Answer :
Final answer:
The correct answer is B. 20 and 45 psi. Air supply valves or control valve protections are designed to close automatically within this pressure range to maintain safety standards in pneumatic systems such as commercial truck air brake systems.
Explanation:
The air supply valve, also known as the control valve protection, in a pressurized system is designed to close automatically to prevent system failure or to maintain safety standards. If the air pressure in such a system drops, this valve should close to prevent further loss of air and potential hazards.
For example, in certain applications, these valves are set to close when the pressure falls below a safety threshold, typically in a defined range. In the context of pneumatic systems in vehicles, particularly in commercial trucks with air brake systems, the safety standards require that the emergency springs in the air brake chamber must be designed to apply the brakes when the system's air pressure drops to a range between 20 and 45 psi.
This pressure range ensures that there is enough force for the emergency brakes to engage effectively, but not so low that there is insufficient time to react to a drop in pressure. Hence the correct answer to the question of when should an air supply valve or control valve protection close automatically when air pressure drops is B. 20 and 45 psi.
