Which type of thermometer is commonly used in steam boiler systems?

In steam boiler systems, mercury thermometers are commonly used because they can provide accurate and reliable temperature readings in high-pressure environments. These thermometers operate based on the expansion of mercury within a glass tube; as the temperature rises, the mercury expands and moves up the tube, allowing for precise temperature measurement.

The use of mercury is particularly beneficial in this context due to its wide range of temperature detection capabilities, its ability to provide consistent readings, and its visibility through the glass. They're also less prone to damage from steam or water compared to other types of thermometers.

While digital thermometers and infrared thermometers offer modern alternatives with quicker readings and enhanced features, they might not be ideal for all steam applications due to factors such as accuracy under high-pressure conditions or the need for surface contact. Alcohol thermometers, on the other hand, are typically used for lower temperature ranges and can be less accurate at elevated temperatures compared to mercury thermometers. Thus, in the context of steam boiler systems, mercury thermometers are preferred for their reliability and performance in handling the specific environmental conditions.