Before we delve into the different materials of flanges, it's important to understand the industry codes it meets. So what are ANSI flanges, AWWA flanges and ASME flanges, what is the difference between ANSI flanges and ASME flanges? And what are the common materials and special materials of flange? We will answer all these questions.
There are four industry standards that cover different flange types:
ANSI flanges, also known as ASME B16.5 flanges
ASME flanges, also known as ASME B16.47 flanges
ASME B16.1 flanges, also known as industry standard flanges
AWWA flanges
ASME B16.5 pipe flanges and flange fittings cover sizes from 1/2" nominal to 24" nominal. The standard covers flange pressures, temperatures, materials, tolerances, dimensions, testing, and marking. 150#, 300#, 600#, 900#, and 1500# pressure classes are included in ASME B16.5 for 10" nominal sizes and 2500# for 12" to 24" sizes.
The ASME B16.5 standard is limited to flanges made of cast or forged materials.
ANSI B16.5 class150 class 300 forged steel flange BL flange
ASME B16.47 covers large diameter steel flanges from 26" nominal to 60" nominal pipe sizes. there are two types of B16.47 flanges, Series A and Series B. Both have slightly different dimensions such as thickness, bolt circle diameter, and number of bolt holes. b16.47 covers pressure classes Class 75, 150, 300, 400, 600, and 900#. The standard covers flanges made from cast, forged, or plate (blind flanges only).
ASME B16.47 SER.B API 605 MSS SP 44
There are no national standards or governing bodies that control industry standard flanges. Industry standard flanges are sized and made of materials that have been "common" industry practice for many years. Note that industry standard flange dimensions and materials are contained in ASME B16.1, the standard for Class 25, 125 and 250 cast iron pipe flanges and flanged fittings. Industrial flanges are pressure rated in accordance with AWWA table 4 class E standards. Industrial standard flanges also match B16.5 flanges in sizes smaller than 24".
This standard covers slip-on flanges and blind flanges for waterworks service in nominal sizes 4" to 144" (100 mm to 3600 mm).
These are just one way of classification--we also differ them by other cretiria like DIN, JIS, and we'll show you that in our later articles.
This standard covers forged carbon steel pipe components used in pressure systems for ambient and higher temperature service. Flanges can be ordered in sizes specified by the buyer or to dimensional specifications such as ASME 16.5 and API 6A. Forgings manufactured to ASTM A105 are typically limited to a maximum weight of 10,000 lbs.
Specifications:
ASTM: A105
ASME: SA105, B16.5
NACE: MRO175
MSS: SP 44
Typical applications: Chemical and related industries, tanks, valves, various process pressure vessels and pipelines.
Type 316 is a molybdenum steel with improved resistance to pitting through solution treatment with chlorides and other halides. It also provides excellent tensile, creep and stress fracture strength at elevated temperatures. 316 type is available in low-carbon (316L) and high-carbon (316H) alloys.
Specifications:
ASTM: A312, A376, A358, A269, A249, A403, A182, A351, A479, A276
ASME: SA312, SA376, SA358, SA269, SA249, SA182, SA276, SA403, SA479, SA351
Typical applications: nuclear industry, chemical processing, rubber, plastic pulp/paper, pharmaceutical and textile industries, heat exchangers, condensers and evaporators
304 stainless steel is a low carbon version (max. 0.08%) of basic 18-8 (also known as 302). 302 type contains 18% chromium and 8% nickel. Due to the lower carbon content, Type 304 is slightly less strong than 302. Type 304 is used in welding applications because the low carbon allows some exposure in the 800° F - 1500° F carbide precipitation range without the need for post annealing operations. However, the severity of the corrosive environment may require annealing after welding or using 304L. Type 304L has a carbon content of 0.03% or less.
Specifications:
ASTM: A312, A376, A358, A269, A249, A403, A182, A351
ASME: SA312, SA376, SA358, SA269, SA249, SA403, SA182, SA351
Typical applications: sanitary systems, dairy and food processing, heat exchangers, evaporators, feedwater heaters.
The following are some special flange materials
A350 LF1, LF2 and LF3 are common low temperature carbon steel flanges available on the market.
350 LF2 is a carbon steel fitting material, very similar to A105, for general industrial applications that can withstand continuous use down to -46F. This material is supplied in standardized conditions and then Charpy V-notch tested at -50F. Unless otherwise noted, the term commonly used for "low temperature flanges" refers to A350 LF2 flanges.
ASTM Specification A694 covers carbon and alloy steel forgings for flanges, fittings, and other high-pressure transmission applications. The specification covers materials for use in high-pressure wellheads, pressure piping, and equipment manifolds.
High yield A694 flanges are available in F42, F46, F48, F50, F52, F56, F60, F65, F70. The last two digits indicate the yield strength in Ksi. High yield strength is critical in high pressure and high temperature applications.
A182 / SA182 specification covers forged low alloy and stainless steel flanges, valves and fittings.
Chromium-molybdenum is an abbreviation for chromium-molybdenum steel. It has high tensile strength and ductility, as well as good weldability. Chromium flanges are less corrosion resistant than common stainless steel flanges, but have a higher tensile strength and weight to strength ratio.
The most common chromium flanges are F5, F9, F11 Grade 2 (CL2) and F22 Grade 3 (CL3).
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