By Grant Lobdell, General Manager
The field sprinkler testing report produced by Dyne Fire Protection Labs identifies several attributes of the sprinkler in the sample information section. The release mechanism and water seal identified are of particular importance as they are the components of the sprinkler directly being evaluated during the periodic testing. According to A.5.3.1.1 of the current 2020 edition of NFPA 25 Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems, sprinklers are to be laboratory tested for sensitivity and functionality. For the purpose of periodic field service testing, sensitivity refers to the evaluation of the sprinkler’s release mechanism whereas functionality refers to the evaluation of the sprinkler’s water seal. Because of their importance, some of the more common release mechanisms and water seals are highlighted below.
Common Release Mechanisms
Frangible Bulb
A glass ampule containing a liquid which consists of water, alcohol or glycerin, and a dye to indicate activation temperature. As the temperature increases, the liquid expands. When the temperature increase reaches the designated activation temperature, it applies enough pressure to break the glass which is holding the water seal in place.
Fusible Link
Two metal plates held together with solder. The melting point of the solder is designed such that the solder will become malleable enough to release the links holding the water seal in place at the designated activation temperature.
Solder Pellet
A pellet made of solder holding a metal rod in place. The melting point of the solder is designed such that the solder will become malleable enough to release the rod holding the water seal in place at the designated activation temperature.
Common Water Seals
Belleville Spring
A conical washer. The release mechanism sits on a cap which then sits in the inner ring of the washer. The outer ring of the washer rests on the frame.
Copper Gasket
A thin piece of copper. The release mechanism sits on a cap which sits on top the copper gasket. The outer edge of the copper gasket rests on the frame.
O-Ring
A rubber O-ring gasket. The release mechanism sits on a cap which rests in the frame only separated by the O-ring gasket.
If you have any questions regarding this article, please contact Dyne Fire Protection Labs at lab@dyneusa.com or (800) 632-2304.
©Dyne Fire Protection Labs 2020