The most used flange types in Petro and chemical industry are:
- Blind pipe flanges
- Lap Joint Flanges
- Slip-On flanges
- Socket weld flanges
- Threaded Flanges
- Weld Neck Flanges
Spectacle flange
A Specialty flange is a component with a flanged joint that has the same bolting structure as a standard flange, but a specialty flange has its own characteristics.
Except the most used standard flanges, there are still a number of specialty flange such as:
- Anchor flange
- Expander Flange
- Large Diameter Flanges
- Long Neck Welding flange
- Nipo flange
- NW Long Weld Neck Flanges
- Orifice flanges
- Reducing Flanges
- Screwed Flanges
ASTM A350 Standard Specification
ASTM A350 is the Standard Specification for Carbon and Low-Alloy Steel Forgings, Requiring Notch Toughness Testing for Piping ComponentsASTM A105 Standard Specification
ASTM A105 is the Standard Specification for Carbon Steel Forgings for Piping ApplicationsPipe Flanges Raw Material Specifications
The usual materials of flanges include stainless steel, carbon steel, aluminum and plastic.
The choice of the material largely depends on the purpose of the flange. For example, stainless steel is more durable and is necessary for heavy use.
On the other hand, plastic is more feasible for use in the home because of its reasonable price and easy installation. The materials used for flanges are under the designation of the American Society of Mechanical Engineers.
Requirements are valid for normal situation, in special you have to contact us to introduce.
Stainless Steel Flange Raw Material Alloy Steel Flange Raw Material
Material | Test basis / Requirements | Delivery Condition |
---|---|---|
C 22.8 (1.0460) | DIN 17243: 01.87 + VdTUEV – WB 350/3: 2009 DIN 17243: 01.87 VdTÜV – WB 350/3: 2009 | +N |
P250GH (1.0460) | DIN EN 10222-2: 04.2000 National Annex | +N |
P245GH (1.0352) | EN 10222-2:1999-12 + AC : 2000-02 | +N |
A105N / C21 | ASTM A105/A105M-05/ ASME BPVC Sec.2 Part.A:04 + VdTUEV399/3: 1996-09 + NACE MR 0175: 2000 | +N |
A105N | ASTM A105/A105M-05/ ASME BPVC Sec.2 Part.A:04 + NACE MR 0175: 2000 | +N |
C21 (1.0432) | VdTUEV – WB 399/3: 1996-09 | +N |
RSt 37-2 (1.0038) | DIN 17100: 1980-01 | +N |
S235JR (1.0038) | DIN EN10025-2: 2005-04 | +N |
16Mo3 (1.5415) | DIN EN10222-2:1999-12 + AC:2000-02 | +N |
WStE355 / TStE355 (1.0565 / 1.0566) | DIN EN17103 :1989-10, + VdTUEV-WB 354/3 : 2001-06 | +N or QT |
P355NH (1.0565) | DIN EN10222-4: 1998 + A1: 2002-12 | +N |
WStE355 / P355NH (1.0565) | DIN EN17103 :1989-10, + VdTUEV-WB 354/3 : 2001-06 + DIN EN10222-4: 1998 + A1: 2002-12 + DIN EN17103 :1989-10 + DIN EN10222-4: 1998 + A1: 2002-12 | +N or QT |
1.4301 (X5CrNi17-10) | DIN EN10222-5: 2000-02 | +AT |
1.4306 (X2CrNi19-11) | DIN 17440:1996-09 | +AT |
1.4401 (X5CrNiMo17-12-2) | DIN EN10222-5: 2000-02 | +AT |
1.4404 (X2CrNiMo17-12-2) | DIN EN10222-5: 2000-02 | +AT |
1.4432 (X2CrNiMo17-12-3) | DIN EN10222-5: 2000-02 | +AT |
1.4541 (X6CrNiTi18-10) | DIN EN10222-5: 2000-02 | +AT |
1.4571 (X6CrNiMoTi17-12-2) | DIN EN10222-5: 2000-02 | +AT |
1.4541 / F321 | DIN EN10222-5: 2000-02 / +ASTM A 182/A 182M :2005 | +AT |
1.4571 / F316Ti | DIN EN10222-5: 2000-02 / +ASTM A 240 | +AT |
1.4404 / F316L | DIN EN10222-5: 2000-02 / +ASTM A 182/A 182M :2005 | +AT |
1.4306 / F304L | DIN 17440.1996-09 / +ASTM A 182/A 182M : 2005 | +AT |
1.4307 / F304L | DIN EN10222-5: 2000-02 / +ASTM A 182/A 182M :2005 | +AT |
Basic requirements for Material and Fitting
Material | Test basis / Requirements | Delivery Condition |
1.4541 (X6CrNiTi18-10) | DIN 17458:1996-09 | +AT |
1.4571 (X6CrNiMoTi17-12-2) | DIN 17458:1996-09 | +AT |
Flange | Test basis / Requirements |
DIN, Carbon Steel | DIN2519:1991-06 + AD2000-W9: 02.04; -W13/ TRD107;TRB100; + Directive 97/23/EG Annex I, Chap. 4.3: 1998-02 |
DIN, corrosion-resistant Steel | DIN2519:1991-06 + AD2000-W9: 02.04; -W2; -W10 / TRD107; TRB100; + Directive 97/23/EG Annex I, Chap. 4.3: 1998-02 |
DIN EN 1092-1, Carbon Steel | DIN EN 1092-1: 2008-09 + AD2000-W9; -W13/TRD107;TRB100 + Directive 97/23/EG Annex I, Chap. 4.3: 1998-02 |
DIN EN 1092-1, Stainless Steel | DIN EN 1092-1: 2008-09 + AD2000-W9; -W2; -W10/ TRD107; TRB100 + Directive 97/23/EG Annex I, Chap. 4.3: 1998-02 |
ANSI | ASME B16.5:2003 ASME B16.47:2006 |
Fittings | Test basis / Requirements |
---|---|
DIN2609 Stainless Steel | VdTUEV –MB 1252/ AD2000- W2; W10/TRD107;TRB100 |
T-Piece | Directive 97/23/EG Annex I, Chap. 4.3:1998-02 |
Bow | DIN2615-1 |
Reducer | DIN2605-1 DIN2616-1 |
Requirements are valid for normal case, in special case you have to contact the technical department.
