Standards, Materials, Sizes and Variations

Size Range: 15 mm-150 mm (1/2"-6")
Thread Standards: NPT (National Pipe Thread), BSP (British Standard Pipe) - BSPP (Parallel), BSPT (Tapered)
Flange Standards: ASME/ANSI B16.5 150 lb-2500 lb
Australian Standards: AS2129 TAB D, TAB E, TAB F, TAB H with boss AS4087 PN 16, PN 21, PN 40
International Standards: EN1092, BS4504, ISO7005, ISO4331, Norsok L005
Asian Standards: JIS B2220
Threading Type: Female threaded (internal threads)
Quality Control: 100% Gaged Threading for dimensional accuracy
Thread Location: Typically central, but other configurations available.
Fast Delivery - Stock items same day, custom orders typically 10-20 days

What is a Threaded Flange?

A threaded flange, characterized by internal (female) threads designed to screw onto pipes or fittings with external (male) threads, that utilizes a screw thread to connect to a pipe.

A male thread is cut onto the pipe end, while a female thread is cut into the bore of the flange, allowing the pipe to be screwed directly into the flange without the need for welding. Key components of a flange include the flange hub (or threaded bore), bolt holes around the perimeter, and the flange face where a gasket is placed for sealing.

Thread Types

The available thread types include NPT (American standard, tapered), BSPP (British Standard Pipe Parallel), and BSPT (British Standard Pipe Tapered).

NPT and BSPT threads are tapered, designed to tighten progressively and create a seal through metal-to-metal contact with the aid of a thread sealant. BSPP threads are parallel and typically rely on a thread sealant, washer or gasket for sealing.

NPT (National Pipe Thread)

American standard, tapered design

60-degree thread angle with flat peaks

Creates seal through thread interference and sealant

BSPP (British Standard Pipe Parallel)

British parallel threads

55-degree thread angle with rounded form

Requires thread sealant, washer or gasket

BSPT (British Standard Pipe Tapered)

British tapered threads

55-degree thread angle with rounded form

Seals like NPT through thread taper with sealant

Threaded Flange Materials

Material options for these flanges include Mild Steel, Stainless Steel (grades 304, 316, and 2205), and Forged Steel (ASTM A105). The diversity in materials allows for suitability across various environments, from general utility services (Mild Steel, A105) to highly corrosive or high-strength applications (316, 2205 Duplex). Nearly all metal and plastic materials can be threaded.

Material	Grades	Key Features	Applications
Stainless Steel	304, 316, 2205	Corrosion resistance	Chemical, marine applications
Forged Steel	A105	High strength, pressure resistance	Oil & gas applications
Mild Steel	GR 250	Cost-effective	General use applications

Advantages of Threaded Flanges

No welding required – safer in explosive environments
Quick and simple installation
Easily dismantled for maintenance or temporary setups

Limitations of Threaded Flanges

More prone to leaks if misaligned or improperly sealed
Not ideal for thin-walled pipes
Require proper thread sealants (PTFE tape or liquid sealants)

Frequently Asked Questions

Weld flanges are permanently joined via welding, offering higher pressure ratings and robust strength. By contrast, threaded flanges screw onto pipes using internal threads. They provide easy, no‑weld installation—ideal for maintenance-heavy systems or environments where hot‑work is restricted.

Threaded flanges can be distinguished by:

Thread standard: NPT (American tapered), BSPP (British parallel), BSPT (British tapered)
Pressure class: Various sizes and pressures
Face type: Raised face (RF), flat face (FF), ring‑joint, etc.
Material: Carbon steel (A105), stainless steel (304, 316, 2205), GR250 mild steel
Size range: Typically NPS ½″–24″. Threads usually 15mm to 150mm. 200mm and above are rare.

Australia predominantly uses BSP threads (both BSPP and BSPT), consistent with British/Commonwealth standards. However, NPT is also common, especially in imported American equipment and in sectors like hydraulics and oil and gas. Many Australian facilities must accommodate both standards.

NPT uses a 60-degree tapered thread angle with flat thread peaks, creating a seal through thread interference and sealant. BSP uses a 55-degree thread angle and rounded form, and comes in parallel (BSPP) and tapered (BSPT) forms. BSPP requires a sealant, while BSPT seals like NPT through thread taper usually with a sealant. Their differing angles and thread pitches make them incompatible.

No. BSP and NPT threads are not compatible due to differences in angle, pitch, and thread shape. Attempting to connect them may result in leaks, thread damage, or safety hazards.

Use a calibrated thread gauge to measure pitch and thread angle:

NPT: 60° angle, typically 14 TPI for ½″ and ¾″ sizes
BSP: 55° angle, similar pitch but different profile

Also check for markings like "NPT" or "BSP" indicating the thread type. Proper identification is crucial for safe and leak-free connections.

A common pipe standard is ASME B1.20.1, which covers threaded flanges (including NPT). It defines dimensions, diameters and thread forms. There are many other flanges that cover threads for specific applications and many large companies have their own standards as to how these threads are used.

Advantages:

No welding required – safer to maintain in explosive environments
Quick and simple installation
Easily dismantled for maintenance or temporary setups

Limitations:

Not suited for high-temperature or high-stress systems
More prone to leaks if misaligned, improperly sealed, or subject to excessive vibration.
Not ideal for thin-walled pipes

There's no universal "better"—each thread type serves different regions and systems. BSP is standard in Australia, UK, and Europe; NPT is standard in North America. BSPP threads are parallel and seal with gaskets, while NPT and BSPT are tapered and seal through thread interference. The best choice depends on regional standards, equipment compatibility and the technical application.

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Threaded Flanges

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Standards, Materials, Sizes and Variations

What is a Threaded Flange?

Thread Types

Threaded Flange Materials

Advantages of Threaded Flanges

Limitations of Threaded Flanges

Frequently Asked Questions

Why Choose Balcombe Engineering

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