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<p><b><font face="Arial" size="5">SENSFIB Fiber Optic Hull Stress Monitoring System
</font></b></p>
<p><font face="Arial" size="4">SENSFIB is a fiber optic hull stress monitoring
system for cargo vessels. The development of hull fatique is measured using
long-life optic sensors located in various positions in the hull. SENSFIB assists
crew, owner and class society in safe operation of the vessel. Hull stresses
are monitored continuously, enabling the crew to avoid stress overload on the
hull during ballasting, cargo operations and during the voyage. The bridge console
displays hull stress information and generates alarms at pre-set limits. Hull
condition data are stored in the system's data storage unit for later analysis.</font></p>
<p><font face="Arial" size="4">Bulk carriers, tankers and container vessels are
particularly at risk of hull fatigue damage, induced by the stresses that can
occur in the hull as a result of ballast, cargo load and sea state. Fatigue
build-up in vessels leads to local cracks, which if left unrepaired, can eventually
endanger the structural integrity of the vessel. To put it bluntly, the vessel
can break up.</font></p>
<p><font face="Arial" size="4">Hull fatigue through the cumulative effects of
dynamic stress can put crew, vessel and cargo in very dangerous situations.
November 25th, 1997, container vessel "MSC Carla" broke into two pieces
during a storm North of the Azores.</font></p>
<p align="left"><font face="Arial" size="4">But damage doesn't necessarily occur
at sea. November 8th, 1999, OBO "Lassia" sagged and sustained structural
damage while discharging iron ore in Taranto, Italy. Overloading in one cargo
hold and / or improper ballasting can cause very high still water bending moments,
which accelerate hull fatigue development.</font></p>
<p align="left"><font face="Arial" size="4">Container stacks can collapse when
the container lashings break in severe weather. SENSFIB provides early warning
by monitoring the movements and accelerations of the vessel. Excessive hull
movements can cause the container fittings to give way, which results in cargo
losses and damage to the vessel.</font></p>
<p><b><font face="Arial" size="5">Fatigue and Hull Life Span</font></b></p>
<p><font face="Arial" size="4">All vessels are built with a given fatigue capacity
when leaving the shipyard. This fatigue capacity is being reduced from the very
first day in operation. Theoretically, this fatigue capacity reduction is evenly
distributed over the projected life span of the vessel. Maintenance schedules
and procedures are based on a gradual reduction of fatigue capacity. Actual
events however might not mirror theory. Peak stress loads during loading, discharging
or heavy weather might accelerate the development of fatigue in the hull. SENSFIB
provides the possibility to monitor hull fatigue development closely and adjust
maintenance schedules accordingly. If fatigue progress is more rapid than planned,
corrective maintenance, such as repair of local cracks and coating damage might
be necessary. The reverse might also be true if fatigue progress is slower than
planned. Unnecessary scheduled maintenance can be avoided and maintenance cost
can be reduced.</font></p>
<p><font face="Arial" size="4">Hull fatigue is a function of dynamic hull stress
amplitude and the number of load cycles. The economic impact for the ship owner
of this simple relation is illustrated in the diagram below. Average dynamic
stress levels of 12% of the instant failure level will result in a hull life
span of 23 years. An increase of average dynamic stress levels to 18% will reduce
hull life span to just 8.6 years before fatigue.</font></p>
<p><font face="Arial" size="4">Onboard preventative measures to reduce dynamic
stress levels greatly inpact the life expectancy of the vessel. SENSFIB monitors
hull stress levels and can help the crew to keep dynamic stress level within
safe operation levels. SENSFIB data can be relayed on-shore for analysis by
the operator's operations department. Maintenance schedules can be optimized
using the hull fatigue data from the vessel. Cargo operations and ballasting
procedures can be altered to reduce hull stress load.</font></p>
<p><font face="Arial" size="5"><b>Applications</b></font></p>
<p><font face="Arial" size="4">The SENSFIB systems can be applied to monitor hull
fatigue in all kinds of vessels. Particularly at risk of hull fatigue are the
following types of vessels:</font></p>
