Introduction

A  blind flange looks like a round plate without a hole in its center, which is used to close the end of a vessel or piping system and can help with pipeline cleaning and maintenance. It is also used for pressure testing to prevent the liquid or air flow. There are several blind flange types as below, Let’s take a look！

Blind flange types

Materials Types

Blind Flange comes in various different materials, which commonly refer to carbon steel, stainless steel, alloy steel, copper, aluminum etc. 

Carbon steel blind flange

It has the advantage of high strength, which is widely used for the pipelines with general usage middle and low pressure.The common materials refer to ASTM A105/N, A350 LF1, LF2, LF3, A694 F42 to F70, etc.

Stainless steel blind flange

It is mainly used for the pipelines that transport the corrosion fluids because it has the advantage of corrosion resistance. The common materials refer to ASTM A182 F304/L, F316/L, F310, F321, etc.

Alloy steel blind flange

It has the advantages of high strength and corrosion resistance, which is mainly used for high temperature and pressure pipelines. The common materials refer to ASTM A182 F1, F5, F9, F11, F22, F91, etc.

Manufacturing Types

They are produced in a variety of ways, generally including forging, cast-forged, medium plate cutting and casting four types.

The best quality is forging and medium plate cutting, cast-forged is a bit worse, and casting is the worst process when compared with others.

Forging Blind Flange

Forging blind flange is usually used for transporting fluids, gasses and drinking water. Compared with casting blind flanges, forging blind flanges have lower carbon content and are not easy to rust. In addition, they can withstand higher shear and tensile forces, but the forging cost is also higher.

Casting Blind Flange

The shape of the casting flange blank is accurate, which has the advantages of small processing capacity and  the low-cost. However, there are casting defects, such as air hole, crack, inclusions, and the streamline of the internal casting part is bad. 

Blind Flange Key Points

Sizes

Available for sale in sizes 1/2” to 60”.

General use OD ( out diameter) range: 1/2”, 1”, 2”,  3”, 4”, 6”, 8”, 10”, 12”, 14” to 24”.

Special made OD (out diameter): Up to 60”.

Pressure Ratings

Class 150, Class 300, Class 400, Class 600, Class 900, Class 1500, Class 2500. PN 2.5 to PN 100.

Flange face type

RF (Raised Face), FF (Flat Face), RTJ (Ring Type Joint).

Coating / Surface Treatment

Anti-rust Oil, Painting (Black, Yellow), Cold and Hot Dip Galvanized, Power Coating.

Manufacturing Standards

ASME / ANSI B16.5 / B 16.47

BS 3293

DIN 86029

EN 1092-1

Common Application

Blind flanges are usually installed at the end of a piping system to terminate a pipe, as well as used for a pipe, shut-off valve and pressure vessel to isolate the production medium. The common industries include petrochemical, natural gas, pipe engineering, public services, water works and more.

Conclusion

In conclusion, the major function of blind flange is to totally separate the production medium. Placing the blind flange at the location where it requires isolation can effectively prevent the shut-off valve from closing tightly, thereby affecting production and even causing accidents.

Blind flange is a detachable equipment, which is easy to replace and do maintenance. According to material types, there are carbon steel, stainless steel and alloy steel three main kinds. Carbon steel and alloy steel are the preferred materials for high strength applications, and stainless steel is usually preferred for corrosion resistant applications. According to manufacturing types, there generally are forging, cast-forged, medium plate cutting and casting four types.