Saturday, January 27, 2007
Fire Suppression Systems
If necessity is the mother of invention, one of its grandkids is bound to be a screw-up. Case in point:
Non-automated fire suppression systems went into use in textile mills in New England as early as 1852. Twenty years later, an engineer from Massachusetts came up with an automated system, and two years after that someone else, a guy named Henry S. Parmalee, made a sprinkler head that really worked. In 1874, Parmalee installed what was probably the first functioning fire suppression system into his piano factory. These, of course, were all mechanically operated sprinkler systems.
While we still have automated systems that work purely by mechanical means, using principles of pneumatic or hydraulic expansion, many, if not most of today’s systems, particularly those on boats and ships, rely on an electrical circuit for fire detection. Herein lies a serious problem, because without early warning capability, the vessel’s crew and passengers are at the mercy of lady luck.
In October of 2004, a fire destroyed the Express Shuttle II, a 65’ passenger vessel operating out of Port Richey, Florida. Following an investigation of the incident, U.S. Coast Guard officials decided to take a long, hard look at custom-engineered fire fighting systems. Systems using DC electric detection components were most suspect.
What happened aboard the Express Shuttle was not atypical of many engine room fires. A high-pressure fuel leak in one of the boat’s two Caterpillar engines sprayed fuel on the engine’s hot manifold, causing the fuel to ignite. Instead of manually triggering the fire suppression system, the crew (a captain and two deck hands were aboard as passengers had just previously disembarked) decided to fight the fire with hand held extinguishers. The fire rapidly became unmanageable and the crew had to abandon ship. Vessel was a total loss.
Coast Guard Investigators determined the loss was due to three factors: poor maintenance of the fuel feed line to the number five cylinder; inadequate crew response to the emergency; a non-functioning fire detection system; in fact, the fire and smoke alarms on the vessel never sounded.
For further reading, try the full NTSB Accident Report on the Web: http://www.ntsb.gov/Publictn/2006/MAR0602.pdf. And note the following U.S.C.G. recommendations:
1) A panel light should notify an operator of a fault or break in the fire detection circuit.
2) Detectors should be UL, FM or LPBC approved.
3) The system should be testable by smoke or heat.