Loading Rack Permission Cycle: Signal Flow
How the loading rack, API socket and FINCH III confirm whether loading conditions are safe.
Signal flow
Loading Rack Permission Cycle
Terminal Loading Rack
The truck connects at the rack. The rack initiates a request for permission to load and remains non-permissive until a valid permit signal is received.
API Rack Socket
The optic or thermistor socket on the trailer receives the rack's request and communicates directly with the FINCH III display.
FINCH III Runs the Safety Checks
- Is the FINCH III powered on?YES
- Are any active error codes present?NO
- Is retain detected in any compartment?NO
- Has any compartment reached its rack shutdown level?NO
FINCH III determines the permit state based on all configured conditions.
Permit State Returns to the Loading Rack
FINCH III sends either a permissive or non-permissive signal through the API socket. The socket relays that state directly back to the loading rack.
Cycle
Permissive
All conditions are met. Loading may begin.
Non-Permissive
A condition is not met. Loading is held.
Fail-Safe OperationLoss of power or a detected shutdown condition results in a non-permissive state.
Permit behaviour
What happens at each shutdown setting
When shutdown is set to HH
- Reaching the HH set point makes the rack non-permissive and stops loading.
- After the level is reduced below HH, the permit status automatically resets within 60 seconds.
- Pressing ACK clears the displayed HH alarm; it does not reset the rack permit state.
When shutdown is set to SPILL
- At HH, the rack remains permissive and HH serves as an early warning.
- Reaching SPILL makes the rack non-permissive and stops loading.
- To resume, reduce the level below SPILL and restart FINCH III.
- SPILL alarms cannot be acknowledged from the display.
Titan recommended configuration
Use SPILL for rack shutdown and HH for early warning
Set SPILL approximately 5–7 inches from the inside top of the tank to match a traditional optic-probe shutdown position.
Measure from the inside top of the tank. Do not measure from the probe nut or include the tank-wall thickness.
Set HH low enough to give the operator time to respond. Avoid placing HH too close to SPILL.
Related guidance