Safety, Fuel Efficiency and Reduced Emissions Key Benefits of Third-Generation Marine Technology
Ferries and ocean going vessels can now sail more efficiently, save fuel, and reduce their CO2 emissions by using the Automated Draft Indicator System (ADIS). Weir-Jones Engineering Ltd. has recently released the third generation of this innovative marine technology.
ADIS defines the position of the static water plane relative to the vessel. In this way, the position of any part of the ship relative to the water plane can be accurately determined. Based on these measurements, the position and orientation of the vessel including the draught, freeboard, heel and trim are precisely established. The calculations are carried out in real-time and these parameters are continuously updated and displayed. The system offers vessel operators the following practical benefits:
• Very accurate draft measurements (better than ±10 mm) are displayed, which is crucial during the loading process. Greater precision is available if required.
• Real-time loading information about hogging, sagging and trim.
• ADIS digital bridge display can show the draft of the vessel, port and starboard, forward, amidships and aft and cargo tonnes to go.
• The ADIS installation requires no underwater hull penetrations and can be completed in as little as eight hours on existing vessels.
Benefits of ADIS
When installed on displacement hulls, high-speed and naval vessels, and marine structures such as semi-submersible drilling platforms, ADIS™ enables operators to:
• Record precisely how much cargo has been loaded or unloaded to avoid overloading or instability.
• Improve the handling of vessels, or precisely monitor the trim of a floating structure.
• Keep accurate hard copy loading records to satisfy regulatory or coast guard requirements.
On cargo vessels and ferries, the system will rapidly pay for itself by improving fuel efficiency, eliminating disputes about the exact weight of cargo loaded and discharged, and optimizing loading.
- Fuel Efficiency (trim control)
In addition to the benefits of enhanced stability and passenger/ cargo safety, the use of ADIS™ on ocean going vessels offers two very tangible benefits that are becoming increasingly important in terms of environmental considerations. These are the improved fuel efficiency and reduced CO2 emissions that can be achieved by optimizing the vessel’s trim. In the case of tankers, this is usually only practical when the vessel is in ballast, but the cost savings and emission reductions are significant, and result in the owner’s cost of ADIS™ being recovered in less than two month’s sailing in ballast. The following example illustrates this.
Consider a 300,000 dwt capesize tanker sailing in ballast at about 17 knots. A thirty day voyage, Europe
to the Gulf, would consume ~ 2400 tonnes of fuel, ~ 80 tpd, costing ~ $700/tonne, or $1.68 million. Recent studies in Europe and by Mitsui in Japan indicate that fuel consumption efficiencies of between 5% and 7% can be achieved by optimizing the trim of the vessel. Using the lower figure of 5% produces a fuel saving of approximately $80,000/trip in ballast, with commensurate reduction in CO2 emissions of more than 300 tonnes.
On this basis, the capital cost of an ADIS™ system on a tanker in the 300,000 dwt category is an investment with a payback period of slightly more than a month of sailing in ballast. This does not take into account the associated benefits of reducing CO2 emissions by almost four hundred tonnes/trip.
ADIS Development History
The first generation of ADIS was utilized with two draught measurement sensors and the system was installed in 1993 on the BC Ferries vessel Queen of Victoria for a three-year test run. After more than 20,000 hours of successful and problem-free operation, the first generation of ADIS became available to marine operators and constructors as a proven commercial product. As a result, ADIS became the standard draught indicating system on BC Ferries and Washington State Ferries vehicle ferry fleets.
Since its initial development, the system has been continuously upgraded and more features have been added. In 2004, the second generation system with four sensors was developed, and in 2010, the third generation was introduced that includes a GPS interface which enables ADIS™ to deactivate the alarm feature once the vessel is underway. The mean time between failures for the third generation is in excess of 50,000 hours.
Principle of Operation
The ADIS system is equipped with four ultrasonic transceivers. In standard configuration, each transceiver generates short bursts of ultrasonic energy and captures the reflections from the water surface. The embedded microprocessor in the sensor measures the travelling time of the generated ultrasonic wave and accurately determines the distance of the water surface from the known position of the transceiver.
In addition, the sensor uses an internal temperature sensor to compensate for temperature effects on the measurements. The sensor digitally sends the distance values which define the position of the water plane relative to the vessel to the central processing unit.
In the central processing unit, the position of any part of the ship relative to the water plane is accurately calculated. The draught of the vessel is determined based on the measuring of the port and starboard freeboard, fore and aft. The depth of the keel below the water plane is calculated using the dimensions of the vessel and proprietary algorithms, which ensure accuracy by correcting for the presence of propeller wash in dock and waves while underway.
Two or more bridge display outputs are available for double ended vessels or for alternate display locations. The bridge display provides six digital readings; draught forward and aft, draught and freeboard amidships, port and starboard. Data can also be routed to other data storage systems such as the Hull Condition Monitoring System and the Voyage Data Monitoring System.
ADIS is currently being used by British Columbia Ferry Services (20 systems), Washington State Ferries (25 systems), Alaska Marine Highway System (3 systems) and the United States Navy (2 systems). The latter are high precision systems.
Dr. Iain Weir-Jones has more than forty years of experience in the design and development of proprietary monitoring and analytical systems. He can be reached at firstname.lastname@example.org