6. JIS flange standard

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JIS B2291 Square Flanges

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Description

JIS B2291 Square Flanges are square flanges manufactured according to Japanese standard JIS B2291. This is a special type of flange that has a square shape instead of a round shape like normal flanges. They are mainly used in piping systems where it is necessary to connect different pipes or equipment together firmly and safely.

Applications

JIS B2291 Square Flanges are widely used in many different industries and systems, including:

Oil and Gas Industry: Connecting oil and gas pipelines.
Chemical industry: Used in chemical piping systems with high pressure and temperature.
Energy industry: Applications in power plants, thermal power plants and hydropower plants.
Construction industry: Used in water supply and drainage systems, HVAC systems.
Machinery Industry: Connecting parts of industrial machinery and equipment.

Standards

JIS B2291 standard defines the requirements for dimensions, materials, and technical features of Square Flanges. Here are some key points of the standard:

Dimensions: According to JIS B2291 standard, with specific dimensions depending on system requirements. Including nominal dimensions (Nominal Size) of flange, thickness (Thickness), and bolt hole diameter (Bolt Hole Diameter).
Materials: Stainless Steel, Carbon Steel, and other alloys.
Surface: Can be flat face (FF) or raised face (RF).
Bolt holes: Symmetrical arrangement for easy assembly and disassembly.
Quality Control: Includes inspection and testing procedures to ensure flanges meet technical and safety requirements.
Machining: Precision machining is required to ensure easy and tight assembly.

JIS B2291 Square Flanges Dimensions and Thickness Table

NPS Size (inches)	Outer diameter (OD) (mm)	Height (H) (mm)	Thickness (T) (mm)	Bolt Hole Diameter (mm)	Number of bolt holes
1/2	95	10	12	12	4
3/4	105	10	12	12	4
1	120	10	14	12	4
1-1/4	130	12	14	14	4
1-1/2	140	12	14	14	4
2	155	12	16	14	4
2-1/2	180	14	16	14	4
3	195	14	18	14	4
4	225	16	18	18	4
5	250	16	20	18	4
6	280	18	22	18	4
8	330	20	22	18	8
10	400	22	24	18	8
12	445	22	26	18	8
14	485	22	28	22	8
16	535	24	30	22	8
18	590	24	32	22	8
20	650	26	34	22	8
24	760	28	36	22	8

Note:

NPS (Nominal Pipe Size) : Nominal diameter of the pipe.
Outside diameter (OD) : Outside diameter of the flange.
Height (H) : Overall height from flange.
Thickness (T) : Thickness of flange.
Bolt Hole Diameter : Diameter size of the bolt holes.
Number of bolt holes : Number of bolt holes present on the flange.

Summary table of materials commonly used to manufacture JIS B2291 Square Flanges

Material Type	JIS Symbol	International Symbols	Main Applications
Carbon steel	S20C, S45C	ASTM A105	Used in high pressure oil, gas, chemical and water piping systems.
Stainless Steel	SUS304, SUS316	ASTM A182 (F304, F316)	Used in systems requiring high corrosion resistance such as food, pharmaceutical, and chemical industries.
Low alloy steel	SCM435	ASTM A350 (LF2)	Used in low temperature environments, such as liquefied natural gas (LNG) pipeline systems.
Nickel alloy	NCF600, NCF625	ASTM B564 (Inconel 600)	Used in highly corrosive and high temperature environments, such as petrochemical and nuclear power industries.
High alloy steel	SNC631	ASTM A182 (F11, F22)	Used in high temperature applications, such as boilers and heat treatment systems.
Brass and Copper	C3771, C2720	ASTM B62	Used in plumbing, air conditioning and steam systems.
Other special alloys	Hastelloy, Monel	ASTM B366 (Hastelloy)	Used in harsh, highly corrosive chemical environments.