A disposable flow set comprising: a spike; a first administration tube-segment; a pumping tube-segment; a second administration tube-segment; an anti-free-flow valve; and an identifying-key configured to be clamped on said pumping tube-segment, the identifying-key comprising: a number of teeth with a unique combination of location and width, said teeth being insertable into compatible niches in a compatible liquid pump so as to prevent insertion of said disposable flow set to a non-compatible liquid pump; and a pressing-plate to be pressed by a door of the liquid pump in order to allow said pumping tube-segment to be pressed against a pressure-sensor of said liquid pump when the door of said liquid pump is closed to enable said liquid pump to use the sensed pressure to verify the presence of said disposable flow set; said disposable flow set being characterized by: a stretching-key configured to be clamped on said pumping tube-segment, said stretching-key being disposed on the pumping tube-segment at a distance from the identifying-key and having a unique pattern to be inserted into a compatible recess in a compatible liquid pump to prevent insertion of the disposable flow set in a non-compatible liquid pump and to maintain the pumping tube-segment under tension, straightened and stretched to a determined degree when inserted into the liquid pump. a spike; a first administration tube-segment; a pumping tube-segment; a second administration tube-segment; an anti-free-flow valve; and an identifying-key configured to be clamped on said pumping tube-segment, the identifying-key comprising: a number of teeth with a unique combination of location and width, said teeth being insertable into compatible niches in a compatible liquid pump so as to prevent insertion of said disposable flow set to a non-compatible liquid pump; and a pressing-plate to be pressed by a door of the liquid pump in order to allow said pumping tube-segment to be pressed against a pressure-sensor of said liquid pump when the door of said liquid pump is closed to enable said liquid pump to use the sensed pressure to verify the presence of said disposable flow set; said disposable flow set being characterized by: a stretching-key configured to be clamped on said pumping tube-segment, said stretching-key being disposed on the pumping tube-segment at a distance from the identifying-key and having a unique pattern to be inserted into a compatible recess in a compatible liquid pump to prevent insertion of the disposable flow set in a non-compatible liquid pump and to maintain the pumping tube-segment under tension, straightened and stretched to a determined degree when inserted into the liquid pump. a number of teeth with a unique combination of location and width, said teeth being insertable into compatible niches in a compatible liquid pump so as to prevent insertion of said disposable flow set to a non-compatible liquid pump; and a pressing-plate to be pressed by a door of the liquid pump in order to allow said pumping tube-segment to be pressed against a pressure-sensor of said liquid pump when the door of said liquid pump is closed to enable said liquid pump to use the sensed pressure to verify the presence of said disposable flow set; said disposable flow set being characterized by: a stretching-key configured to be clamped on said pumping tube-segment, said stretching-key being disposed on the pumping tube-segment at a distance from the identifying-key and having a unique pattern to be inserted into a compatible recess in a compatible liquid pump to prevent insertion of the disposable flow set in a non-compatible liquid pump and to maintain the pumping tube-segment under tension, straightened and stretched to a determined degree when inserted into the liquid pump.