Sanmar built LNG terminal tugs – in detail
Tugs & Towing recently reported delivery of the last of a five-tug order from Sanmar Shipyard for Smit Lamnalco specifically modified for LNG terminal operations, let’s take a closer look.
Increasing numbers of LNG terminals are being developed globally meaning new opportunities for towage service providers in assisting the berthing and un-berthing of large LNG tankers at the terminals. Requirements often extend beyond providing just ship-handling duties however, perhaps also including fire-fighting and other value-added services.
Safety measures surrounding operations at LNG terminals are among the most stringent in the shipping industry, an approach extending to the ship-handling element, a dynamic operation involving close quarters situations where tug crews are put at particular risk should something go wrong.
When new port operations are established, or existing services expanded, additional towage provision will often be required and for new LNG terminals the opportunity may be taken to mould a complete package using either specially selected (and modified) existing vessels or as in this example, a bespoke fleet of vessels designed specifically for that particular role.
BUILDER AND DESIGNER EXPERTISE
The examples here relate to the Port of Gladstone LNG terminal on Australia’s Queensland coast, part of the Australia Pacific LNG Project involving a complex process with Coal Seam Gas exported in LNG form.
The requirement was for four terminal support tugs to serve three LNG export terminals involving escort services through narrow channels which experience extreme weather with wave heights up to 3m and wind speeds over 40 knots. The contract to support operations at the terminal was awarded to established towage and marine support provider Smit Lamnalco and the subsequent order awarded to Turkey’s Sanmar Denizcilik Shipyard. Given their connection with Robert Allan Ltd it was perhaps natural that a design from the Canadian naval architect was selected for the role.
The five vessels, now all in operation are customised RAstar 3400 escort/offshore tugs with the names: SL Wiggins Island, SL Quoin Island, SL Curtis Island, SL Boyne Island and SL Heron Island. They are specially modified for the LNG role to which we will return later but first a look at their basic particulars.
Built in accordance with SOLAS, MARPOL, IMO and other regulations the series are classed by BV with notations: BV 1+Hull +Machinery, Escort Tug, AUT-UMS, CLEANSHIP(2), IWS, Fire-Fighting 1, waterspraying, Unrestricted Service. They are also constructed to flag state requirements (Australian Maritime Safety Authority Class 2B vessel).
Dimensions include: LOA 34m, breadth moulded 14.5m, depth moulded 6.2m, maximum draught 6m, GRT 690t and frame spacing 0.55m. Tank capacities include fuel oil 217,200 litres, fresh water (ballast and potable) 122,400 litres, lube oil 7,200 litres and foam 22,800 litres. Performance figures include bollard pull ahead 86t, astern 80t (both minimum), free running speed 13.5 knots minimum and zero speed turn rate of 360’ in 30 seconds.
Main machinery consists of two air-start medium speed, Wärtsilä 8L26 electronically controlled marine diesels rated at 2,720kW each, certified to IMO Tier II emission standards and box cooler cooling systems. Two Rolls-Royce US35 CP azimuth thrusters provide propulsion with contra-rotating controllable pitch propellers turning inward at the top running ahead. The propellers, with combinator control provision (full ahead to full astern in 12 seconds) turn in nozzles, inner sides of which are stainless steel. Three electric start Volvo 6XD7TA generator sets, each providing 2,720ekW at 1,000 RPM are included, also conforming to IMO Tier II standards.
The notable feature of the series are modifications providing protection from LNG risks. The electrical system received particular attention, certified suitable for use in Zone 2 LNG environments with all non-essential equipment able to be isolated from the wheelhouse. Accommodation and wheelhouse HVAC intakes have gas detection alarms, the wheelhouse becoming a temporary refuge for crew through closing all intakes and making exhausts gas tight, a system that can be activated from the wheelhouse, a sensor and alarm monitors oxygen levels.
Gas detection alarms are provided in the machinery space with remote shutdown and isolation of fans and dampers carried out from the wheelhouse. Gas detection alarms are set at 20% and 40% of lower explosion limits of natural gas, all external lighting is explosion proof. Non explosion proof equipment including radar and searchlights switch off automatically when a gas alarm activates, a system that can be over-ridden by the master.