- DIN flanges
- AWWA Standard flange
- Alloy steel flanges
- Carbon steel flanges
- Forged steel flanges
- Stainless Steel Flanges
Flange Tolerance
Sunny Steel is one of the oldest manufacturers, dealer, distributor, stockist & suppliers of Blind Flanges, Reducing Threaded Flanges, Lap Joint Flanges, Flange Gaskets, Threaded Flanges, Socketweld Flanges, Flanges Bolts, Ring Flange, Spectacle Blind Flanges, Weld Neck Flanges, Orifice Flange, Slip-On-Flanges, High Hub Blinds Flanges, which are manufactured using superior grade of steel like SS Flanges / Stainless Steel Flange, 310 Flanges, 321 Flanges, 202 Flanges, 347 Flanges, 304 Flange, 316 Flanges, 316L Flanges.,
These Flanges are most durable and manufactures to fit in different size of Pipes.

Our company offers a wide range of flanges like PL, SW, BL, WN,SO,LJ, ASME/ANSI B16.5 etc., which is precisely engineered in tolerance of welding neck flanges.

Outside Diameter | When O.D. is 24″ or less | ±1.6mm﹡ |
Inside Diameter | 10″ and smaller | ±0.8mm |
12″ thru 18″ | ±1.6mm | |
20″ and larger | +3.2mm, -1.6mm | |
Outside Diameter of hub | 5″ and smaller | +2.4mm, -0.8mm﹡ |
6″ and larger | +4.0mm, -0.8mm | |
Diameter of contact face | 1/16″ rasied face tongue and groove male, female | ±0.8mm |
1/4″ rasied face tongue and groove male, female | ±0.4mm | |
Diameter of hub at base | when hub base is 24″ or smaller | ±1.6mm﹡ |
Diameter of hub at point of welding | 5″ and smaller | +2.4mm, -0.8mm |
6″ and larger | +4.0mm, -0.8mm | |
Drilling | Bolt circle | ±1.6mm |
Bolt hole spacing | ±0.8mm | |
Eccentricity of bolt circle with respect to facing | 2 1/2″ and smaller: 0.8mm, max﹡ | |
Eccentricity of bolt circle with respect to bore | 3″ and larger: 1.6mm, max﹡ | |
Thickness | 18″ and smaller | +3.2mm, -0mm |
20″ and larger | +4.8mm, -0mm | |
Length of thru hub | 10″ and smaller | ±1.6mm |
12″ and larger | ±3.2mm |
Tolerance of Threaded Flanges, Socket Welding Flanges, Slip-On Flanges
Lap Joint Flanges and Blind Flanges
Outside Diameter | When O.D. is 24″ or less | ±1.6mm﹡ |
Inside Diameter | Threaded | Within limits on boring gauge |
Socket welding, Slip-on and Lap joint, 10″ and smaller | +0.8mm, -0mm | |
Socket welding, Slip-on and Lap joint, 12″ and larger | +1.6mm, -0mm | |
Outside Diameter of hub | 5″ and smaller | +2.4mm, -0.8mm﹡ |
6″ and larger | +4.0mm, -0.8mm | |
Diameter of contact face | 1/16″ rasied face tongue and groove male, female | ±0.8mm |
1/4″ rasied face tongue and groove male, female | ±0.4mm | |
Diameter of counterbore | same as for inside diameter | |
Drilling | Bolt circle | ±1.6mm |
Bolt hole spacing | ±0.8mm | |
Eccentricity of bolt circle with respect to facing | 2 1/2″ and smaller: 0.8mm, max﹡ | |
Eccentricity of bolt circle with respect to bore | 3″ and larger: 1.6mm, max﹡ | |
Thickness | 18″ and smaller | +3.2mm, -0mm |
20″ and larger | +4.8mm, -0mm | |
Length of thru hub | 10″ and smaller | ±1.6mm |
12″ and larger | ±3.2mm |
Dimensional tolerances for AWWA pipe flanges
Listed below are the Dimensional Tolerances to which flanges are manufactured.
