Blind Flange

Blind flange is like a flange cover, also called blind disk or flanged pipe plug. Blind flange has no holes in the center, for to seal the pipe opening. So it's function is the same as the pipe plug or the pipe cap. The difference is blind flange is a detachable equipment, easy to replace or do maintenance.

Major Function - Where to use

The blind flange's the major function is totally to separate the production medium. Which preventing the shut-off valve close not tightly, then affecting production, and even causing accidents.

At the location where is requires isolation should place the blind flange, such as at the equipment nozzle. Between the front and rear of the shut-off valve or between the two flanges, it is often recommend to use a figure 8 blind flange (figure-8 blank); For single-use parts such as pressing and purging usually use common round blind flange.

Sealing Surface

There are many types of sealing surfaces, such as flat, convex, concave and convex, grooved surface and ring joint surface.

Material Types and Standards

Blind Flange material usually required in carbon steel, stainless steel, alloy steel, copper, aluminum and etc.

Carbon steel blind flange: ASTM A105
Alloy steel: ASTM A182 F5, F9, F11, F22, F91
Stainless steel blind flange: ASTM A182 F304/L, F316/L

Manufacturing Standards

ASME B16.5
BS 3293
DIN 86029

Dimensions

General use OD range: 1/2'', 2'',  3'', 4'', 6'', 8'', 10'', 12'', to 24”.
Special made OD: Up to 60”.
Class range: Class 150, Class 300, 400, 600, 900, 1500, 2500
Flange face type: RF (Raised Face), RTJ (Ring Type Joint)

Manufacturing Types and Costs

Generally has four types: Forging, casting and forging, medium plate cutting, casting, the price of forging products is the highest, the middle plate is the second, casting and forging is the lowest and casting is the worst process when compared with others.

The best quality is forging and medium plate, casting and forging is a bit worse.

Casting Blind Flange

The shape of the the casting flange blank is accurate, has the small processing capacity, the cost is low, but there are casting defects (air hole crack inclusions); And the streamline of the internal casting part is bad (if it is a cutting part, the streamline is worse).

Forging Blind Flange

Forged blind flange generally have lower carbon content than cast flanges and are not easily to rust. Forgings have better streamlined shape, denser structure and better mechanical properties than cast flanges;

If the forging process is improper, the grain will be large or uneven, and the hardening crack will occur. The forging cost is higher than the casting flange.

Forgings can withstand higher shear and tensile forces than castings.

Precautions When Use

• Under the premise of meeting the process requirements, use as few blind plates as possible.
• The blind plate set must be marked as normally open or normally closed.
• The location of the blind plate is determined by the cutting effect, safety and process requirements.

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