Flanges standards

Steel pipe flange dimensions and specifications

ASME B16.5 flange

ASME B16.47 flange

ASME B16.36

BS 3293

Weld neck flange Dimensions

DIN Standards

Other standards

What is the flange standard?

Flanges are typical components used in many industrial applications to connect pipes with mechanical devices. A flange code standard specifies the dimensions, finish, markings, facing type, and material. It also decides any other technical specifications. Flange standards differ across geographical regions. In Europe, the EN 1092 series is popular. It includes the Din flange standard and gets employed by many national bodies. For example, you can use DIN EN 1092 and NF EN 1092. The numerical value represents the maximum applicable pressure at a reference temperature of 20 degrees Celsius. You can find definitions for cast iron, copper, aluminium, and steel. The ISO 7005 standard is also internationally accepted. It covers DIN and ASME flanges, specifying the DN and PN designations for the latter. A Sae flange designed by the Society of Automotive Engineers conforms to SAE J518 standards.

What is the difference between ASME and DIN?

The American National Standards Institute laid down ANSI specifications. An Asme flange, designed by the American Society of Mechanical Engineers, meets the process requirements of ANSI. It uses millimetres and inches. The ASME B16.5 specification includes sizes up to 24″.  DIN uses sizes in millimetres only. Usually, DIN mandates stricter tolerance compared to ANSI. The two standards also differ in tolerance levels and diameter sizes. The above differences result in variations across many other areas, like the equipment required for processing, the weight of the manufacturing material, and overall production processes. ASME is also called an Asa flange and is the most commonly referred standard across industries, along with DIN.

What is the nominal size of the flange?

When you take measurements for a flange, the nominal size is critical. It refers to the bore size of the component. A European flange standard and specifics from America use the nominal pipe size or NPS. The bottom line is it should match the bore size of the pipe. Based on this metric, you can find the specifications for your requirement. Most standard charts by manufacturers cover the bolt diameter, the number of bolts, and the bolt length for a pressure class based on the NPS. So, this definition will help you adapt the dimensions to low-pressure applications if you use an Awwa flange designed by the American Water Works Association. You can also use the nominal pipe size to assess the outer diameter of the component and the thickness. For instance, an Api flange, which adheres to standards developed by the American Petroleum Institute, is available in sizes up to 24″. The NPS also helps you understand the weight of the weld neck.

How can you order a flange?

Ordering the best component for your application is a prerequisite for optimum performance. While purchasing a flange, you can refer to the pressure rating, say, 150#, 2500#, etc. You must include the nominal pipe size, the pipe schedule, and the surface finish (e.g., stock or concentric serrated). The flange connection comes in various types, like socket weld, threaded, swivel flanges, lap joints, etc. A thumb rule is to consider the pressure and temperature at which it will operate. For instance, a socket weld flange works well in high-pressure applications. The flange specification and material will depend on your industry. The common standards are ASME B16.5, En flange, JIS, DIN, etc. JIS flanges have classes from 5k to 30k, but European and Russian ones range from PN 6 to PN 100. The standard will also dictate the flange-facing types, like raised, flat-face, or ring-type. Similarly, a Bs flange designed per the British Standard can get manufactured in stainless steel, carbon steel, alloys like Inconel, etc. The decision depends on your priorities: corrosion resistance, strength, and welding suitability.

How do I know my standard flange?

You can find your standard flange by referring to the manufacturer charts. For instance, a B16.5 flange can range from 1/2″ to 24″ in pressure classes 150 to 2500. Different flange types cater to multiple needs and operate at variable pressures and temperatures. For example, threaded ones are better for low pressures, but you should go for lap joint flanges if you need connections with stub ends. These charts indicate the flange size based on the nominal pipe size and the diameter of the bolt circle. You can assess the diameter of the bolt hole and the inner diameter of the pipe within 1/8″ if you cannot find the exact flange.

How do I check my ANSI standards?

The American Society of Mechanical Engineers (ASME) first developed ANSI, or the American National Standard, for flanges and fittings. These standards cover ratings for pressure and temperature, dimensions, materials, and tolerance levels. The document also covers testing techniques for an Ansi flange. Here, the class depicts the pressure and temperature, like Class 150, 300, and 2500. You can check the corresponding standard from the stamp printed on the flange. Or, you can count the bolt holes if the stamping is unclear. Next, you have to find the diameter of the bolt circle. Once you have these two metrics, you can find the specification in the charts. You can get a list of the standards on the official portal. You can search by the title or the standard number.