Screwed Flange

Screwed Flange manufacturer in USA

At SVR Global, we produce screwed flanges in various material types such as carbon steel, stainless steel, alloy steel, duplex steel, super duplex steel, and nickel alloys in accordance with ASME B16.5, ASME B16.47, BS 10, DIN, and MSS SP-44 dimension standards. The screwed flanges available with pressure class options from 150# to 2500#, in nominal bore (NB) sizes from 1/2” to 48”, and for pipeline applications where welding cannot be done.

What is a Screwed Flange?

Screwed flanges are a type of flanges where the bores of the flanges are threaded internally and mate with male threads (NPT, BSP, BSPT) present at the end of the pipes. These flanges are connected using mechanical means by screwing the pipe inside the bore of the flange, thereby negating the requirement of a welding operation in the joint area. Therefore, they can be used for low pressure, low temperature pipelines.

Key Characteristics of Screwed Flanges:

• Thread internal to NPT (National Pipe Thread) or BSP (British Standard Pipe) standards 

• No need for welding for joining the pipe with the flange, saving time during installation 

• Flanges may be with RF (Raised Face), FF (Flat Face) or RTJ (Ring Type Joint) faces 

• Good choice for use with schedule 40, 80, 160 and XXS pipes

• Manufactured through forging, not casting, for improved grain structure and mechanical strength

• Bolt hole pattern and outside diameter conform to standard flange dimension tables for interchangeability with weld neck, slip on, and blind flanges of the same class and size

Working Principle of a Screwed Flange:

A screwed flange works on a mechanical thread engagement principle rather than fusion or bonding:

1. Thread Mating - The flange bore is machined with internal NPT/BSP threads. The pipe end is externally threaded to the matching taper and pitch.

2. Torque Driven Engagement - The pipe is rotated into the flange bore as threads engage, the taper creates increasing metal to metal contact, building a tight interference fit.

3. Sealing Action - Thread sealant or PTFE tape fills micro gaps between thread flanks, blocking leak paths as the joint is torqued to the required makeup.

4. Load Transfer - Once seated, axial and pressure loads from the pipeline are transferred through the thread flanks into the flange body, and then into the bolted joint at the mating flange face.

5. Face Compression - The flange face (RF/FF/RTJ) is bolted to the counter flange with a gasket, and bolt torque compresses the gasket to complete the pressure tight seal.

Manufacturing Process:

SVR Global produces screwed flanges through a hot forging process using round bar stock, followed by precision CNC machining, heat treatment, and thread cutting. The manufacturing sequence includes:

1. Raw material selection and testing - chemical composition and mechanical property verification of billets before forging

2. Hot forging - shaping the flange blank under controlled temperature to achieve directional grain flow for uniform strength

3. Normalizing / heat treatment - relieving internal stresses and refining grain structure per ASTM specifications

4. CNC turning and facing - machining outer diameter, bore, bolt circle, and facing to ASME B16.5 or MSS SP-44 tolerances

5. Thread tapping - cutting internal NPT/BSP threads to the required taper and pitch

6. Surface finishing - facing finish per stock removal (63 AARH) or as specified

7. Inspection and testing - dimensional check, hardness testing, ultrasonic testing (UT), radiography (RT), positive material identification (PMI), and third-party inspection (TPI) where required

8. Marking and traceability - heat number, size, class, and material grade stamped per ASME B16.5 marking requirements

Materials Offered:

• Carbon Steel - ASTM A105, A350 LF2

• Stainless Steel - ASTM A182 F304, F304L, F316, F316L, F321, F310, F347

• Alloy Steel - ASTM A182 F5, F9, F11, F22, F91

• Duplex & Super Duplex Steel - ASTM A182 F51 (UNS S31803), F53 (UNS S32750), F55 (UNS S32760)

• Nickel Alloys - Monel 400, Inconel 600/625, Hastelloy C276, Incoloy 800/825

• Titanium - ASTM B381 Grade 2, Grade 5

Dimensional Standards and Specifications:

Applications of Screwed Flanges:

Screwed flanges are specified in piping systems where welding is restricted, where lines carry non corrosive fluids at moderate pressure and temperature, or where equipment needs to be periodically dismantled without cutting the pipe. Typical applications include:

• Instrumentation and gauge piping lines requiring frequent disassembly

• Low pressure utility piping such as compressed air and service water lines

• Piping systems in hazardous or classified areas where hot work (welding) permits are restricted

• Skid mounted equipment and modular piping assemblies fabricated off site

• Chemical processing lines carrying fluids compatible with thread sealants

• Small bore piping in offshore platforms and onshore process units

• Retrofit and maintenance piping where existing lines have threaded pipe ends

• Pump and valve end connections in low pressure hydraulic circuits

• Fire protection and sprinkler branch piping

• Pneumatic conveying and gas distribution networks operating within schedule 40/80 limits