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Standards of pipe fittings

Application standard system

At present, most pressure pipes and their components have been serialized and supported by corresponding application standards.

Therefore, the first thing to consider when designing pressure pipe materials is the selection of standard series of pressure pipes and their components.

Apply the standardization system. A collection of series standards used by each component in a piping system (road).

These standards should include pipe series standards, pipe fitting series standards, flange and connecting parts standards, valve standards, etc.

These standards are applied in a piping system through certain rules. They correspond to each other and cooperate with each other to determine the basic

parameters of the pipeline and its components. Among these standards, pipe standards and flange standards are the most representative, and they are the basis

for other application standards. The following mainly introduces the application standards, focusing on pipe standards and flange standards.


At present, there are many standard systems applied in various countries in the world. Different countries and different industries have different application

standards and standards.

Systems, some of which are very different from each other, cannot be used in conjunction with each other and are interchangeable, thus causing a lot of trouble to users.

Therefore, the first step in the design of pressure pipelines is to choose and apply a standard system as a unified regulation for design, so as to avoid errors

caused by the use of other standard systems that cannot be replaced by various related disciplines.


Application standards in various countries around the world are generally divided into two categories:

  • Pipes----The outer diameter series of steel pipes are divided into international common series (large outer diameter series) and British pipes:
  • commonly used series in China (small outer diameter series) (diameter series) metric pipe (or metric pipe)
  • Flange:
    European flange and American flange
    Pressure level: PS 0.1 0.25 0.6 1.0 1.62.5 4.06.3 10.0 16.0 25.0 40.0 MPa
    European flange (DIN)
    Pressure level: PS 2.05.0 6.8 10.0 15.0 25.0 42.0 MPa
    American flange (ANSI)
    CL 150 300 400 600 900 1500 2500 PSI
    It can be seen from this that the above two series or two systems cannot be mixed, whether it is flanges or pipes.
  • ANSI-American National Standards Organization
    ASTM-American Society of Testing Materials
  • Method of expressing steel pipe wall thickness

              There are three ways to express the wall thickness of steel pipes: pipe number, steel pipe wall thickness size and pipe weight.
1) The pipe number “sch” represents the wall thickness. The pipe number is the ratio of the pipe design pressure to the allowable stress of the material

at the design temperature multiplied by 1000 and rounded.

That is: Sch=P/[σ]×1000
ANSI B36.10 wall thickness grades: Sch10, Sch20, Sch30, Sch40, Sch6o, Sch8o, Sch10o, Sch120, Sch140, Sch160 ten grades:
ANSI B36.19 wall thickness grades: Sch5s, Sch10s, Sch40s, Schsos four grades;
2) Expressed in terms of steel pipe wall thickness (adopted by some steel pipe standards in China, IS0, and Japan)
3) The pipe wall thickness is expressed by the weight of the pipe, which divides the pipe wall thickness into three types:
a.Standard weight tube, expressed as STD b. Thickened tube, represented by XS c. Extra thick pipe, represented by xxs. For pipes with DN≤250mn,

Sch40 is equivalent to STD, and for pipes with DN<200mm, Sch80 is equivalent to XS.

  • Commonly used international standard systems
   With China's reform and opening up and joining the WT0. Various industries are increasingly connected with the international community in order to 
better integrate with international standards.
It requires personnel engaged in pressure pipeline design to have an understanding of the internationally common and advanced relevant standard systems. 
The following introduces several main application standard systems.
Application standard system in Germany and the former Soviet Union
a.Germany (DIN)
Pipe: Large outer diameter series
Pipe flange: European flange
Pressure level: PN 0.1, 0.25, 0.6, 1.0, 1.6, 2.5, 4.0, 6.4, 10.0, 16.0, 25.0, 32.0, 40.0
13 levels
Nominal diameter: DN6~4000mm
Flange sealing surface: 7 types: flat surface, convex table surface, concave and convex surface, tongue and groove, rubber ring connection surface, 
lens surface and diaphragm welding surface
Flange type: flat welded plate type, flat welded loose sleeve type, flanged loose sleeve type, butt welding flanged loose sleeve type, butt welding ring
 flanged loose sleeve type, butt welding ring flanged loose sleeve type,
There are 9 types of welded, threaded, integral and flange covers.
DIN2410. T. 1 Overview of pipe and steel pipe standards
Seamless sodium tube
Dimensions and mass per unit length
Welded steel pipe dimensions and unit length mass
flange  A description
DIN2501. T. 1
flange  Connection size
Steel flange: technical delivery conditions
Threaded steel pipe fittings

