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Fusible Link vs. Glass Bulb Sprinkler Heads — What are the Differences?

Posted by: Piyush Singh
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In the category of wet-pipe fire sprinkler systems — there are two types of sprinkler heads: the Fusible Link and the Glass Bulb. Although both these fire sprinkler heads serve the same purpose and work almost similarly, there are still multiple points where these two differ.

millbrook So, to determine whether which fire sprinkler head can better suit your requirements — we have explained the difference between both of these fire sprinkler heads in this article.

So, keep on reading!

Starting with Fusible Link Fire Sprinkler Head:

Fusible Link Fire Sprinkler Head
A Fusible Link Sprinkler Head contains a heat-sensitive alloy covered with a two-part metal element — with a link holding the plug ready. When the temperature of the surrounding rises to a preset degree, the alloys melt — releasing the metal elements to separate and freeing the pip cap to dispense water (that is already pre-filled in the pipes).

And, how does a Glass Bulb Fire Sprinkler Headwork?

Glass Bulb Fire Sprinkler Head
A Glass Bulb Fire Sprinkler Head consists of a metal frame incorporating a glass container filled with a heat-sensitive liquid that holds the pip cap in place and ready to dispense.
When the temperature of the surrounding rises to the sensitivity extent of the liquid, the glass bulb explodes — releasing the pip cap and dispersing the water to the heat-affected area.

The sole physical difference between the two fire sprinkler heads is that the glass bulb head has a glass reservoir containing heat-sensitive liquid whereas, in the fusible link head, there is a heat-sensitive alloy that is supposed to melt and release the two parts of the metal frame.

Now that we know the functioning of these fire sprinkler heads and the physical differences between the two, we will further discuss their temperature setting, application, and other dissimilarities.

millbrookDifferences between the Two Types of Fire Sprinklers Heads:
Following are the points of distinction between the two types of fire sprinkler heads.

• Sealing Assembly: Sealing Assembly or as termed as “Plug” is the cap that is held firm by a heat-sensitive element in the fire sprinkler head. In the case of a fusible link sprinkler head — the sealing assembly is held firm by an alloy that binds the metal frames together. And in the case of a glass bulb sprinkler head — the plug is held down by the glass container storing a heat-sensitive liquid.

• Heat Sensitive Element: The wet sprinkler systems have one thing in common — a heat-sensitive element that acts as a plug (as explained above). These heat-sensitive elements are different in both the sprinkler heads.

In the case of a fusible link sprinkler — the heat-sensitive element is a compound that holds the two parts of the metal frame together. While in the case of a glass bulb sprinkler system — the heat-sensitive element is a glycerin-based liquid that is contained in a glass bulb; both of them react to extreme heat.

• Deflectors: Deflectors are the plates installed at the opening of the water flow. These are supposed to direct the flow of the water in the desired pattern, direction and speed.
Now, there are different types of deflector plates for both of these fire sprinkler heads. The decision regarding this element is concluded upon the time of the installation process and its purpose.

• Frame: A frame is the metal body of a fire sprinkler head that holds everything together. The fusible link sprinkler head has a two-part metal body — that sticks together with the help of a heat reactive alloy, that melts when sensing high temperature and releases the plug free, letting the water flow free. On the other hand, the glass bulb fire sprinkler has a united metal body with the bulb located in the center of it — that weighs the plug down. After reaching the specified temperature — the glass bulb detonates, releasing the plug and dispersing the water.

So, these are the main differences between the fusible link fire sprinkler and the glass-bulb fire sprinkler head. Both of these have minute differences and work about the same.

However, it depends upon the owner of the premises — as to which fire sprinkler head would suit his needs, the surroundings, and preferences.

The Bottom-Line:
We hope that this information resolved your doubts and helps you pick the right fire sprinkler head for your property.

And, if you require a fire sprinkler system and need further guidance — well, we are here for you!

Millbrook Fire Protection provides fire sprinkler services for both residential and commercial buildings.

Contact us right away to stay safe from any fire accidents.

Author: Piyush Singh