LNG Ship Construction

LNG Ship Construction presents the following content: Definition of Ship; Basic Design of a Ship; Ship Contracts;Terminology; Ship Types; Development of Ships; LNG Carriers; Materials and Strength of Ships; Ship Building Steels; Gas Carrier Rules and Regulations; SOLAS Convention.

LNG Ship Construction Jayan Peter Pillai MSc CEng FIMarEST MRINA MIBM Braemar Engineering Fullbridge Mill Fullbridge, Maldon Essex, CM9 4LE www.braemar.com Index Page 4.1 4.2 4.3 4.4 4.5 4.6 4.7 5.1 5.2 5.3 10 10.1 10.2 10.3 10.4 10.5 10.6 10.7 11 12 13 14 15 Introduction……………………………………………………… History of LNG Shipment……………………………………… Definition of Ship……………………………………………… Basic Design of a Ship………………………………………… Ship Contracts…………………………………………………… Terminology……………………………………………………… Ship Types………………………………………………………… Development of Ships…………………………………………… 10 LNG Carriers……………………………………………………… 13 Materials and Strength of Ships………………………………… 16 Ship Building Steels……………………………………………… 18 Gas Carrier Rules and Regulations……………………………… 19 SOLAS Convention ……………………………………………… 21 IGC Code………………………………………………………… 22 STCW Convention………………………………………………… 26 Testing of Materials……………………………………………… 27 Stresses on Ships………………………………………………… 29 Welding and Cutting……………………………………………… 37 Shipyard Layout…………………………………………………… 38 Design Information for Production……………………………… 39 Assembly of Ship Structures……………………………………… 40 Shell Plating and Framing……………………………………… 46 Bulkhead and Pillars……………………………………………… 48 Decks, Hatches and Superstructures……………………………… 50 Fore End Structure………………………………………………… 53 Aft End Structure………………………………………………… 54 Tanker Construction……………………………………………… 56 Launching…………………………………………………………… 56 Liquified Gas Carriers…………………………………………… 57 Sea Trials………………………………………………………… 64 Ship Inspection…………………………………………………… 65 Dry Docking and Ship Repairs………………………………… 67 Annex Annex References………………………………………………… Useful Websites………………………………………… 69 70 Introduction Braemar Engineering (Wavespec Limited) is an engineering company specialising in the marine, offshore and land based gas industries The Company has three main divisions: - Ship Design, Ship Construction and Ship Operation - Offshore Dynamic Positioning Studies and Projects - Land Based LNG Import and Export Terminals, LNG Liquefaction Plants, Peak Shaving Plants, LNG Regasification Plants, LNG Fuelling Stations and LNG Distribution & Trucking Braemar Engineering (Wavespec Limited) has offices in Maldon in the United Kingdom and in Houston, Texas Braemar Engineering is part of the Braemar Technical Services Group It is supported by a worldwide network of offices with over 380 technical staff of all disciplines LNG Ships are expected to work the same route for its working life, which may exceed 40 years Design for operation is the result The key requirement of a new ship is that it can trade profitably, so economics is of prime importance in designing them An owner requires a ship that will give the best possible returns for the owner’s initial investment and running costs The final design should be arrived at taking into account not only present economic considerations, but also those likely to develop within the life of the ship 2 History of LNG Shipment LNG Carrier (Membrane Tanks) LNG Carrier (MOSS Tanks) Definition of “Ship” A ship is a vessel of considerable size for deep water navigation The Historic Ships Committee have designated a vessel below 40 tons and 40 feet in length as a boat Submarines and Fishing Vessels are always known as boats, whatever their size The Statutory Definition of a “ship” in the UK Merchant Shipping Act of 1995, is provided in s.313 “ Ship includes every description of vessel used in Navigation” Basic Design of a Ship The main requirement of a new ship is that it can trade profitably The owner requires a ship that will give the best possible returns for the initial investment and running costs With LNG Ships, the vessel could work the same route for its working life of 40 years With the aid of computers it is possible to make a study of a large number of design parameters, and hence design of a ship that is technically feasible and economically efficient The design should take into consideration first cost, operating cost and future maintenance The initial design of a ship goes through stages: concept; preliminary and contract design A concept design should, from the objectives, provide sufficient information for a basic