Flow based pressure isolation mechanism for a fluid delivery system

A fluid delivery system with flow-based pressure isolation, comprising:

• a pressurizing device for delivering injection fluid under pressure;
• a low pressure fluid delivery system;
• and
• a pressure isolation mechanism adapted for fluid communication with the pressurizing device and low pressure fluid delivery system, and comprising:
• a housing body defining an inlet port, an isolation port, a lumen in fluid communication with the isolation port, and an internal cavity, the housing body further defining a seal seat in the internal cavity between the inlet port and the isolation port;
• a valve member disposed in and free floating in the internal cavity and adapted to engage the seal seat, the valve member comprising an open position permitting fluid communication between the inlet port and the isolation port, and wherein the valve member is fluid flow responsive to fluid flow in the inlet port to engage the seal seat and attain a closed position preventing fluid flow between the inlet port and the isolation port;
• a flow initiating mechanism disposed in the lumen and in fluid communication with the isolation port, the flow initiating mechanism adapted to initiate flow around the valve member such that the valve member operates to the closed position substantially upon flow initiation;
• a retainer associated with the lumen for retaining the flow initiating mechanism within the lumen;
• and a spring disposed in the lumen and adapted to engage and spring-bias the flow initiating mechanism in the lumen.