This practice of using a solid ID is NOT RECOMMENDED, however, for several reasons. 

 The first is that the gasket will probably not completely stop the fluids from reaching the blind flange. Keep in mind that we do not publish zero leakage for test results such as the ASTM F37B Sealability; there is some small amount of permeation that occurs when gaskets are at low compressive loads, like they are in the ASTM F37B test, but especially when the center of the disc is under NO compressive load. 

 Another issue is that the solid center of the gasket will be uncompressed and probably will be affected by the fluids. Fiber gaskets, such as Style 3000, etc, will often be damaged in the uncompressed area, even in fluids that are compatible with the gasket, including water. Fiber gaskets are simply not meant to be immersed in fluids with no compression. That means that the gasket may contaminate the process fluids when the uncompressed area swells or breaks apart. 

 There is also a VERY IMPORTANT SAFETY ISSUE: Because the center, uncompressed portion of the gasket might be permeable over time, fluids and even fluid pressure can build up between the solid gasket disc and the blind flange. This is because the pressure will try to equalize on both sides of the solid gasket disc. This will even happen with a GYLON gasket, despite the very tight sealing properties of the GYLON gaskets. Remember the center is not under compressive loads. When the space behind the disc becomes filled with fluid, this fluid is under pressure. If the system is shut down and brought back to zero pressure, the fluid that is trapped cannot escape back through the solid disc fast enough. So when the bolts are loosened to remove the blind flange, liquids or gases can spray out of the connection. If this fluid is dangerous, toxic, or flammable, the mechanic can be in danger. 

For these reasons, We recommends that gaskets for blind flanges be cut as standard rings or full face gaskets, and not with a solid center

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