NDLI: Delayed Fracture of Glass Bulbs Used in Fire Sprinklers

Content Provider	Springer Nature Link
Author	Huet, Roland Martora, Scott Ames, Nicoli Currens, Ethan
Copyright Year	2016
Abstract	Very rarely, glass bulb sprinkler heads activate when there is no fire or elevated temperatures. In such cases, the bulb fragments are never recovered. Speculation may arise that there was a defect in the bulb from manufacturing or installation, which led to its eventual failure. We investigated the growth of such defects using the principles of fracture mechanics and the well-known laws of slow crack growth in glass. These laws include the existence of a threshold, below which cracks do not grow at all, and above which cracks grow at a velocity that is greater than a minimum value. As a result, bulbs either never fail, or fail within a relatively short time after the crack or defect is created. Finite element and fracture mechanics analyses for a typical bulb indicates that the maximum delay is of the order of hours or weeks, not years. Experiments confirm this phenomenon. Over 100 bulbs were intentionally damaged, then placed under a constant load. A total of 44 bulbs, for which the combination of damage and load happened to be above the threshold for crack growth, failed within days (up to 36 days), while all other 58 bulbs survived over 2 years without failure. The theoretical analysis and the experiments demonstrate that fracture of sprinkler bulbs occurs relatively quickly after the introduction of a defect: if a bulb fractures in service without apparent cause, there must have been some event to damage the bulb or the sprinkler head in the days or weeks before the activation.
Starting Page	629
Ending Page	647
Page Count	19
File Format	PDF
ISSN	00152684
Journal	Fire Technology
Volume Number	53
Issue Number	2
e-ISSN	15728099
Language	English
Publisher	Springer US
Publisher Date	2016-03-28
Publisher Place	New York
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Glass Sprinkler Bulb Fracture Civil Engineering Classical Mechanics Characterization and Evaluation of Materials Physics
Content Type	Text
Resource Type	Article
Subject	Materials Science Safety, Risk, Reliability and Quality

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1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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