Blind Flanges – Types, Uses, Classes & Selection Guide

Blind Flanges are solid flange components used to close the end of a pipe, nozzle, valve or piping connection. Unlike flanges with a central bore, a Blind Flange has no pipe opening through the flange body.

Blind Flanges are commonly used where a piping system needs a removable closure for isolation, maintenance, inspection, future expansion or pressure-boundary applications.

Vandan Alloys manufactures and supplies Blind Flanges in different sizes, pressure classes, materials, facing configurations and international standards.

What is a Blind Flange?

A Blind Flange is a solid circular flange designed to block the flow through a piping connection.

It is normally bolted to a mating flange using suitable gasket and bolting arrangements. When the line needs to be opened again, the Blind Flange can be removed.

Blind Flanges are particularly useful where a permanent welded closure is not preferred.

Blind Flange Types

Blind Flanges can be supplied in different configurations according to the application and applicable standard.

Raised Face Blind Flange

RF Blind Flanges have a raised gasket seating surface and are widely used in industrial piping systems.

Flat Face Blind Flange

FF Blind Flanges have a flat sealing face and are used where the piping system requires a flat-face connection.

RTJ Blind Flange

RTJ Blind Flanges have a precision-machined ring-type joint groove for applications requiring a metallic ring gasket connection.

Spectacle Blind / Figure-8

Spectacle Blinds are used for positive isolation in piping systems. They combine an open section and a solid section connected by a central web.

The selection and dimensions should follow the applicable piping specification.

Custom Blind Flanges

Special Blind Flanges can be manufactured according to customer drawings, dimensional requirements or project specifications.

Blind Flange Pressure Classes

Blind Flanges are available in different pressure classes depending on the applicable standard.

Common ASME pressure classes include:

• Class 150

• Class 300

• Class 400

• Class 600

• Class 900

• Class 1500

• Class 2500

The applicable pressure-temperature rating depends on factors including flange material, size, temperature and governing standard.

For European-standard requirements, customers may specify PN ratings such as PN10, PN16, PN25, PN40, PN63, PN100 or PN160, subject to the applicable standard.

Blind Flange Sizes

Blind Flanges are available for a wide range of piping sizes.

Requirements may include:

• Small-bore Blind Flanges

• Medium-size Blind Flanges

• Large-diameter Blind Flanges

• Custom-size Blind Flanges

For large-diameter requirements, the applicable standard and configuration should be confirmed before manufacturing.

Blind Flange Materials

Vandan Alloys can supply Blind Flanges in a broad range of material grades according to the applicable specification.

Common material groups include:

Carbon Steel

Stainless Steel

Alloy Steel

Duplex Stainless Steel

Super Duplex Stainless Steel

Nickel Alloys

Nickel-Copper Alloys

High Temperature Alloys

Titanium and other special materials

Commonly requested grades include:

• ASTM A105

• ASTM A105N

• ASTM A182 F304

• ASTM A182 F304L

• ASTM A182 F316

• ASTM A182 F316L

• F321

• F347

• F310

• F904L

• Duplex 2205

• Super Duplex 2507

• Monel

• Inconel

• Incoloy

• Hastelloy

Material selection should be based on the applicable piping specification and service conditions.

A105N Blind Flanges

ASTM A105N Blind Flanges are normalized carbon steel Blind Flanges used for applications where the specified material requirement calls for A105N.

A105N should be clearly specified in the purchase requirement where normalization and the associated material specification are required.

Customers can request:

A105N Blind Flange + Size + Class + Facing + Quantity

For example, a quotation enquiry may specify an A105N Blind Flange, NPS 4, Class 300, Raised Face.

The final flange dimensions and material requirements should always follow the applicable standard and purchase specification.

Stainless Steel Blind Flanges

Stainless Steel Blind Flanges are selected for applications where corrosion resistance and material compatibility are important.

Common stainless steel grades include:

• 304

• 304L

• 316

• 316L

• 321

• 347

• 310 / 310S

• 904L

The appropriate grade depends on the process medium, temperature, corrosion environment and project requirements.

Duplex & Super Duplex Blind Flanges

Duplex and Super Duplex Blind Flanges are used where a combination of strength and corrosion resistance is required.

Common grades include:

Duplex 2205 – UNS S31803 / S32205

Super Duplex 2507 – UNS S32750 / S32760

The exact grade should be specified according to the applicable material specification.

Blind Flange Facing Options

Blind Flanges can be supplied with different facing configurations, including:

• Raised Face (RF)

• Flat Face (FF)

• Ring Type Joint (RTJ)

The selected facing must match the mating flange and gasket arrangement.

For RTJ applications, the groove and ring gasket dimensions should be confirmed according to the applicable standard.