techno-economic assessment of the alternatives to be made Preliminary design refines and analyses the agreed concept design, fills out the arrangements and structure, and aims to optimize service performance At this stage the builder should have sufficient information to tender Contract design details the final arrangements and systems agreed with the owner and satisfies the building contract conditions Post-contract design requires confirmation that the ship will meet all operational requirements, including safety requirements from regulators It addresses design for production, where the structure, outfit, and systems are planned in detail to achieve a cost and time effective building cycle The post contract design will also ideally consider the future maintainability of the ship in the arrangements of equipment and services Information provided by design: - Dimensions - Displacement - Stability - Propulsive characteristics and hull form - Preliminary General Arrangements - Principal Structural details Each item of information may be considered in more detail The dimensions of most ships are mainly influenced by the cargo carrying capacity of the ship and the draft Increase in length produces higher longitudinal bending stresses Breadth may be such as to provide adequate transverse stability A minimum depth is controlled by the draft plus statutory freeboard Increase in depth is preferred to increase in length Draft is limited by area of operation Displacement is made up of lightweight plus deadweight Lightweight is the weight of the ship as built Deadweight is the difference between the lightweight and loaded displacement ( weight of cargo plus weight of fuel, stores, water ballast, fresh water, crew and baggage) In determining the dimensions, static stability is kept in mind, in order to ensure that this is sufficient in all possible conditions of loading Beam and depth are the main influences Statutory freeboard and sheer are important together with the weight distribution in arranging the vessel’s layout Adequate propulsive performance will ensure that the vessel attains the required speeds The hull form is such that it offers a minimum resistance to motion Service Speed is the average speed at sea with normal service power and loading, under average weather conditions Trial Speed is the average speed obtained using the maximum power over a measured course in calm weather with a clean hull and specified load condition This speed may be a knot or so more than the service speed Unless a hull form similar to that of a known performance vessel is used, a computer generated hull form and its predicted propulsive performance can be determined Propulsive performance can be confirmed by subsequent tank testing of a model hull This may lead to further beneficial modifications The owner may specify their choice of propulsion plant The general arrangement is prepared in cooperation with the owner All LNG vessels are built to the requirements of a classification society (Lloyds Register, American Bureau of Shipping, Bureau Veritas, Det Norske Veritas, RINA) Class have rules on structural scantlings Computer programs can determine the minimum hull structural scantlings Owners may specify thicknesses and materials in excess of IMO and Class requirements 4.1 Ship Building Contracts Ship Owners may employ a firm of consultants to provide the preliminary design, prepare the tender specifications, evaluate tenders and oversee the construction on their behalf The successful shipbuilder will prepare building specifications for approval by the owner The technical specification will normally include:1 Brief description and essential qualities and characteristics of the ship Principal dimensions Deadweight, cargo and tank capacities, etc Speed and power requirements Stability requirements Quality and standard of workmanship Survey and certificates Accommodation details Trial conditions 10 Equipment and fittings 11 Machinery Details, including electrical installation Typical Payment Schedule - 10% on signing contract - 10% on arrival of materials on site - 10% on keel laying - 20% on launching - 50% on delivery 4.2 Terminology Aft Perpendicular (AP): A perpendicular drawn to the waterline at the point where the after side of the rudder post meets the summer load line Where no rudder post is fitted it is taken as the centre line of the rudder stock Forward Perpendicular (FP): A perpendicular