What is a Blind Flange? A blind flange is a solid flange as shown below. The purpose of these is to block off a section of pipe or a nozzle on a vessel that is not used. (A nozzle is typically a pipe coming out of a vessel and is usually flanged so it can be connected to valves or piping). Many times a nozzle will be blanked off with a blind flange for pressure tests in a plant, or simply because the customer does not need all the nozzles that were supplied on the tank. The best practice is to use a standard Gasket for these blinds. Blind flanges, just like standard pipe flanges, can be raised face (RF) or flat faced (FF). If the flange is RF we would recommend a standard ring gasket that is appropriate for the service and/or test. If it is FF we would TYPICALLY use a full face gasket, because the most common reason the flange is FF is that it is not designed to handle the bending forces that result when using a ring gasket or a RF flange against the FF flange. Again, we treat a blind flange just like any other pipe flange. 

A common request for gaskets with a blind flange is for a gasket with no ID; a gasket with a solid center. The customer might ask for these solid gaskets with bolt holes or without. If the blind flange is a standard ASME flange, the OD of the gasket will be the same as the OD of the standard ring or standard full face gasket. Many times, the customer expects that the solid gasket will protect the blind flange from the fluid in the system. They might be trying to save money by using a carbon steel (CS) blind in chemicals that require a more expensive metal, so they want the gasket to keep the fluids away from the low cost blind flange. 

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