<ul>
<li><font face="Arial" size="4">Bulk carriers;</font></li>
<li><font size="4" face="Arial">Tankers;</font></li>
<li><font size="4" face="Arial">Container vessels, in which cargo damage as
a result of heavy weather can be reduced by early warning of excessive vessel
movement;</font></li>
</ul>
<p><font face="Arial" size="4">But there are other types of vessels that can benefit
from the SENSFIB system as well:</font></p>
<ul>
<li><font face="Arial" size="4">FPSOs and shuttle tankers, in which actual stress
levels can be monitored during offloading operations in high seas;</font></li>
<li><font face="Arial" size="4">Heavy lift and project cargo vessels, in which
knowledge of the global and local stress levels might contribute to operational
safety.</font></li>
</ul>
<p><font size="4" face="Arial">Certainly operators are not the only ones benefitting
from the installation of the SENSFIB hull stress monitoring system:</font></p>
<ul>
<li><font size="4" face="Arial">Class societies can check the accuracy their
hull design and structural analysis software;</font></li>
<li><font size="4" face="Arial">Naval architects and shipyards can incorporate
structural improvements in their new designs, based on information from the
vessels fitted with SENSFIB;</font></li>
<li><font size="4" face="Arial">Charterers have a in-depth tool to assess vessel
fatigue development and the likelyhood of extended off-hire due to the need
for structural repairs;</font></li>
<li><font face="Arial" size="4">Insurance companies can evaluate hull, equipment
and cargo damage claims using voyage data from the SENSFIB system.</font></li>
</ul>
<p><b><font face="Arial" size="5">Benefits of Installing SENSFIB</font></b></p>
<p><font face="Arial" size="4">The economic consequences of hull fatigue, and
its consequences, in commercial vessels are enormous: </font></p>
<ul>
<li><font face="Arial" size="4">Accelerated depreciation of the value of the
vessel;</font></li>
<li><font face="Arial" size="4">Off-hire;</font></li>
<li><font face="Arial" size="4">Salvage and towage;</font></li>
<li><font face="Arial" size="4">Dry-docking;</font></li>
<li><font face="Arial" size="4">Repairs;</font></li>
<li><font face="Arial" size="4">Environmental pollution cleaning cost and fines;</font></li>
<li><font face="Arial" size="4">Potential loss of lives, vessel and cargo;</font></li>
<li><font face="Arial" size="4">Litigation.</font></li>
</ul>
<p><font face="Arial" size="4">By using the information generated by SENSFIB throughout
the 23 year commercial life of a typical European owned tanker, the potential
savings are estimated to be over EUR 4,000,000. </font><font face="Arial" size="4">hese
benefits are estimates and it is not guaranteed to apply to each and every vessel.
</font></p>
<p class=MsoNormal><font face="Arial" size="4">Installing the SENSFIB system will
allow for a reduction in insurance rates, since the condition of the hull can
be determined and monitored over time. The causes of damage to hull and cargo
can be analysed and damage prevention schemes can be introduced, reducing the
number of insurance claims. SENSFIB offers the potential for cost reduction
in the operation of vessels by reducing maintenance and repair cost, while increasing
charter rates and second hand value.</font></p>
<p><font face="Arial" size="5"><b>Fiber Optic Hull Stress Sensors</b></font></p>
<p><font face="Arial" size="4"> SENSFIB is the only fiber optic hull stress monitoring
system currently available. Fiber optic stress sensors (or strain gauges) have
a number of advantages over existing electronic systems:</font></p>
<ul>
<li><font face="Arial" size="4">Very long sensor life;</font></li>
<li><font face="Arial" size="4">Virtually maintenance free;</font></li>
<li><font face="Arial" size="4">Easy to install;</font></li>
<li><font face="Arial" size="4"> Installation almost anywhere in the vessel.</font></li>
</ul>
<p><font face="Arial" size="4">The exact number of sensors and the location of
each sensor is determined by the requirements of the owner and the specifications
of the Class Society. Additional sensors can be plugged in when and where required
by way of a connection box.</font></p>
<p><font face="Arial" size="4">The sensors are used to monitor hull stresses in
various parts of the vessel:</font></p>
<ul>
<li><font face="Arial" size="4">Sensors fitted on deck longitudinals record
global hull stesses. These sensors provide data on hogging, sagging and torsion
of the hull;</font></li>
