--- title: What is a Blind flange? Types, Thickness Calculation & Dimensional Standards date: 2024-09-13T01:59:03Z modified: 2024-12-14T04:27:38Z permalink: "https://www.longanflange.com/blog/what-is-blind-flange/" type: post status: publish excerpt: "" wpid: 841 categories: - Blog featured_image: "https://www.longanflange.com/wp-content/uploads/2024/07/0fcd8bdad853546b0ea7.jpg" featured_image_alt: blind flange timestamp: 2024-12-14T04:27:38Z tags: - Blog --- > A blind flange is a solid, circular component used to close off the end of a pipeline, valve, or nozzle, effectively halting the flow of fluids or gases. Blind flanges are widely employed across various industries, including oil and gas, chemical processing, and water treatment. > > This blog will discuss more about blind flanges. You’ll learn more about what a blind flange is, its types, industrial applications, and key factors like flange thickness calculation and dimensional standards. All of which will help you understand its versatile functionality. ## **1. Understanding the Blind Flange** A [blind flange](https://longanflange.com/products/blind-flange/) is a type of pipe flange used to seal the end of a piping system or block off a pipeline entirely. Unlike other flanges, it does not have a central bore, making it ideal for isolating piping systems during maintenance, testing, or when expansion of the system is planned. In piping, blind flanges provide a secure closure that prevents leakage and maintains system integrity under varying pressure and temperature conditions. ### **Applications Across Industries** Blind flanges are indispensable in industries like: - **Oil and Gas:** For isolating sections of pipelines during repairs or testing. - **Chemical Processing:** To ensure safety by securely sealing hazardous fluid systems. - **Water Treatment:** For terminating unused pipeline sections or facilitating maintenance operations. ## **2. Types of Blind Flanges** ### **[Raised Face (RF) and Flat Face (FF)](https://longanflange.com/blog/raised-face-vs-flat-face-flange/) Blind Flanges** - **RF Blind Flanges: Feature a slightly raised area around the sealing face to enhance gasket compression. These are commonly used in systems with higher pressure ratings. _Use Case:_ Suitable for moderate to high-pressure piping where leakage prevention is critical. - **FF Blind Flanges: Have a flat sealing face that comes in full contact with the gasket. They are generally used in low-pressure systems where uniform load distribution is required. _Use Case:_ Ideal for lightweight, non-critical applications like water pipelines. ### **[Ring Type Joint (RTJ) Blind Flanges](https://longanflange.com/blog/what-is-rtj-flange/)** These flanges include a precision-machined groove for a metallic gasket, providing a leak-proof seal in high-pressure and high-temperature environments. _Use Case:_ Widely used in oil and gas or chemical industries for pressure ratings exceeding 900#. ### **Spectacle Blind Flange** A spectacle blind flange consists of two metal discs connected by a hinge or strap—one solid and one with a central hole. This design allows switching between open and closed states by rotating the flange. _Use Case:_ Common in situations requiring frequent isolation and reconnection of pipelines. ### **[Customizable Options](https://longanflange.com/product_cat/customized-products/)** Blind flanges can be tailored to specific needs, including unique flange dimensions, material grades, and compatibility with [various pressure ratings](https://longanflange.com/blog/industrial-flange-pressure-class-rating/). Customizations are especially relevant for non-standard systems or extreme environments. In response to growing demand, many [blind flange manufacturers](https://longanflange.com/) now offer customization options, enabling clients to specify parameters like material composition, surface coatings, and dimensional adjustments. These services ensure that the flanges align perfectly with system requirements. ## **3. What is the Difference Between a Blind Flange and a Blank Flange?** **Blind Flange:** A blind flange is a standalone component that bolts onto piping systems to seal the end of a pipeline or valve. _Use Case:_ Common in systems requiring frequent access for maintenance or testing. **Blank Flange:** A blank flange is not bolted onto a system; instead, it is a disk used within flanges or between flange pairs. _Use Case:_ Primarily for temporary closures or sealing an unused flange. | **Aspect** | **Blind Flange** | **Blank Flange** | | --- | --- | --- | | **Connection Type** | Bolted to the pipeline | Used within flanges | | **Application** | Permanent or temporary | Temporary sealing | | **Accessibility** | Easier to remove | Requires disassembly | ## **4. What is a Blind Flange Used For?** Blind flanges are primarily used for: - **Sealing pipeline ends:** To prevent leakage and allow system shutdown. - **Pressure testing:** Isolating a section for testing pressure integrity. - **Maintenance access:** Providing a removable barrier for pipe cleaning or modifications. ## **5. How to Calculate Blind Flange Thickness** To ensure safety and durability, the thickness of a blind flange is calculated by considering factors like pressure ratings, flange dimensions, and material grade. A common formula is: ![](https://lh7-rt.googleusercontent.com/docsz/AD_4nXcxLDNCPAqzkWGNY0EL1e-xq99KjfTtIHrwY-GKXbuy7IB4cTyCEPlR8E5T-vv5d5RkiJLT_II_bRKs9ISd6u_dcN6F5OePTEKiqiSythRSDh7QnwcAYAm1jQ8gBuwt_7XNroAK?key=_OzMdueCKdR9APj3f0IGAdW0) Where: - t: Flange thickness - P: Internal pressure (psi) - D: Flange outer diameter (inches) - S: Allowable material stress (psi) - C: Corrosion allowance (inches) The **[ASME B16.5](https://longanflange.com/blog/asme-b16-5-pipe-flange-fitting-definition/)** standard provides guidelines to refine calculations, ensuring compliance with operational demands. ## **5. Detailed Dimensions Chart** ### **Overview of Standard Dimensions** Blind flange dimensions are governed by standards like **ASME B16.5** and **[ASME B16.47](https://longanflange.com/blog/asme-b16-47-series-a-vs-b/)**, specifying parameters like bolt circle diameter, flange outer diameter, and thickness for pressure ratings from 150# to 2500#. ### **Thickness Calculation for Various Applications** Using the ASME guidelines, the thickness of blind flanges can vary with **pressure ratings**: - _Low-pressure systems_: Minimal thickness with basic corrosion allowance. - _High-pressure systems_: Thicker flanges and robust materials like stainless steel or alloy steel. ![](https://lh7-rt.googleusercontent.com/docsz/AD_4nXfKKiX4TsP7uX8UYFttWvTE_d8e1uouu2kyPLoGzaddEfL0PgyVM0Qp85N1K8z02HPYP4N6vLQOxGBVHVZhIGlj-AplP3nh3y500gb--t5YdiT5fGUsJZj6jUIX5x6qqj2i8RfmyQ?key=_OzMdueCKdR9APj3f0IGAdW0)