FUSIBLE PLUG
Function:
Its function is to protect the boiler against damage due to overheating for low
water level. It is fitted in the crown of the furnace or firebox at appropriate
place.
Working:
In the normal working conditions of the boiler, the fusible plug is fully
submerged under water. This is so because under normal condition, proper water
level is maintained & can be checked by water level indicator. Under the
circumstances, the heat from the fusible plug is being conducted to water. This
keeps the fusible metal at an almost constant temperature, much below its
melting point. When the water level falls below the fusible plug, the plug gets
uncovered from water. The upper portion of the plug gets exposed to the steam
space. The steam cannot keep the plug cool. This will over heat the fusible
metal. The plug falls down along with the fusible metal making a hole. The
steam and water, being under pressure immediately reach the firebox and
extinguish the fire.
Fig. - Fusible Plug
Good one
ReplyDeleteAn early form of water-level indicator, now rarely used, consists of a float inside the boiler attached to a thin brass rod which passes vertically through a gland in the boiler shell.
ReplyDeleteboiler cooling treatment service in Ontario