Threaded Flanges – Types, Uses, Classes & Selection Guide

Threaded Flanges are flanges with an internal thread machined into the bore, allowing them to connect with externally threaded pipes or components without requiring a welding operation at the flange connection.

They are commonly considered for piping applications where welding is difficult, undesirable or restricted by the project requirements.

Vandan Alloys manufactures and supplies Threaded Flanges in carbon steel, stainless steel, alloy steel, duplex, super duplex and selected nickel alloy materials for industrial and international requirements.

What is a Threaded Flange?

A Threaded Flange, also called a Screwed Flange, contains an internal thread that matches the external thread of the pipe.

The pipe is screwed into the flange bore to create the mechanical connection.

Unlike Slip-On, Weld Neck or Socket Weld Flanges, the flange-to-pipe connection does not depend on a weld at the flange itself.

Thread type, pitch and dimensions must match the specified pipe thread and applicable standard.

How Does a Threaded Flange Work?

The internal thread of the flange is machined to the required specification.

A compatible externally threaded pipe is then screwed into the flange.

Correct thread engagement, dimensional compatibility and alignment are essential for proper assembly.

Threaded connections should be selected only where permitted by the applicable piping code, design specification and service conditions.

Threaded Flange Types

Threaded Flanges may be supplied in different configurations depending on the applicable standard and customer requirement.

Raised Face Threaded Flange – RF

RF Threaded Flanges have a raised gasket seating surface and are commonly specified for standard bolted flange connections.

Flat Face Threaded Flange – FF

FF Threaded Flanges have a flat gasket seating surface and may be selected where a flat-face connection is required.

RTJ Threaded Flange

Where permitted by the applicable standard and configuration, RTJ Threaded Flanges can be supplied for ring-type joint applications.

RTJ groove dimensions must correspond to the applicable standard and mating flange.

Threaded Flange Construction

A typical Threaded Flange includes:

• Flange body

• Internally threaded bore

• Bolt holes

• Bolt circle / PCD

• Gasket seating face

• Outside diameter

• Flange thickness

The dimensions vary according to nominal size, pressure class, material and governing standard.

Threaded Flange Pressure Classes

Common ASME pressure classes include:

• Class 150

• Class 300

• Class 400

• Class 600

• Class 900

• Class 1500

• Class 2500

The applicable pressure class depends on the size, material, temperature and governing standard.

For EN applications, PN-rated configurations may also be required, such as:

• PN10

• PN16

• PN25

• PN40

• PN63

• PN100

• PN160

Availability depends on the specific standard, size and configuration.

Threaded Flange Size Range

Threaded Flanges are commonly associated with smaller and medium nominal pipe sizes.

Typical enquiries may include:

• 1/2"

• 3/4"

• 1"

• 1-1/4"

• 1-1/2"

• 2"

• 2-1/2"

• 3"

• 4"

• 6"

• 8"

Larger sizes may be considered subject to the applicable standard and thread configuration.

For special requirements, Vandan Alloys can review customer drawings or technical specifications.

Thread Types for Threaded Flanges

Thread compatibility is a critical part of threaded flange selection.

Depending on the requirement, customers may specify a particular pipe-thread standard or configuration.

The enquiry should clearly mention the required:

Thread standard

Thread size

Thread form

Pitch

Nominal pipe size

Bore / internal thread dimensions

Thread details should not be assumed from nominal pipe size alone.

Threaded Flange Materials

Vandan Alloys supplies Threaded Flanges in multiple material groups.

Carbon Steel

Common grades include:

• ASTM A105

• ASTM A105N

Stainless Steel

Common grades include:

• ASTM A182 F304

• ASTM A182 F304L

• ASTM A182 F316

• ASTM A182 F316L

• F321

• F347

• F310

• F904L

Duplex Stainless Steel

• Duplex 2205

• UNS S31803

• UNS S32205

Super Duplex Stainless Steel

• UNS S32750

• UNS S32760

• Super Duplex 2507

Nickel & Special Alloys

Depending on application and specification, Threaded Flanges may also be supplied in selected:

• Monel

• Inconel

• Incoloy

• Hastelloy

• Titanium

• Other special alloys

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

A105N Threaded Flanges

ASTM A105N Threaded Flanges are normalized carbon steel forged flanges manufactured according to the applicable A105N requirements.

Where the normalized condition is required, it should be clearly stated in the purchase specification.

A typical requirement can be written as:

ASTM A105N + Threaded Flange + NPS + Class + Facing + Thread Requirement + Quantity

Material certification and inspection requirements should be agreed before production.

Stainless Steel Threaded Flanges

Stainless Steel Threaded Flanges are commonly selected where corrosion resistance and material compatibility are important.

Popular grades include:

304 / 304L

316 / 316L

321

347

310 / 310S

904L

The appropriate grade depends on the operating environment, temperature, process medium and project specification.

Duplex & Super Duplex Threaded Flanges

Duplex 2205 Threaded Flanges can be considered for applications requiring specific corrosion resistance and mechanical performance.

Common designations include:

• UNS S31803

• UNS S32205

For more demanding corrosion environments, Super Duplex 2507 grades such as UNS S32750 and UNS S32760 may be specified where suitable.

