Threaded Flange

Key Features:

No Welding Required: Ideal for applications where welding is not feasible or safe (e.g., in explosive environments).

Easy Installation and Removal: Especially suitable for maintenance or temporary systems.

Low Pressure Use: Typically used in low-pressure, non-critical systems.

Thread Standards: Usually conform to NPT (National Pipe Thread) or BSPT (British Standard Pipe Tapered) standards.

Parts of a Threaded Flange:

1. Flange Body: This is the main circular part of the flange.

It provides the structural integrity for the connection.

2. Threaded Bore (Hub): This is the central hole within the flange body that has internal screw threads.

The threads match the external threads on the pipe, allowing the flange to be screwed onto the pipe.

3. Flange Face: This is the mating surface of the flange that comes into contact with the gasket and the facing flange.

Threaded flanges typically have a raised face, which is a slightly elevated ring around the bore. This concentrates the pressure on the gasket to create a tight seal.

4. Bolt Holes: These are holes evenly spaced around the circumference of the flange body.

Bolts are inserted through these holes to tighten the connection between two flanges, compressing the gasket in between.

Common Types of Sealing Faces

Raised Face (RF): This is the most common type. The gasket surface is raised above the bolting circle face.

The primary purpose of a raised face is to concentrate the pressure on a smaller gasket area, increasing the sealing capability of the joint.

Flat Face (FF): This type has a flat gasket surface in the same plane as the bolting circle face.

Flat face flanges are often used when the mating flange or flanged fitting is made of a fragile material like cast iron, as the flat face prevents excessive stress that could crack the flange.

Standard Specification For Threaded Flange

Sealing Face	RF, FF, FTJ
Size Range	1/2” – 48” / DN15 – DN1200
Pressure Rating	Class 150, 300, 600, 900, 1500, 2500lb
ASME Standard	ASME / ANSI B16.5, ASME B16.47 Series A/B
EN Standard	EN 1092-1
DIN Standard	DIN2566, DIN 2565, DIN 2567, DIN 2568, DIN 2569
BS Standard	BS4504 , BS10

Material & Grades of Threaded Flange :

Carbon Steel Threaded Flanges :

Carbon Steel: ASTM A105 / A105N,ASTM A350 LF2 / LF3, A694 F42 / 46 / 52 / 56 / 65 / 70

Alloy Steel Threaded / Screwed Flanges :

ASTM A 182 F5, F9, F11, F12, F22, F91

Stainless Steel Threaded Flanges :

ASTM A 182 F304, 304L, 304H, 316, 316L, 316Ti, 310, 310S, 321, 321H, 317, 347, 347H, 904L

Duplex & Super Duplex Steel Threaded Flanges :

ASTM A 182 F 44, F 45, F51, F 53, F 55, F 60, F 61

Copper Alloy Steel Threaded Flanges :

 ASTM SB 61 , SB62 , SB151 , SB152 UNS No. C 70600 (Cu-Ni 90/10), C 71500 (Cu-Ni 70/30), UNS No. C 10100, 10200, 10300, 10800, 12000, 12200

Nickel Alloy Threaded Flanges :

ASTM SB564, SB160, SB472, SB162 Nickel 200 (UNS No. N02200), Nickel 201 (UNS No. N02201), Monel 400 (UNS No. N04400), Monel 500 (UNS No. N05500), Inconel 800 (UNS No. N08800), Inconel 825 (UNS No. N08825), Inconel 600 (UNS No. N06600), Inconel 625 (UNS No. N06625), Inconel 601 (UNS No. N06601), Hastelloy C 276 (UNS No.N10276), Alloy 20 (UNS No. N08020)

Thread Types of Threaded Flange

1. NPT (National Pipe Thread)

Type: Tapered (conical threads)

Standard: ANSI/ASME B1.20.1

2. BSPT (British Standard Pipe Tapered)

Type: Tapered (conical threads)

Standard: ISO 7-1 / EN 10226

3. BSPP (British Standard Pipe Parallel)

Type: Parallel (straight threads)

Standard: ISO 228

4. ISO Thread

Type: Can be either parallel or tapered threads.

Standard: ISO 7-1 (tapered) or ISO 228 (parallel)

5. NPTF (National Pipe Thread Fuel)

Type: Tapered (conical threads), but designed for a more precise seal compared to NPT.

Standard: ANSI B1.20.3

How to Install Threaded Flange

Threaded flanges are easy to install without welding. To install, simply apply a suitable thread sealant, such as PTFE tape or pipe compound, to the male pipe thread. Carefully screw the threaded flange onto the pipe by hand to avoid cross-threading, then tighten securely using a pipe wrench. Align the flange bolt holes with the mating flange and connect using appropriate bolts and a gasket if needed. This type of flange suits low-pressure systems and applications where welding is not permitted.

Advantages of Threaded Flange

No Welding Required

Easy Installation and Removal

Cost-Effective

Quick Assembly

Suitable for Smaller Pipe Sizes

Leak-Free Connection

Corrosion-Resistant Materials

Flexibility

Uses of Threaded Flanges:

Oil & Gas Industry Chemical Processing

Water Treatment

Marine Systems

Fire Protection Systems

HVAC Systems

Pharmaceutical & Food Processing

Compressed Air Systems

Frequently Asked Questions (FAQs)

1. What is the difference between a slip-on flange and a threaded flange?

The main difference between a slip-on flange and a threaded flange lies in their connection method. Workers slide the pipe through a slip-on flange and then weld the flange in place, typically using both a fillet weld on the inside and outside, making it suitable for higher pressure and temperature applications. In contrast, a threaded flange has internal threads and connects to a pipe with external threads, allowing for installation without welding. This makes threaded flanges ideal for low-pressure systems and in environments where welding is not feasible, such as explosive or flammable areas.

2. What are different types of flanges?

Weld Neck Flange – Butt-welded to pipe; used for high pressure and temperature.

Slip-On Flange – Slides over pipe and welded; easy to install; for low–medium pressure.

Threaded Flange – Screws onto threaded pipe; no welding; used in low-pressure systems.

Socket Weld Flange – Pipe fits into socket and is welded; good for small high-pressure lines.

Blind Flange – Solid plate; used to block or close a pipe end.

Lap Joint Flange – Used with a stub end; good for systems needing frequent disassembly.