Spectacle Blind Flanges

Understanding your choice of spectacle blind flanges options

Spectacle blind flanges are indispensable components in various industries, offering safety and versatility for diverse applications. Understanding the different options, materials, standards, and maintenance requirements of figure-8 blind flanges can help you select the right product for your piping system and ensure its safe and efficient operation. Spectacle blind flanges are essential in piping systems, providing a safe and efficient means of isolating sections for maintenance, inspection, or repair. These specialized flanges are designed with two interconnected sections: a solid plate to block the flow of fluids and a spacer to allow fluid passage when needed.

What is a spectacle blind flange?

A spectacle blind flange, also known as a figure-of-8 blind, “spectacle flange,” is made by a steel spade and spacer, united by a welded handle: one is actually a ring (i.e., a disc with a hole of the same diameter as the pipe) and the other is a solid disc. The figure 8 blind blocks or isolates a portion of the piping system during maintenance operations and provides a firm seal when closed.
Under normal conditions, the spectacle blind is installed in the open position and does not interrupt the flow of fluid conveyed by the pipeline.
To block the pipeline and interrupt the flow, field personnel unscrew the flange bolts and rotate the eight-hole blind to the closed position.
If the spectacle blind is in the open or closed position, this is easy to understand because one of the two discs is always on the outside of the pipe (so when the ring is visible, the pipe is closed; when the solid disc is visible, the line is open). For shovels and ring gaskets, the holes in the hanger will inform the crew.

Advantages of Using Spectacle Blind Flanges

Spectacle Blind Flanges offer numerous benefits to industries requiring efficient and reliable isolation of piping sections. Some of these advantages include the following:

1. Safety: Spectacle blind flanges provide a safe method of isolating pipeline sections, preventing the accidental release of hazardous substances during maintenance or inspection.
2. Versatility: These flanges can be used in various applications, including high-pressure, high-temperature, and corrosive environments, making them suitable for multiple industries.
3. Ease of Use: The design of spectacle blind flanges allows for easy installation and removal, reducing downtime and labor costs associated with maintenance and repair.
4. Leak Prevention: High-quality spectacle blind flanges are manufactured with precision, ensuring proper alignment and sealing, thereby reducing the risk of leakage and improving overall system performance.
5. Cost-effective: By using spectacle blind flanges, industries can eliminate the need for additional valves, reducing overall costs and simplifying the piping system.

Types of spectacle blind flanges

There are several types of Spectacle Blind Flanges available in the market, each designed for a specific application. Some common types include:
Raised Face Spectacle Blind Flanges
Raised face spectacle blind flanges are the most common type and feature a raised surface around the bore to ensure proper sealing. They are suitable for applications with high pressure and temperature requirements.
Flat Face Spectacle Blind Flanges
Flat face spectacle blind flanges have a flat sealing surface and are typically used in low-pressure applications or when mating with other flat-faced flanges.
Ring Type Joint Spectacle Blind Flanges
Ring type joint spectacle blind flanges feature a grooved sealing surface and are used in high-pressure applications where a metal-to-metal seal is required.

How to measure a spectacle blind flange?

To measure a spectacle blind flange accurately, you should follow these steps:
Measuring Flange Diameter

• Lay the spectacle blind flange on a flat surface.
• Use a measuring tape or a caliper to measure the outer diameter (OD) of the flange from one edge to the other, passing through the center.

Measuring Flange Thickness

• Place the measuring tool, such as a caliper or a ruler, on the edge of the flange.
• Measure the thickness of the flange, ensuring that you’re measuring the thickest part.

Measuring Bolt Hole Diameter

• Position the measuring tool over a bolt hole.
• Measure the diameter of the hole from one side to the other.

Measuring Bolt Circle Diameter

• Locate two opposing bolt holes on the flange.
• Use a measuring tape or a caliper to measure the distance between the center of one bolt hole to the center of the opposite bolt hole, ensuring that the measurement passes through the center of the flange. This is the bolt circle diameter (BCD).