Ring type Slip-on and Blind flanges | HUB type slip-on | ||||
O.D. | <=24" | +/- 0.6"(1.6mm) | O.D. | <=24" | +/- 0.6"(1.6mm) |
>24" | +/- .12"(3.2mm) | >24" | +/- .12"(3.2mm) | ||
I.D. | Socket-Welding | 10" and Samller +.03"(0.8mm),-0" |
I.D. | 10" and Samller | +.03"(0.8mm) |
Slip-on and Lap Joint |
12" and Larger +.06"(1.6mm),-0" |
12"-18" | +/-.06"(1.6mm) | ||
20"-42" | +.12"(3.2mm) +.06"(1.6mm) |
||||
O.D. of Hub | <=12" | +.09"(2.4mm), -.06"(1.6mm) |
Diameter of Contact Face |
0.06" Raised Face | +/-.03"(0.8mm) |
14"-42" | +/-.12"(3.2mm) | ||||
Diameter of Contact face | 0.06" Raised Face | +/- .03"(0.8mm) | Diameter of Hub at base | X<=24" | +/-.06"(1.6mm) |
X>24" | +/-.12"(3.2mm) | ||||
Deameter of Contact face | <=10" | +.03"(0.8mm), -0" |
Diameter of Hub at point of Welding | <=5" | +.09"(2.4mm), -.03"(0.8mm) |
12"-42" | +.06"(1.6mm), -0" |
>=6" | +.16"(4.0mm), -.03"(0.8mm) |
||
Drilling | Bolt Circle | 1/2"-24" /26"-42" |
Drilling | Bolt Circle | 1/2"-24" /26"-42" |
+/-.06"(1.6mm) +/-.06" |
+/-.06"(1.6mm) +/-.06" |
||||
Bolt hole spacing |
+/-.03"(0.8mm) |
Bolt hole spacing |
+/-.03"(0.8mm) | ||
Eccentricity of Bolt circle with respect to bore | .03" Max. (0.8mm) |
Eccentricity of Bolt circle with respect to bore | .03" Max. (0.8mm) |
||
Thickness | 18"& Small | +.12"(3.2mm),-0" | Thickness | 18"& Small | +.12"(3.2mm),-0" |
20"-42" | +.19"(1.6mm) | 20"-42" | +.19"(1.6mm) | ||
Length Thru Hub | <=10" | +/-.06"(1.6mm) | Length Thru Hub | <=10" | +/-.06"(1.6mm) |
12"-42" | +/1.12"(3.2mm) | 12"-42" | +/1.12"(3.2mm) |
These tolerances are a part of ANSI B16.5 and AWWA C207-01 Sec. 4.2 except where noted otherwise.
The limits given are maximum. Rigid inspection procedure assures the maintenance of high standards of accuracy in regular day to day production.

Dimensional tolerances for AWWA pipe flanges
Ring type Slip-on and Blind flanges | HUB type slip-on | ||||
O.D. | <=24" | +/- 0.6"(1.6mm) | O.D. | <=24" | +/- 0.6"(1.6mm) |
>24" | +/- .12"(3.2mm) | >24" | +/- .12"(3.2mm) | ||
I.D. | Socket-Welding | 10" and Samller +.03"(0.8mm),-0" |
I.D. | 10" and Samller | +.03"(0.8mm) |
Slip-on and Lap Joint |
12" and Larger +.06"(1.6mm),-0" |
12"-18" | +/-.06"(1.6mm) | ||
20"-42" | +.12"(3.2mm) +.06"(1.6mm) |
||||
O.D. of Hub | <=12" | +.09"(2.4mm), -.06"(1.6mm) |
Diameter of Contact Face |
0.06" Raised Face | +/-.03"(0.8mm) |
14"-42" | +/-.12"(3.2mm) | ||||
Diameter of Contact face | 0.06" Raised Face | +/- .03"(0.8mm) | Diameter of Hub at base | X<=24" | +/-.06"(1.6mm) |
X>24" | +/-.12"(3.2mm) | ||||
Deameter of Contact face | <=10" | +.03"(0.8mm), -0" |
Diameter of Hub at point of Welding | <=5" | +.09"(2.4mm), -.03"(0.8mm) |
12"-42" | +.06"(1.6mm), -0" |
>=6" | +.16"(4.0mm), -.03"(0.8mm) |
||
Drilling | Bolt Circle | 1/2"-24" /26"-42" |
Drilling | Bolt Circle | 1/2"-24" /26"-42" |
+/-.06"(1.6mm) +/-.06" |
+/-.06"(1.6mm) +/-.06" |
||||
Bolt hole spacing |
+/-.03"(0.8mm) |
Bolt hole spacing |
+/-.03"(0.8mm) | ||
Eccentricity of Bolt circle with respect to bore | .03" Max. (0.8mm) |
Eccentricity of Bolt circle with respect to bore | .03" Max. (0.8mm) |
||
Thickness | 18"& Small | +.12"(3.2mm),-0" | Thickness | 18"& Small | +.12"(3.2mm),-0" |
20"-42" | +.19"(1.6mm) | 20"-42" | +.19"(1.6mm) | ||
Length Thru Hub | <=10" | +/-.06"(1.6mm) | Length Thru Hub | <=10" | +/-.06"(1.6mm) |
12"-42" | +/1.12"(3.2mm) | 12"-42" | +/1.12"(3.2mm) |
These tolerances are a part of ANSI B16.5 and AWWA C207-01 Sec. 4.2 except where noted otherwise. The limits given are maximum. Rigid inspection procedure assures the maintenance of high standards of accuracy in regular day to day production.
Industry Specification for Pipe Flange
Before we dive in to the different types of flange, it is important to understand the industry specification it conforms to. So what is ANSI Flange, AWWA Flange and ASME Flange? What is the difference between ANSI Flange and ASME Flange? What is the difference between Series A and Series B Flange. We will answer all these questions.
There are four types of industry standards covering different flange types;
- ANSI Flange, also called ASME B16.5 Flange
- ASME Flange, also called ASME B16.47 Flange (Series A and Series B)
- Industry Standard Flange (ASME B16.1 Flange)
- AWWA Flange
ANSI 16.5 / ASME B16.5 Flange Specification
ASME B16.5 pipe flange and flanged fittings cover sizes from 1/2″ nominal to 24″ nominal. The standard covers pressure, temperature, material, tolerance, dimension, testing and marking of flange. The pressure classed included in ASME B16.5 are 150#, 300#, 600#, 900# and 1500# for sizes up to 10″ nominal and 2500# for sizes 12″ through 24″.
ASME B16.5 standard is limited to flanges made from cast or forged material.
ASME B16.47 Series A and Series B Flange Specification
ASME B16.47 covers large diameter steel flanges from 26″ nominal to 60″ nominal pipe sizes. There are two types of B16.47 flanes, Series A and Series B. Both have slightly different dimensions such as thickness, bolt circle diameter and number of bolt holes. Pressure class covered by B16.47 is Class 75, 150, 300, 400, 600 and 900#. Standard covers flanges made of cast, forged or plate material (for blind flange only).
