The present invention involves, in some embodiments, mechanisms and methods of occluding collapsible tubing with an occluder to prevent fluid flow therethrough. In some embodiments, a tube occluding mechanism is disclosed that includes a bendable occluding member for creating a force that can be applied to a collapsible tube to occlude the tube. In some embodiments, the collapsible tube can be an inlet/outlet tube on a removable pumping cartridge that is coupled to a reusable pump drive component when the system is in operation. In such embodiments, the occluding mechanism can be attached to the reusable component and can be used to block fluid flow to and from the pumping cartridge. In some embodiments, the occluding member can comprises a spring plate which can create a force to occlude tubing when in a relaxed, unbent configuration, and which can be bent to unocclude the tubing. In some preferred embodiments, in a default configuration of the tube occluder mechanism (when no external force is applied to the occluding member) the tubes are occluded, so that the tube occluder mechanism provides a fail-safe configuration preventing fluid flow to and from a pumping cartridge to which the tubes can be connected.