b. Former Soviet Union (rOCT)
Pipe: small outer diameter bar, outer diameter size is the same as China’s JB bar
Pipe flange: European flange
Pressure level: PS0.1, 0.25, 0.6, 1.0, 1.6. 2.5, 4.0, 6.4, 10.0, 16.0, 20.0 11 levels
Nominal diameter: DN6-3000mm
Flange sealing surface: full plane, boss surface, four-convex surface, tongue and groove surface for PTFE, lens surface and oval ring pressing surface 7
Flange type: flat welding plate type, flat welding loose sleeve type, flanged loose sleeve type, butt welding type, threaded connection type, integral type 
and flange 7 types
*The German pipe flange standard DIN and the former Soviet Union pipe flange standard "OCT" can be used in pairs in the PN ≤ 16.0 level, 
but cannot be interchanged 
(because the nozzle size series are different). With the disintegration of the former Soviet Union, its application standard system " OCT is currently rarely used
 in international engineering.
c. American Application Standards System (ANSI)
The American national standard ANSI B16.5 "Steel Pipe Flanges and Flange Fittings" is a relatively complete and mature standard that is also internationally
 popular and universal. 
The pressure pipeline application standard system composed of this standard and other related ANSI, API, ASTM, and MSS is formed on the basis of a large number of 
experimental studies and has experienced decades of practical testing. Therefore, it can be regarded as a scientific and advanced standard, and Widely accepted by various countries.
Pipe: Large outer diameter series
(ANSI B36. 10 and ANSI B36. 19)
Nominal diameter range: (DN6^ DN2000) mm
Wall thickness expression method:
1) The pipe number “Sch” represents the wall thickness;
2) The thickness of the pipe wall is expressed by the weight of the pipe.
Pipe flange: American flange
Pressure level: CL 150 300 400 600 900 1500 2500 Psi 7 levels
Nominal diameter: DN15^600mm
Flange sealing surface: 4 types: convex surface (RF), concave and convex surface (MF), mortise and tenon surface (TG), metal ring connection surface
Flange types: 6 types: flat welding type, socket welding type, butt welding type, threaded connection type, loose sleeve type and flange cover

Commonly used standards in the American applied standards system ANSI include:
Seamless and welded steel pipes
Stainless steel seamless and welded steel pipes
Factory made steel butt weld fittings
Socket welding and threaded forged pipe fittings
 Steel butt welding small radius elbows and return elbows
Valves with flanged, threaded and welded connections
 Pipe flanges and flange fittings
Orifice plate flange
Ductile Iron Flanges and Flange Fittings
Large Diameter Steel Flange
Wrap-type, covered gaskets and ring-grooved metal gaskets for pipe flanges
Non-metallic flat gaskets for pipe flanges
Square and Hex Head Bolts and Threads
 Square and Hex Head Nuts

API std605
Large diameter flange, flange cover
API std526
flanged steel pressure relief valve Inspection and testing of API std598 valves
API std599
flanged and welded metal plug valves
API std600
 Steel gate valves with flange and butt weld connections
API std602
 small steel gate valve (compact gate valve)
API std603
150 pound corrosion resistant flange valve
API std608
metal ball valve with flange connection and butt welding connection
API std609
lug type and wafer type butterfly valve
API std6D
Pipeline valve specifications
 flat welding flange with neck

 d.Japanese Application Standard System (JIS)
Pipe: Large outer diameter series (JIS C3454, JIS G3458, JIS C 3459) are mostly the same as ANSI
Nominal diameter of seamless steel pipe: (DNG^DN650) mm
Method of expressing wall thickness: Pipe table number "Sch" indicates wall thickness
Carbon steel and alloy steel JIS G3454, JIS G3458: Sch10, Sch20, Sch30, Sch40, Sch6o, Sch80,
Sch100, Sch120, Sch140, Sch160 10 levels:
Stainless steel JIS G 3459: Sch5s, Sch10s~Sch20s, Sch40s, Sch80s, Sch120s, Sch160s
7 levels;
Nominal diameter of welded steel pipe: (DN350~DN2000) mm
Wall thickness expression method: Press directly to express the wall thickness numerical value.
Pipe flanges: (JIS B2201, JIS B2220, etc.) form their own system and are neither "American flanges" nor "European flanges"
Nominal diameter: (DNI0^DN1000) mm
Nominal pressure levels: 2K, 5K, 10K, IGR, 20K, 30K, 40K, 63K, 8 levels in total
Flange sealing surface: 5 types: smooth surface, large convex surface, small convex surface, four-convex surface, and tongue and groove surface
Flange types: 6 types: flat welding type, socket welding type, butt welding type, threaded press type, loose sleeve type and flange cover

 *The JIS application standard system cannot be used in conjunction with ANSI and DIN. In order to make up for this shortcoming, 
the Japan Petroleum Institute compiled a set of JPI standards, which are basically equivalent to the ANSI/API application standard system, so it can be 
interchanged with ANSI.

