Stainless Steel Flange

A flange is a mechanical device used to connect pipes, valves, pumps, and other equipment in a piping system. It allows for easy assembly, disassembly, inspection, and maintenance. Flanges are essential for creating secure, leak-proof connections.

The most common stainless steels are:

• 304/304L Stainless Steel 8-11% nickel, 18-20% Chromium
  This is a general purpose stainless steel that is suitable for outdoor use.
• 316/316L Stainless Steel 10-14% nickel, 16-18% Chromium, 2-3% Molybdenum.
  This has better corrosion ability specifically where chlorine is present.
• Duplex Stainless Steel. Known as A240 2205 or A182 F51
  4.5-6.5% nickel, 21-23% Chromium, 2.5-3.5% Molybdenum
  Used where extreme corrosion resistance is required such as in seawater.

These stainless steels require specific manufacturing techniques and heat treatment to achieve the corrosion resistance ability.

The material used to manufacture the flange is chosen specifically to cope with the fluid being transported and the environment.

Sizes and Specifications grades/shapes

• Available sizes (e.g., 1/2" to 24")
• Pressure ratings (e.g., 150#, 300#, 600#)
• Standards (e.g., ASME, DIN, JIS)
• Flange Type

• Oil and Gas – used where corrosive fluids are being transported for their process or to clean the lines
• Chemical Processing. Many processes are very corrosive and it is not uncommon to use stainless steel with a protective paint.
• Food and Beverage. Everything in food is done with stainless steel that does not contaminate the contents and resists the cleaning chemicals used
• Water Treatment. 2205 and 316 is used extensively in desalination plants and associated piping.

Stainless flanges are used when either the process demands it or the environment is corrosive or both. Sometimes stainless flanges are used because they look terrific such as in engine rooms in boats where everything is kept clean and shiny.

Stainless flanges are always more expensive than the carbon steel variant. It comes down to corrosion resistance and cost, and in some cases, presentation.

A stainless flange from A240 2205 or A182 F51.

Use 316 where more corrosion resistance is required and the extra cost is justified.

Stainless flanges are welded to the stainless pipe providing a corrosion resistant joint that can be bolted to a valve or more piping.

Pressure ratings of flanges are found in the standard applicable to the flange being used. Additional standards mostly include temperature derating charts so the capability of the flange to withstand pressure is documented as the temperature increases. Generally, the ranges are pressure dependent, so AS4087 PN 16 means 16 bar and ASME B16.5 300 lbs is indicative of the pressure withstood.

Yes, it is OK to bolt stainless steel flanges to carbon steel flanges.

Flange tables are produced to assist engineers in selecting the right flange. Always refer the selection of flanges to a qualified person.
Learn about flange standards

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