What is the correct classification of a check valve in a pumping system?

A check valve is designed to prevent backflow in a pumping system, ensuring that fluid flows in only one direction. This essential function aligns well with the characteristics of a controlling valve, which regulates the flow of liquids or gases within a system. By allowing fluid to pass in a forward direction while automatically closing to stop backflow, the check valve helps maintain the integrity and efficiency of the system.

In the context of the other options, isolating valves are primarily used to completely stop the flow of fluid in a pipeline for maintenance or repairs, rather than regulating the flow direction and preventing backflow. Flow rate valves typically involve control systems that allow for precise adjustments of flow rates, rather than the automatic, one-way function of a check valve. Safety valves, on the other hand, are specialized devices designed to release pressure and protect against overpressure conditions, which differs from the primary function of a check valve in managing flow direction.