Which component in the Start Air System is the air pressure regulator valve?

Which component in the Start Air System is the air pressure regulator valve?

• A. Air pressure regulator valve.
• B. Starter air filter valve.
• C. Starter air control valve.
• D. Air regulator sensor.

Answer: (C)

The function being tested is who keeps the start air at the right pressure for the starter to operate safely. In the Start Air System, the regulator role is performed by the starter air control valve. This valve not only routes air to the starter, but also contains the mechanism that trims and maintains the correct pressure going to the starter, preventing overpressure and controlling the starter speed during starting. When starting, the control valve opens to supply air and automatically regulates the flow and pressure; once starting is complete, it closes or bleeds off excess as needed. The other options don’t fit because a starter air filter valve handles filtration, not pressure regulation; a sensor is used for sensing pressures but doesn’t regulate flow; and there isn’t a separate component simply called an air pressure regulator valve in this system—the regulation function is built into the starter air control valve.

The function being tested is who keeps the start air at the right pressure for the starter to operate safely. In the Start Air System, the regulator role is performed by the starter air control valve. This valve not only routes air to the starter, but also contains the mechanism that trims and maintains the correct pressure going to the starter, preventing overpressure and controlling the starter speed during starting. When starting, the control valve opens to supply air and automatically regulates the flow and pressure; once starting is complete, it closes or bleeds off excess as needed.

The other options don’t fit because a starter air filter valve handles filtration, not pressure regulation; a sensor is used for sensing pressures but doesn’t regulate flow; and there isn’t a separate component simply called an air pressure regulator valve in this system—the regulation function is built into the starter air control valve.