Standard for spectacle blind flanges

Several international standards and specifications govern the design, dimensions, and manufacturing of spectacle blind flanges. Some of the most widely recognized standards include:

• ASME B16.48: This American standard covers the pressure-temperature ratings, materials, dimensions, tolerances, and marking requirements for spectacle blind flanges.
• MSS SP-44: A standard developed by the Manufacturers Standardization Society, MSS SP-44 covers the dimensions, materials, and manufacturing requirements for spectacle blind flanges in the petroleum and natural gas industries.
• EN 1092-1: This European standard specifies the dimensions, materials, and design requirements for spectacle blind flanges used in piping systems.

Materials of spectacle blind flanges

Depending on the specific application requirements, spectacle blind flanges are made from a variety of metal materials, including:

Selecting the Right spectacle blind flange Material

• Material selection is crucial when choosing spectacle blind flanges for your piping system. Factors to consider include corrosion resistance, temperature, and pressure requirements. Common materials used for spectacle blind flanges include:
• Carbon Steel: Offers excellent strength and durability, making it suitable for high-pressure applications.
• Stainless Steel: Provides outstanding corrosion resistance, making it ideal for use in harsh environments or applications where chemical compatibility is essential.
• Alloy Steel: Delivers enhanced resistance to heat and corrosion, making it suitable for high-temperature and high-pressure environments.
• Nickel Alloys: Offer superior corrosion and heat resistance, as well as excellent mechanical properties, making them suitable for use in demanding applications such as aerospace, power generation, and petrochemical industries.

Dimensions of spectacle blind flanges

Spectacle blind flanges are available in various sizes and dimensions, ranging from 1/2″ to 60″ in diameter, with pressure ratings from 150 to 2500 Class. The size and dimensions of a spectacle blind flange depend on the pipe size, pressure, and temperature requirements.

Dimensions of ASME B16.48 Figure-8 Blanks/Spectacle Blinds RF/FF

Dimensions for ASME B16.48 Class 150 figure-8 blanks (spectacle blind flanges) with FF or RF.

Dimensions for ASME B16.48 Class 300 figure-8 blanks (spectacle blind flanges) with FF or RF.

Dimensions for ASME B16.48 Class 600 figure-8 blanks (spectacle blind flanges) with FF or RF.

Dimensions for ASME B16.48 Class 900 figure-8 blanks (spectacle blind flanges) with FF or RF.

Dimensions for ASME B16.48 Class 1500 figure-8 blanks (spectacle blind flanges) with FF or RF.

Dimensions for ASME B16.48 Class 2500 figure-8 blanks (spectacle blind flanges) with FF or RF.

Weights for spectacle blinds in sizes NPS 1/2″ through 24″ of Class 150, 300 & 600.

Weights for spectacle blinds in sizes NPS 1/2″ through 24″ of Class 900, 1500 & 2500.

Dimensions of ASME B16.48 Figure-8 Blanks/Spectacle Blinds Female RTJ

Dimensions for ASME B16.48 Class 150 figure-8 blanks/spectacle blind flanges with female ring-joint facing (F/RTJ).

Dimensions for ASME B16.48 Class 300 figure-8 blanks/spectacle blind flanges with female ring-joint facing (F/RTJ).

Dimensions for ASME B16.48 Class 600 figure-8 blanks/spectacle blind flanges with female ring-joint facing (F/RTJ).

Dimensions for ASME B16.48 Class 900 figure-8 blanks/spectacle blind flanges with female ring-joint facing (F/RTJ).

Dimensions for ASME B16.48 Class 1500 figure-8 blanks/spectacle blind flanges with female ring-joint facing (F/RTJ).

Dimensions for ASME B16.48 Class 2500 figure-8 blanks/spectacle blind flanges with female ring-joint facing (F/RTJ).

Weights for spectacle blinds in sizes NPS 1/2″ through 24″ of Class 150, 300 & 600.

Weights for spectacle blinds in sizes NPS 1/2″ through 24″ of Class 900, 1500 & 2500.

