Which instrument is commonly used to monitor fuel feed in a boiler?

The correct instrument for monitoring fuel feed in a boiler is a fuel flow meter or fuel level gauge. This instrument is integral to maintaining efficient boiler operation, as it accurately measures the quantity of fuel being delivered to the combustion process. By continuously monitoring fuel flow or level, operators can ensure that the boiler receives the appropriate amount of fuel for optimal performance, avoiding issues such as fuel starvation or wastage.

A fuel flow meter provides real-time data on the flow rate of fuel, allowing operators to adjust feed rates as necessary to match the boiler's demand. Meanwhile, a fuel level gauge indicates the quantity of fuel available in storage, ensuring that there is sufficient supply for ongoing operations. Both functions are crucial for maintaining safety, efficiency, and reliability in boiler operation.

In contrast, other instruments mentioned, such as a temperature gauge or pressure relief valve, serve different purposes related to the overall operation and safety of the boiler system but do not specifically monitor fuel feed. A temperature gauge measures the thermal state of the boiler or process fluids, while a pressure relief valve is a safety device designed to prevent excess pressure buildup. An air quality monitor, on the other hand, is focused on the emissions and combustion air quality rather than fuel supply.