What is the purpose of a quick release valve?
- (a) To allow faster application of the service brakes
- (b) To allow faster release of the service brakes ✓
- (c) To allow automatic application of the service brakes
- Both (a) and (b)
Answer: B. (b) To allow faster release of the service brakes
The quick release valve lets the service brakes release faster by exhausting air close to the brake chambers.
Why this is the answer
The handbook explains that when a driver lets off the foot valve, the used air normally has to travel all the way back to the foot valve exhaust port, which creates a lag before the brakes let go. A quick release valve mounted near the brake chambers vents that air right there instead, so the brakes release quickly and fully. Air still reaches the chambers through the valve in the usual way when you apply the brakes, so the valve is about releasing, not applying.
Why the other answers are wrong
- A. (a) To allow faster application of the service brakes — It does not speed up applying the brakes, because the handbook says air flows through the valve to the chambers in the normal way when you apply them.
- C. (c) To allow automatic application of the service brakes — Nothing in the valve applies the brakes by itself; it only vents air so the brakes let go, and automatic application is not its job.
- D. Both (a) and (b) — Only the release side is correct, since the handbook describes the valve as speeding up release, not application.
Remember it
Think of it as a shortcut door for spent air: it lets air out near the chambers so the brakes let go sooner.