Fusible Plug is a fitting used in Steam Boilers to enhance the safety during operation. It’s working depends upon the water level in the Boiler shell. A fusible Plug is a threaded metallic cylindrical object, with a tapered hole in it which goes through its entire length. It is usually of brass, bronze or even gunmetal. In a smoke tube steam boiler , it is fitted on the front tube sheet, just above the tubes (used for flue gas flow) arrangement but below the perforated feed line inside the shell. But the question is how exactly this little thing helps in preventing a huge disaster. It’s working is dependent only on the temperatures not on pressures. What happens is that during steam boiler operation , the feed pumps to supply water for steam conversion in the Boiler shell on the basis of the signal sent to it by the electrical panel. And electrical panel receives this signal from the mobrey (automatic water level controller) based on the fluctuating water levels due to continu...