If the air pressure reaches 150 psi, the safety valve will open. Where is the safety valve located?
- Governor
- Supply tank ✓
- Service tank
- Brake chamber
Answer: B. Supply tank
The safety valve is located on the supply tank.
Why this is the answer
The handbook describes the safety valve as being on the first reservoir, and it later explains that the first reservoir, often called the wet tank, is the supply reservoir. So the supply tank is where this valve belongs. The valve vents excess air if pressure reaches about 150 p.s.i., and it does this when the governor fails to unload the compressor. The other named parts are not where the passage places the safety valve.
Why the other answers are wrong
- A. Governor — The governor is the device that unloads the compressor, and the safety valve is described as backup protection if the governor fails, not as part of the governor.
- C. Service tank — The service reservoirs supply the primary and secondary brake sections, while the safety valve is placed on the first reservoir, which is the supply reservoir, not a service tank.
- D. Brake chamber — Brake chambers are where air pressure applies the brakes, and the passage mentions them only in connection with water freezing, not as the safety valve's location.
Remember it
Picture the supply tank as the system's first reservoir, so it carries the valve that lets excess air escape.
Official handbook: ICBC Driving Commercial Vehicles, 8 Air brakes – Foot valve, p. 153