A closure for pressure vessels provides ease in access to the inside of a pressure vessel and at the same time provides a tight pressure seal for the closure. The closure for pressure vessels includes a hub adapted to fit on to an opening on the pressure vessel, a door connected to the hub, a hinge assembly to secure the door to the hub, and a locking assembly attached to the door. The locking assembly includes a slide lock operating around a central support, a plurality of locking lug arms radially operating around the central support, a pressure alert valve connected to the door, and a handle connected to the slide plate operating around the central support. The handle moves the locking assembly from a locking position to an unlocking position as the result of the groove pattern machined in the back of the slide plate.