Blind Flange Applications

Blind Flanges are used in many industrial applications, including:

• Oil & Gas

• Refineries

• Petrochemical Plants

• Chemical Processing

• Power Generation

• Water Treatment

• Marine & Shipbuilding

• Process Piping

• Pressure Equipment

• Industrial Fabrication

• Pipeline Systems

• Maintenance & Shutdown Projects

Why Are Blind Flanges Used?

Blind Flanges can be used for several purposes:

Pipeline Isolation

They can provide a physical closure at the end of a piping section.

Maintenance

A Blind Flange can allow a section of piping or equipment to be isolated for maintenance work.

Future Expansion

A piping connection can be closed until additional equipment or piping is installed.

Testing

Blind Flanges may be used as part of certain pressure or testing arrangements when specified by the applicable procedure.

Equipment Connections

They can be used to close unused equipment nozzles or piping connections.

Blind Flange Installation

Before installation, confirm:

• Correct flange size

• Pressure class

• Material

• Facing

• Gasket compatibility

• Bolt-hole alignment

• Bolt and nut specification

• Flange face condition

The mating flange faces should be clean and properly aligned.

The correct gasket should be positioned between the sealing surfaces, and bolts should be tightened according to the approved engineering or project procedure.

Blind Flange Leakage Prevention

Reliable sealing depends on the complete flange assembly.

Important considerations include:

• Correct gasket selection

• Clean sealing surfaces

• Proper flange alignment

• Suitable bolting

• Controlled tightening

• Undamaged flange faces

• Correct flange dimensions

Excessive tightening should be avoided unless specifically required by the approved procedure.

Blind Flange Standards

Blind Flanges can be manufactured or supplied according to applicable standards such as:

• ASME B16.5

• ASME B16.47

• EN 1092-1

• DIN

• JIS

• BS

• Customer drawings and project specifications

The exact dimensions depend on the applicable standard, size, rating and flange configuration.

Blind Flange Inspection

Depending on customer requirements, inspection may include:

• Dimensional inspection

• Visual inspection

• Flange face inspection

• Bolt-hole inspection

• Thickness verification

• Material identification

• Chemical test documentation

• Mechanical test documentation

• Heat treatment records where applicable

• Third-party inspection

• Marking and traceability

Material Test Certificate

For applicable orders, EN 10204 Type 3.1 Material Test Certificates can be supplied.

The documentation may include material chemistry, mechanical properties, heat number and other relevant information according to the applicable specification.

Custom Blind Flanges

Vandan Alloys can evaluate special Blind Flange requirements based on customer drawings or specifications.

Custom requirements may include:

• Special OD

• Special thickness

• Customized bolt-hole pattern

• Special PCD

• Special facing

• Non-standard dimensions

• Special material grades

• Drawing-based machining

Customers can provide a PDF, CAD drawing, dimensional sketch or technical specification for review.

Blind Flange vs Weld Neck Flange

A Blind Flange is primarily used to close a piping connection.

A Weld Neck Flange is designed to connect a pipe through a butt weld.

They therefore serve different functions within a piping system.

Blind Flanges are often used together with Weld Neck, Slip-On and other mating flange types where a bolted closure is required.

How to Order Blind Flanges

For an accurate quotation, provide:

Size / NPS:
Pressure Class / PN Rating:
Material Grade:
Flange Type: Blind
Facing: RF / FF / RTJ
Standard:
Thickness / Special Requirement:
Quantity:
Inspection Requirement:
Delivery Location:

For custom requirements, please provide the drawing or dimensional details.

Vandan Alloys – Blind Flange Manufacturer & Exporter

Vandan Alloys manufactures and supplies Blind Flanges for industrial piping, engineering, fabrication, process plants and international export requirements.

We supply Blind Flanges in:

• Carbon Steel

• Stainless Steel

• Alloy Steel

• Duplex

• Super Duplex

• Nickel Alloys

• Other special materials

Available requirements can include different sizes, pressure classes, standards, facing types and custom dimensions.

Customers looking for an A105N Blind Flange Manufacturer in India, Stainless Steel Blind Flange Supplier, ASME Blind Flange Manufacturer or Custom Blind Flange Exporter can contact Vandan Alloys with their complete specification.

Send your Blind Flange enquiry, drawing or specification to Vandan Alloys for quotation.

Vandan Alloys 

Manufacturer of All Types of Flanges

3/5, Sakar Bhavan, Ground Floor, 6th  Khetwadi lane, SVP Road ,Mumbai – 400 004. India

TEL+91 022 6610 9925Mobile no: 09892882255  GSTIN:  27AUMPS2067F1ZB

Email: info@vandanalloys.com ; Web: www.vandanalloys.com

Please visit Our Flanges Division:www.vandanalloys.net

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