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Engineering Controls Database

Vessel Downflooding Prevention – Multi-level Flood Sensor

In 2008, over 8 billion pounds of seafood was harvested in the United States earning over $4.4 billion. There are approximately 115,000 harvesters in the United States using a variety of different fishing gear and vessels [NOAA 2010]. Species that contributed the most to this revenue include shrimp, Pacific salmon, pollock and lobster.

Commercial fishing is one of the most dangerous occupations in the United States. Many commercial fishing operations are characterized by hazardous working conditions, strenuous labor, long work hours and harsh weather. During 1992-2008, an annual average of 58 deaths occurred (128 deaths per 100,000 workers), compared with an average of 5,894 deaths (4 per 100,000 workers) among all U.S. workers [DOL 2010].
The National Institute for Occupational Safety and Health (NIOSH) maintains the Commercial Fishing Incident Database (CFID), a surveillance system for workplace fatalities in the commercial fishing industry in the United States. A review of data from the CFID indicates that vessel sinking accounted for 52% of commercial fishing fatalities from 2000-2008.

The sinking of the F/V Alaska Ranger and F/V Katmai in 2008 where 12 men perished highlight the need for a hatch and door monitoring system. In both cases water flooded across watertight compartments through open hatches rapidly decreasing stability and affecting control of the vessel. Fishermen need a system that will provide an immediate and continuous status of watertight openings to prevent downflooding or cross-compartment flooding of their vessel. In addition to the danger of downflooding from open watertight doors and hatches, vessels can flood via a hull breach or leak around the rudder or propeller in a compartment known as the lazarette. Both the sinking of the F/V Katmai and F/V Alaska Ranger were accelerated due to flooding in the vessel’s lazarette.
NIOSH engineers have developed a system that is an improvement to traditional float-style bilge alarm switches to indicate compartment flooding. It not only indicates flooding, but some measure of the rate and whether or not the bilge pumps are keeping up with the in-rush of water. A prototype of the system is being tested aboard commercial fishing vessels in Alaska.

Rows of lamps are mounted on the front of a control box; the lamps turn on or off indicating the relative water level of a flooded compartment. The fluid level set-point for each lamp to activate is field-adjustable, making it simple to configure the monitor to various compartment shapes. In addition to activating a lamp, the fluid level set-point can switch on a pump relay and/or an alarm.

Watching the line of lamps turn on or off provides the relative fluid level of the compartment. As the water rises to a pre-determined level another lamp goes on, and, as the pump drains water from the compartment another set-point is reached and the top lamp in the line is turned off. The severity of the flooding is known without opening the water-tight compartment hatch/door.

All of this information is provided by a pressure transducer that can be tuned to report rises in water pressure and hence water level. The system involves few mechanical parts and reduces the chances of the sensor being fouled by machine oil or grease, fish slime, or other debris.

This system can also be integrated with the NIOSH Hatch and Door Monitoring prototype to provide further information to the captain and crew about the condition of the vessel and its watertight integrity. The Hatch and Door Monitoring system is described in a separate Data Base summary report.
Figure 1. Testing the lazarette door sensor on F/V Gladiator

Figure 1. Testing the lazarette door sensor on F/V Gladiator

Figure 2. Level indicators on prototype.

Figure 2. Level indicators on prototype.
DOL [2010]. Injuries, illnesses, and fatalities: Census of Fatal Occupational Injuries (CFOI)--current and revised data. Washington, DC: US Department of Labor, Bureau of Labor Statistics. Available at Accessed September 29, 2011.

NIOSH. Vessel downflooding prevention: Multi-level flood sensor. Commercial Fishing Safety and Health Research. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Spokane Research Laboratory, Alaska Pacific Regional Office.

NOAA [2010]. Fisheries Economics of the United States, 2008. US Department of Commerce. National Oceanographic and Atmospheric Administration. National Marine Fisheries Service. Available at Accessed September 29, 2011.
commercial fishing