What are Square Flanges?

Introduction to Flanges:

A pipe flange is used in the assembly of pipe to pipe or other components like valves, tees, elbows etc. The flanges are bolted together, creating several lengths of pipes or other assemblies. There are many different flange standards to be found worldwide. Common world standards include ASA/ANSI/ASME (USA), PN/DIN (European), BS10 (British/Australian), and JIS/KS (Japanese/Korean). Flanges in each standard are divided into “pressure classes”, allowing flanges to be capable of taking different pressure ratings.

Square Flanges:

Square Flange made in accordance to JIS B2291 standard is a connecting piece that links JIS (Japanese Industrial Standards) nominal bore size pipes together and has a working pressure of up to 210kgf/cm2. This is equivalent to 210 Bar, or 21MPa. They are usually used in high pressure systems such as hydraulic and steam lines for up to 3,000 PSI working pressure.

There are three types of Square Flanges under this standard:

  1. SHAB – Used with hexagon hex bolts, larger flange body size (Figure 1)
  2. SSAB – Used with socket cap screw, smaller flange body size than SHAB (Figure2)
  3. LSA – Oring side only, L shaped internal flow (Figure 3)Untitled

A complete set of square flanges consist of the female flange (oring side), male flange (flat side), oring, and bolts. The female flange is identified as part A. The male flange is identified as part B. And the complete set is AB.

Figure 4 – Left : SHAB Square Flange using Hexagon bolts (larger flange body), Right: SSAB Square Flange using Socket Cap Screw (smaller Flange body)

Blind Flanges:

Another type of flange available are Blind Flanges. These are used to seal the end of a piping system or pressure vessel openings to prevent flow.  Blind pipe flanges are commonly used for pressure testing the flow of liquid or gas through a pipe or vessel.  They also allow easy access to the pipe in the event that work must be done inside the line.  Only one side of a blind flange is used for the termination of the piping system. Either the female blind flange (oring side), or male flange (flat side) will be connected to the component to close off the pipe line  (Figure 5).

Figure 5:  Oring and Flat Square Blind Flanges


Material, Size Range and Connection:

Square Flanges are available in either carbon steel (SF440A) or stainless steel (SS316) material. The size range from 1/4″NB to 6”NB and the connection type is Socket Welding.

Brands of Square Flanges:

A highly recommended manufacturer for square flanges is KPL Industry Co., Ltd. KPL Industry Co., Ltd is a Korean manufacturer that specializes in producing various forged products in the field marine & offshore, seawater desalination plant, nuclear power plant and industrial sites.

To find out more about how to assemble Square Flanges, please watch:


Chuan Kok Hardware & Machinery is a stockist of KPL JIS B2291 Square Flanges in Singapore. To find out more about square flanges do visit us at www.chuankok.com/square-flanges.html

03 KPL