What is the difference between ASME B16.47 Series A and Series B (API605) flanges?
ASME B16.5 standard covers Steel Pipe Flanges and Flanged Fittings from NPS 1/2 through NPS 24 Metric/Inch in pressure class 150 to class 2500. It covers pressure-temperature ratings, materials, dimensions, tolerances, marking, testing, and methods of designating openings for pipe flanges and flanged fittings. Two very important flanges such as weld neck flange and blind flanges are very commonly used in piping systems. The term “B16.5” or “B16 5” is used interchangeability and refers to same standard. However, the standard ASME B16 5 (ANSI B16 5) only covers size up to 24 inches. For bigger sizes, ASME B16.47 standard covers pressure-temperature ratings, materials, dimensions, tolerances, marking, and testing for pipe flanges in sizes NPS 26 through NPS 60 and in ratings Classes 75, 150, 300, 400, 600, and 900.
However, the standard ASME B16.47 is further divided into ASME B16.47 series A and ASME B16.47 series B flange for Blind flange and Weldneck flange. Series B flange was also formerly known as API 605 flange. Term B16.47 or B 16 47 or ANSI B 16 47 are all used interchangeabily and refers to the same standard.
The ASME B16.47 standard incorporate MSS SP-44: Steel Pipe Flanges and API 605: Large Diameter Flanges for Carbon Steel. Hence MSS SP44 flanges are equivalent to Series A flange where as API 605 flanges are equivalent to Series B flange. Materials covered in this standard are as that in ASME / ANSI B16.5 except for nickel alloys. They also share the same pressure temperature rating as B16.5 flanges.
So what is the difference between ASME B16.47 Series A and Series B (API605) flanges?
ASME B16 47 Series A flanges are much thicker, heavier and stronger than Series B flanges for the same pressure ans size. Series A flange can withstand more external loading than Series B flange. ASME B16.47 Series B flanges need smaller fasteners, in larger quantity, than Series A flanges. They also have a smaller bolt circle diameter than that of Series A flanges. The smaller bolt circle diameter results in less flange movement after installation. Both Series A and Series B standards define weld neck flanges and blind flanges in raised face type (RF) but only Series A defines ring type joint (RTJ) flanges from Class 300 through Class 900 within this standard. Price wise, ASME B16.47 Series A flanges are more expensive than ASME B16 47 Series B flanges.
Most piping users or designers may choose Series A flanges for the new pipeline or equipment. But if you are doing some refurbishment, replacement job or non-critical piping design, Series B flanges are more popular.
See documents below for comparison of flange sizes in two main standards (B16.5 and B16.47)
Flange Dimensions as per ASME B 16 5 standard for 150# Welding Neck Flange, Blind Flange, Slipon, Socketweld & Lapjoint flange is here
Flange Dimensions as per ASME B16 47 series A standard for 150# weldneck and blind flange is here
Flange Dimensions as per ASME B 16.47 series B standard for 150# weld neck and blind flange is here
Conclusions: Standard weld neck, slip on, blind etc. flanges are covered by standard B16.5 for sizes up to 24″ nominal pipe. Sizes 26″ and bigger are covered by B16.47 series A or series B for weldneck and blind flanges. Series A flange is heavier, thicker and cost more whereas series B flange has more bolt holes and is lighter cheaper than series A. API605 flange and series B flanges are same thing.
Industry Standard Flange (ASME B16.1 Flange)
No national standard or governing body controls the Industry Standard Flange. The dimension and material of Industry Standard Flange has been adopted after years of “common” industry practice. It is important to note that size and material of industry standard flange are covered by standard ASME B16.1 whic his a standard for Class 25, 125 and 250 Cast Iron Pipe Flange and Flanged Fittings. Pressure rating of industry flange matches the AWWA table 4 class E standard. In sizes smaller than 24″, Industry Standard Flange also matches B16.5 flanges.
AWWA Flange
This standard covers slip-on and blind flanges for waterworks service in sizes 4″ through 144″ nominal (100mm through 3600 mm).
Difference between ANSI and AWWA flange
We have already covered that ANSI flange means ASME B16.5 flange. ANSI and AWWA standard for flanges differ in several ways. The AWWA standard is intended for potable water use. Where as ANSI/ASME standard is aimed at industrial application. AWWA flange rating are applicable only at atmospheric temperature whereas ANSI rating covers from -20°F to 1500°F.
The two standards also differ in the scope of application. ANSI standard includes information for welding auxiliar connections while AWWA does not cover the installations. The AWWA standard only covers hub-type, ring, blind and threaded flange whereas ANSI standard has more types such as weld neck, lap joint, socket weld flange etc.
Standards covering AWWA and ANSI flanges are;
- ANSI/AWWA C115/A21.15-99: “American National Standard for Flanged Ductile-Iron Pipe with Ductile-Iron or Gray-Iron Threaded Flanges”
- ANSI/AWWA C207-94: “AWWA Standard for Steel Pipe Flanges for Waterworks Service-Sizes 4 In. Through 144 In.”
- ANSI / ASME B16.5-1981: “Pipe Flanges and Flanged Fittings”.

Flange gasket
A flange gasket is a type of gasket made to fit between two sections of pipe that are flared to provide higher surface area.
Flange gaskets are used to create a static seal between two flanges faces, at various operating conditions, with varied pressure and temperature ratings. A gaskets fills the microscopic spaces and irregularities of the flange faces, and then it forms a seal that is designed to keep liquids and gases. Correct installation of damage-free gaskets and demage-free flange faces is a requirement for a leak-free flange connection.
Steel pipe flange gaskets are used to create seal between two flange faces. The flange face acts at the seal seat and the flange gasket compresses between two flanges, with the bolt compression, to fill all irregularities in the flange face and create a seal. The gasket is selected based on the operating condition such as pressure, temperature and chemical exposure.