drawn to the waterline at the point where the fore-side of the stem meets the summer load line Length Between Perpendiculars (LBP): The length between the forward and aft perpendiculars measured along the summer load line Amidships: A point midway between the after and forward perpendiculars Length Overall (LOA): Length of vessel taken over all extremities Lloyd’s Length : Used for obtaining scantlings if the vessel is classed with Lloyd’s Register It is the same as length between perpendiculars except that it must not be less than 96% and need not be more than 97% of the extreme length on the summer load line Register Length: Length of ship measured from the fore side of the head of the stem to the aft side of the head of the stern post In the case of a ship not having a stern post, to the fore side of the rudder stock If the ship does not have a stern post or a rudder stock, the aft terminal is taken to the aftermost part of the transom or stern of the ship This length is the official length in the register of ships maintained by the flag state IMO Length: is defined as 96% of the total length on a waterline at 85% of the least molded depth measured from the top of keel Molded dimensions are taken to the inside of plating on a metal ship Base Line: A horizontal line drawn at the top of the keel plate All vertical molded dimensions are measured relative to this line Molded Beam: Measured at the midship section This is the maximum molded breadth of the ship Molded Draft: Measured from the base line to the summer load line at the midship – section Molded Depth: Measured from the base line to the heel of the upper deck beam at the ship’s side amidships Extreme Beam: The maximum beam taken over all extremities Extreme Draft: Taken from the lowest point of keel to the summer load line Draft marks represent extreme drafts Extreme Depth: Depth of vessel at ship’s side from upper deck to lowest point of keel Half Breadth: A ship’s hull is symmetrical about the longitudinal centre line , so half the beam or half breadth in any section if given Freeboard: The vertical distance measured at the ship’s side between the summer load line and the freeboard deck Freeboard Deck: Normally the uppermost complete deck exposed to weather and sea, and has a permanent means of closing all openings, and below which all openings in the ship’s side have watertight closings Sheer: A rise in the height of the deck (curvature or in a straight line) in the longitudinal direction Measured as the height of deck at side at any point above the height of deck at side amidships Camber (Round of beam): Curvature of decks in the transverse direction Measured as the height of deck at centre above the height of deck at side Straight line camber is often used on large ships to simplify construction Rise of Floor (Deadrise): The rise of the bottom shell plating line above the base line This rise is measured at the line of moulded beam Large ships often have no rise of floor Half Siding of Keel: The horizontal flat portion of the bottom shell measured to port or starboard of the ship’s longitudinal centre line Useful to know when dry docking Tumblehome: The inward curvature of the side shell above the summer load line Not common on large modern ships Flare: the outward curvature of the side shell above the waterline At the fore end of the ship Stem Rake: Inclination of the stem line from the vertical Keel Rake: Inclination of the keel line from the horizontal Parallel Middle Body: The length over which the midship section remains constant in area and shape Entrance: The immersed body of the vessel forward of the parallel middle body Run: The immersed body of the vessel aft of the parallel middle body Gross Tonnage: is a measure of the enclosed internal volume of the vessel (originally computed as 100 cubic feet per ton) Suezmax: the largest tanker than can transit the current Suez Canal fully laden (150 000 dwt) Suez maximum breadth & draft limits are 75 and 20 metres Aframax: (American Freight Rate Association) 80 000 to 115 000 dwt Panamax: Vessel with beam & length restrictions of 32.2 and 275 metres Upto 70 000 dwt Handymax: Tankers of 35 000 to 45 000 dwt Capesize: Ships too large to transit the Panama Canal, so have to voyage around Cape Horn 4.3 Ship Types Liquid Cargo Ships: Oil Tankers, Liquefied Gas Carriers , Chemical Tankers Dry Cargo Ships: Tramps, Bulk Carriers, Cargo Liners, Container Vessels, Barge