Various Types of Flanges: Pipe Flange Types, Uses and Selection Guide

Flanges are detachable pipe connectors used to join pipe, valves, pumps, vessels, heat exchangers and other equipment. Because every piping system has different pressure, temperature, maintenance and space requirements, engineers choose from various types of flanges rather than using one universal design.

This guide explains the most common pipe flange types, how each flange type works, where it is normally used and what buyers should confirm before ordering. It is written for plant engineers, procurement teams, fabricators and distributors comparing different types of flanges for industrial service.

Why There Are Different Flange Types

Flanges may look similar from a distance, but their bore, hub, face, connection method and pressure behavior can be very different. Some are designed for high pressure and high temperature. Some are chosen because they are economical and easy to install. Others are used for frequent disassembly, pipe end closure or corrosion-resistant service.

When people search for flanges types or types of flanges in piping, they are usually trying to match a piping problem with the correct mechanical connection. The right choice affects leak performance, welding cost, inspection time, replacement speed and project safety.

Main Types of Pipe Flanges

Flange Type	How It Connects	Typical Application	Main Advantage
Weld neck flange	Butt welded to pipe through a tapered hub	High pressure, high temperature, cyclic load	Excellent stress distribution and reliability
Nắp trượt	Pipe slips through flange and is fillet welded	General industrial piping and utility lines	Lower cost and easier alignment
Bích hàn socket	Pipe inserts into socket and is fillet welded	Small-bore high-pressure piping	Good strength for small pipe sizes
Threaded flange	Pipe screws into internal flange thread	Small-bore systems where welding is not preferred	No field welding required
Lap joint flange	Works with a stub end; backing flange rotates freely	Systems requiring frequent dismantling or bolt alignment	Easy alignment and economical backing flange option
Nắp bịt	Bolted blank plate closes a pipe or nozzle	Line ends, pressure testing, inspection ports	Strong removable closure
Plate flange	Flat ring welded to pipe	Low to moderate pressure and economical projects	Simple fabrication and competitive cost

Weld Neck Flange

A weld neck flange has a long tapered hub and is butt welded to the pipe. Among the common types of pipe flanges, it is one of the best options for severe service because the hub helps transfer stress gradually from the flange to the pipe wall.

Choose weld neck flanges for high pressure lines, high temperature service, pressure vessels, oil and gas piping, steam systems and applications with vibration or repeated bending. The main tradeoff is cost: weld neck flanges require more material, precise welding and proper inspection.

Slip On Flange

A slip on flange slides over the pipe and is normally welded with fillet welds on the inside and outside. This type of flange is popular because installation is straightforward and the product is widely available.

Slip on flanges are common in water treatment, HVAC, low-pressure process piping, general factory utilities and non-critical lines. They are not usually the first choice for severe cyclic loads or very high-pressure systems, but they offer a practical balance of cost and performance for many projects.

Socket Weld Flange

Socket weld flanges are used mainly for smaller pipe sizes. The pipe is inserted into a recessed socket, leaving a small gap before welding. Compared with threaded flanges, socket weld flanges avoid thread leakage paths and can handle stronger small-bore service.

They are common in chemical plants, hydraulic systems, small high-pressure pipelines and instrument-related piping. Buyers should confirm socket depth, pipe schedule, material grade and whether the project permits socket weld joints.

Đai ốc ren

Threaded flanges, also called screwed flanges, have internal threads that match the external pipe thread. They are useful when welding is not allowed, when hot work permits are difficult, or when assembly must be fast.

This flange type is normally limited to small-bore piping and suitable service conditions. It should be selected carefully for vibration, high temperature cycling, hazardous fluid or corrosive service because thread engagement and sealant quality become critical.

Lap Joint Flange

A lap joint flange works together with a stub end. The stub end contacts the process fluid, while the backing flange provides bolt load and can rotate around the pipe. This design is useful when bolt-hole alignment matters or when the line must be dismantled frequently.

Lap joint flanges are often used in stainless steel or alloy piping where the backing flange may be made from a lower-cost material. They are also practical in large pipe sizes because flange rotation simplifies field alignment.

