What is a Blind Flange
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.
Certain factors that buyers should consider before buying blind flanges are as follows:
- End Type
- Pressure Rating
- Materials (tested for corrosion resistant)
- Tested and verified for durability, accuracy and precision etc.
- Stainless Steel
- Nickel Alloy
- Carbon Steel
- Cast Iron
- PVC etc.
Features of blind flanges:
Some important features of blind flanges are as follows:
- Blind flanges are sometimes supplied with NPT fittings which allow pressure test connections to be fitted.
- They are used to blank off the ends of pipe.
- They are also used to blank off the ends of valves and pressure vessel opening.
- Considering factors like internal pressure and bolt loading, blind flanges, especially in the larger sizes, are the most highly stressed of all types of flanges.
- Since the maximum stresses in a blind flange are bending stresses at the center, they can safely be allowed to be higher than in other types of flanges.
- Blind flanges are made to fit standard pipes in all sizes.