When is an air-release valve used in a pumping system?

An air-release valve is an essential component in a pumping system primarily used to reduce the risk of air pockets. Air pockets can form in pipelines, particularly in areas where the elevation changes or where there are bends in the pipe. These pockets can disrupt the fluid flow, leading to reduced efficiency, increased wear and tear on the pumps, and even potential damage due to water hammer or cavitation.

The air-release valve allows trapped air to escape from the system, ensuring that the flow of the liquid remains uninterrupted and stable. By venting out any accumulated air, the valve supports the continuous operation of the pumping system, reduces the risk of air-related issues, and contributes to the overall reliability of the operation.

The other choices focus on functions that are not related to the specific role of an air-release valve. Increasing system pressure, stopping fluid flow, or enhancing fluid filtration fall outside of what these valves are designed to accomplish. Thus, the correct answer highlights the critical function of maintaining fluid integrity by mitigating the issues caused by air entrapment in the system.