Gaskets are available in following three types;
- Full Face Gasket: covers the full face of the flange. Generally used on flat face flanges
- Flat ring Gasket: covers only the sealing surface or the raised face of the flange.
- Metallic Ring Gakset: designed to be fitted in RTJ Flanges.

Gasket, Flange gasket, Bolts for Flange Connections
Flange connection is to two pipes, fittings or equipment before each fixed at a flange on the flange between the two, together with flange pad, fastened together with bolts to complete the connection.
Some of pipe fittings and equipment have been built-flange, also falls within the flange connection. Has flanged pipe and fittings, also belongs to the flange. Flange connections are an important connection for pipeline construction. Flange connections easy to use, able to withstand greater pressure.
Sub-threaded flange connection (wiretapping) flange and welding flange. Low-pressure small-diameter wire access flange, high pressure and low pressure are the use of large-diameter welded flange, different pressure, flange thickness and bolt diameter and the number of connections are different.
Within the family, pipe diameter, and are low-voltage, see flange connection. If produced in a boiler room or scene is full of flanged pipes and fittings.
As iron welded flange, a lot of customers have doubts is the quality is better than the forging of iron welding flange welding flange. Actually iron welding flange of quality and forged of welding flange of quality is as of, but iron welding flange what place cannot has guarantees does, is iron welding flange of material most no guarantees has, because General of process among, iron welding flange of density is no problem of, but in for production of process among, iron welding flange of rough rarely for detection, so for, by production out yahoo, not after detection of iron welding flange of material cannot guarantee.
The different grades based on the pressure, flange pad also has a variety of materials, from the low-pressure asbestos pad, high-pressure pads to the metal pads are asbestos.
Within the family, pipe diameter is small, but also ow-voltage, see flange connection. If a boiler room or a production site, full of flanged pipes and equipment. Flange connection is to two pipes, fittings or equipment before each fixed at a flange on the flange between the two, together with flange pad, fastened together with bolts to complete the connection. Some of pipe fittings and equipment have been built-flange, also falls within the flange connection.
How to select the gasket for Flange Connections?
One of the best all-around seals, the spiral wound gasket offers a low-cost solution that has the ability to handle temperature and pressure fluctuations. Multiple plies of metal and filler in the spiral create a barrier that reduces the possibility of leaks.

Temperature and Chemical Considerations
Be certain that the gasket you order is as resistant as possible to the media and temperature involved. Check the chemical compatibility of the metal as well as the filler material for the media to be sealed. As a general rule, the metal used in either the spiral winding or double-jacketed gasket should be similar to the flange material.
The compressibility of flexible graphite makes it an excellent filler material for metallic gaskets. Flexible graphite may be used in services with temperatures up to 950ºF (485ºC), though it should not be used with strong oxidizers such as nitric or sulfuric acid.
PTFE filler material provides excellent chemical resistance at temperatures below 500ºF (260ºC). In accordance with ASME B16.20, an inner ring is required when using conventional PTFE filler materials, in order to protect the winding from radial buckling.
Pressure Classes of Flanges
The Pressure Class or Rating for flanges will be given in pounds. Different names are used to indicate a Pressure Class.
Forged steel flanges, according to ASME B16.5, are made in seven primary Pressure Classes:
150 300 400 600 900 1500 2500
The concept of flange ratings likes clearly. A Class 300 flange can handle more pressure than a Class 150 flange, because a Class 300 flange are constructed with more metal and can withstand more pressure. However, there are a number of factors that can impact the pressure capability of a flange.
The Pressure Class or Rating for flanges will be given in pounds. Different names are used to indicate a Pressure Class.
For example: 150 Lb or 150 Lbs or 150# or Class 150, all are means the same.
The concept of flange ratings likes clearly. A Class 300 flange can handle more pressure than a Class 150 flange, because a Class 300 flange are constructed with more metal and can withstand more pressure. However, there are a number of factors that can impact the pressure capability of a flange.
The Pressure Class or Rating for flanges will be given in pounds. Different names are used to indicate a Pressure Class.
For example: 150 Lb or 150 Lbs or 150# or Class 150, all are means the same.
Example of Pressure Rating
Flanges can withstand different pressures at different temperatures. As temperature increases, the pressure rating of the flange decreases. For example, a Class 150 flange is rated to approximately 270 PSIG at ambient conditions, 180 PSIG at approximately 400°F, 150 PSIG at approximately 600°F, and 75 PSIG at approximately 800°F.
In other words, when the pressure goes down, the temperature goes up and vice versa. Additional factors are that flanges can be constructed from different materials, such as stainless steel, cast and ductile iron, carbon steel etc.. Each material have different pressure ratings.
Below an example of a flange NPS 12 with the several pressure classes. As you can see, inner diameter and diameter of the raised face at all the same; but outside diameter, bolt circle and diameter of bolt holes become larger in each higher pressure class.
The number and diameters (mm) of the bolt holes are:
CL 150 – 12 x 25.4 CL 300 – 16 x 28.6 CL 400 – 16 x 34.9 CL 600 – 20 x 34.9
CL 900 – 20 x 38.1 CL 1500 – 16 x 54 CL 2500 – 12 x 73

Pressure-temperature ratings are maximum allowable working gage pressures in bar units at the temperatures in degrees celsius. For intermediate temperatures, linear interpolation is permitted. Interpolation between class designations is not permitted.
Pressure-temperature ratings apply to flanged joints that conform to the limitations on bolting and on gaskets, which are made up in accordance with good practice for alignment and assembly. Use of these ratings for flanged joints not conforming to these limitations is the responsibility of the user.
