What is a blind flange​ and its application?

Check out this blog if you want to learn more about blind flanges. This blog
covers everything about these types of flanges, including definitions, uses,
advantages, and much more.

What is a Blind Flange?
A blind flange is a solid flange, as shown below. The purpose of these is to
block off a section of pipe or a nozzle on a vessel that is not used. (A nozzle
is typically a pipe coming out of a vessel and is usually flanged so it can be
connected to valves or piping.) Many times, a nozzle will be blanked off with a
blind flange for pressure tests in a plant, or simply because the customer does
not need all the nozzles that were supplied on the tank.
The primary function of a blind flange is straightforward: to temporarily or
permanently block the flow of fluids or gases within a pipeline.
This becomes indispensable when a section of a piping system needs to be
isolated for critical tasks such as maintenance, repairs, inspection, or when a
line is simply not in active use. By creating an impenetrable barrier, blind
flanges prevent the escape of hazardous substances and maintain system
integrity.

steel blind flange

Despite their simple appearance, blind flanges are incredibly versatile. They
are available in a wide array of diameters, materials (e.g., carbon steel,
stainless steel, alloy steels), and pressure ratings, ensuring there’s a
suitable option for virtually any operational demand. Installation is also
relatively uncomplicated: the flange is aligned with the pipe’s open end, a
gasket is positioned between the two, and bolts are tightened evenly around the
circumference to create a secure connection.

Blind Flange Face Types:
The efficacy of a blind flange largely depends on its face type, which dictates
the gasket and sealing mechanism:

Raised Face (RF) Blind Flange
Featuring a raised, serrated surface around the bore, this is the most common
type. It concentrates the bolting force over a smaller area, increasing the
joint’s pressure containment capability. Typically paired with spiral wound or
non-metallic flat gaskets.

Flat Face (FF) Blind Flange
As its name suggests, this flange has a flat sealing surface. It’s ideal for
lower pressure applications and when connecting to cast iron flanges or
equipment that are more sensitive to concentrated stresses. Often used with
full-face gaskets made of softer materials like rubber or neoprene.

Ring Type Joint (RTJ) Blind Flange
Engineered for extreme high-pressure and high-temperature environments, RTJ
flanges utilize a precisely machined groove that accommodates a metallic ring
gasket. This metal-to-metal seal offers superior leak resistance under severe
conditions.

High Hub Blind Flange
While less common for simple closure, a high hub blind flange integrates the
strength of an extended hub, often found on weld neck flanges, with the solid
face of a blind flange. This can be beneficial in applications requiring
additional structural integrity.

ANSI Blind Flange Dimensions by Class
Spec Class Available Size Range
B16.5 150 0.5” – 24”
B16.5 300 0.5” – 24”
B16.47 150 26” – 60”
B16.47 300 26” – 60”
Industry Forged Steel Blind Flanges Key Applications:
The utility of blind flanges extends across numerous sectors, making them a
staple in various industrial scenarios:

1. Pressure Testing:

During the crucial phase of pressure testing new or repaired pipelines, blind
flanges are vital for sealing off sections, allowing for accurate pressure
checks and ensuring system integrity before commissioning.

2. System Isolation:

Perhaps their most common application, blind flanges are used to safely isolate
specific sections of a pipeline or equipment for scheduled maintenance,
emergency repairs, or modifications without affecting the rest of the system.

3. Temporary Line Closure:

When a particular pipeline segment is temporarily out of service or awaiting
future connection, blind flanges provide a secure and reliable temporary
closure, protecting the system from contaminants and accidental access.

4. Vessel & Tank End Caps:

Beyond pipelines, these flanges frequently serve as secure end caps for
pressure vessels, storage tanks, and heat exchangers, maintaining internal
pressure and preventing external contamination.

5. Instrumentation & Inspection Ports:

Cleverly, blind flanges can also be adapted to create access points. By
removing a blind flange, technicians can gain entry for internal inspections,
cleaning, or the installation of monitoring instruments like pressure gauges
and thermometers.

Blind flanges are far more than just metal discs; they are crucial components
that safeguard operations, facilitate essential maintenance, and provide
unparalleled flexibility in managing fluid and gas transfer systems. Their
ability to securely and efficiently close off pipelines makes them
indispensable across the petrochemical, power generation, water treatment, and
manufacturing industries.
Whether you’re contending with high-pressure systems, seeking to isolate a
critical section for repair, or simply capping off a temporary line, the blind
flange offers a reliable, cost-effective, and adaptable solution. Don’t
underestimate the silent strength of these essential fittings.

Need expert guidance on selecting the perfect blind flange for your next
project?

Contact us today – we are ready to help you navigate the specifications and
ensure your system is sealed for success.

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