What is a Blind Flange?

Blind flange is also called blind flange, and its real name is blind plate. Blind flange is a solid disc used to close a pipe or form a stopper. Similar to ordinary flanges, blind flanges have mounting holes around the periphery and gasket seals are machined on the mating surface. The difference is that the blind flange does not have an opening for fluid to pass through. Instead, it is placed between two open flanges, thereby blocking the fluid from passing through the pipe. This type of closure is often used when adding another pipeline to an existing pipeline or adding a new valve. One of its functions is to block the end of the pipe, and the second is to facilitate the removal of debris in the pipe during maintenance. In terms of the blocking effect, it has the same effect as the head and pipe cap. However, there is no way to disassemble the head, while the blind flange is fixed with bolts and is very convenient to disassemble. The materials of the blind flange are carbon steel, alloy steel, stainless steel, plastic, etc. The blind flange is used to seal the end of the pipeline. There are welded blind flanges and flange covers (flange covers are bolted). Flange covers are blind flanges, and blind flanges are not only flange covers, but also welded blind flanges, butt-wound blind flanges, etc. Where are blind flanges most commonly used? Blind flanges are commonly used in petrochemicals, pipeline engineering, utilities, and water conservancy projects. Blind flanges can be used to repair pipelines upstream. In fact, during pipeline construction, blind flanges can be embedded into the final length of the pipeline. In this way, the pipeline can be extended or continued by simply adding to the final flange. How are blind flanges designed? In the design of blind flanges, there are several key points that we need to pay attention to during design: to design the flange reasonably, that is, to properly design the ratio of the cone neck and flange ring of the alloy flange, so that the flange torque is as small as possible to reduce the various stress indicators of the flange; according to the use conditions, the gasket material and the gasket width are reasonably selected to reduce the preload and operating force of the bolts; the bolt material, bolt diameter and number of bolts are reasonably selected, and the value of the bolt center circle diameter is as small as possible; the flange material is reasonably selected, and the overall design of the flange should be as full stress design as possible to achieve the purpose of both safety and cost saving.

Without the blind flange, it would be almost impossible to repair or maintain the pipeline unless the flow was closed at the early valve, which could affect miles of pipelines.

The use of flanged pipes has greatly accelerated the construction process of pipelines. It also makes maintenance and pipe section replacement easier. Pipe sections can now be assembled anywhere in the world and then transported to the construction site. Once on site, they only need to be bolted in place and the repair is complete.

Blind flanges are commonly used in petrochemical, pipe engineering, public services and water works.

A blind flange is useful for making repairs to a pipeline further up the line. In fact, during construction of a pipeline, a blind flange may be built into the final length of pipe. This allows for expansion or continuation of the pipeline simply by adding onto the final flange.

Pipeline Termination:

Blind flanges are used to cap the end of a pipeline during construction or maintenance.

Access Points for Maintenance:

By sealing off sections of a pipeline, blind flanges provide a removable barrier that allows for inspection, cleaning, and repair.

Pressure Testing:

During hydrostatic or pressure testing, blind flanges ensure a sealed environment to evaluate the integrity of the pipeline or vessel.

Temporary Closures:

In systems where future expansion is anticipated, blind flanges are used to temporarily close off the pipeline.

Material:

Select a material compatible with the fluid, pressure, and temperature of the system.

Pressure Rating:

Ensure the pressure class of the blind flange matches the requirements of the pipeline or system.

Dimensions:

Verify that the dimensions, such as outer diameter, bolt circle diameter, and thickness, conform to industry standards like ASME, ANSI, or API.

Surface Finish:

Blind flanges are indispensable components in piping systems, offering a reliable way to terminate or seal pipelines. Their solid construction, compatibility with various materials, and adaptability to different pressure classes make them a preferred choice across industries. Whether used for temporary closures, maintenance, or pressure testing, blind flanges provide safety, durability, and efficiency in demanding applications.

For any piping project, selecting the correct blind flange ensures optimal performance and long-term reliability.