The temperature shown for a corresponding pressure rating is the temperature of the pressure-containing shell of the component. In general, this temperature is the same as that of the contained fluid. Use of a pressure rating corresponding to a temperature other than that of the contained fluid is the responsibility of the user, subject to the requirements of applicable codes and regulations. For any temperature below -29°C, the rating shall be no greater than the rating shown for -29°C.
ASTM GROUP 2-1.1 MATERIALS
Nominal Designation | Forgings | Castings | Plates |
C-Si | A105(1) | A216 Gr.WCB (1) | A515 Gr.70 (1) |
C Mn Si | A350 Gr.LF2 (1) | … | A516 Gr.70 (1), (2) |
C Mn Si V | A350 Gr.LF6 Cl 1 (3) | … | A537 Cl.1 (4) |
3.1/2Ni | A350 Gr.LF3 | … | … |
Notes:
- (1) Upon prolonged exposure to temperatures above 425°C, the carbide phase of steel may be converted to graphite. Permissible but not recommended for prolonged use above 425°C.
- (2) Do not use over 455°C.
- (3) Do not use over 260°C.
- (4) Do not use over 370°C.
ASTM GROUP 2-2.3 MATERIALS
Nominal Designation | Forgings | Cast | Plates |
16Cr 12Ni 2Mo | A182 Gr.F316L | … | A240 Gr.316L |
18Cr 13Ni 3Mo | A182 Gr.F317L | … | … |
18Cr 8Ni | A182 Gr.F304L (1) | … | A240 Gr.304L (1) |
Note: Do not use over 425°C.
PRESSURE-TEMPERATURE RATINGS FOR ASTM GROUP 2-1.1 MATERIALS
Working pressure by Classes, BAR
TEMP(°C) | 150 | 300 | 400 | 600 | 900 | 1500 | 2500 |
-29 TO 38 | 19.6 | 51.1 | 68.1 | 102.1 | 153.2 | 255.3 | 425.5 |
50 | 19.2 | 50.1 | 66.8 | 100.2 | 150.4 | 250.6 | 417.7 |
100 | 17.7 | 46.6 | 62.1 | 93.2 | 139.8 | 233 | 388.3 |
150 | 15.8 | 45.1 | 60.1 | 90.2 | 135.2 | 225.4 | 375.6 |
200 | 13.8 | 43.8 | 58.4 | 87.6 | 131.4 | 219 | 365 |
250 | 12.1 | 41.9 | 55.9 | 83.9 | 125.8 | 209.7 | 349.5 |
300 | 10.2 | 39.8 | 53.1 | 79.6 | 119.5 | 199.1 | 331.8 |
325 | 9.3 | 38.7 | 51.6 | 77.4 | 116.1 | 193.6 | 322.6 |
350 | 8.4 | 37.6 | 50.1 | 75.1 | 112.7 | 187.8 | 313 |
375 | 7.4 | 36.4 | 48.5 | 72.7 | 109.1 | 181.8 | 303.1 |
400 | 6.5 | 34.7 | 46.3 | 69.4 | 104.2 | 173.6 | 289.3 |
425 | 5.5 | 28.8 | 38.4 | 57.5 | 86.3 | 143.8 | 239.7 |
450 | 4.6 | 23 | 30.7 | 46 | 69 | 115 | 191.7 |
475 | 3.7 | 17.4 | 23.2 | 34.9 | 52.3 | 87.2 | 145.3 |
500 | 2.8 | 11.8 | 15.7 | 23.5 | 35.3 | 58.8 | 97.9 |
538 | 1.4 | 5.9 | 7.9 | 11.8 | 17.7 | 29.5 | 49.2 |
TEMP (°C) | 150 | 300 | 400 | 600 | 900 | 1500 | 2500 |
PRESSURE-TEMPERATURE RATINGS FOR ASTM GROUP 2-2.3 MATERIALS
Working pressure by Classes, BAR
TEMP(°C) | 150 | 300 | 400 | 600 | 900 | 1500 | 2500 |
-29 TO 38 | 15.9 | 41.4 | 55.2 | 82.7 | 124.1 | 206.8 | 344.7 |
50 | 15.3 | 40 | 53.4 | 80 | 120.1 | 200.1 | 333.5 |
100 | 13.3 | 34.8 | 46.4 | 69.6 | 104.4 | 173.9 | 289.9 |
150 | 12 | 31.4 | 41.9 | 62.8 | 94.2 | 157 | 261.6 |
200 | 11.2 | 29.2 | 38.9 | 58.3 | 87.5 | 145.8 | 243 |
250 | 10.5 | 27.5 | 36.6 | 54.9 | 82.4 | 137.3 | 228.9 |
300 | 10 | 26.1 | 34.8 | 52.1 | 78.2 | 130.3 | 217.2 |
325 | 9.3 | 25.5 | 34 | 51 | 76.4 | 127.4 | 212.3 |
350 | 8.4 | 25.1 | 33.4 | 50.1 | 75.2 | 125.4 | 208.9 |
375 | 7.4 | 24.8 | 33 | 49.5 | 74.3 | 123.8 | 206.3 |
400 | 6.5 | 24.3 | 32.4 | 48.6 | 72.9 | 121.5 | 202.5 |
425 | 5.5 | 23.9 | 31.8 | 47.7 | 71.6 | 119.3 | 198.8 |
450 | 4.6 | 23.4 | 31.2 | 46.8 | 70.2 | 117.1 | 195.1 |
TEMP(°C) | 150 | 300 | 400 | 600 | 900 | 1500 | 2500 |
As an example, below you will find two tables with material groups acc. to ASTM, and two other tables
with flange pressure-temperature ratings for those ASTM materials acc. to ASME B16.5.
Requirements are valid for normal situation, in special you have to contact us to introduce.