<li><font face="Arial" size="4">Sensors fitted on side girders in the forepeak
provide data on hull response to wave impact and even on the direction of
the waves;</font></li>
<li><font face="Arial" size="4">Sensors mounted on side griders in the ballast
tanks monitor local stresses. The exact correlation between sensor data and
hot spot stresses in related brackets and frames is to be provided by the
classification society.</font></li>
</ul>
<p><font face="Arial" size="4"></font><font face="Arial" size="4">Included in
the SENSFIB system is one accelerometer, which is to be mounted in a dry space
in the forecastle on the centerline of the vessel. The accelerometer is equipped
with an electro-optic converter and is coupled to the fiber optic network via
the connection box in the forecastle.</font> </p>
<p><b><font face="Arial" size="5">SENSFIB Technology</font></b></p>
<p><font face="Arial" size="4">The fiber-optic sensors used in the SENSFIB system
are based on Bragg gratings. These gratings are short sections of optical fiber
that have been sensitized to strain and temperature through a periodic modulation
of the refractive index of the fiber core. A grating reflects a narrow range
of wave lengths determined by the period of the modulation. The most strongly
reflected wave length is called the Bragg wave length and is a characteristic
of the grating. Strain on the fiber or a change in temperature will modify the
modulation period, and hence the reflected wave length. Gratings with different
Bragg wave lengths can be connected on the same fiber, forming a wave length
multiplexed system. </font></p>
<p><font face="Arial" size="4">The fiber-optic sensors have a number of advantages
over the electrical alternatives, especially in harsh environments: </font></p>
<ul>
<li><font face="Arial" size="4">High sensitivity;</font></li>
<li><font face="Arial" size="4">Good resistance toward water and chemicals;</font></li>
<li><font face="Arial" size="4">Signal is wave length coded, and unaffected
by the environment along the cable path;</font></li>
<li><font face="Arial" size="4">Immune to electro-magnetic interference;</font></li>
<li><font face="Arial" size="4">No emission of electro-magnetic radiation;</font></li>
<li><font face="Arial" size="4">Safe for use in EX rated spaces;</font></li>
<li><font face="Arial" size="4">Multiplexing, many sensors can be connected
to a single cable.<br>
</font></li>
</ul>
<p align="left"><font face="Arial" size="4">A functional sensor system is a combination
of a light source, sensors and an analyzer that receives the optical signals
from the sensors and converts them to a format suited for digital signal processing.
The fiber Bragg grating analyzer used in the SENSFIB system is based on a scanning
filter that gates the light from a broadband source. The analyzer determines
the Bragg wavelength of each grating with high precision. </font></p>
<p><font face="Arial" size="5"><b>SENSFIB Configurations</b></font></p>
<p><font face="Arial" size="4">SENSFIB can be configured to meet all the requirements
of each individual customer. SENSFIB can be integrated with the onboard loading
computer or be part of an elaborate control and monitoring system. The fiber
optic network installed for the sensors can also carry the data flows for other
control systems, e.g. DPP system, engine room remote control, bridge wing stations,
tank level gauging system, heeling system, etc. </font></p>
<p><font face="Arial" size="4">The SENSFIB system in its most basic configuration
consist of four global sensors and one accelerometer. The optic strain gauges
are mounted on the deck longitudinals to record global stress on the hull as
a result of hogging, sagging and torsion. The accelerometer record vessel movement
and accelerations. The bridge unit is connected with the loading computer to
represent both static and dynamic stress levels. </font></p>
<p><font face="Arial" size="4">The Lloyd's Register's ShipRight SEA (Ship Event
Analysis) class notation requires the SENSFIB basic configuration, augmented
with a pressure sensors on the forward part of the bottom of the hull. This
sensor records the impact of slamming on the hull condition.</font></p>
<p><font face="Arial" size="4">DNV HMON-2 class notation for vessels comprises
the SENSFIB system, augmented with a range of local sensors in the bow area
and the side tanks. The local sensors in the bow are mounted on side girders
and are designed to record hull response to wave impact and wave direction.