Threaded Flange Facing Options

Common facing configurations include:

RF – Raised Face

FF – Flat Face

RTJ – Ring Type Joint, where applicable

The selected flange face should be compatible with the mating flange and gasket system.

Threaded Flange Standards

Depending on the requirement, Threaded Flanges can be manufactured or supplied according to applicable international standards, including:

• ASME B16.5

• EN 1092-1

• DIN

• JIS

• BS

• Customer drawings

• Project-specific specifications

The standard should be clearly stated in the enquiry to avoid dimensional or thread compatibility issues.

Applications of Threaded Flanges

Threaded Flanges may be considered for:

• Process piping

• Utility piping

• Instrumentation systems

• Chemical plants

• Oil & Gas applications

• Petrochemical systems

• Water systems

• Compressed air systems

• Hydraulic applications

• Maintenance and replacement work

• Industrial fabrication

Their suitability depends on the applicable design code and operating conditions.

Advantages of Threaded Flanges

No Flange Welding Required

The pipe is mechanically connected through the internal thread of the flange.

Useful Where Welding is Restricted

Threaded connections can be considered in applications where welding at the flange connection is not preferred or is restricted, subject to engineering approval.

Convenient for Certain Piping Systems

They can provide a practical bolted flange arrangement for compatible threaded piping.

Suitable for Selected Small-Diameter Applications

Threaded Flanges are commonly used for smaller piping systems where the design specification permits threaded connections.

Limitations of Threaded Flanges

Threaded Flanges are not suitable for every piping service.

Selection should carefully consider:

• Operating pressure

• Operating temperature

• Thermal cycling

• Vibration

• Corrosive service

• Thread integrity

• Pipe wall thickness

• Applicable piping code

• Maintenance requirements

For severe service conditions, an alternative flange connection may be preferred depending on engineering requirements.

Threaded Flange vs Socket Weld Flange

Threaded Flange:
The pipe connects through an internal flange thread.

Socket Weld Flange:
The pipe enters a recessed socket and is welded.

The choice depends on the piping design, service conditions and applicable specification.

Threaded Flange vs Slip-On Flange

Threaded Flange uses a mechanical threaded pipe connection.

Slip-On Flange is positioned over the pipe and connected by welding.

Threaded Flanges may be useful where welding is restricted, while Slip-On Flanges are commonly used where welded fabrication is acceptable.

Threaded Flange Installation

Before installation, verify:

• Correct flange size

• Pressure class

• Material grade

• Thread standard

• Thread size

• Thread pitch

• Thread condition

• Facing

• Bolt-hole alignment

• Gasket compatibility

The mating pipe thread and flange thread should be clean and undamaged.

Thread engagement should comply with the applicable specification.

Excessive force should be avoided during assembly because damaged threads can affect connection integrity.

Threaded Flange Inspection

Inspection requirements may include:

• Visual inspection

• Dimensional inspection

• Thread inspection

• Thread gauge verification

• Face inspection

• Bolt-hole inspection

• Material identification

• Chemical analysis

• Mechanical testing

• Heat treatment verification where applicable

• Marking and traceability

• Third-party inspection

The inspection plan should be agreed according to the purchase specification.

MTC & Quality Documentation

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

Documentation may include:

• Material grade

• Heat number

• Chemical composition

• Mechanical properties

• Heat treatment information where applicable

• Dimensional inspection

• Thread inspection

• Traceability records

Additional inspection or documentation can be arranged according to project requirements.

Custom Threaded Flanges

Vandan Alloys can evaluate special Threaded Flange requirements based on customer drawings and technical specifications.

Custom requirements may include:

• Special flange OD

• Special thickness

• Customized PCD

• Special bolt-hole arrangement

• Special thread

• Special bore

• Special facing

• Special material

• Non-standard dimensions

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

How to Order Threaded Flanges

For quotation, provide:

Size / NPS:
Pressure Class / PN:
Material Grade:
Flange Type: Threaded / Screwed
Facing: RF / FF / RTJ
Thread Standard:
Thread Size / Pitch:
Bore Requirement:
Standard:
Quantity:
Inspection Requirement:
Delivery Location:

For special or non-standard requirements, provide the drawing with the enquiry.

Vandan Alloys – Threaded Flange Manufacturer & Exporter

Vandan Alloys manufactures and supplies Threaded Flanges / Screwed Flanges for industrial piping, process plants, engineering projects, maintenance applications and international export requirements.

Our supply range includes:

• Carbon Steel Threaded Flanges

• A105 Threaded Flanges

• A105N Threaded Flanges

• Stainless Steel Threaded Flanges

• Duplex Threaded Flanges

• Super Duplex Threaded Flanges

• Alloy Steel Threaded Flanges

• Nickel Alloy Threaded Flanges

• Custom Threaded Flanges

We support requirements for different sizes, pressure classes, materials, standards, thread configurations and facing options, subject to the applicable specification.

If you are looking for a Threaded Flange Manufacturer in India, A105N Threaded Flange Supplier, Stainless Steel Threaded Flange Manufacturer, ASME Threaded Flange Supplier or Custom Threaded Flange Exporter, send your complete requirement to Vandan Alloys.

Send your Threaded Flange enquiry, drawing or specification 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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Vandan Alloys manufactures and exports Threaded Flanges in A105, A105N, stainless steel, duplex and nickel alloys. ASME, EN and custom screwed flanges.

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