Dimensions of ASME B16.48 Figure-8 Blanks/Spectacle Blinds Male RTJ

Dimensions for ASME B16.48 Class 150 figure-8 blanks/spectacle blind flanges with male ring-joint facing (M/RTJ).

Dimensions for ASME B16.48 Class 300 figure-8 blanks/spectacle blind flanges with male ring-joint facing (M/RTJ).

Dimensions for ASME B16.48 Class 600 figure-8 blanks/spectacle blind flanges with male ring-joint facing (M/RTJ).

Dimensions for ASME B16.48 Class 900 figure-8 blanks/spectacle blind flanges with male ring-joint facing (M/RTJ).

Dimensions for ASME B16.48 Class 1500 figure-8 blanks/spectacle blind flanges with male ring-joint facing (M/RTJ).

Dimensions for ASME B16.48 Class 2500 figure-8 blanks/spectacle blind flanges with male ring-joint facing (M/RTJ).

Weights for spectacle blinds in sizes NPS 1/2″ through 24″ of Class 150, 300 & 600.

Weights for spectacle blinds in sizes NPS 1/2″ through 24″ of Class 900, 1500 & 2500.

Difference between the blind flange and spectacle blind flange

A blind flange and a spectacle blind flange are integral components of piping and process systems. They serve distinct purposes and possess different features. This technical document aims to elucidate the primary differences between the two in terms of design, function, and applications.

Design:

Blind Flange: A blind flange is a solid, flat, circular plate devoid of any opening in its center. It is designed to be bolted to a pipe, valve, or another flange, effectively sealing the end of a pipe or system. The outer edge of the blind flange is equipped with bolt holes that align with those on the mating flange, facilitating easy installation and removal.

Spectacle Blind Flange: A spectacle blind flange, also known as a figure-8 blind, comprises two interconnected discs – one solid and one with an opening matching the pipe’s inner diameter. The reliable and holed discs resemble an “8” shape, hence the name. This unique design allows easy switching between the open and closed positions by rotating the spectacle blind flange.

Function:

Blind Flange: The primary function of a blind flange is to provide a secure, leak-proof closure at the end of a piping system, isolating it from the rest of the process. This is particularly useful during maintenance, testing, or decommissioning activities, ensuring a safe working environment for personnel and equipment.

Spectacle Blind Flange: The spectacle blind flange serves a dual purpose – isolation and flow control. In the closed position (solid disc covering the pipe), it isolates a section of the piping system for maintenance or repairs, similar to a blind flange. The open position (holed disc aligned with the pipe) allows for the unobstructed flow of fluid or gas through the pipeline, thus enabling regular operation.

Applications:

Blind Flange: Blind flanges are widely used across various industries, such as oil and gas, petrochemical, chemical, power generation, and water treatment plants, to isolate or terminate pipelines, pressure vessels, or equipment during maintenance, inspection, or repairs.

Spectacle Blind Flange: Spectacle blind flanges are commonly employed in industries with stringent safety and operational requirements, such as oil refineries, chemical plants, and offshore platforms. They offer quick and easy flow control without disassembling the piping system, reducing downtime and increasing overall efficiency.

The primary differences between a blind flange and a spectacle blind flange lie in their design, function, and applications. While a blind flange is a solid, flat plate used for isolating sections of a piping system, a spectacle blind flange comprises interconnected solid and holed discs, allowing for both isolation and flow control. Depending on the application’s specific requirements, these distinct features dictate their respective usage in different industrial settings.

How to use a spectacle blind flange?

The Spectacle Blind is usually used on the oil line with two different functions:

• If the spade is put in between the flanges, it stops the fluid’s passage;
• The fluid path is allowed if the spacer is placed between the flanges.

The Spectacle Blind is inserted between two flanges: to guarantee a perfect watertight, two gaskets usually are mounted, one on each side of the spectacle blind.
Spectacle blind flanges are a type of flow control device used in piping systems to isolate sections or regulate fluid flow. They consist of two circular plates, one with a hole (spacer) and the other without (spade), connected by a handle or web. The spacer and spade can be rotated to allow or block the flow through the pipe.

