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Prismatic Coefficient

What Hull Shape Is Best?

Back at the dawn of maritime history, a coastal dweller first took a log and ventured out on the water. Over time his craft evolved from a rough log to one that had shape at the ends and was hollowed out. These changes to the basic log shape were the first example of modifying a hull form to increase carrying capacity, improve ride comfort, and to reduce resistance. Since then, shipbuilders, naval architects, and ship owners have experimented with hull shapes and the number of hulls to find the "best" design. Let's look at some of those variations to understand the challenges of choosing a hull shape. Monohull Design The basic monohull can be defined by six key numbers: length, beam, depth of hull at midships, design draft, prismatic coefficient, and displacement. Length, beam, and draft are familiar to everyone. Depth of hull at midships gives an idea of the freeboard as well as an indication of the hull strength in bending. The prismatic coefficient is a measure of how much shape there is in the ends of a hull. A high prismatic coefficient means that the ends are full such as a tanker bow. A low prismatic means that the ends are fine, with little volume, such as a tugboat stern. The choice of what dimensions to use depends on the intended use of the vessel. For a passenger vessel, there are considerations of carrying capacity, operating environment, and type of operation


Safety: Slip and Fall Accidents in the Marine Environment

Because the exposure to the marine environment and motions of a vessel, slips and falls are a significant source of personal injuries in floating equipment, probably substantially greater than most industry groups. Although there are a good number of publications, books and articles written regarding the subject of slip and falls, there are almost none addressing the conditions found in a marine environment, which influence slips and falls. Consensus


RoPax Propulsion Concept Proves Efficient

Wärtsilä, in conjunction with the Finnish research project SEATECH 2000+, has been developing some new machinery solutions for RoPax vessels. A promising concept is a semi-diesel electric machinery, where mechanical propulsion is combined with a diesel electric power plant. This new RoPax concept was presented for the first time at the Europort 2001 exhibition. The RoPax vessel has a semi-diesel electric machinery featuring a diesel mechanical part driving a conventional CP propeller and a


MHI LNG-FPSO Approval for Two Tank Types

Mitsubishi Heavy Industries, Ltd. (MHI) completed development related to floating production, storage and offloading units for liquefied natural gas (LNG-FPSO), and has obtained two kinds of approval in principle (AIP) from major international ship classification societies. In tandem with intensified activity in medium- and small-scale offshore gas field development, demand for LNG-FPSOs, a new method of gas production offering movable capability, has been increasing globally


DSME's New LNG Tank Technology Approved by LR

ACTIB ((Aluminium Cargo Tank Independent Type B) tanks - prismatic, large, independent cargo tanks -  reduce sloshing, suitable for LNG containment The ACTIB tanks, constructed of insulated aluminium 5083, will have the world’s largest storage capacity in an independent, insulated LNG tank system. The volume capacity in the initial design will be nearly three times larger than comparable types currently in operation.


MOL Ink Deal to Build, Charter 300m LNG Carrier

New LNG carrier rendering courtesy of MOL

Mitsui O.S.K. Lines (MOL) inform it has signed a Head of Agreement on joint ownership and 20-year charter contract for a newbuilding LNG carrier with Tokyo LNG Tanker Co., Ltd. At the same time, MOL signed a contract with Japan Marine United Corporation to build the new vessel. The ship is slated for completion in 2017. MOL will manage the new carrier, which will transport LNG mainly from the Cove Point LNG Project in the United States to Tokyo Gas facilities.


Lloyd’s Register and GTT Reveal LNG Study Results

Lloyd's Register and Gaz Transport & Technigaz (GTT) have jointly commissioned MARINTEK to carry out a series of model tests to investigate the effects of sloshing in partially filled prismatic LNG tanks. A typical four-tank ship design with a capacity of 140,500 cu m has been used for the purposes of the study. For the moment, the results show that: for the filling levels below 10% of tank length and over 70% of tank height the tests showed good results


Teekay Builds on its LNG Service Offering

Teekay has purchased two unique liquefied natural gas (LNG) carriers that, in future, may help its customers develop smaller gas fields and open up markets that were previously inaccessible. Teekay acquired two specialized LNG carriers. The Polar Eagle pictured here has been renamed the Polar Spirit. He says the SPB (Self Supporting Prismatic shape IMO Type “B”) cargo tank is a robust design which has been likened to “an egg in a carton


DSME Technology Approved by LR

lloyds register.png

ACTIB tanks, prismatic, large, independent cargo tanks, will reduce sloshing and are suitable for widespread use for LNG containment.   Lloyd’s Register has approved new prismatic IMO Type B independent cargo tanks, so called ACTIB (Aluminium Cargo Tank Independent Type B). The initial approval is for use in a DSME-developed 210,000 m3  STD LNG-RV design in accordance with LR’s Guidance notes for liquefied gas carriers and floating offshore installations adopting IMO


NLI, WTS Win DNV Approval for LNG Tank Design

LNG Fuel Tank solution based on the NLI LNG tank design.

NLI Solutions and Wilhelmsen Technical Solutions have received Approval in Principle from DNV on a jointly developed LNG Fuel Tank solution based on the NLI LNG tank design. Oslo, 4th of June 2013. Wilhelmsen Technical Solutions (WTS) and offshore oil and gas engineering specialist NLI Solutions (NLI) have received Approval in Principal (AiP) from the Norwegian class society Det Norske Veritas (DNV) on their jointly-developed LNG fuel tank design.  