 *Commonly used standards in the Japanese Application Standard System JIS are:
JIS G3452
general purpose carbon sodium tube
JIS G3454
carbon steel pipe for pressure bearing
JIS G3455
carbon steel pipe for high temperature
JIS G3457
arc welded carbon steel pipe
JIS G3458
alloy steel pipe
JIS G3459
stainless steel pipe
JIS G3468
 arc welding large diameter stainless steel pipe
JIS B2201
defective material pipe flange pressure grade
JIS B2202
Pipe flange size
JIS B2210
Ferritic material pipe flange basic dimensions
JIS B2220
 steel pipe flange
JIS B2302
steel threaded connecting pipe fittings
JIS B2311
 Steel butt welding pipe fittings for general purposes
TIS B2312
Steel Butt Welding Pipe Fittings
JIS B2313
steel plate butt welding pipe fittings
JIS B2316
Socket welded pipe fittings
JIS B2401
JIS B2404
Wound gasket for pipe valve flange
JIS B3453
Compressed Asbestos Gasket

e.International Organization for Standardization (ISO) application standards system

Pipe: basically a large outer diameter series (ISO4200)
*Standard Huai (ISO4200) series 1 basically uses ANSI dimensions. Only when DN>1100mm (no longer commonly used), the "small outer diameter series"
 dimensions are used.
Pipe flange: including both "American flange" and "European flange" series. (ISO7005-1) It represents the current application trend of world flange standards.

Nominal pressure level:
The first series: pS 1.0, 1.6~2.0, 5.0, 11.0, 15.0, 26.0, 42.0 8 levels:

The first series: PN 0.25, 0.6, 2.5, 4.0 8 levels:

The first series is the basic series, and the second series is the limited series.

In the two series: PN0.25, PNO.6, PN1.0, PNI.6, PN2.5, PN4.0, the six grades belong to "European flange", PN2.0, PN5.0, PN11.0 ( 600Psi), PN15.0, 
PN26.0 (1500Psi), PN42.0 are "American flanges":

The structural dimensions and sealing surface dimensions of the two are not interchangeable.
 Commonly used standards in the ISO application standard system are:
pipe fittings nominal size definition
Welded and Seamless Plain End Steel Pipe Dimensions and Unit Lengths
Stainless steel pipe Dimensional tolerances and mass per unit length
 ISO3183  Steel pipes for the oil and gas industry
 ISO6759  seamless steel pipe for heat exchanger
 ISO7005-1  metal pipe flange
ISO7483  pipe flange gasket conforming to ISO005 standard
ISO3419  non-alloy steel and alloy steel pipe fittings
 ISO5251   stainless steel butt welding pipe fittings
 ISO7121  flange type steel ball valve
ISO10497 Valve test fire test requirements
 f.British Applied Standards System (BS)
 Pipe: Large outer diameter series
BS1600 Its diameter range and wall thickness classification are the same as ANSI B36.10/B36.11;
BS3600 Basically, it adopts the ISO standard, and its diameter range and wall thickness classification are the same as ISO4200.
*Flange standard: includes both "American flange" and "European flange" series.
BS1560 Basically it adopts the ANSI standard, and its structural type and sealing surface type are the same as ANSI B16.5;
BS4504 is basically equivalent to the DIN standard, and its structural type and sealing surface type are the same as DIN2500.
 Commonly used standards in today’s BS include:
Steel pipe dimensions for petroleum industry
Size and mass per unit length of welded steel pipes and seamless steel pipes for pressure
Welded and seamless stainless steel pipes for pressure purposes
Pipe flange (American flange)
Pipe flange (European flange)
BS1560 pipe flange
pipe flange (American flange)
BS4504 pipe flange
(European style flange)
Forged steel pipe fittings
butt welding pressure-bearing pipe fittings
butt welding pipe fittings for petroleum industry
Threaded and socket welded pipe fittings for petroleum industry



Post time: Oct-13-2023