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Pipe flanges

Pipe flanges are basically plates or rings used to connect pipes, valves and other piping equipment to form a piping system.

The most used flange types in Petro and chemical industry are:

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:


ASTM A350 Standard Specification

ASTM A350 is the Standard Specification for Carbon and Low-Alloy Steel Forgings, Requiring Notch Toughness Testing for Piping Components

ASTM A105 Standard Specification

ASTM A105 is the Standard Specification for Carbon Steel Forgings for Piping Applications

Pipe 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.

MaterialTest basis / RequirementsDelivery 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

MaterialTest basis / RequirementsDelivery Condition
 1.4541 (X6CrNiTi18-10) DIN 17458:1996-09+AT
 1.4571 (X6CrNiMoTi17-12-2) DIN 17458:1996-09+AT
FlangeTest 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
FittingsTest 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
ReducerDIN2605-1
DIN2616-1
Requirements are valid for normal case, in special case you have to contact the technical department.

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;

  1. ANSI Flange, also called ASME B16.5 Flange
  2. ASME Flange, also called ASME B16.47 Flange (Series A and Series B)
  3. Industry Standard Flange (ASME B16.1 Flange)
  4. 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 – Example

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
ForgingsCastingsPlates
C-SiA105(1)A216
Gr.WCB (1)
A515
Gr.70 (1)
C Mn SiA350
Gr.LF2 (1)
A516
Gr.70 (1), (2)
C Mn Si VA350
Gr.LF6 Cl 1 (3)
A537
Cl.1 (4)
3.1/2NiA350
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
ForgingsCastPlates
16Cr 12Ni 2MoA182
Gr.F316L
A240
Gr.316L
18Cr 13Ni 3MoA182
Gr.F317L
18Cr 8NiA182
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)15030040060090015002500
-29 TO 3819.651.168.1102.1153.2255.3425.5
5019.250.166.8100.2150.4250.6417.7
10017.746.662.193.2139.8233388.3
15015.845.160.190.2135.2225.4375.6
20013.843.858.487.6131.4219365
25012.141.955.983.9125.8209.7349.5
30010.239.853.179.6119.5199.1331.8
3259.338.751.677.4116.1193.6322.6
3508.437.650.175.1112.7187.8313
3757.436.448.572.7109.1181.8303.1
4006.534.746.369.4104.2173.6289.3
4255.528.838.457.586.3143.8239.7
4504.62330.74669115191.7
4753.717.423.234.952.387.2145.3
5002.811.815.723.535.358.897.9
5381.45.97.911.817.729.549.2
TEMP (°C)15030040060090015002500
PRESSURE-TEMPERATURE RATINGS FOR ASTM GROUP 2-2.3 MATERIALS

Working pressure by Classes, BAR

TEMP(°C)15030040060090015002500
-29 TO 3815.941.455.282.7124.1206.8344.7
5015.34053.480120.1200.1333.5
10013.334.846.469.6104.4173.9289.9
1501231.441.962.894.2157261.6
20011.229.238.958.387.5145.8243
25010.527.536.654.982.4137.3228.9
3001026.134.852.178.2130.3217.2
3259.325.5345176.4127.4212.3
3508.425.133.450.175.2125.4208.9
3757.424.83349.574.3123.8206.3
4006.524.332.448.672.9121.5202.5
4255.523.931.847.771.6119.3198.8
4504.623.431.246.870.2117.1195.1
TEMP(°C)15030040060090015002500

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.