What feature does a sequence valve have related to its drainage?

A sequence valve is designed to control the flow of hydraulic fluid in a way that allows one function to operate before another. One important feature of a sequence valve is its drainage system, which is key to maintaining proper pressure conditions for the operation of connected hydraulic circuits.

The correct answer highlights that the sequence valve has an external drain line to the tank. This external drainage is essential because it helps to prevent pressure buildup in the valve, ensuring that the hydraulic fluid can return to the tank, which aids in effective operation and system responsiveness. By using an external drain line, the flow is managed more efficiently, ensuring that the valve functions correctly without trapping fluid or creating unwanted pressure differentials that could lead to operation issues or system failures.

The specifics of how a sequence valve drains fluid are critical for a millwright when setting up or troubleshooting hydraulic systems, as it affects how various components interact with each other. Understanding that an external drain line is part of the design helps in comprehending the overall fluid dynamics and pressure management in hydraulic applications.