What is the function of a non-return valve in a steam system?

The function of a non-return valve, also known as a check valve, in a steam system is to prevent backflow of steam. This is crucial in maintaining the efficiency and safety of the system. When steam is produced in a boiler, it needs to move in a specific direction towards its intended use, whether that be heating or producing mechanical work. The non-return valve ensures that once the steam moves forward through the pipes, it cannot flow backward into the boiler or other sections of the system.

Having steam flowing in the reverse direction can lead to various issues, such as loss of pressure, potential contamination of the steam with water or other substances, and even damage to the equipment. Thus, by preventing backflow, the non-return valve plays a vital role in the overall functionality and reliability of steam systems, ensuring that steam flows in the right direction and maintaining system integrity.

The other options describe functions that are not typical for non-return valves: regulating pressure is usually done by pressure relief valves or regulators; increasing steam flow pertains to valves that control flow rates; and filtering impurities is the role of filters or strainers, not non-return valves.