Device and method for air-free filling of a fluid management system

A dialysis machine comprising a machine-internal fluid line that is completely or partially inside the dialysis machine, and a fluid management system that is configured to be connected to a fluid input and a fluid output, the fluid input being configured to form a fluid communication with a supply of a flushing liquid, and the fluid output being configured for discharging the flushing liquid,

• the fluid management system comprising a locking device in the fluid line, which divides the fluid line into a first fluid line portion and a second fluid line portion, a first fluid conveying means in the first fluid line portion arranged upstream of the locking device, a second fluid conveying means in the second fluid line portion arranged downstream from the locking device, and a control device for controlling the locking device, the first fluid conveying means, and the second fluid conveying means, wherein
• the control device is configured to control the first fluid conveying means for conveying liquid in the direction of the locking device in order to increase a pressure of liquid in the first fluid line portion relative to a pressure of liquid in the second fluid line portion, and
• the control device is configured to control the second fluid conveying means for conveying liquid away from the locking device in order to decrease a pressure in the second fluid line portion relative to the pressure in the first fluid line portion, and
• the control device is configured to open the locking device at least once when the pressure in the first fluid line portion is greater than the pressure in the second fluid line portion.