Blind Flange

A blind flange has no center bore. It closes the end of a pipe, vessel nozzle or valve outlet. Among the different kinds of flanges, blind flanges often carry high stress because pressure acts directly across the closed face.

They are used for pressure testing, future expansion points, maintenance isolation and inspection openings. The gasket, bolting and pressure class must be selected carefully because a blind flange can see significant bolt load and bending force.

Special Industrial Types of Flanges

Beyond the standard designs, there are several industrial types of flanges for special piping needs. These include reducing flanges, orifice flanges, swivel ring flanges, spectacle blinds, long weld neck flanges and custom large-diameter flanges.

Special Flange	Purpose	Common Use
Reducing flange	Connects different pipe sizes without a separate reducer	Compact equipment connections
Orifice flange	Supports flow measurement with pressure taps	Process instrumentation and metering
Swivel ring flange	Allows bolt-hole rotation for alignment	Subsea, offshore and large-diameter piping
Long weld neck flange	Extended neck for vessel or nozzle connection	Pressure vessels and tanks
Custom flange	Made according to drawing or non-standard dimensions	OEM equipment and retrofit projects

Flange Face Types Matter Too

Choosing among kinds of flange is only part of the decision. The flange face controls how the gasket seals. Common face types include raised face, flat face, ring type joint, tongue and groove, and male-female designs.

Face Type	Phù hợp nhất cho	Important Note
Raised face	Most ASME process piping	Works with many gasket materials
Flat face	Cast iron, low-pressure equipment, full-face gaskets	Do not casually mate with raised face designs
Ring type joint	High pressure and critical service	Uses metal ring gasket and precision groove
Tongue and groove	Controlled gasket positioning	Mating pair must match exactly

How to Choose the Right Flange Type

When comparing pipe flange types, do not start only with price. Start with the service conditions, piping code and maintenance plan. A low-cost flange can become expensive if it causes welding rework, bolt misalignment or leakage during testing.

1. Confirm the applicable standard: ASME, EN, DIN, JIS, GOST or project drawing.
2. Define pressure class, temperature range and fluid service.
3. Choose the flange connection method: butt weld, fillet weld, threaded, lap joint or blind closure.
4. Confirm material grade, such as ASTM A105, A182 F304, A182 F316 or alloy steel.
5. Select the face type and gasket style together.
6. Check pipe schedule, bore, bolt holes and dimensional standard before production.
7. Request MTC, dimensional report, marking photos and packing details for export projects.

Quick Selection Table

Project Requirement	Recommended Flange Type	Reason
High pressure steam or oil and gas	Weld neck flange	Strong butt-welded connection and good fatigue resistance
Economical general piping	Slip on flange or plate flange	Simple installation and competitive cost
Small-bore high-pressure line	Bích hàn socket	Compact and strong for smaller sizes
No welding allowed	Threaded flange	Mechanical assembly through pipe threads
Frequent dismantling or bolt alignment issue	Lap joint flange with stub end	Backing flange can rotate freely
Pipe end closure or pressure test point	Nắp bịt	Removable strong closure

FAQ

What are the most common types of flanges in piping?

The most common types of flanges in piping are weld neck, slip on, socket weld, threaded, lap joint and blind flanges. Plate flanges and special flanges are also widely used depending on the market and standard.

Which flange type is best for high pressure?

Weld neck flanges are often preferred for high pressure, high temperature and cyclic service because the hub and butt weld provide better stress transfer than many other designs.

Are flange types and flange face types the same?

No. Flange type describes the body design and connection method, such as weld neck or slip on. Face type describes the sealing surface, such as raised face, flat face or ring type joint.

How do I compare different kinds of flanges for purchase?

Compare standard, pressure class, material, face type, pipe schedule, end connection, inspection document and application. If any item is unclear, confirm it before manufacturing.

Final Thoughts

There are many various types of flanges, and each one solves a different piping problem. Understanding pipe flange types, face designs, materials and standards helps buyers avoid leakage, wrong dimensions and costly installation delays. Songhai Flange can support standard and custom flanges for industrial piping, pressure vessels, oil and gas, chemical equipment, water treatment and OEM projects.