What instrument is essential for monitoring steam pressure in a boiler?

The steam pressure gauge is essential for monitoring steam pressure in a boiler because it provides real-time readings of the internal pressure of steam generated within the boiler system. Maintaining the correct steam pressure is crucial for safe and efficient boiler operation, as it ensures optimal performance and helps prevent potential hazards associated with overpressure conditions.

A water level gauge is important for monitoring the water level within the boiler, which helps in preventing dry firing and ensuring there is enough water to produce steam. However, it does not provide information about the steam pressure.

A temperature gauge measures the temperature of the steam or water within the boiler, which can inform about the thermal performance, but it does not directly indicate the pressure, which is critical for overall system safety and efficiency.

A flow meter monitors the flow rate of steam or water in the system, which is important for understanding the operation and efficiency of the system but is not designed to gauge steam pressure.

Therefore, the steam pressure gauge is the key instrument specifically for monitoring boiler steam pressure, making it the correct answer in this context.