What is the primary purpose of a two-way check valve?

Answer: B — To direct air flow from either of two sources into a common line

The primary purpose of a two-way check valve is to direct airflow from either of two sources into a common line. This type of valve allows air to flow in either direction, depending on which source is generating the pressure. This is particularly useful in systems where multiple air supplies may need to be managed, ensuring that the correct source can contribute to the system's operation without allowing backflow which could create a pressure imbalance or malfunction. In terms of practical applications, two-way check valves are often used in air brake systems to allow air to come from multiple sources or compartments, which enhances the system's flexibility and reliability. The design facilitates easy switching between air supplies, making it essential for maintaining consistent pressure in braking systems.