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How can a driver distinguish normal governor cut-out from a safety valve event?
- A.Cut-out is a quiet unloading at about 120 to 135 psi, while the safety valve vents loudly at about 150 psi because control has failed
- B.They are identical and cannot be distinguished
- C.Cut-out vents more air than the safety valve
- D.The safety valve operates at a lower pressure than cut-out
Correct answer
A. Cut-out is a quiet unloading at about 120 to 135 psi, while the safety valve vents loudly at about 150 psi because control has failed
Why
Normal regulation should never let pressure reach the safety valve setting. Treating a 150 psi vent as routine hides a governor fault that will keep stressing the system.
Manual topic: Air Brakes - Safety Valve and Low Pressure Warning · From the Air Brakes practice bank (AB-065).