Fusible Plug in Boilers

Fusible plugs are safety devices used in steam boilers to prevent overheating and explosions. They are typically threaded cylinders with a low-melting-point seal that melts when the temperature reaches a predetermined level. This allows steam or hot gases to escape, preventing excessive pressure buildup and potential explosions.

The main function of a fusible plug is to enhance safety during boiler operation. Its working principle depends on the water level in the boiler shell. If the water level drops too low, the fusible plug is exposed to high temperatures, causing the seal to melt and allowing the steam or hot gases to escape. This helps prevent the formation of excessive pressure and potential boiler explosions

Fusible plug material in boiler

The fusible plug material in a boiler is typically tin, which has a melting point of 232°C (450°F). The plug is made of a brass, bronze, or gunmetal body with a tapered hole drilled completely through its length. The hole is sealed with a slug of tin, which melts when the boiler overheats. This allows steam to escape from the boiler, which prevents it from exploding.

Other materials that can be used for the fusible alloy in a boiler include lead, bismuth, and cadmium. These materials have melting points that are lower than tin, so they will melt at a lower temperature. This can be helpful in boilers that are exposed to very high temperatures.

The fusible plug is an important safety feature in boilers. It helps to prevent catastrophic accidents that can cause serious injury or death. Boiler operators should regularly inspect the fusible plug to make sure that it is in good condition and that the fusible alloy is not corroded or damaged.

Here are some additional facts about fusible plugs in boilers:

• The fusible plug is typically located on the crown sheet of the boiler, which is the highest point in the boiler.
• The fusible plug is usually threaded so that it can be easily replaced.
• Fusible plugs should be replaced annually, or more often if the boiler is used in harsh conditions.

Fusible Plug Function

 

What happens is that during steam boiler operation, the feed pumps 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 continuous steam generation.

 

 

So, if anyhow, this loop of supplying water to the Steam boiler does not work (because of any fault) during Boiler operation then after some time the water level in the Boiler shell will first go down the low water level, then the perforated line.

Other Products

• • Buy Baghouse Filters

• • Buy Fusible Plug

• • Buy Small Boilers

• • Buy Superheaters

• • Buy Watertube Boilers

Now because of the reduced quantity of water in the Steam Boiler shell, the steam volume in the shell rises and because of continuous combustion in the furnace the temp of this steam goes up and it gets superheated.

When the water level goes below the fusible plug, the lead present inside the Plug gets melted because of super-heated steam and now the water from the boiler shell comes out and wets the flue gases and even disrupting the combustion thereby protecting the Steam Boiler from any mishap that may have happened otherwise.

Buy Bronze Boiler Fusible – Plug

We, at Thermodyne, supply Smoke Tube Steam Boilers with all such desired protections to avoid a tension-free and reliable operation of the Steam Boiler.

Fusible Plug-Related FAQs

Boiler Resources Page Here

• • Boiler Losses That Eat Away Your Profits

• • Dissolved Gases in Feed Water and Its Effect

• • Pressure Reduction System

• • How to minimize the Blowdown Losses