Manufacturing Process of spectacle blind flanges

Spectacle blind flanges are crucial components in piping systems, utilized to provide flexibility in managing flow and isolating specific sections when needed. These flanges are designed with a unique figure-eight shape, consisting of one solid and one open section. This configuration allows for easy flow manipulation through the piping system, depending on the operational requirements.

Section 1: Raw Materials and Spectacle Blind Flange Composition

The manufacturing process of spectacle blind flanges begins with selecting high-quality raw materials. Commonly used materials include carbon steel, stainless steel, alloy steel, and various other metals, depending on the specific requirements and application. The material selection is crucial to ensure the flanges’ durability, resistance to corrosion, and ability to withstand the operating conditions they will be subjected to.

Section 2: Cutting and Shaping the Spectacle Blind Flange

Once the appropriate material is selected, the manufacturing process moves to the cutting and shaping stage. The raw material is precisely cut to the desired figure-eight shape using advanced machinery, such as CNC, plasma, and water jet cutting machines.

The cutting process must be accurate, ensuring that the dimensions of the solid and open sections of the spectacle blind flange meet the required specifications. Additionally, the edges of the flange must be smooth and burr-free to ensure proper sealing when installed in the piping system.

Section 3: Drilling and Machining the Bolt Holes

After cutting the flange to its unique shape, the next step involves drilling and machining the bolt holes. These holes allow the spectacle blind flange to be securely fastened to the adjacent flanges in the piping system, ensuring a leak-free connection. The drilling process must be precise, guaranteeing that the bolt holes are evenly spaced and aligned.

Section 4: Heat Treatment and Surface Finishing

To enhance the mechanical properties of the spectacle blind flange, heat treatment processes, such as normalizing, annealing, or quenching and tempering, may be employed. These treatments improve the flange’s strength, ductility, and resistance to wear and corrosion.

Once the heat treatment is complete, the spectacle blind flange undergoes surface finishing. This step involves sandblasting, pickling, or electro-polishing, which remove any surface imperfections and enhance the flange’s appearance and corrosion resistance.

Section 5: Quality Assurance and Testing

Quality assurance and testing are vital stages in the manufacturing process of spectacle blind flanges. Various tests ensure that the flanges meet the required standards and specifications. These tests may include the following:

• Dimensional inspection: Verifying that the flange’s dimensions, such as thickness, diameter, and bolt-hole spacing, are within the specified tolerances.

• Visual inspection: Checking for surface defects, such as cracks, pits, or other imperfections.

• Material analysis: Confirm that the flange’s composition matches the required material specifications.

• Mechanical and physical testing: Evaluating the flange’s mechanical properties, such as tensile strength, yield strength, and elongation, to ensure it meets the required standards.

Section 6: Marking and Packaging

Once the spectacle blind flange passes all quality assurance tests, it is marked with essential information, such as material grade, size, pressure rating, and the manufacturer’s name or logo. This marking ensures traceability and confirms that the flange meets the required standards.

Packing of spectacle blind flanges

Inspection and Measurement of spectacle blind flanges

There are several factors that need to be considered when inspecting and measuring spectacle blind flanges, including:

To inspect and measure spectacle blind flanges, you will need a set of calipers or a micrometer to accurately measure the dimensions of the flange. It is also a good idea to have a torque wrench on hand to ensure that the bolts are tightened to the correct torque specification.

Installation and Maintenance of Spectacle Blind Flanges

Proper installation and maintenance of spectacle blind flanges are crucial to ensure their optimal performance and longevity. Follow these guidelines to maintain the integrity of your piping system:
Installation of figure 8 blind flanges
Proper installation of the figure 8 blind flange is critical to the safe and efficient operation of the piping system. For a successful installation, perform the following steps:

• Inspect the flange: Prior to installation, inspect the figure 8 blind flange for any visible defects such as cracks, dents or warpage.

