Steel Flange Dimensions Chart

What is a steel flange?

A steel flange is a steel annular disc-shaped component used to connect pipes, valves, and equipment. It is bolted and sealed to achieve a detachable connection of the pipeline system. It is a key component in industrial pipeline systems and is widely used in petroleum, chemical, electric power, shipbuilding and other fields.

Steel Flange Dimensions & Sizes:

The dimension & size of a steel flange depends on its flange type, pressure rating and applicable standards. The following are the typical size ranges of steel flanges under international general standards (ASME, EN, GB, etc.):

1. American Standard Flange (ASME B16.5 & B16.47)

Flange Type	Size Range (NPS)	Pressure Rating (Class)	Applicable Standards
Welding Flange (WN)	1/2" ~ 24"	150 ~ 2500	ASME B16.5
Socket Weld (SW)	1/2" ~ 4"	300 ~ 6000	ASME B16.5
Threaded Flange (THD)	1/2" ~ 12"	150 ~ 2500	ASME B16.5
Blind Flange (BL)	1/2" ~ 60"	150 ~ 2500	ASME B16.5/ASME B16.47
Large Diameter Flange	26" ~ 60"	75 ~ 900	ASME B16.47

Note:

NPS (Nominal Pipe Size): Nominal diameter expressed in inches (e.g. NPS 2" ≈ DN50).
Class: American standard pressure class (Class 150 ≈ PN20, Class 300 ≈ PN50).

2. European standard flange (EN 1092-1)

Flange type	Size range (DN)	Pressure class (PN)	Applicable standard
PL (slip-on flange)	DN10 ~ DN4000	PN6 ~ PN100	EN 1092-1
WN (butt-weld flange)	DN10 ~ DN2000	PN10 ~ PN400	EN 1092-1
SO (loose flange)	DN15 ~ DN600	PN6 ~ PN40	EN 1092-1
BL (blind flange)	DN15 ~ DN3000	PN6 ~ PN400	EN 1092-1

Note:

DN (nominal diameter): expressed in millimeters (e.g. DN100 ≈ NPS 4").
PN (nominal pressure): European standard pressure level (PN16 ≈ 16 bar).

3. Chinese standard flange (GB/T 9119 & HG/T 20592)

Flange type	Size range (DN)	Pressure level (PN)	Applicable standards
Slip-on flange (PL)	DN10 ~ DN2000	PN0.25 ~ PN10	GB/T 9119
Butt welding flange (WN)	DN10 ~ DN2000	PN10 ~ PN160	GB/T 9115
Socket welding (SW)	DN10 ~ DN80	PN10 ~ PN160	HG/T 20592
Threaded flange (TH)	DN8 ~ DN150	PN10 ~ PN63	GB/T 9114

Note:
Chinese standard flange is compatible with both American standard (Class) and European standard (PN) systems, for example, HG/T 20592 includes Class 150 ~ 2500 flanges.

4. Special flange size range

API 6A flange
Size range: 2-1/16" ~ 21-1/4"
Applicable standard: API 6A (wellhead equipment)

JIS flange
Size range: DN10 ~ DN1000
Applicable standard: JIS B2220

DIN flange
Size range: DN10 ~ DN4000
Applicable standard: DIN 2576/2633

American standard flanges (ASME B16.5 & B16.47):

The following mainly introduces the size specification table of American standard flanges (ASME B16.5 & B16.47), covering common flange types, pressure levels and key size parameters.

American standard flange standard classification:

ASME B16.5: pipe flanges and flange fittings
Pressure level (Class): 150, 300, 600, 900, 1500, 2500
Size range (NPS): ½" ~ 24"

ASME B16.47: large diameter flange (Series A/B)
Pressure level (Class): 75, 150, 300, 400, 600, 900
Size range (NPS): 26" ~ 60"

API 6A: high pressure flange for wellhead equipment
Pressure level (Class): 2000, 3000, 5000, 10000 psi

Size range (NPS): 2-1/16" ~ 21-1/4"

Steel Flange Dimensions & Sizes Chart:

ASME B16.47 Reducing Flange Dimension Chart:

ASME B16.47 B16.47 Series A（MSS SP-44）Reducing Flange Dimensions Chart:

ASME B16.47 Series B Reducing Flange Dimensions Chart:

How to choose flange size?

Material matching:
ASTM A105 (carbon steel) is suitable for conventional working conditions.
ASTM A182 F304/F316 (stainless steel) for corrosive media.

Matching pipe size: The DN/NPS of the flange must be consistent with the pipe.
Pressure level: Select PN/Class according to the system working pressure (e.g. PN16 ≈ Class 150).
Bolt specification: Class 300 flanges require ASTM A193 B7 bolts (high-strength alloy steel).
High temperature/high pressure correction: Class 150 flanges need to be derated above 200°C.

Flange type:
High pressure/high temperature → Butt welding flange (WN)
Low pressure/small diameter → Flat welding flange (PL)
Frequent disassembly → Loose flange (SO)

Conclusion:
Steel flanges have a wide range of sizes, from DN10 (NPS 1/8") to DN4000 (NPS 160"), covering almost all industrial pipeline needs. When selecting, factors such as standards, pressure, temperature, and media should be considered.

Read more: How to choose the appropriate pipe flange size? or How are pipe flanges manufactured?