Blind flanges are circular plates used to seal the end of a pipe or vessel. They are primarily used in piping systems where a pipe is intended to be closed off for maintenance, testing, or to block a flow path in a system. They are often used when it's not necessary to connect a pipe or fitting to the end of a system, providing a reliable and secure seal.

Blind flanges are commonly made from a variety of materials such as stainless steel, carbon steel, and alloy steel, depending on the application requirements. Stainless steel blind flanges, like SS 304 or SS 316, are highly resistant to corrosion and are often used in industries where durability and resistance to harsh conditions are critical.

The right blind flange can be selected by considering factors such as the material, pressure rating, size, and the specific environmental conditions (e.g., temperature, corrosive substances). It's important to match the flange to the pipe size and pressure system to ensure a proper seal and safe operation.