Flange facing types according to DIN EN 1092-1
Flanges and their joints – Circular flanges for pipes, valves, fittings and accessories, PN designated – Part 1: Steel flanges
This European standard specifies requirements for circular steel flanges in PN designations PN 2,5 to PN 400 and nominal sizes from DN 10 to DN 4000. This standard specifies the flange types and their facings, dimensions, tolerances, threading, bolt sizes, flange face surface finish, marking, materials, pressure/ temperature ratings and flange masses.
Flange faces have to be smooth enough to ensure a tight, leak-free seal for bolted flanges.
Type A: flat face
Type B: raised face
Type C: tongue face
Type D: groove face
Type E: spigot
Type F: recess
Type G: O Ring recess
Type H: O Ring groove

Flange facing dimensions (units [mm])
DN | PN | f1 | f2 | f3 | f4 | w | x | y | z | α | R | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
2.5 | 6 | 10 | 16 | 25 | 40 | 63 | 100 | 160 | 250 | 320 | 400 | |||||||||||
d1 | ||||||||||||||||||||||
10 | 35 | 35 | 40 | 40 | 40 | 40 | 40 | 40 | 40 | 40 | 40 | 40 | 2 | 4.5 | 4 | 2 | 24 | 34 | 35 | 23 | – | 2.5 |
15 | 40 | 40 | 45 | 45 | 45 | 45 | 45 | 45 | 45 | 45 | 45 | 45 | 29 | 39 | 40 | 28 | – | |||||
20 | 50 | 50 | 58 | 58 | 58 | 58 | 58 | 58 | 58 | 58 | 58 | 58 | 36 | 50 | 51 | 35 | 41º | |||||
25 | 60 | 60 | 68 | 68 | 68 | 68 | 68 | 68 | 68 | 68 | 68 | 68 | 43 | 57 | 58 | 42 | ||||||
32 | 70 | 70 | 78 | 78 | 78 | 78 | 78 | 78 | 78 | 78 | 78 | 78 | 51 | 65 | 66 | 50 | ||||||
40 | 80 | 80 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 88 | 3 | 61 | 75 | 76 | 60 | |||||
50 | 90 | 90 | 102 | 102 | 102 | 102 | 102 | 102 | 102 | 102 | 102 | 102 | 73 | 87 | 88 | 72 | ||||||
65 | 110 | 110 | 122 | 122 | 122 | 122 | 122 | 122 | 122 | 122 | 122 | 122 | 95 | 109 | 110 | 94 | ||||||
80 | 128 | 128 | 138 | 138 | 138 | 138 | 138 | 138 | 138 | 138 | 138 | 138 | 106 | 120 | 121 | 105 | ||||||
100 | 148 | 148 | 158 | 158 | 162 | 162 | 162 | 162 | 162 | 162 | 162 | 162 | 5 | 4.5 | 2.5 | 129 | 149 | 150 | 128 | 32º | 3 | |
125 | 178 | 178 | 188 | 188 | 188 | 188 | 188 | 188 | 188 | 188 | 188 | 188 | 155 | 175 | 176 | 154 | ||||||
150 | 202 | 202 | 212 | 212 | 218 | 218 | 218 | 218 | 218 | 218 | 218 | 218 | 183 | 203 | 204 | 182 | ||||||
200 | 258 | 258 | 268 | 268 | 278 | 285 | 285 | 285 | 285 | 285 | 285 | 285 | 239 | 259 | 260 | 238 | ||||||
250 | 312 | 312 | 320 | 320 | 335 | 345 | 345 | 345 | 345 | 345 | 345 | – | 292 | 312 | 313 | 291 | ||||||
300 | 365 | 365 | 370 | 378 | 395 | 410 | 410 | 410 | 410 | – | – | – | 4 | 343 | 363 | 364 | 342 | |||||
350 | 415 | 415 | 430 | 438 | 450 | 465 | 465 | 465 | – | – | – | – | 5.5 | 5 | 3 | 395 | 421 | 422 | 394 | 27º | 3.5 | |
400 | 465 | 465 | 482 | 490 | 505 | 535 | 535 | 535 | – | – | – | – | 447 | 473 | 474 | 446 | ||||||
450 | 520 | 520 | 532 | 550 | 555 | 560 | 560 | 560 | – | – | – | – | 497 | 523 | 524 | 496 | ||||||
500 | 570 | 570 | 585 | 610 | 615 | 615 | 615 | 615 | – | – | – | – | 349 | 375 | 376 | 548 | ||||||
600 | 670 | 670 | 685 | 725 | 720 | 735 | 735 | – | – | – | – | – | 5 | 649 | 675 | 676 | 648 | |||||
700 | 775 | 775 | 800 | 795 | 820 | 840 | 840 | – | – | – | – | – | 751 | 777 | 778 | 750 | ||||||
800 | 880 | 880 | 905 | 900 | 930 | 960 | 960 | – | – | – | – | – | 856 | 882 | 883 | 855 | ||||||
900 | 980 | 980 | 1005 | 1000 | 1030 | 1070 | 1070 | – | – | – | – | – | 961 | 987 | 988 | 960 | ||||||
1000 | 1080 | 1080 | 1110 | 115 | 1140 | 1180 | 1180 | – | – | – | – | – | 6.5 | 6 | 4 | 1062 | 1092 | 1094 | 1060 | 28º | 4 | |
1200 | 1280 | 1295 | 1330 | 1330 | 1350 | 1380 | 1380 | – | – | – | – | – | 1262 | 1292 | 1294 | 1260 | ||||||
1400 | 1480 | 1510 | 1535 | 1530 | 1560 | 1600 | – | – | – | – | – | – | 1462 | 1492 | 1494 | 1460 | ||||||
1600 | 1690 | 1710 | 1760 | 1750 | 1780 | 1815 | – | – | – | – | – | – | 1662 | 1692 | 1694 | 1660 | ||||||
1800 | 1890 | 1920 | 1960 | 1950 | 1985 | – | – | – | – | – | – | – | 1862 | 1892 | 1894 | 1860 | ||||||
2000 | 2090 | 2125 | 2170 | 2150 | – | – | – | – | – | – | – | – | 2062 | 2092 | 2094 | 2060 | ||||||
2200 | 2295 | 2335 | 2370 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | |
2400 | 2495 | 2545 | 2570 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | |
2600 | 2695 | 2750 | 2780 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | |
2800 | 2910 | 2960 | 2000 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | ||
3000 | 3110 | 3160 | 3210 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | |
3200 | 3310 | 3370 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | |
3400 | 3510 | 3580 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | |
3600 | 3720 | 3790 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | |
3800 | 3920 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | |
4000 | 4120 | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – | – |
Flange facing types C, D, E, F, G and H are not used for PN 2,5 and PN 6.
