Flanges Explained Types, Face Finishes & Pressure

Flanges are one of the most important components in any piping system. They connect pipes, valves, pumps, and equipment — ensuring a safe, leak-proof flow in industrial plants.

But many engineers, buyers, and project managers struggle with questions like:

Which flange type should I use?
What is RF, FF, RTJ face finish?
What do pressure ratings like 150, 300, 600 mean?
Which flange is best for high-pressure or corrosive service?

This guide explains everything in simple, humanized English so anyone can choose the right flange confidently.

What Are Flanges?

A flange is a mechanical connector that joins pipes or equipment using bolts and gaskets.

✔ Why flanges are important

Allow easy assembly & disassembly
Provide leak-proof sealing
Handle high pressure
Help in inspection & maintenance

Types of Flanges (Most Common in 2025)

1. Weld Neck Flange (WNRF)

Long tapered neck
Best for high pressure & temperature
Used in boilers, heat exchangers, chemical plants

2. Slip-On Flange (SORF)

Pipe slips inside the flange
Easy installation
Suitable for low to medium pressure

3. Blind Flange (BLRF)

Used to close pipe ends
Common in testing & maintenance

4. Socket Weld Flange (SWRF)

Small pipe inserted into socket
Best for small bore, high-pressure lines

5. Threaded Flange (THRF)

No welding required
Used in flammable environments where welding is unsafe

6. Lap Joint Flange (LJRF)

Used with stub ends
Ideal for systems requiring frequent dismantling

Flange Face Finishes (Very Important for Leak-Proof Seal)

Flange faces determine the type of gasket used & sealing performance.

1. Raised Face (RF)

Most common
Suitable for 150, 300, 600 class flanges

2. Flat Face (FF)

Used for cast iron and low-pressure service

3. Ring Type Joint (RTJ)

Metal-to-metal sealing
Excellent for very high pressure + high temperature
Used in petrochemical and offshore plants

Flange Pressure Ratings (Class 150 to Class 2500)

Class	Pressure Capacity (Approx)	Common Use
150	Low pressure	Water, HVAC
300	Medium pressure	Petrochemical
600	High pressure	Steam, Oil
900	Higher pressure	Offshore
1500	Very high	Refineries
2500	Extreme pressure	Critical plants

Material Selection Guide

Stainless Steel (304, 316, 321): For water, food, chemical, pharma lines.
Carbon Steel (A105): For general & low-temperature service.
Alloy Steel (F5, F9, F11, F22): For high-temperature & power plant use.
Duplex / Super Duplex: For seawater & chloride environments.
Nickel Alloys (Inconel, Hastelloy, Monel): For highly corrosive chemical processing.

How to Select the Right Flange? (Simple Guide)

Choose based on:

Pressure rating
Temperature
Corrosion level
Piping design
Gasket compatibility
Assembly frequency
Welding requirement

If unsure → Moksh Tubes can analyze your operating conditions and recommend the best flange type.

Why Moksh Tubes Is a Trusted Flange Supplier

Full range: WNRF, SORF, BLRF, THRF, SWRF, LJRF
Stainless, Alloy Steel, Carbon Steel, Duplex, Nickel Alloys
MTC 3.1 / 3.2 provided
Large ready stock for fast delivery
Export to 40+ countries
Precision machining & perfect surface finish
Customized flanges available on request

Conclusion

Flanges are essential for creating strong, leak-proof, and safe piping connections. Understanding types, face finishes, and pressure ratings makes it easier to select the right one for your project and avoid costly failures.

If you need help choosing the right flange for your pressure or temperature conditions, the Moksh Tubes technical team is always ready to assist.