What is the purpose of a pressure reducing valve in a steam system?

In a steam system, the primary purpose of a pressure reducing valve is to maintain a constant lower pressure. This is crucial for the safe and efficient operation of the system, as it allows high-pressure steam to be reduced to a suitable level required for various processes without causing fluctuations that could lead to potential system failures or inefficiencies.

By ensuring that the steam pressure remains stable at a desired lower level, the pressure reducing valve helps to prevent damage to equipment that may not be rated for high pressures, improving the overall safety of the operation. Additionally, maintaining consistent pressure is essential for optimal steam quality, which directly affects the performance of heating or processing equipment downstream.

The other options pertain to functions that are not related to the role of a pressure reducing valve. Increasing system pressure or relieving excess pressure serves different functions typically managed by other components in the system, while shutting off water flow does not involve pressure regulation at all. Thus, focusing on maintaining a constant lower pressure is the key reason for the use of a pressure reducing valve in steam applications.