Raised and flat face flanges are two of the most commonly used flange types for various applications in numerous industries.
Flanges play a pivotal role in joining pipes, valves, and fittings, providing a secure, leakproof, long-lasting connection you can have confidence in.
Available in a range of shapes, sizes, and specifications, you can buy RTJs to suit all environments and situations.
When it comes to flanges, the flange face is what will determine the surface finish of the pipe flange, making it essential that you choose the correct type in order to ensure perfect alignment and correct sealing and pressure containment because the type you choose can significantly impact overall performance and reliability of the system.
Difference between raised face and flat face flanges
The main difference between the raised and flat-faced flange is that the raised-face flange has a raised area (above the bolting circle) that surrounds the pipe bore where the gasket is then placed, and the flat-faced flange does not.
The raised face flange is the most common, where users can achieve a secure seal by using semi-metallic gaskets for compression.
Raised-face flanges are suitable for most applications as they can withstand high and low temperature and pressure ranges.
When we look at this flange in more detail, you will see that the flange focuses more pressure on the smaller gasket area to increase the joint’s pressure containment capabilities.
It’s important to note that when pressure ratings increase when using the raised face flange, the diameter will also increase, alongside bolt requirement and thickness levels of the flange and raised face.
Flat faced flanges are similar to metal ring gaskets with a raised face, simply without the raised area. This means the whole surface of this o ring is flat, so it will make full contact with the entire surface where the two flanges are mated.
Manufactured from non-metallic materials, like Viton or EPDM, it is uncommon for this type of flange to use metallic materials.
This flange type is most desirable when trying to avoid bending, which can occur when the bolts on the flange are torqued, as some flange materials can easily break (primarily cast iron and fibreglass).
Flat-faced flanges are typically used in less intense, low-pressure, and low-temperature applications, such as low-pressure water piping.
When creating the perfect seal, both the raised and flat-faced flange can be used alongside two types of gaskets:
Ring-type gasket – sitting around the pipe bore and inside the flange bolts; this type of gasket requires less material and cutting. However, it can be more challenging to clamp into position. Inside and outside diameter, as well as thickness, must be considered when opting for this gasket.
Full-face gasket – can be used with both types of flanges but is often preferred with the flat-faced flange as it has the same outer diameter. The full-face gasket must have holes for the bolts that secure the flanges to pass through. This gasket is easy to align, but installation requires the entire joint to be taken apart. Great at preventing dirt from entering the joint, you will need to account for inside and outside diameter, bolt circle diameter, number of bolt holes required, and gasket thickness.
Qualities of raised and flat-faced flanges
Raised face flanges – the raised element is above the bolting circle face. This type of flange is most commonly used in oil and gas pipelines. Raised face flanges can endure more challenging situations as the raised element of this flange creates an incredibly secure seal when compressed. Installation is quick, providing a barrier and preventing liquids and gases from escaping. This type of flange is chosen when integrity is non-negotiable. Resistant to erosion and corrosion, this flange also reduces the need for frequent maintenance.
Flat-faced flanges are one of the simplest flanges available; the main aim of this type of flange is to prevent the bending movement that is put on the flanges as the bolts are torqued. A smooth, even surface with no protrusions, this type of flange is paired with non-metallic gaskets to ensure a secure and proper seal. Providing a larger contact area to offer a more secure seal, this type of flange helps to enhance pipe system safety and integrity.
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It’s vital that you choose the right flange face for your application to ensure a smooth operation and secure seal.
Considering pressure, temperature, alloy properties, and purpose, you need to choose a flange and gasket type that meets the requirements and conditions of your application to ensure optimal performance and longevity.
At Specialist Sealing Products, we supply a range of flange types suitable for various applications.
Contact our sales team today to find out more.
