What is a blind flange​ and its application?

A blind flange is a solid flange with no center bore, used to close the end of a pipeline, valve or pressure vessel connection. For piping distributors and industrial buyers, selecting the right blind flange means checking the size, pressure class, material and facing type against the project specification.

This guide explains the main blind flange types, their applications and the key details to confirm before purchasing. If you are sourcing blind flanges for stock or project orders, you can also view our blind flange product range for product specifications and quotation support.

1. What Is a Blind Flange?

A blind flange, also called a pipe blind flange or blank flange in many commercial contexts, is designed to close a flanged pipe end or equipment opening. Unlike a weld neck or slip-on flange, it has no central opening for fluid flow.

Blind flanges are bolted to a matching flange, with a suitable gasket installed between the sealing faces where required. Because the closed end is exposed to pressure loads, the flange must be selected according to the applicable piping standard and operating conditions.

Blind flanges are commonly used for:

• Closing unused pipe ends and equipment nozzles
• Isolating piping sections during maintenance
• Providing access for future pipeline extensions
• Sealing connections during specified pressure tests

For permanent or temporary isolation, the correct design depends on the piping system and the applicable safety procedures.

2. Main Blind Flange Types

Blind flange types are most commonly classified by their sealing face. The correct choice depends on the mating flange, gasket and service conditions.

Raised Face Blind Flange (RF)

A raised face blind flange has a raised sealing surface around its perimeter. The gasket sits on this designated area, creating a sealing joint when the flange is properly assembled and bolted.

RF blind flanges are widely used in industrial piping systems, including oil and gas, petrochemical processing and power generation.

When ordering an RF blind flange, confirm the pressure class, raised face dimensions, gasket requirements and mating flange specification.

Flat Face Blind Flange (FF)

A flat face blind flange has a flat sealing surface across the flange face. It is commonly used where the mating flange and equipment require a flat-face connection.

FF configurations are often specified for certain waterworks and equipment connections, including applications involving cast iron flanges. The mating components and gasket must be compatible to avoid excessive loading or damage.

Ring Type Joint Blind Flange (RTJ)

An RTJ blind flange has a machined ring groove designed to accommodate a compatible metallic ring gasket. It is used in specified high-pressure or demanding service applications, including some oil and gas systems.

The ring groove, gasket profile, material and pressure rating must match the applicable specification. Do not select RTJ components solely on the basis of a general pressure or temperature claim.

3. Blind Flange Standards, Sizes and Materials

Blind flanges are manufactured to different standards depending on the piping system, market and application.

Do not assume that dimensions or pressure ratings from different standards are interchangeable. For large-diameter applications, confirm the applicable standard and series before placing an order.

Common material requirements may include:

• Carbon steel: ASTM A105 or other specified grades for suitable industrial service
• Low-temperature carbon steel: ASTM A350 LF2 where required by the design conditions
• Stainless steel: Specified grades such as F304/L or F316/L
• Alloy steel: Specified grades such as F11 or F22 for applicable service conditions

Actual availability depends on the required grade, dimensions, pressure class and manufacturing specification.

When requesting a quotation, provide the nominal size, pressure class or PN rating, material grade, facing type and quantity. Drawings and project specifications are particularly helpful for non-standard requirements.

4. Blind Flange Applications

Oil and Gas Pipelines

Blind flanges close unused connections, pipeline ends and equipment nozzles. The selected flange must match the line specification and operating conditions.

Petrochemical and Chemical Plants

Process systems often require flanged closures for equipment connections and piping sections. Material selection must account for the specified service environment.

Power Generation

Blind flanges are used to close designated piping and equipment connections in utility and process systems. Pressure, temperature and applicable code requirements must be checked.

Water Treatment and Industrial Facilities

Blind flanges provide removable closures for pipe ends, tanks and other compatible flanged connections, supporting maintenance and future modifications.

Pressure Testing and Maintenance

Blind flanges may be used to isolate a section of a system during an approved pressure test or maintenance procedure. The test setup, flange rating, bolting and other components must be suitable for the intended test conditions.

A blind flange is not a substitute for a complete isolation procedure. Where personnel safety is involved, follow the applicable site rules and engineering requirements.

5. How to Choose the Right Blind Flange

Before purchasing blind flanges, check the following points.

1. Nominal size

Confirm the NPS or DN and the dimensions required by the applicable standard.

2. Pressure class or PN rating

Specify the required rating and verify that it is suitable for the system’s design conditions. ASME Class and PN designations should not be treated as directly interchangeable.

3. Facing type

Identify whether the connection requires RF, FF or RTJ. The flange face must match the mating flange and gasket arrangement.

4. Material grade

Select the material according to the design specification, operating temperature, pressure and service environment.

5. Quantity and supply requirements

For distributors and stockists, prepare a size-and-quantity list covering the required material grades and pressure classes. For project orders, include drawings, inspection requirements, marking and packing instructions where applicable.

These details help reduce specification questions and make quotations easier to compare.

6. Blind Flange vs. Blank Flange: Are They the Same?

In commercial purchasing, “blind flange” and “blank flange” are often used interchangeably. However, the term “blank” can also refer to unfinished flange material or a line blank, such as a paddle blind or spectacle blind.

A standard blind flange is a finished, bolted flange with no center bore. A paddle blind or spectacle blind is designed for a different installation arrangement and isolation purpose.

If your specification uses the term “blank flange,” confirm the intended component before ordering.

For a more detailed explanation, read our guide: Blind Flange vs. Blank Flange in Piping Projects.

7. Sourcing Blind Flanges for Stock or Project Orders

For distributors, wholesalers and industrial buyers, consistent specifications and clear documentation are important when sourcing blind flanges for repeat orders.

JS FITTINGS manufactures and supplies industrial flanges and pipe fittings. Established in 1983, the company works with customers on product specifications and order requirements for industrial applications.

When requesting a blind flange quotation, please provide:

• Size and pressure class
• Applicable standard
• Material grade and facing type
• Required quantity
• Destination country
• Drawing or inspection requirements, if applicable

These details help our team review the requirements and prepare a quotation based on the requested specification.

Looking for a blind flange supplier for your next stock replenishment or project?

Visit our Blind Flange Product Page to review the product information and submit your requirements.

Email: admin@jsfittings.com

WhatsApp: +86 180 0311 9682

Contact JS FITTINGS with your size list or technical drawing to discuss your blind flange requirements.