Why cannot a flare fitting be used for sizes 3/4 inch or larger?

A flare fitting is designed to create a seal by using a conical surface that forms a connection between two pipes or tubes. For sizes 3/4 inch and larger, achieving a proper and secure seal becomes increasingly difficult due to the limitations of the sealing mechanism. As the size of the fitting increases, the amount of torque required to tighten the fitting adequately also increases, which can lead to issues with maintaining a reliable seal.

This challenge prevents flare fittings from being effectively used in larger sizes because the risk of leakage can rise significantly if the fitting cannot be torqued properly to achieve a tight seal. Flare fittings are typically used for smaller sizes where the connection can be tightened adequately to provide the necessary pressure integrity. For larger piping systems, alternative fitting types, such as compression or welded fittings, are often preferred to ensure a secure and leak-proof connection.