Flange facing types G and H are only used for PN 10 to PN 40.
The type of forged flange and sealing face for flange
Flanges provide the necessary connections to link pipelines. Faces are the mating surface of a flange.
Different types of flange faces are used as the contact surfaces to seat the sealing gasket material.
The type of flange |
The type of sealing face |
Pressure Class(PN,MPA) |
Plate flange(PL) |
Raise Face(RF) |
0.25-2.5 |
Flat Face( FF) |
0.25-1.6 |
|
Slip on flange(SO) |
Raise Face(RF) |
0.6-4.0 |
Flat Face( FF) |
0.6-1.6 |
|
male and female face (MFM) |
1.0-4.0 |
|
Tongue and groove face (TG) |
1.0-4.0 |
|
Welding Neck Flange(WN) |
Raise Face(RF) |
1.0-25.0 |
male and female face (MFM) |
1.0-16.0 |
|
Tongue and groove face (TG) |
1.0-16.0 |
|
Ring Joint Face(RTJ) |
6.3-25.0 |
|
Flat Face( FF) |
1.0-1.6 |
|
Integral type flange(IF) |
Raise Face(RF) |
0.6-25.0 |
male and female face (MFM) |
1.0-16.0 |
|
Tongue and groove face (TG) |
1.0-16.0 |
|
Ring Joint Face(RTJ) |
6.3-25.0 |
|
Flat Face( FF) |
0.6-1.6 |
|
Socket Weld Flange(SW) |
Raise Face(RF) |
1.0-10.0 |
male and female face (MFM) |
1.0-10.0 |
|
Tongue and groove face (TG) |
1.0-10.0 |
|
Thread Flange(Th) |
Raise Face(RF) |
0.6-4.0 |
Flat Face( FF) |
0.6-1.6 |
|
Lap joint Flange(LP) |
Raise Face(RF) |
0.6-1.6 |
male and female face (MFM) |
1.0-1.6 |
|
Tongue and groove face (TG) |
1.0-1.6 |
|
Blind flange(BL) |
Raise Face(RF) |
0.25-25.0 |
male and female face (MFM) |
1.0-16.0 |
|
Tongue and groove face (TG) |
1.0-16.0 |
|
Ring Joint Face(RTJ) |
6.3-25.0 |
|
Flat Face( FF) |
0.25-1.6 |
Other flange facings covered by these standards include the large and small tongue-and-groove facings, and the ring joint facing specifically for ring joint type metal gaskets.

ANSI Flange Standards
The American National Standard Institute, ANSI, has been overseeing guidelines and standards for products manufactured through several sectors. ANSI-approved flanges are used for the industrial market which handles gas, air and steam process systems.
WHAT IS ANSI?
ANSI-approved flanges are used for the industrial market which handles gas, air and steam process systems. Originally formed in 1918, the American National Standards Institute is headquartered in Washington, DC, and is widely recognized as the American organization responsible for overseeing the national standards and conformity assessment system for products, services, processes, systems, and personnel.
ANSI works domestically with American government agencies and organizations, as well as with international entities, to make ANSI standards useful around the world.
Prior to the creation of ANSI, standards for engineering and equipment such as flanges were developed by the American Institute of Electrical Engineers (AIEE or IEEE), the American Society of Mechanical Engineers (ASME), the American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME), the American Society of Civil Engineers (ASCE), and the American Society for Testing and Materials (ASTM International) as members of the United Engineering Society, or UES.
Types of ANSI Flanges

The types of ANSI flanges are: slip on flange, welding neck flange, lap joint flange, plate flange, threaded flange on forge steel, carbon steel, stainless steel, alloy steel and blind flange. The classes of the flanges are the pressure ratings, which is between Class 150 and Class 2500. The dimensions of the flange are determined by the size of the pipe and the class of the pressure, which are required for the flange to be able to withstand water pressure and heat. Temperatures and materials of the flange can withstand pressures from -20 (degrees, Celsius) to 200 (degrees, Celsius).
Purpose
Flanges are used to attach a series of pipes or other flanges together. Some flanges, such as in the oil and gas sector, are required to sustain under high amounts of pressure. ASNI provides standards to flange manufactures to test flanges before they can be marketed to a particular sector.
Significance
ANSI provides standards on flanges depending upon pressure in pounds per second per inch (PSI), according to size in inches of the flange. Pressure and size are dependent upon whether the flange is welded to the pipe, threaded or bolted.
Considerations
Depending on the material the flange is made from, such as cast iron or steel, and the type of threaded material used for fittings, every flange is designated to a particular class. From these class ratings, several requirements, such as pressure-temperature rating, bolt and nut dimensions, coating material and several other factors, make up the standards according to the flange characteristics.
Standards of ANSI Flanges
The classes for flat face flanges are Class 125 and Class 250. The classes for ring joint flanges, tongue and groove flanges and raised flanges are: Class 150, Class 300 (Class 400 – rarely), Class 600, Class 900, Class 1500 and Class 2500. ANSI flanges are divided into classes, depending on pressure, temperature and the type of material used.