Improved flow control assemblies for fluid systems (e.g., industrial and/or commercial systems) are provided. More particularly, the present disclosure provides for advantageous ball valve assemblies for fluid systems. In exemplary embodiments, the present disclosure provides for improved ball valve assemblies and related features, systems and methods of use. Exemplary ball valve assemblies of the present disclosure offer advantages over conventional assemblies including, without limitation, advantages in the sealing mechanisms of the ball valve assemblies, and advantages with the user interfaces of the ball valve assemblies (e.g., advantages with the lockout mechanisms). Improved, convenient and effective systems and methods for utilizing improved ball valve assemblies in fluid systems are provided.