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|Notes from a maritime-sector AHJ|
Notes from a maritime-sector AHJ
By LCDR Doug Simpson, USCG | Fire Protection Engineering
Transportations changing. Although moving people and their stuff from here to there has always been important, transportation has never been more convenient or as integrated into societys daily routine as it is today. Transportation powers the workforce and supplies livelihoods. As the mobile population increases, so will the importance of transportation capabilities and infrastructure.
An online scan through various U.S. federal agency statistics reveals the same trend in all transportation sectors: throughput of highways, waterways, airports, seaports and pipelines is increasing. Even as congestion thickens, these sectors are being tasked to deliver more goods more rapidly.
This challenge is being met through expansion and the use of new technologies. In the maritime arena, ships are getting bigger and faster. Ports are expanding where they can, and when they cant, they are changing operations to leverage efficiency. Regardless how the face of transportation changes to meet increasing demands, the safe arrival of the people and things transported continues to be a fundamental requirement.
Fire protections niche in transportation rests in this requirement, and expertise will be needed to effectively apply fire protection principles to transportations changing designs, technologies and operations.
As an authority having jurisdiction over U.S.-registered vessels, the Coast Guard Marine Safety Center reviews the designs of high-occupancy ships for their compliance with domestic and international requirements.
Since ships are basically floating buildings, the requirements to which they are reviewed are remarkably similar to building code: How a space is used drives its boundary requirements, occupancy determines exit discharge component sizes, atria smoke must be managed and the like.
However, a building that floats and moves obviously introduces unique fire protection needs. Construction, exit discharge and emergency responder availability must all be considered when designing a ships fire protection.
Concrete is too heavy to make an economically viable ship,so steel is typically used. Instead of the three-hour separation one might find on a land-based, concrete restaurant assembly, the most that is found on a steel ship is 60 minutes.
On land, it is possible to discharge a high-rises occupants to ground-level safe refuge away from the affected building.Not so on a cruise ship, as salt water makes a poor substitute for a parking lot. Instead of exiting to ground level, exit paths must lead to protected refuge areas onboard. Since ships underway are further from assistance than typical buildings,they must often provide their own fire-fighting capabilities.
In the same way building code accounts for special-use facilities, the Coast Guard has policy and regulations that address unique design needs. For instance, high-speed passenger ferries are often built using aluminum, which is lighter than steel, to quickly move passengers along their commuting routes. Since it has a lower melting point, aluminum must be carefully insulated to provide protection similar to that of steel. In some applications, insulating the aluminum can be tricky and unwieldy, almost to the point of losing the benefit of its lighter weight. By implementing strict control of fire load in appropriate spaces, fire growth and heat-release potential are minimized, allowing for decreased insulation requirements and a lighter, faster ship.
The past few years have seen the maritime sector implement performance-based design. In 2001, the Coast Guard issued policy through its Navigation and Vessel Inspection Circular (NVIC) 3-01 that allows certain passenger vessels to use performance-based design as an alternative to meeting the prescriptive structural fire protection requirements contained in the Code of Federal Regulations. Internationally, the Convention for Safety of Life at Sea1 (SOLAS) Chapter II-2,Regulation 17, entered into force in 2002, allowing for alternative designs to be evaluated and approved using performance-based principles.
The Coast Guard has reviewed vessels using both instruments and found that perhaps the most difficult (and beneficial) part of the process is agreeing to the entering arguments. From identifying heat-release rates to calculating response times, assigning mass fractions to applying toxicity, it is this exercise that digs into the first principles of fire protection and provides the most reasonable, safe engineering analysis.
As face of transportation changes, the requirement for people and their stuff to arrive safely at their destination remains unchanged. Fire protection engineers in the transportation industry have the opportunity and tools to provide creative, safe fire protection solutions while helping the transportation system remain flexible and robust.
LCDR Doug Simpson is with the U.S. Coast Guard Marine Safety Center.