The example shows a normally open logic element to block flow from supply to Port A before B is connected to return.
- Normally closed logic element: LO*C
- Fixed orifice, flow fuse valve: FQCA
Benefits of this circuit arrangement:
- When port A is connected, pressure builds up downstream of the flow fuse valve FQCA. The pressure blocks the logic valve preventing flow to Port A. After connecting port B to the return line, the pressure collapses and the logic valve fully opens.
- This circuit does not prevent ports A and B being connected to the incorrect line. This is normally addressed by using two different size quick couplers.
- The circuit also ensures that the return line is connected before port A sees pump pressure.