Carriers, Ro-Ro Ships, Refrigerated Cargo Ships, Timber Carriers, Livestock Carriers, Car Carriers Passenger Ships: Liners, Cruise Ships, Emigrant & Pilgrim Ships (STP’s), Cross-channel Ferries, Coastal Ferries, Harbour Ferries, Passenger Submarines High Speed Craft: Multi-hulls including Wave Piercers, Small Waterplane Area Twin-hull (SWATH), Surface Effect Ship (SES) & Hovercraft, Hydrofoil, Wing in ground effect craft (WIG) Off Shore Vessels: Supply Ships, Pipe Layers, Crane Barges, Semi-Submersible Drill Rigs, Drill Ships, Accommodation Barges, Production Platforms, Floating Storage Unit (FSU), Floating Production & Storage unit (FPSO), Fishing Vessels: Factory Ships, Trawlers, Purse Seiners 10.7 Tanker Construction 11 Launching Launching involves the transference of the weight of the ship from the keel blocks on which it is supported during construction, to a cradle on which it is allowed to slide into the water Normally the vessel is launched end on, stern first Shipyards located on rivers or narrow channels are obliged to launch sideways 56 ************************************************** 12 Liquefied Gas Carriers A large number of ships are in service for carrying gases in liquid form in bulk Many of the smaller ships are designed to carry Liquefied Petroleum Gas (LPG) There are close to 400 ships that carry Liquefied Natural Gas (LNG) 57 Liquefied Petroleum Gas (LPG) LPG is the name given by the oil industry to a mixture of petroleum hydrocarbons (Propane and Butane, and a mixture of the two LPG is used as a clean fuel for domestic and industrial purposes These gases may be converted to the liquid form and transported in one of three conditions: Solely under pressure at ambient temperature Fully refrigerated at their boiling point ( -30 to -480C ) Semi-refrigerated at reduced temperature and elevated pressure Other gases with similar physical properties (ammonia, propylene and ethylene) are also shipped on LPG carriers These gases are liquefied and transported in the same conditions as LPG, except ethylene, which boils at a much lower temperature ( 1040C), and is carried in the fully refrigerated or semi-refrigerated condition Liquefied Natural Gas LNG is natural gas from which most of the impurities (sulphur and carbon dioxide) have been removed It is cooled to or near its boiling point of -1650C, or at near atmospheric pressure and is transported in this form as liquid methane Methane has a critical pressure of 45.6 kg/cm2, and a critical temperature of -82.50C ( the pressure and temperature above which liquefaction cannot occur) So the methane can only be liquefied by pressure at very low temperatures The IMO International Gas Carrier Code In 1975 the 9th Assembly of the IMO adopted the Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk, A.328(IX), which provides international standards for ships that transport liquefied gases in bulk It became mandatory in 1986, and is generally referred to as the IMO International Gas Carrier Code The requirements of this code are incorporated in the rules for ships carrying liquefied gases published by Classification Societies The code covers damage limitations to cargo tanks and ship survival in the event of collision or grounding, ship arrangements for safety, cargo containment and handling materials of construction, environmental controls, fire protection, use of cargo as fuel and more The code defines the basic cargo containment types and indicates a secondary barrier is required, to protect the ship’s hull structure from the embrittling effect of the low temperature should cargo leak from the primary tank structure The cargo containment types are described below: Integral Tanks These tanks form a structural part of the ship’s hull and are influenced in the same manner and by the same loads that stress the hull structure These are used for the carriage of LPG at or near atmospheric conditions (Butane for example), where no provision for thermal expansion and contraction of the tank is necessary 58 Membrane Tanks These are non-self-supporting tanks consisting of a thin layer (membrane) supported through insulation by the adjacent hull structure The membrane is designed in such a way that thermal and other expansion or contraction is compensated for without undue stressing of the membrane Membrane tanks are primarily used for LNG cargoes Semi-Membrane Tanks These are non-self-supporting tanks in the load