A blind flange is a solid disk used to block off a pipeline or to create a stop. It is machined in the same manner as a regular flange with the mounting holes around the perimeter and the gasket sealing rings machined into the mating surface. The difference is that a blind flange has no opening to allow fluid to pass through. The blind flange can be inserted between two open flanges and used to block off the flow of liquid through a pipeline.
Often a blind flange is inserted into a pipeline when a repair is required further up the line. This allows the flanges down stream to be disconnected without fear of losing liquid. Many times this type of blockade is used when adding another line onto an existing pipeline or when a new valve is being added. This blockade is also used to shut down a line when it is no longer needed.
Without the blind flange it would be difficult to perform maintenance or repairs on a pipeline. The flow would need to be shut off at the nearest valve, which could be miles away from the repair area. Valves are also very expensive and are prone to sticking. The blind flange is a much more cost efficient way of sealing a pipe.
When a pipeline is being constructed, a blind flange is often incorporated into the final length of pipe. This design allows for expansion or continuation of the pipeline by simply adding onto the final flange. This holds true for the addition of tees in the pipeline as well. A tee can be installed and then blocked in order to leave the option of running a pipe at a later date.
The use of flanged pipe has allowed pipelines to be built in a much faster manner than traditional welded seam pipelines. Moreover, it has made the task of repair and sectional replacement a simpler job. Sections of pipe can now be assembled anywhere in the world and shipped to the job site. Once there, they can simply be bolted into place and the pipeline can resume transportation of its liquid cargo.
By utilizing a universal design, any pipe flange in the world can be used in any pipeline as long as the proper diameter is selected. This allows emergency repairs with locally manufactured pieces and eliminates the need to have special parts shipped all over the world.