The system has connectors (3) for connecting fluid lines (2), each comprising distal and proximal ends (5, 6), a fluid flow passage protected by a cap (4) placed at the distal end and a physical connection unit to maintain the connectors. The caps and/or connectors have a locking unit to fix temporarily and firmly the caps at the connectors. The caps have coupling unit (11) so as to couple the caps of the connectors during deactivation of the locking unit. The caps prevent physical connection of the connectors as long as the caps protect the fluid flow passage. An independent claim is also included for a method for removing caps from connectors without handling caps.