condition The flat portions of the tank are supported, transferring the weight and dynamic forces through the hull, but the rounded corners and edges are not supported so that tank expansion and contraction is accommodated Such tanks were developed for the carriage of LNG, but have been used for a few LPG ships Independent Tanks These are self-supporting and independent of the hull They are completely self supporting and not form part of the ship’s hull There are three types, depending upon the design pressure Type A : designed using standard traditional methods of ship structural analysis LPG at or near atmospheric pressure or LNG may be carried in such tanks 59 60 Type B: are designed using more sophisticated analytical tools and methods to determine stress levels, fatigue life, and crack propagation characteristics The overall design concept of these tanks is based on the “crack detection before failure principle”, which permits their use with a reduced secondary barrier LNG is normally carried in these tanks 61 62 Type C: are designed as pressure vessels, the dominant design criteria being the vapour pressure Normally used for LPG and Ethylene Internal Insulation Tanks These are non-self-supporting and consist of thermal insulation materials, the inner surface of which is exposed to the cargo supported by the adjacent inner hull or an independent tank There are two types: Type 1: the insulation or combination of insulation and one or more liners act only as the primary barrier The inner hull or independent tank forms the secondary barrier Type 2: the insulation or combination of insulation and one or more liners act as both the primary and secondary barriers and are clearly distinguishable as such Liners on their own not act as liquid barriers and therefore differ from membranes These tanks are a later addition to the Code, and Type has been used for the carriage of LPG 63 Secondary Barrier Protection The requirements for secondary barrier protection are given in the table below: Liquefied Natural Gas Ships There are over 20 approved patent designs of containment vessel for LNG ships The majority fall into the membrane or independent tank categories LNG ships are of the double-hull construction, within which are fitted the cargo tanks and the secondary barrier system At the beginning of 2011, some 350 large LNG ships were trading Older ships have independent Type B tanks of the Kvaerner-Moss design, with most being of the membrane type The GAZ Transport membrane system is twice as prevalent as other membrane systems 13 Sea Trials Sea trials are conducted to measure a vessel’s performance and general seaworthiness Testing of a vessel’s speed, manoeuverability, equipment and safety features are usually conducted In attendance are Technical representatives from the builder, flag and certification officials, and representatives of the owners Successful sea trials lead to a vessel’s certification for commissioning and acceptance by its owner 64 Speed Trial: The vessel is ballasted or loaded to a predetermined draft and the propulsion machinery is set to the contracted maximum service setting, usually a percentage of the machinery’s maximum continuous rating ( 90% MCR) The ship’s heading is adjusted to have the wind and tide as close to bow-on as possible The vessel is allowed to come to speed, and the speed is continuously recorded using differential GPS The ship is then turned through 1800 and the procedure is followed again This reduces the impact of wind and tide The final “Trials Speed” is determined by averaging all of the measured speeds during each of the runs This process may be repeated in various sea states 14 Ship Inspections Surveys fall into two types: those required by Class or for compliance with other regulatory bodies, and those requested by Owners for structural assessment purposes Class and statutory surveys include annual and intermediate surveys., bottom/ docking surveys, special or periodical surveys and occasional surveys Owners surveys are based on a requirement to assess general condition, corrosion rate, detailed condition or for repair assessment Statutory surveys for fulfilling Convention requirements of Load Line and SOLAS, are very similar to Class requirements So they are generally done at the same time, to minimise duplication Flag Administrations may delegate Class to carry our statutory surveys Special (Periodical) surveys are generally