What is RF in flange, and why they are widely used in oil refineries and petrochemical plants?

If you are involved in the construction of refineries and petrochemical plants,high-temperature and high-pressure pipelines are the norm. These systems transport critical fluids such as crude oil, steam, and process chemicals under extreme operating conditions. Ensuring a reliable, leak-free connection between pipes, valves, and equipment is essential to maintain safety and system integrity.

This is where Raised Face (RF) flanges come into play. For example, in a crude distillation unit operating at over 400°C and up to Class 600 pressure, RF flanges are commonly used to connect heat exchangers, pressure vessels, and process piping. But what exactly is RF in flange? Let’s take a closer look.

What is RF in Flange?

RF stands for Raised Face, one of the most common flange face types used in industrial piping and mechanical systems. In a Raised Face flange,the main part of the flange is flat and is used to pass bolts. Around the center hole connected to the pipe, there is an annular protrusion that is slightly higher than the other surfaces of the flange.The raised face area can also have different finishes (e.g., serrated, smooth, or spiral), which influence gasket performance and sealing reliability.

ASME B16.5 A105 RF Slip On Flanges

The typical height of the raised face depends on the pressure class of the flange:

For pressure classes 150 and 300: 1.6 mm (0.06 inches)

For pressure classes 400 and above: 6.4 mm (0.25 inches)

This design helps concentrate the compressive force on a smaller gasket area, improving the sealing performance under high pressure and temperature conditions.

Benefits of Using RF (Raised Face) Flanges in refineries and petrochemical plants

RF (Raised Face) flanges offer several critical advantages in refineries and petrochemical plants. First, The raised surface allows the gasket to be compressed more effectively, which reduces the risk of leaks. Second,their compatibility with a wide range of gasket materials, including spiral wound and metallic gaskets, provides flexibility for corrosive, toxic, or flammable media. Finally, the standardized raised face design (per ASME/EN) allows for easier inspection, replacement, and interchangeability across systems, reducing maintenance downtime and improving operational efficiency.

RF Flange vs. Other Flange Face Types

There are several types of flange faces, including:

Flat Face (FF): No raised surface; used where full contact is needed, often in low-pressure systems.

Ring Type Joint (RTJ): Features a groove for metal ring gaskets; used in high-pressure, high-temperature environments.

Tongue & Groove / Male-Female (T&G / M&F): Precise alignment, often for special sealing requirements.

Compared to these, the RF flange offers a balance of performance, cost, and ease of use, which is why it remains the most widely used face type in piping systems.

ASTM A182 F51 S31803 JIS B2220 10K RF blind flange

Where to find a reliable supplier of RF flanges?

When sourcing RF (Raised Face) flanges for demanding applications such as oil refineries and petrochemical plants, choosing a reliable manufacturer is essential to ensure product quality, performance, and compliance with international standards. Haihao Group is a trusted global supplier with decades of experience in manufacturing industrial pipe fittings and flanges. Our RF flanges are produced in accordance with ASME, EN, DINand other international standards, and are widely used in high-pressure and high-temperature environments. With strict quality control, complete testing certifications (including PMI, UT, RT, and MTC), and fast global delivery, Haihao Group provides safe, durable, and cost-effective flange solutions for some of the most challenging projects worldwide. Whether you need carbon steel, stainless steel, or alloy flanges, Haihao is your dependable partner.

ASME B16.5 class 600 ASTM A105 RF weld neck flange

In the harsh and demanding environments of oil refineries and petrochemical plants, the need for secure, high-performance pipe connections cannot be overstated. Raised Face (RF) flanges offer a proven solution, delivering superior sealing performance under high temperature and high pressure conditions. With experienced manufacturers like Haihao Group, securing reliable RF flanges for your projects becomes easier and more efficient—ensuring safety, durability, and compliance every step of the way.