• Prepare the pipe: Make sure the pipe is clean and free of debris. In addition, make sure the flange faces are clean and undamaged.

• Position the flange: Align the figure 8 blind flange with the mating flange on the pipe or equipment, making sure the bolt holes are properly aligned.

• Install Gasket: Place a suitable gasket between the flange faces to create a tight seal and prevent leakage. Ensure that the gasket material is compatible with the piping media and operating conditions.

• Insert Bolts: Insert the appropriate bolts through the bolt holes and secure with nuts. Tighten bolts and nuts evenly in a crisscross pattern to ensure proper pressure distribution across the flange.

• Rotate flange: Rotate the figure-of-8 blind flange to open (gasket side) or close (spade side) the pipe, depending on the desired flow configuration.

• Verify installation: After installation, visually inspect the flanges for proper alignment and ensure that all bolts are tightened evenly.

Inspection of figure 8 blind flange
Periodically inspect the figure 8 blind flange for signs of wear, corrosion or damage. Monitor for any leaks and address them promptly to prevent further damage to the system.
Maintenance of figure 8 blind flange
Perform routine maintenance on the figure 8 blind flange, including cleaning, tightening bolts and replacing gaskets as necessary – shut down periodically for thorough inspection and maintenance of the entire piping system.
Replacement of figure 8 blind flange
Replace worn or damaged figure 8 blind flanges with new flanges that meet the original flange specifications. Ensure proper installation and alignment to maintain the integrity of the piping system.

Application of spectacle blind flanges

ASME B16.5 spectacle blind flanges are known to deliver exceptional performance and are generally developed to meet the demands. We offer a broad range of spectacle blind flanges through a worldwide network of stock-keeping branches.

This spectacle blind flange is used in various industries:

• Spectacle blind flanges used in Oil and Gas Pipelines;

• Spectacle blind flanges used in Chemical Industry;

• Spectacle blind flanges used in Plumbing;

• Spectacle blind flanges used in Heating;

• Spectacle blind flanges used in Water Supply Systems;

• Spectacle blind flanges used in Power Plants;

• Spectacle blind flanges used in the Paper & Pulp Industry;

• Spectacle blind flange uses in General Purpose Applications;

• Spectacle blind flanges used in Fabrication Industry;

• Spectacle blind flange uses in Food Processing Industry;

• Spectacle blind flanges Use in Structural Pipe.

How do I choose between a spectacle blind flange, weld neck flange, and slip-on flange?

The choice between these flanges depends on your specific application requirements, such as pressure and temperature conditions, installation ease, maintenance needs, and budget constraints. Understanding the advantages and disadvantages of each flange type will help you make an informed decision.

How to purchase the correct spectacle blind flanges?

• Flat face (FF): This type of flange face has a flat, smooth surface that is perpendicular to the axis of the pipe. It is typically used for low-pressure applications and when the sealing is achieved by a gasket.
• Raised face (RF): This type of flange face has a raised ring on the surface that surrounds the bolt holes. The ring provides a surface for the gasket to rest on, which helps to create a better seal. It is commonly used in applications with moderate pressure.
• Ring joint face (RTJ): This type of flange face has a specially designed groove to accommodate a metallic ring gasket. The groove is cut into the surface of the flange, and the gasket sits in the groove to create a tight seal. This type of flange face is typically used in high-pressure applications.

Once you have identified the material and spectacle blind flange type, the next step is to determine the size and pressure class of the spectacle blind flange. spectacle blind flanges are available in various sizes and pressure ratings, and it’s crucial to select the correct size and pressure class to ensure that the flange can withstand the intended operating conditions. You should consult the system specifications and design to determine the appropriate size and pressure class.

Surface Finish

The flange face’s surface finish directly impacts the seal’s quality between the flanges. Common surface finishes include smooth, serrated, and grooved. Consult with the gasket manufacturer and consider the specific requirements of your application to select the most appropriate surface finish for your spectacle blind flanges.

How to select spectacle blind flanges manufacturer?