New Thorplas-Blue Bearings on the Market

ThorPlas group

Thordon Bearings Inc. has launched the newest addition to their grease‐free polymer lineup: ThorPlas‐Blue. The lifetime lubricated bearing formula is capable of operating pressures up to 45MPa (6,527 psi) and can be easily back‐fit into virtually all deck machinery applications where greased


Protect Synthetic Ropes

Carreras Bushings

Fluoron Inc. is an aggressive and innovative company that has set out to remedy chafing issues at points of interface between synthetic mooring lines and deck or dock equipment throughout the maritime industry. They have developed various chafe and wear protection technologies including their


Joint Effort Pioneers Large LNG Containerships

Photo: UASC

United Arab Shipping Company (UASC) will expand its fleet with new super-efficient container vessels, prepared for “dual fuel” through a later LNG Fuel Gas Supply System (FGSS) retrofit after the delivery of the vessels. Through a technical cooperation with Japan Marine United


New Submarine and SWATH Capabilities for HydroComp NavCad

The screen image displays the data entry table and process buttons.

HydroComp NavCad is a software tool for the prediction and analysis of vessel speed and power performance. It also provides for the selection of suitable propulsion system components – engines, gears and propellers. A recent development effort has been undertaken to provide new submarine


BV Approves LNG-powered Ultra-Large Containership

LNG-powered ULCC mid section.jpg

Leading international classification society Bureau Veritas has given approval in principle for the basic design of a 14,000 teu containership to be powered by LNG.  The design was developed in a joint industry project between Korea’s Daewoo Shipbuilding & Marine Engineering


CrystalCoat Extends Cylinder Head Life

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CrystalCoat - good news for engines running on heavy fuel and gas. Simplex-Turbulo, agents for Märkisches Werk (MWH), are now able to actively promote a very interesting new product which extends the life of cylinder head valves. High combustion temperatures in engines operating on HFO


Safe Transfer of Wind Farm Personnel

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James Fisher and Sons plc announces the launch of two new exciting products to assist in the safe transfer of personnel during offshore wind farm operations.   • Vessel Motion Monitoring System (VMMS) provides accurate motion monitoring


MHI Installs MALS (Mitsubishi Air Lubrication System)

MALS Concept Sketch: Air bubbles covering the vessels bottom, like a carpet of air.

For First Time and Verifies Over 5% Fuel Efficiency Improvement - Sights On Expanded System Applications to High-speed, Slender Hull-form Ships.   Mitsubishi Heavy Industries, Ltd. (MHI) has installed its innovative "Mitsubishi Air Lubrication System" (MALS) for the first time on


Ship Energy, BWMS, Recycling on MEPC Agenda

The IMO's Marine Environment Protection Committee (MEPC) meets for its 65th session from 13 to 17 May 2013, at IMO HQ in London. Items on a busy agenda include the implementation of energy-efficiency regulations and the ballast water management and ship-recycling treaties.


Power Below the Waves: ABB Subsea Transformers

Subsea Transformer Located in Åsgard Compressor Station: Schematic credit ABB

ABB has delivered subsea transformers for fields in the North & Norwegian seas & the Gulf of Mexico for operation at depths of up to 2,000 m. Subsea transformers are an ABB innovation. Deployed in extreme conditions in ultra-deepwater


Pumps and Piping: A Curious Turn to the Right

SIMS product depiction web.jpg

Owners and shipyards come to the realization that alternative composition piping and pumps represent the way forward. You cannot put a vessel to work without pumps, valves and piping. Too often, product selection is left to the discretion of those who view these items as inconsequential decisions


Public Notification of Amendments to the Rules and Guidance

Classification society ClassNK (Chairman and President: Noboru Ueda) announced the release of the latest version of its Rules and Guidance for the Survey and Construction of Steel Ships. These versions include all amendments dated 30 May 2013.


Honda’s Flagship BF250 Engine

Twin Honda BF250 engines in action; Inset: Honda Airflow Diagram.

Innovative four stroke engine is Honda’s most powerful and now its flagship entry in the crowded outboard propulsion markets. The new BF250 horsepower (hp) four-stroke engine, the most powerful outboard ever to join the Honda Marine lineup, is also the company’s flagship model


'Missing Link' LNG Bunker Barge Concept

LNG Bunker Barge Concept: Image credit NLI

NLI Solutions (NLI) has developed a concept for a LNG Bunker Barge (often described as the 'missing link' in prospective LNG bunkering plans) based on the NLI LNG tank design. The concept has been further developed in a design study together with the Marine division of Rolls-Royce and Wilhelmsen


Babcock’s LGE Process Enhances Dorian/Seacor LPG Vessels

The new reliquefaction plant design from Babcocks LGE Process showing the vent gas cooler (in yellow) in the middle of the skid-mounted unit.

Dorian/Seacor‘s liquefied petroleum gas (LPG) carriers are to benefit from the latest reliquefaction plant development from Babcock’s LGE Process, following a contract signed last month (May) for the innovative vent gas cooler enhancement to be fitted on two new very large gas carriers


 
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