--- title: Difference Between Lap Joint Flange and Stub End date: 2025-02-05T09:43:25Z modified: 2026-07-16T08:38:15Z permalink: "https://www.longanflange.com/blog/lap-joint-stub-end-difference/" type: post status: publish excerpt: "" wpid: 1808 categories: - Blog featured_image: "https://www.longanflange.com/wp-content/uploads/2025/02/lap-joint-stub-end-flange-difference.jpg" featured_image_alt: lap joint stub end flange difference timestamp: 2026-07-16T08:38:15Z tags: - Blog --- [A lap joint flange](https://longanflange.com/products/stainless-steel-lap-joint-flange/) (LJF) is a two-piece assembly consisting of a stub end welded to the pipe and a separate backing flange that slides over it. A stub end is just the short pipe section that is welded to the main pipeline and provides the sealing surface for the flange connection. The key difference is that a lap joint flange allows for rotation and easier alignment, whereas a stub end is a fixed component that must be welded to the pipe. ![Lap Joint Flanges](https://longanflange.com/wp-content/uploads/2024/07/2aebc75de14c6b4b9bad.png) ![stub end flange dimension](https://longanflange.com/wp-content/uploads/2024/07/12beab0746f1e37d93ce.png) ## **Function and Components** A lap joint flange is designed for flexibility and cost savings in piping systems that require frequent maintenance or disassembly. It consists of two parts: 1. **Stub end:** Welded to the pipe, it provides the sealing face for the flange connection. 2. **Backing flange:** A loose flange that slides over the stub end and allows for easy bolt alignment. A stub end alone does not serve as a flange—it needs a lap joint flange to function as a complete connection. ## **A Closer Comparison** Lap joint flanges and stub ends have different roles in a piping system. A stub end is welded to the pipe and provides the sealing surface. A lap joint flange includes a stub end and a loose backing flange that helps with alignment. This table shows the main differences between them: | **Feature** | **Lap Joint Flange (LJF)** | **Stub End** | | --- | --- | --- | | Function | A complete flange system with a rotating backing flange. | A short pipe section welded to the main pipe. | | Rotation | The backing flange rotates for easy alignment. | Does not rotate—fixed in place. | | Sealing Face | No sealing face—relies on the stub end for sealing. | Provides the sealing surface for the connection. | | Maintenance | Easy to remove without cutting the pipe. | Must be welded to the pipe, making removal harder. | | Material Flexibility | Backing flange can be a lower-cost material. | Stub end must match pipe material. | | Best Used For | Systems requiring frequent disassembly or realignment. | Welded piping systems where flexibility isn’t needed. | ## **When to Use a Stub End vs. a Lap Joint Flange** Deciding when to use a stub end vs. a lap joint can be confusing. To help, we’ve shared some ideal scenarios where one of options works better than the other. ### **Use a Stub End** - In permanent piping systems where the connection does not need frequent disassembly. - When a welded connection is required for structural integrity. - If a standard flange type (weld neck, slip-on, or socket weld) is being used instead of a lap joint flange. ### **Use a Lap Joint Flange** - In systems that require frequent maintenance or cleaning. - When bolt-hole alignment is difficult, and a rotating flange is needed. - In cost-sensitive applications, where the backing flange can be made from a lower-cost material. - For large pipes or high-precision installations, where rotation helps ensure an accurate fit. Need Stainless Steel Flanges for Your Project? Manufacturer since 2011 · Exported to 50+ countries · SS304, 316L, duplex 2205 & 2507 · Up to DN4000 · ASME, DIN, GOST & JIS · ISO 9001 & PED certified · MOQ 1 piece · Quote within 24 hours [Get a Factory-Direct Quote →](https://www.longanflange.com/wp-content/uploads/wp-mfa-exports/page/contact.md) ## **Conclusion** Now that you know the difference, you can choose the right fitting for your system. A stub end provides the sealing face, whereas a lap joint flange makes installation easier and helps reduce costs. If your system needs frequent maintenance or easier alignment, a lap joint flange is the better option. At Longan Flange, we provide [high-quality lap joint flanges](https://longanflange.com/products/stainless-steel-lap-joint-flange/) designed for durability and efficiency. [Get in touch with us](https://longanflange.com/contact/) today to learn more or [visit our website](https://longanflange.com/) to see a full range of flange products with details. ## Reference [Lap Joint Flange (LJF) Explained – saVRee](https://savree.com/en/encyclopedia/lap-joint-flange-ljf)