Choosing the right spectacle blind flanges manufacturer is essential to ensure you get high-quality products that meet your needs. Look for a manufacturer with quality certifications, experience, a good reputation, customization capabilities, and a competitive price. By following these tips, you will be able to find the right manufacturer for your flange needs.

Why Choose Guanxin to Be Your Spectacle Blind Flange Supplier?

Guanxin is a well-established and reputable manufacturer and supplier of spectacle blind flanges that has been providing high-quality products to customers worldwide for many years. Here are some reasons why you might choose Guanxin to be your spectacle blind flange supplier:

• High-quality products: Guanxin is committed to providing high-quality spectacle blind flanges made from the best materials and manufactured to the highest standards. The company has strict quality control procedures in place to ensure that each product meets or exceeds customer expectations.
• Competitive pricing: Guanxin offers competitive pricing on its products, which means you can get high-quality spectacle blind flanges at an affordable price.
• Wide range of products: Guanxin offers a wide range of spectacle blind flanges, including ANSI, DIN, JIS, EN, and other international standards. This means you can find the right product to meet your specific needs.
• Excellent customer service: Guanxin is committed to providing excellent customer service and support to all of its customers. The company has a team of experienced professionals who are available to answer any questions or concerns you may have.
• Fast delivery: Guanxin understands the importance of timely delivery and works hard to ensure that all orders are shipped out quickly and efficiently.

Export Country For spectacle blind flanges

FAQs

Q1: Can spectacle blind flanges be custom-made?

A1: Many manufacturers offer custom-made spectacle blind flanges to meet specific application requirements, such as unique sizes, materials, or pressure ratings.

Q2: How often should I inspect my spectacle blind flanges?

A2: The inspection frequency depends on system operating conditions, the environment, and the manufacturer’s recommendations. Generally, inspect spectacle blind flanges during scheduled maintenance or shutdowns.

Q3: Can I use a spectacle blind flange in a high-pressure application?

A3: Spectacle blind flanges are available in various pressure ratings to accommodate high-pressure applications. Choose a flange with a pressure rating suitable for your system.

Q4: How do I know if my spectacle blind flange needs to be replaced?

A4: Replace a spectacle blind flange if you notice signs of wear, corrosion, or damage during inspection or if it no longer meets the system’s pressure or temperature requirements.

Q5: Can I use a spectacle blind flange for isolation and flow control?

A5: Yes, spectacle blind flanges are versatile and can be used for isolation and flow control purposes, depending on the position of the spacer and spade. By rotating the spacer or spade, you can allow or block fluid flow through the piping system, making it an effective solution for both purposes.

Q6: Are there any alternatives to spectacle blind flanges for isolating sections of a piping system?

A6: Yes, alternatives to spectacle blind flanges include ball valves, gate valves, and line blinds. Each has advantages and disadvantages, so consider your application requirements and constraints when selecting the best solution.

Q7: What tools and equipment are needed to install and maintain spectacle blind flanges?

A7: Common tools and equipment for installing and maintaining spectacle blind flanges include torque wrenches, gaskets, bolt tensioners, flange spreaders, and lifting equipment. Always follow the manufacturer’s guidelines and safety precautions when working with these tools.

Q8: How do I determine the size of my spectacle blind flange?

A8: The size of the spectacle blind flange depends on your piping system’s pipe size, pressure, and temperature requirements. Consult the manufacturer’s guidelines or seek the advice of an experienced engineer to determine the appropriate size for your specific application.

Q9: Can spectacle blind flanges be used in extreme temperature conditions?

A9: Yes, spectacle blind flanges made from materials capable of withstanding extreme temperatures, such as stainless steel and alloy steel, or exotic materials like Inconel, Monel, and Hastelloy, can be used in high-temperature applications. Ensure that the chosen flange material meets the temperature requirements of your system.

Q10: How can I prevent corrosion on my spectacle blind flanges?

A10: To prevent corrosion, choose a spectacle blind flange material that offers adequate corrosion resistance for your specific application. Additionally, perform regular inspections and maintenance to detect and address any signs of corrosion early on.