Blind Flange Definition and Details

A blind flange is a solid disk used to block off a pipeline or to create a stop. It is machined in the same manner as a regular flange with the mounting holes around the perimeter and the gasket sealing rings machined into the mating surface. The difference is that a blind flange has no opening to allow fluid to pass through. The blind flange can be inserted between two open flanges and used to block off the flow of liquid through a pipeline.

Often a blind flange is inserted into a pipeline when a repair is required further up the line. This allows the flanges down stream to be disconnected without fear of losing liquid. Many times this type of blockade is used when adding another line onto an existing pipeline or when a new valve is being added. This blockade is also used to shut down a line when it is no longer needed.

Blind Flange Application

Without the blind flange it would be difficult to perform maintenance or repairs on a pipeline. The flow would need to be shut off at the nearest valve, which could be miles away from the repair area. Valves are also very expensive and are prone to sticking. The blind flange is a much more cost efficient way of sealing a pipe.

A Blind flange is round plate which has all of the relevant boltholes but no center hole, and because of this feature this flange is used to close off the ends of a piping systems and pressure vessel openings. It also permits easy access to the interior of a line or vessel once it has been sealed and must be reopened.Blind Flanges are commonly used in petrochemical, pipe engineering, public services & water works.

Blind Flange Standards:

ASME B16.5 Pipe Flanges and Flanged Fittings
ASME B16.47 Series A Steel Flanges NPS 26 Through NPS 60
API 605/ASME B16.47 Series B Steel Flanges NPS 26 Through NPS 60
BS EN 1759 Flanges and their joints. Circular flanges for pipes, valves, fittings and accessories, class-designated. Steel flanges
EN 1092 Circular flanges for pipes, valves, fittings

BS 4504 Circular flanges for pipes,valves and fittings
JIS B2220 Steel pipe flanges
ATK 24.200.02 Blind Flange
GOST 12836 PN4 Blind Flange

Blind Flange Materials:

Carbon Steel Blind Flange:
A105 GradeⅠ Carbon Steel Blind Flange
A105 GradeⅡ Carbon Steel Blind Flange
Alloy Steels Blind Flange:
A182 Grade F1 Alloy Steel Blind Flange
A182 Grade F5 Alloy Steel Blind Flange
A182 Grade F7 Alloy Steel Blind Flange
A182 Grade F9 Alloy Steel Blind Flange
A182 Grade F11 Alloy Steel Blind Flange
A182 Grade F12 Alloy Steel Blind Flange
A182 Grade F22 Alloy Steels Blind Flange
Low-Temperat Steel Blind Flange:
A350 Grade LF1 Low-Temperat Steel Blind Flange
A350 Grade LF3 Low-Temperat Steel Blind Flange
A350 Grade LF4 Low-Temperat Steel Blind Flange
A350 Grade LF6 Low-Temperat Steel Blind Flange
A350 Grade LF8 Low-Temperat Steel Blind Flange
Stainless Steel Blind Flange:
A182 Grade F304 Stainless Steel Blind Flange
A182 Grade F304H Stainless Steel Blind Flange
A182 Grade F304L Stainless Steel Blind Flange
A182 Grade F316 Stainless Steel Blind Flange
A182 Grade F316H Stainless Steel Blind Flange
A182 Grade F316L Stainless Steel Blind Flange
A182 Grade F321 Stainless Steel Blind Flange
A182 Grade F321H Stainless Steel Blind Flange
A182 Grade F347 Stainless Steel Blind Flange
A182 Grade F347H Stainless Steel Blind Flange

From the standpoint of internal pressure and bolt loading, blind flanges, particularly in the larger sizes, are the most highly stressed flange types.Blind Flanges are manufactured without a bore and used to blank off the ends of piping, Valves and pressure vessel openings.

However, most of these stresses are bending types near the center, and since there is no standard inside diameter, these flanges are suitable for higher pressure temperature applications.