Explanation:
The fusible plug is a safety device installed in the water wall of the boiler. The purpose of the fusible plug is to extinguish the fire in the furnace of the boiler in case of low water level. When the water level in the boiler falls below the minimum level, the temperature of the furnace increases rapidly, and the fusible plug melts due to high temperature. The molten metal of the fusible plug falls into the water, and the water turns into steam, which expands and pushes the water away from the heat source, thus extinguishing the fire.

Importance of Fusible Plug:
The fusible plug is a crucial safety device in a boiler as it prevents accidents caused by low water level. If the water level in the boiler falls below the minimum level, the furnace temperature increases rapidly, which can lead to an explosion or fire. The fusible plug helps to prevent such accidents by extinguishing the fire in the furnace when the water level falls below the minimum level.

Working of Fusible Plug:
The fusible plug is made of a low-melting-point alloy that melts at a temperature lower than the normal operating temperature of the boiler. The fusible plug is installed in a hole in the water wall of the boiler. When the water level in the boiler falls below the minimum level, the temperature of the furnace increases rapidly, and the fusible plug melts due to high temperature. The molten metal of the fusible plug falls into the water, and the water turns into steam, which expands and pushes the water away from the heat source, thus extinguishing the fire.

Conclusion:
In conclusion, the fusible plug is a vital safety device installed in a boiler to prevent accidents caused by low water level. The fusible plug helps to extinguish the fire in the furnace of the boiler when the water level falls below the minimum level, thus preventing accidents like explosion or fire. Therefore, it is essential to ensure that the fusible plug is functioning correctly and is replaced when it is worn out.