required at four year intervals, but may be postponed for up to one year if a General Examination is satisfactorily completed The scope of the General Examination varies according to the age of the ship, and would include an overall survey of ballast tanks and other tanks if deemed necessary., together with thickness measurements and tank testing required for the forthcoming Special Survey as far as the tanks are accessible Instead of carrying out the survey at one time, it is possible to it on a continuous basis over a five year cycle Societies are also prepared to surveys at sea 65 66 15 Dry Docking and Ship Repairs Ships are to be examined in Dry Dock at intervals not exceeding two and a half years At the dry docking survey, particular attention is paid to the shell plating, stern frame and rudder, external and through hull fittings, and all parts of the hull particularly liable to corrosion and chafing, and any unfairness of the bottom Class may accept In-water Surveys in lieu of any one of the two dockings required in a five year period The in-water survey is to provide the information normally obtained for the docking survey Generally, consideration is only given to an in-water survey where a suitable high-resistance paint has been applied to the underwater hull When a vessel requires repairs to damaged equipment or to the hull, the work has to be carried out to the satisfaction of the Class In order that the ship maintains its class, approval of the repairs undertaken must be obtained from the surveyors, either at the time of the repair or at the earliest opportunity 67 68 Annex References IGC Code International Code for the Construction & Equipment of Ships carrying Liquefied Gases in Bulk (1993 Edition) 166 pages plus ISBN 978 92 801 1277 (IMO 1104E) £ 14.00 Liquefied Gas Carriers Your Personal Safety Guide nd (2 Edition) (2013) SIGTTO ISBN 978 85609 5723 £ 15.00 50 pages Guidance Manual for the Inspection & Condition Assessment of Tanker Structures Tanker Structure Co-operation Forum (Witherby ) 2009 ISBN 13: 978 948691 119 A4 200 pages £ 50.00 Guidelines on the Enhanced Programme of Inspections During Surveys of Bulk Carriers & Oil Tankers 2008 Edition (IMO IA265E) ISBN 978 92 801 14966 357 pages £ 14.00 Ship Construction DJ Eyres & GJ Bruce (7th Edition) 2012 ISBN 978 008 0972398 388 pages £ 49.99 Ballast Water Management Convention (2009 ISBN 978 92 801 15031 234 pages Tanker Safety Training (Liquefied Gas) : Specialised Level Witherby Publishers 312 pages £142.80 ISBN 13:978 1856 093 415 (2007) A4 312 pages Specialized Training for Liquefied Gas Tankers, 1999 (IMO:TA106E) ISBN 978 92 801 61090 220 pages £ 33.68 Design & Operation of Gas Carriers 2004 Conference Proceedings RINA Publications £ 95.00 Edition) (IMO I621E) £ 10.00 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 69 Annex Web Sites SIGTTO http://www.sigtto.org/ Merchant Navy http://www.merchantnavy.com Warsash Nautical Bookshop http://www.nauticalbooks.co.uk IMO http://www.imo.org Marine Equipment Directive http://www.mared.org Lloyds List http://www.lloydslist.com Marine Accident Investigation Branch http://www.maib.dft.gov.uk Maritime & Coastguard Agency http://www.mcga.gov.uk Chemical Data Sheets http://hazard.com/msds Data Sheets (Oxford University) http://physchem.ox.ac.uk/msds/#msds Dept of Environment (DTi) http://www.shipping.dft.gov.uk/ Health & Safety Executive http://www.hse.gov.uk US Coast Guard http://www.uscg.mil/ US Code of Federal Regulations http://www.access.gpo.gov/nara/cfr/cfr-tablesearch.html International Association of Classification Societies www.iacs.org.uk Lloyds Register www.lr.org American Bureau of Shipping www.eagle.org Bureau Veritas www.bureauveritas.co.uk Det Norske Veritas www.dnv.co.uk Braemar Engineering www.braemar.com 70 ... the ship 2 History of LNG Shipment LNG Carrier (Membrane Tanks) LNG Carrier (MOSS Tanks) Definition of ? ?Ship? ?? A ship is a vessel of considerable size for deep water navigation The Historic Ships... independent, self regulating and no commercial interests relating to ship design, ship building, ship ownership, ship operation, ship management, ship maintenance or repairs, insurance or chartering In drawing... History of LNG Shipment……………………………………… Definition of Ship? ??…………………………………………… Basic Design of a Ship? ??……………………………………… Ship Contracts…………………………………………………… Terminology……………………………………………………… Ship Types…………………………………………………………