Lap joint flanges are ring-type joints used to connect pipe systems, components, and equipment.
These particular types of flanges are popular within piping and duct system designs due to the benefits and the high level of performance they provide.
At Specialist Sealing Products, we stock a range of seals, gaskets, and flanges suitable for various applications across all industry sectors.
To find out more about our full range, go to our page online and see how we can help you today.
You can also contact us at 01535 274 776 or email your specific requirements to sales@specialistsealingproducts.co.uk, and a member of the SSP team will be happy to help.
In this post, we look at what is a lap joint flange and what the advantages of using this type of RTJS are.
Lap Joint Flanges Explained
Similar to slip-on ring type joints, a lap joint flange is curved at the bore, and it is this curved bore that engineers use to connect stub end fittings allowing them to slide over the pipe and create the connection.
Typically used in low-pressure applications, lap joint welds go by several other terms, such as:
- Stub end flange
- Loose flange
- Backing flange
- Vanstone
- Backing ring
The design of lap joint flanges includes a smooth flat surface face. However, when used with the stub end (see below), a raised sealing face is apparent.
There are two parts to the assembly of a lap joint flange.
- The lap joint flange slides onto the pipe, acting as a connector
- The ljf is then welded to the stub end, which is then butt welded to the application (pipe end).
Note: For all the stub end is not officially part of the lap joint flange. It is always used in conjunction.
Lap ring joints can be manufactured in various materials, and you can choose the most appropriate material to suit your application.
The most common materials include:
- Stainless steel
- Carbon steel
- Other alloys
Lap joint flanges are also available in standard dimensions, making them easy to integrate into a range of piping systems and component parts.
This makes them highly flexible and a popular choice in engineered piping systems.
Stub Ends
Lap joint flanges and stub ends work hand in hand (with the stub end used as a backing flange to a lap joint flange), and the good news is stub ends are available to match both the pipe material and the wall schedule, helping to maintain both the inside and outside dimensions of the piping process.
Stub ends are also available in two lengths (short and long), and you have the option of different face finishes to meet your requirements. For example, plain, serrated, or grooved.
Assembly requirements
Assembly requires sliding the stub end into the flange ring’s bore, where it will then be welded (this must be a butt weld) to the application. On one side you will then form the sealing face while the other edge of the stub end will be secured to the lap joint flange.
Rotation of the lap joint flange is then available (after the stub end is secured to the pipe application) however, once set in place and tightened securely, the flange will no longer move freely.
Advantages of using lap joint flanges
- You have the choice of a wide range of materials, making them a suitable ring-type joint for all applications.
- You can realign and rotate the flange to ensure a secure connection. This level of flexibility also helps to speed up maintenance and inspection processes.
- Welding the stub end to the pipe means the lap joint flange is still able to rotate so you can achieve easy alignment of the bolt hole.
- This ring joint type is easy to install and uninstall, making it incredibly convenient to carry out maintenance checks and cleaning.
- They don’t require fillet welds on the plates, helping to reduce installation times.
- Lap joint flanges are available in many sizes and classes depending on application.
- They are suitable for numerous pressure and temperature applications.
- The flange can be recycled for reuse, making it a cost-effective option.
- Lap joint flanges are economical and considered inexpensive.
- Suitable for corrosive applications
- Easily configured to align with the mating flange
- Available in a range of pipe diameters.
Note: Lap joint flanges are not suitable for high-pressure applications, and they can often be bulky in their design, so they are not ideal or suitable for small piping systems or applications with high-bearing loads.
Ring Type Joints
It’s always good to know how different ring-type joints work and how the design differences between flanges can impact overall application performance.
This is vital to ensure safety (most applications involve the transfer of liquid or gas), reliability, and cost-effectiveness.
At SSP, all of our products are quality-assured and tested.
Check out our full range of seals, gaskets, and ring-type joint flanges today.
