What is the main function of a check valve in a pipeline?

The main function of a check valve in a pipeline is to prevent reverse flow. This is a critical purpose because check valves are designed to allow fluid to flow in one direction while automatically closing to prevent flow in the opposite direction. This feature is essential in sewage treatment systems to maintain proper flow direction and to prevent backflow, which can lead to contamination, system failure, and other operational issues. By ensuring that sewage can only flow towards treatment facilities and not back into the collection system, check valves help maintain the integrity and efficiency of the sewage treatment process.

Other options, though relevant in different contexts, do not align with the primary role of a check valve. For example, while some valves can relieve pressure or help remove air, these tasks are typically the responsibility of other specific types of valves designed for those functions. Similarly, metering flow is a function associated with flow control devices rather than check valves. Hence, the capability to prevent reverse flow stands out as the defining characteristic of check valves in pipeline systems.