, facilitating international trade, and ensuring the reliability and safety of countless systems worldwide.

ISO 5752

ISO 5752 covers the face-to-face (FTF) and center-to-face (CTF) dimensions (mm) for various metal valves used in flanged pipe systems. The document specifies dimensions compatible with flanges conforming to equivalent EN (European Norm) or ASME (American Society of Mechanical Engineers) standards. To understand the document, it's important to clarify the meaning of PN, Class, DN, and NPS as they relate to valves and piping systems.

PN (pressure nominal)

PN stands for "Pressure Nominal," which is a way to rate how much pressure a pipe or fitting can handle. It's measured in bars, and the number after "PN" indicates the safe operating pressure. For instance, PN 10 means the item can take up to 10 bar of pressure. ISO 5752 lists PN values from PN 2.5 for low pressure up to PN 400 for very high pressure.

Class (pressure class)

Class is a label used mainly in American standards to show how much pressure a pipe, valve, or fitting can handle, measured in pounds per square inch (psi). Each Class number matches a certain pressure level and temperature a material can safely work with. For example, Class 150 means the item can withstand up to 150 psi. In ISO 5752, Class ratings go from Class 125 for low pressure to Class 2500 for very high pressure.

DN (diameter nominal)

DN is "Diameter Nominal," a European size standard for pipes and valves. It's given in millimeters and roughly shows how wide the inside of a pipe is or the size of the part of a valve that controls the flow. In ISO 5752, DN sizes go from DN 10 for small pipes or valves to DN 2000 for very large ones, fitting many different uses across industries.

NPS (nominal pipe size)

NPS means "Nominal Pipe Size," a North American way to describe how big pipes and fittings are. It's different from DN because it doesn't measure the actual size but is a name that relates to the outside width of the pipe. NPS is calculated in inches, and in ISO 5752, it goes from NPS ⅜ for small pipes to NPS 80 for larger sizes.

Other notes

• Although DN is a metric size and NPS is an imperial size, there's a rough match between DN and NPS for converting sizes.
• Annex B of ISO 5752 helps convert between DN and NPS, ensuring valves can safely work in different industrial piping systems.
• ISO 5752 lists dimensions for valves to fit with EN or ASME standard flanges.

DIN EN standards 558 & 1092-1

DIN standards originate from Germany and are recognized internationally. DIN standards cover aspects such as dimensions, materials, testing, and performance criteria to ensure that valves meet the necessary requirements for a wide range of applications.

One of the key DIN standards related to valve sizing is DIN EN 558. This standard specifies the face-to-face and end-to-end dimensions of metal valves used in flanged, welded, or threaded end connections. It ensures that valves from different manufacturers can be interchanged without system modifications. The standard covers a range of valve types, including gate valves, globe valves, check valves, ball valves, and butterfly valves.

Another important standard is DIN EN 1092-1, which defines the dimensions of flanges and their mating with valves. This standard ensures that the valve's connection points align with the piping system's flanges, providing a secure and leak-free joint.

ANSI standards B16.34, B16.10, & B16.5

ANSI, the American National Standards Institute, is a private non-profit organization overseeing voluntary consensus standards for products, services, processes, systems, and personnel in the United States. ANSI standards for valve sizing are crucial for ensuring uniformity, interoperability, and safety across various industries, including HVAC, water treatment, oil and gas, and manufacturing.

There are three key ANSI standards for valve sizing:

• ANSI B16.34: This standard has the requirements for the design and construction of valves, including wall thickness, end flanges, weld end, and overall dimensions.
• ANSI B16.10: This standard specifies the face-to-face and end-to-end measurements for straightway valves, as well as the center-to-face and center-to-end measurements for angle valves.
• ANSI B16.5: This standard covers the dimensions and ratings of pipe flanges and flanged fittings used with valves.

British standards

British Standards (BS) are the national standards of the United Kingdom, established and maintained by the British Standards Institution (BSI). These standards cover a wide range of subjects, including the sizing and specification of valves for various applications.

For valve sizing, several BS standards are particularly relevant:

• BS 5150: This standard specifies the requirements for cast iron wedge and double-disc gate valves for general purposes. It covers valves with flanged or threaded ends and provides dimensions, material specifications, and pressure testing requirements.
• BS 5163: This standard outlines the specifications for ductile iron gate valves for the water industry. This standard includes details on sizes, pressure ratings, materials, design, performance, and testing of these valves. It ensures that the valves are suitable for use in water and sewage applications.
• BS 5351: This standard covers steel ball valves for the petroleum, petrochemical, and allied industries. BS 5351 provides guidelines on materials, dimensions, pressure/temperature ratings, and testing for ball valves, ensuring their reliability in controlling fluid flow in demanding environments.
• BS 5352: This standard specifies the requirements for steel wedge gate, globe, and check valves with screwed or socket welding ends. It includes information on design, materials, and testing, focusing on smaller-sized valves typically used in the oil and gas industry.
• BS 6364: This standard pertains to the specification of valves for cryogenic service. BS 6364 includes requirements for design, materials, testing, and operation of valves intended for use at extremely low temperatures, such as those encountered in liquefied gas storage and transportation.
• BS EN 12334: This standard specifies the requirements for check valves made of cast iron and steel. It includes sizing, design criteria, materials, and test methods, ensuring that check valves function correctly to prevent backflow in systems.
• BS EN 558: This standard specifies face-to-face and end-to-end dimensions of metal valves for use in flanged pipe systems. It covers a range of valve types, including gate, globe, plug, ball, check, and butterfly valves, and is essential for ensuring interchangeability and proper fit within the piping network.

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