ANSI/ASME B16.5 and B16.47 Blind Flange

What is Blind Flange?

A Blind Flange is a type of flange that is used to close the end of a pipe, valve, or vessel in a piping system. It is called a "Blind" Flange because it lacks a central opening, which means it does not have a bore or a hub. Blind Flanges are typically solid disks with bolt holes around the perimeter for fastening to another flange or the end of a pipe. Blind flanges come in various materials, sizes, and pressure classes to suit different applications and industry specifications. They play a critical role in maintaining the integrity and safety of piping systems.

1. Closing Function: The primary purpose of a blind flange is to close or seal the end of a pipe or a vessel. It is commonly used in situations where the continuation of the pipeline is not required, or when future access to the piping system is needed.

2. No Bore: Unlike other types of flanges, blind flanges do not have a central opening (bore) as they are designed to provide a solid barrier. This distinguishes them from flanges with bores designed to accommodate the flow of fluids or gases.

3. Bolt Holes: Blind flanges have bolt holes around the perimeter, usually arranged in a circular pattern. These bolt holes allow the blind flange to be bolted to another flange, a pipe, or a vessel.

4. Facing Type: Blind flanges can have different facing types, such as flat face (FF) or raised face (RF), depending on the sealing requirements of the application.

A High Hub Blind Flange is a specific type of blind flange that has a taller or extended hub compared to a standard blind flange. The hub is the raised portion in the center of the flange where the bolt holes are located. The extended hub provides additional structural support and reinforcement, making high hub blind flanges suitable for applications where higher pressure and temperature conditions are encountered.

Forging Blind Flange

Forged blind flanges are manufactured through a forging process, which involves shaping metal through compressive forces to produce components with specific shapes and properties. In comparison to cast flanges, forged blind flanges offer several advantages, primarily due to the differences in the manufacturing processes and the resulting material characteristics.

Advantages of Blind Flange?

1. Closure and Sealing: The primary purpose of a blind flange is to close or seal the end of a pipe, valve, or vessel. It provides a solid barrier, preventing the flow of fluids or gases through the closed end.

2. Isolation during Maintenance: Blind flanges are commonly used during maintenance or repair activities. By installing a blind flange, a specific section of the piping system can be isolated, allowing maintenance work to be carried out on other parts of the system without affecting the closed-off section.

3. Pressure Testing: Blind flanges are useful for conducting pressure tests on piping systems. By installing a blind flange at the end of a pipeline, pressure can be applied to the system to check for leaks or weaknesses in the piping and associated components.

4. Future Expansion: In situations where future expansion of a piping system is anticipated, blind flanges provide a means to temporarily close off the system until additional piping is added. This flexibility is beneficial in industries where system modifications or expansions are common.

5. Preventing Contamination: By sealing the end of a pipe or vessel with a blind flange, the interior is protected from external contaminants. This is particularly important in industries where maintaining a clean and uncontaminated environment is crucial.

6. Facilitating Flange Connections: Blind flanges are often used as part of a flange connection. When a pipe or valve needs to be closed off temporarily, a blind flange can be bolted to the mating flange to secure the connection.

7. Providing Structural Support: In the case of high hub blind flanges, the extended hub design offers additional structural support, making them suitable for applications involving higher pressures and temperatures.

8. Versatility: Blind flanges come in various materials, sizes, and pressure classes, making them versatile for a wide range of applications across different industries.

9. Easy Installation and Removal: Blind flanges are relatively easy to install and remove, allowing for quick and efficient maintenance procedures.

The Three Main Components of A Blind Flanged Joint Are?

BLRF Flange:

The central component is the BLRF flange itself. This type of flange is designed to close or seal the end of a pipe, valve, or vessel. It features a raised face (RF) on the flange surface, which creates a smooth, flat area around the bolt holes. The raised face provides a better sealing surface for gaskets and helps achieve a tight connection when the flange is bolted to another flange or a matching component.

Gaskets:

The gasket is placed between the raised face of the BLRF flange and the mating flange surface to create a seal. Gaskets are crucial for preventing leaks and ensuring a tight connection in the joint. The choice of gasket material depends on factors such as the fluid or gas being transported, temperature, and pressure conditions of the piping system. Common gasket materials include rubber, neoprene, spiral wound, and others.

Bolts and Nuts:

Bolts and nuts are used to secure the BLRF flange to the mating flange or another component in the piping system. The number, size, and strength of the bolts are determined by the pressure and temperature requirements of the application. Proper tightening of the bolts is crucial to achieving a reliable and leak-free joint. Bolt tightening should be done in a specified sequence to ensure uniform pressure distribution across the gasket and avoid uneven loading on the flange.