Definition of ASME B16.5
ASME B16.5 is a standard recommended by the American Society of Mechanical Engineers. It is also a more authoritative and recommended standard, so it is widely used. It specifies in detail the dimensions, tolerances, markings, materials and other related requirements of pipe flanges and flanged fittings. The standard covers the use pressure, temperature and other parameters of ASTM standards. ASME B16.5 is an American standard for pipe flanges and flanged fittings, and is highly recognized worldwide.
According to the ASME B16.5 standard, steel flanges have 7 pressure levels: Class 150 - 300 - 400 - 600 - 900 - 1500 - 2500. The pressure level of the flange is very clear. For example, a Class 300 flange can withstand greater pressure than a Class 150 because a Class 300 flange needs to be made of more materials to withstand greater pressure. However, the pressure bearing capacity of the flange is affected by many factors. The pressure level of the flange is expressed in pounds, and there are different ways to express a pressure level. For example: 150Lb, 150Lbs, 150# and Class150 mean the same thing.
ASME B16.5 carbon steel flange types
Common ASME B16.5 carbon steel flange types include: butt welding flange, flat welding flange, socket flange, threaded flange, loose flange, blind flange;
Size range: DN15-DN600 (1/2IN-24IN) flanges follow the ASME B16.5 production standard, applicable pressure levels: Class150, 300, 400, 600, 900, 1500, 2500 and other 7 levels;
Specifically, the ASME B16.5 standard covers the following aspects:
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Category
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Description
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Dimensions & Tolerances
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Specifies key flange dimensions, including outside diameter, thickness, bolt hole size, bolt circle diameter, etc., along with permissible manufacturing tolerances.
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Materials
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Defines acceptable materials for flange manufacturing such as carbon steel, stainless steel, alloy steel, etc., and outlines required material properties like tensile strength.
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Facing Types
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Details the types of flange facings to ensure proper sealing between flanges:• RF (Raised Face)• FF (Flat Face)• MFM (Male-Female Face)• TG (Tongue and Groove)• RJ (Ring Joint)
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Pressure Classes
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Specifies various pressure ratings to suit different operating conditions: Class 150, 300, 400, 600, 900, 1500, and 2500.
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Markings
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Requires markings on the flange such as manufacturer name, size, pressure class, material grade, heat treatment status, and standard (e.g., B16.5) for identification and traceability.
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Other Requirements
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Includes manufacturing processes (e.g., forging, machining), heat treatment, and inspection methods (such as radiographic testing, dimensional checks, pressure testing) to ensure quality and reliability.
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Flange sealing surface type: raised face (RF), flat face (FF), concave and convex face (MFM), tongue and groove face (TG), ring joint face (RJ), etc. There are three common sealing surface types: RF, FF, and RTJ.
American standard flange ASME B16.5 implementation standard
Plate flat weld steel pipe flange Chemical Ministry standard:
HG20593-2009
HG20615-2009
National standard: GB/T9119-2010
GB/T2555-81
Mechanical Ministry standard: JB/T81-94
JB/T74-94
JB/T75-94
Marine standard:
Large flat weld flange
CB M1001-81
Using pressure PN0.25MPa, PN0.6MPa, PN1.0MPa, PN1.6MPa, PN2.5MPa, PN4.0MPa
Product category Flat plate flange (FF), raised plate flange (RF)
Making materials Stainless steel (
304, 316, etc.), carbon steel (20# 25#, etc.)
Pipe: Large outer diameter series (ANSI B36.10 and ANSI B36.19)
Nominal diameter range: (DN6~DN2000) mm
Wall thickness indication method:
1) The wall thickness is indicated by the pipe number "Sch";
2) The wall thickness is indicated by the pipe weight.
Pipe flange: American flange
Pressure level: CL 150 300 400 600 900 1500 2500 Psi 7 levels
Nominal diameter: DN15~600mm
Flange sealing surface: convex surface (RF), concave and convex surface (MF), tongue and groove surface (TG), metal ring connection surface 4 types
Flange type: flat welding type, socket welding type, butt welding type, threaded connection type, loose sleeve type and flange cover 6 types
American standard flange ASME B16.5 process
It is divided into pure material forging, rough material forging (secondary) suitable for flat welding and butt welding flanges, steel plates suitable for flat welding flanges, and centrifugal casting and casting flanges
Commonly used standards in the American Application Standards System ANSI are:
ANSI/ASME B36.10 Seamless and welded steel pipe
ANSI/ASME B36.19 Stainless steel seamless and welded steel pipe
ANSI/ASME B16.9 Factory-made steel butt-weld pipe fittings
ANSI/ASME B16.11 Socket-weld and threaded forged pipe fittings
ANSI/ASME B16.28 Steel butt-weld small radius elbows and return elbows
ASME/ANSI B16.34 Flanged, threaded and welded valves
ASME/ANSI B16.5 Pipe flanges and flanged fittings
ASME/ANSI B16.36 Orifice flanges
ASME/ANSI B16.42 Ductile iron flanges and flanged fittings
ASME/ANSI B16.47 Large diameter steel flanges
ASME/ANSI B16.20 Wrap-around, wrapped and grooved gaskets for pipe flanges
ASME/ANSI B16.21 Non-metallic flat gaskets for pipe flanges
ASME/ANSI B18.2.1 Square and hexagonal bolts and threads
ASME/ANSI B18.2.2 Square and hexagonal nuts
API std605 Large-diameter flanges and flange covers
API std526 Flange-connected steel pressure relief valves
API std598 Inspection and testing of valves
API std599 Flange-connected and welded metal plug valves.
API std600 Flange-connected and butt-welded steel gate valves
API std602 Small steel gate valves (compact gate valves)
API std603 150-pound corrosion-resistant flange valves
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