Pressure-generating pipe device for a pressure vessel (11) arranged for intake and discharge of fluid (15) to and from the pressure vessel (11), which pipe device (1) comprises a first section (3) that can be connected to a compressed air source (17), 5 which first section (3) has a duct arrangement (5); a second section (7) comprising a discharge part (21); and at least one discharge device (25) that is in communication with the duct arrangement (5) and the pressure vessel (11). The first and the second sections (3, 7) are arranged to move in relation to each other, 10 the first section (3) comprising a control device (29) for operating an air-regulating device (39) in the discharge part (21) that is arranged to change the direction of the airflow through the discharge device (25), bringing about overpressure or underpressure in the pressure vessel (11), and the second section having the discharge device (25).