Blind Flanges and Spectacle Blinds: Types, Dimensions & Applications

 

Introduction

A blind flange is a solid flange used to close the end of a pipeline or pressure vessel, preventing flow. These flanges are crucial in industries where maintenance, inspection, and modifications are required. Blind flanges come in various types and dimensions, catering to different pressure ratings and material specifications.

A spectacle blind, also known as a spectacle flange, is a safety device used to isolate pipeline sections. It consists of a blind flange and an open spacer, allowing easy switching between open and closed states without removing the entire flange assembly.

This article provides a detailed overview of blind flanges, spectacle blinds, slip blinds, spade blinds, and their specifications.



Types of Blind Flanges

  1. Flat Face (FF) Blind Flange – Used in low-pressure applications where a flat surface ensures even pressure distribution.

  2. Raised Face (RF) Blind Flange – Features a raised sealing surface for improved gasket seating.

  3. Ring-Type Joint (RTJ) Blind Flange – Designed for high-pressure systems, incorporating a metal ring gasket.

  4. Threaded Blind Flange – Has internal threads for non-welded connections.

  5. High Hub Blind Flange – Provides additional reinforcement for high-stress applications.

Blind Flange Dimensions (ANSI/ASME B16.5)

Blind flanges come in different sizes and pressure ratings, generally categorized as 150#, 300#, 600#, 900#, 1500#, and 2500#. Below are the standard dimensions:

Nominal Pipe Size (NPS)Outer Diameter (OD) (inches)Bolt Circle Diameter (BCD) (inches)Number of Bolt HolesBolt Hole Diameter (inches)Flange Thickness (inches)
1/2"3.502.3840.620.44
1"4.253.1240.620.56
2"6.004.7540.750.69
6"11.009.5080.881.00
12"19.0016.00121.131.50

(For complete dimensions, refer to ASME B16.5 standard)

Spectacle Blind (Spectacle Flange)

A spectacle blind is a combination of a blind and an open ring (spacer), used for pipeline isolation. It allows switching between open and closed positions by rotating the flange assembly. Spectacle blinds are commonly used in chemical, oil, and gas industries for maintenance purposes.

Slip Blind Flange

A slip blind is a single solid plate inserted between flanges to block flow. Unlike a spectacle blind, it is removable and does not remain attached when the line is open.

Spade Blind & Spacer

A spade blind, also called a paddle blind, is a single solid disc used for isolating pipelines. It is often used with a matching spacer to alternate between open and closed configurations.

FAQs

1. What is the purpose of a blind flange?

A blind flange is used to close the end of a pipeline, preventing flow while allowing easy reopening for maintenance.

2. What materials are blind flanges made from?

Blind flanges are commonly made from carbon steel, stainless steel, alloy steel, and ductile iron, depending on the application.

3. How do spectacle blinds work?

A spectacle blind consists of a solid plate and an open ring. It is rotated to either block or allow flow in the pipeline without removing the flange assembly.

4. What are the pressure ratings for blind flanges?

Blind flanges are available in ANSI pressure ratings: 150, 300, 600, 900, 1500, and 2500.

5. How do spade blinds differ from spectacle blinds?

A spade blind is a single disc used for isolation, while a spectacle blind consists of both a solid and open plate connected by a bridge.

6. Are blind flanges reusable?

Yes, blind flanges can be reused if they are not damaged during installation or removal.

7. What industries commonly use blind flanges?

Blind flanges are used in oil & gas, chemical processing, water treatment, power plants, and manufacturing.

Conclusion

Blind flanges, spectacle blinds, and spade blinds play a crucial role in pipeline safety and maintenance. Understanding their types, dimensions, and applications helps industries choose the right component for their systems. Proper selection ensures efficiency, safety, and compliance with industry standards.

For detailed specifications and custom orders, consult ANSI/ASME B16.5 standards or reach out to certified manufacturers.

Comments

Post a Comment

Popular posts from this blog

Check Valve (Non-Return Valve): Types, and Pricing

  Introduction A check valve , also known as a non-return valve (NRV) , is a mechanical device that allows fluid to flow in only one direction, preventing backflow. It is commonly used in pipelines, water supply systems, industrial processes, and pumps to maintain directional flow and prevent equipment damage due to reverse flow. Check Valve Symbol The check valve symbol used in engineering diagrams consists of a valve body with an arrow indicating the permitted flow direction and a barrier preventing reverse flow. It is commonly seen in process flow diagrams (PFDs) and piping and instrumentation diagrams (P&IDs). Types of Check Valves (Non-Return Valves) There are several types of check valves (NRVs) designed for specific applications: Swing Check Valve – Uses a hinged disc that swings open with forward flow and closes when the flow reverses. Dual Plate Check Valve – Features two spring-loaded plates that automatically open and close with the...
Read more

Heavy Machinery Bolt Manufacturer in Rajasthan

  Introduction Finding a reliable heavy machinery bolt manufacturer in Rajasthan is crucial for ensuring high-strength, durable, and corrosion-resistant fasteners for various industries. From construction to mining and heavy engineering , selecting the right supplier ensures superior performance and cost-effectiveness. Udhhyog , a leading supplier, provides insights into the best heavy machinery bolt manufacturers in Rajasthan . Importance of High-Quality Heavy Machinery Bolts Ensuring Structural Integrity – High-tensile bolts provide secure and stable connections . Corrosion Resistance – Galvanized and stainless steel fasteners prevent rust and degradation . Load-Bearing Strength – Heavy machinery requires high-strength nuts and bolts . Compliance with Industry Standards – Ensuring adherence to ISO, ASTM, and BIS certifications . Best Heavy Machinery Bolt Manufacturers in Rajasthan 1. Udhhyog – Leading Supplier for Heavy Machinery Fasteners Specialty: High-tensile, stainles...
Read more

SS Pipe Price Comparison: India vs International Market

  Introduction Stainless steel (SS) pipe s play a vital role in various industries, including construction, manufacturing, and oil & gas. This article provides an in-depth price comparison between Indian and global markets, analyzing factors influencing costs and tips for businesses and Udhhyog owners. SS Pipe Price Comparison: India vs Global Markets Stainless Steel Pipe Prices in India (March 2025) Prices in India vary based on grade, thickness, and supplier. Below is an estimated price range: SS Grade Thickness (mm) Price (INR per kg) 202 1.2 – 3.0 200 – 250 304 1.2 – 5.0 280 – 350 316 1.2 – 6.0 400 – 500 409 1.2 – 4.0 180 – 230 Global Stainless Steel Pipe Prices Prices vary across different international markets: Region Average Price (USD per ton) USA 3,000 – 4,500 Europe 2,800 – 4,000 China 2,500 – 3,800 Middle East 2,700 – 4,200 Key Differences: India vs Global Market Raw Material Costs: Nickel & chromium prices affect global rates. Manufacturing Expenses: Labor and...
Read more