Lap Joint Flange

What is a Lap Joint flange?

A lap joint flange (LJ flange) consists of two parts: a stub end and a lap joint ring flange. To be technically correct, the stub end is not part of a lap joint flange. A stub end always uses a lap joint flange. They often call it a “lap joint flange.”

Because of their design, lap joint flanges always have a flat face with a smooth surface. But when you combine it with the stub end, the sealing face rises. This occurs because the sealing face of the stub end is above the flange’s bolting plane.

The forged steel lap joint flange has no sealing face; only the stub end has the sealing face.

What is a lap joint flange used for？

Lap Joint Flanges have many uses in various sectors due to their distinctive design and practical qualities.

These lap joint flanges work perfectly for low to moderate-pressure applications. They are commonly used where access is limited or regular maintenance is needed.

• Chemical Processing Industry

Lap Joint Flanges excel in chemical facilities where pipelines must be routinely maintained, checked, and repaired.
They enable quick disconnection of parts, providing effective maintenance access without the need for extensive welding. This benefit reduces downtime, improves safety, and supports maintaining the integrity of chemical processes.

• Food and Beverage Industry

Lap Joint Flanges are essential in maintaining the sterility and cleanliness of processing pipes. These flanges facilitate disassembly, providing access to vital parts for thorough cleaning and sterilization.

• Water Treatment Facilities

Water treatment facilities require regular maintenance and repair to ensure the efficient treatment and distribution of water. Lap Joint Flanges offer an ideal solution, as they allow for quick access to critical components without disrupting the entire system. This feature significantly reduces downtime and helps maintain the continuous operation of water treatment processes.

Material Standards and Dimensions

Lap joint flange dimensions are defined by ANSI/ASME B16.5 for sizes NPS ½″ to 24″ and pressure classes from 150 to 2500. For larger pipe sizes, NPS 26″ to 60″, dimensions follow ASME B16.47 standards. They are commonly manufactured from materials such as A105 forged carbon steel, A182, 304/316 forged stainless steel, and alloy steel to suit a wide range of service conditions.

Click here to get more standard dimensions. 

The advantages of the lap joint flange design are:

1. Inexpensive.
2. Well-suited for corrosive applications.
3. Requires only a single full penetration butt weld.
4. Only the stub end has contact with the process medium
5. It can be easily adjusted to align with the mating flange (the flange can be rotated until the bolt holes align).
6. It is available in almost all pipe diameters.
7. They allow for quick disconnection of parts. This makes maintenance easier without needing much welding.
There are some limitations on the lap joint flange’s usage, mostly due to its bulkier multiple-component design. Lap joint flanges cannot be used for small-sized piping.

Lap Joint Flanges Process:

How does it compare with other flange types?

We’ll compare the most commonly used flanges used in the industry with lap joint flanges. It will guide you in selecting the best flange for different conditions and scenarios.

Weld neck flange VS. Lap joint flanges

Weld neck flanges are welded to the pipe with the long tapered hub. They are good for applications under high-pressure conditions, but they are expensive. Also, since they are welded, their maintenance is costly and time-consuming.

On the other hand, lap joint flanges can be installed and maintained easily due to their rotating design. It makes them perfect for systems requiring regular maintenance and adjustments.

Slip-on flanges VS. Lap joint flanges

Slip-on flanges, as the name suggests, slide over the pipe. Then, they are welded on both sides to provide strength. They are not costly, but their strength under fatigue conditions is low.

Lap joints flange provide easy alignment compared to slip on flanges. Its because the flange itself doesn’t require to be aligned properly before welding.

Socket weld flanges VS. Lap joint flanges

Socket weld flanges are usually used in pipes with small diameters. The pipe is inserted into the flange, and then it is welded.

While lap joint flanges don’t require any welding. It eliminates the risk of weld fatigue and makes assembly and disassembly faster.

Threaded flanges VS. Lap joint flanges

Threaded flanges do not require any welding. They are screwed directly into the threaded pipes. This makes them suitable to be used in explosive environments. However, they are not suitable for high-pressure environments.

Lap joint flanges can be installed in piping systems with varying pressure and temperature. You can simply change the stub end and gasket based on the conditions. It gives you more flexibility and ensures easier alignment.

While all these flange types have their own pros and cons, it is suggested to use multiple flange types aligned with lap joint flanges. It gives you more flexibility and ensures safety under different conditions.

As a leading manufacturer of carbon steel pipe fittings and flanges across China, JSFITTINGS has more than 35 years of experience serving industries of all sizes. Our expert sales analysts are available today to help you choose the ideal lap joint flanges or rolled angle rings for your needs.

Contact us today to learn more about our selection of high-quality steel flanges.

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