The local sensors in the side tanks record stress levels, which correlate with
hot spot stresses in the hull. The SENSFIB system is integrated with the loading
computer, a GPS reciever and a wave radar system.</font></p>
<p><font face="Arial" size="5"><b>Components</b></font></p>
<p><font face="Arial" size="4">The SENSFIB system consists of the following components:</font></p>
<ul>
<li><font face="Arial" size="4">Global sensors on deck longitudinals;</font></li>
<li><font face="Arial" size="4">Local sensors on frames (subject to configuration);</font></li>
<li><font face="Arial" size="4">Accelerometer with electro-optic converter;</font></li>
<li><font face="Arial" size="4">Connection boxes to connect the fiber optic
cables from the sensors and the accelerometer with the main fiber optic network
on the vessel;</font></li>
<li><font face="Arial" size="4">Fiber optic network from the deckhouse to the
forepeak;</font></li>
<li>
<div align="left"><font face="Arial" size="4">Sensor interface unit, located
in the deckhouse. This unit contains the sensor interrogation unit and the
electro-optic converter. The unit recieves and processes the data from the
sensors. The data are transmitted to the hull info unit through a conventional
electronic data link. The power supply to the sensor interface unit is safeguarded
with a UPS unit;</font>
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</div>
</li>
<li><font face="Arial" size="4">Hull info unit on the bridge, which runs the
software for data processing and presentation. This unit also processes the
data received from the loading computer, the GPS receiver and the wave radar.
The bridge display gives the user clear information on actual stress levels
through easy to read mimic screens. The hull info unit also handles data transfer
to the on-shore operations office through satellite communication. Back-up
power is supplied by a UPS unit;</font></li>
<li><font face="Arial" size="4">Data mass storage device to record individual
sensor data, processed data and systems status;</font></li>
<li><font face="Arial" size="4">Printer to generate pre-formatted reports (optional);</font></li>
<li><font face="Arial" size="4">External alarm (optional).</font></li>
</ul>
<div align="center"></div>
<p align="left"><font face="Arial" size="5"><b>SENSFIB Installation</b></font></p>
<p><font face="Arial" size="4">The SENSFIB system is suitable for installation
in newbuilding vessels and for retrofitting onto existing vessels:</font></p>
<ul>
<li><font face="Arial" size="4">The sensors can be installed in almost any space
in the vessel. Ballast tanks, void spaces and even EX rated spaces are ideal
to mount sensors to side girders or deck longitudinals;</font></li>
<li><font face="Arial" size="4">The sensors are connected to the fiber optic
network by way of a fiber optic cable, which can be routed through existing
cable trays or ducts for 220 / 440 V cables. The fiber optic cables are insensitive
to temperature and electro-magnetic noise. The cables can be routed through
EX rates spaces;</font></li>
<li><font face="Arial" size="4">The accelerometer and associated electro-optic
converter are to be installed in a dry space in the forecastle, e.g. the bosun
store. The accelerometer is to be installed on the centerline of the vessel;</font></li>
<li><font face="Arial" size="4">The connection boxes are suitable for EX rates
areas and can also be mounted on the open deck. Connection boxes are to be
bolted to the cable pipe or duct or to a seperate foundation;</font></li>
<li><font face="Arial" size="4">The fiber optic network from the deckhouse to
the forecastle can be routed through exiting cable pipes for 220 / 440 V on
the main deck;</font></li>
<li><font face="Arial" size="4">The sensor interface unit is to be installed
inside the deckhouse, e.g. the cargo control room. A support for the unit
is to be welded on the deck and bolted to the unit;</font></li>
<li><font face="Arial" size="4">The hull info unit on the bridge can be integrated
with other control systems into a main bridge console or the system can be
mounted as a seperate, stand-alone console;</font></li>
<li><font face="Arial" size="4">The connection between the sensor interface
unit and the hull info unit is a regular electronic data link, with associated
shielding requirements.</font></li>
</ul>
<p align="left"><font face="Arial" size="5"><b>Compatibility & Integration</b></font></p>
<p><font face="Arial" size="4">The SENSFIB systems can be easily integrated with
the following systems:</font></p>
<ul>
<li><font face="Arial" size="4">Loading computer;</font></li>
<li><font face="Arial" size="4">Ballast control system;</font></li>
<li><font face="Arial" size="4">Heel and trim control system;</font></li>
<li><font face="Arial" size="4">GPS receiver;</font></li>
<li><font face="Arial" size="4">Wave radar;</font></li>
<li><font face="Arial" size="4">Voyage data recorder (VDR)</font></li>
<li><font face="Arial" size="4">Satellite communication equipment.</font></li>
</ul>
<p align="left"><font face="Arial" size="4">SENSFIB supports the NMEA 0183 (RS232)
data communication protocol to enable communication with other systems. The
TCP protocol is used for data transfer via the satellite communication system.</font></p>
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