As well as the usual on-board fire-fighting systems, the tugs meet Australian Fi-Fi 1 standards with fire pumps driven by PTO shafts off each engine. Concentrations of foam (between 0 and 3%) are supplied by two inline educators and two wheelhouse roof mounted 1,200m3/hr water (600m3/hr foam) monitors have 120m minimum throw length and 45m minimum throw height: limit stops prevent monitor discharges damaging the vessel.
Towing operations over the bow are from a DMT TW-E1000KN double-drum electric-powered towing winch with remote operated clutch and capacity on each drum for 200m of 76mm UHMWPE nylon rope. Fully variable speed controls provide pay-out of between zero and 60m/min and recovery at variable line tensions of up to 85t at minimum 8m/min and slack rope speed of 60m/min. Automatic spooling gear is provided for working sections of the drum along with towline monitoring readout in the wheelhouse and data collection ability. Two separately clutched cable lifters are included and a towing fairlead fitted forward of the winch.
Provision for towing over the stern is from two Data Disk type 110t SWL towing hooks with remote release and a heavy duty towing staple, future installation of an aft towing winch is also provided if required. Bow fendering comprises a 30m long cylindrical rubber fender of 1m OD (upper course) and a 3m long 450mm deep, 500mm wide ‘W’ fender (lower course). Extruded hollow 350mm D-section fenders are fitted along both sides with 18m of 600mm OD cylindrical fender around the stern. A flood-type deluge system protects port, centre and starboard sections of bow fendering, configured so as not to spray crew and machinery forward.
INTERIOR LAYOUT AND FIT
The series have a conventional profile, main deck including accommodation block and a raised forecastle. Starting at the top of the vessel, atop of the wheelhouse the foldable mast includes a ladder and cage (to Australian standards) allowing maintenance of lights and antennas without crew leaving the safety of the cage. Three Xenon type searchlights, radar mast and the two fi-fi monitors are also on the wheelhouse roof.
The wheelhouse itself is a standard layout outfitted to a high level of quality and detail, configured for the engineer to operate the winches while the master cons the tug itself. Provision is made for aft towing winch controls should one be fitted later. Consoles containing main control and alarm systems are located either side of a rail-mounted chair on the vessel’s centreline. As the engineer requires access to the forward window area along with the obligatory degree of visibility and line-of-sight, main consoles are kept to a minimum size through provision of overhead panels containing common use instrumentation including VHF radio. A chart table is included port side aft.
A typically comprehensive outfit of navigation, communication and monitoring systems are provided by among others: Furuno, Zenitel and Lyngsø Marine. Instrumentation and alarms comply with regulatory requirements for periodically unattended machinery space notation and includes graphic screen displays. An engineer safety system (ESS) is installed in the engine room with a key locking device and acceptance points throughout the engine room, thruster room, workshop/store and other locations. Other monitoring systems include watch alarms and vessel video monitoring. Space precludes a full description of the various monitoring systems other than to say it is particularly comprehensive.
Navigation aids comply with both Flag State and Class requirements and are again comprehensive and include: magnetic and satellite compass; clocks, barometer, clinometers and wind speed and direction indicator; Furuno Navnet chart plotter, echo sounder and radar system and GPS with charts including Eastern Australia coast; and Simrad autopilot.
The communications installation meets Flag State GMDSS requirements for Sea Area A3. Particular attention has been paid to eliminating interference from land-based transmissions including mobile phones and pagers when operating in port. A gooseneck microphone along with foot and knee operated switches are installed for the VHFs. The radio specification includes Icom VHF-DSC, Furuno MF/HF DSC, Furuno Felcom INMARSAT-C mobile earth station, three handheld Icom portable VHFs and an owner supplied Simoco domestic UHF fleet radio. Furuno also provide a Navtex, weather fax receiver and AIS system.
As standard, an internal communications system is provided throughout the vessel with call stations at thirteen locations including a talk-back system linked to the handheld radio system allowing a continuously open line between the master and all other communications over handheld radios. A sound-powered telephone installation with headset is provided in the wheelhouse, main switchboard room, propulsion room and engine room.
The boat deck forward contains lockers and an explosion-proof battery stowage area while aft of the wheelhouse is home to a rescue boat, served by a davit positioned on the starboard side largely within the tumblehome line of the funnel uptakes.
Accommodation is provided for eight persons, a single cabin with separate WC area for the master located on the main deck. Also at this level is a spacious communal mess area and galley which also includes a separate store area, abaft of which is a small galley area. The after part of the main accommodation block is home to various stowage areas including a paint store, filling station, fire control station and genset. Immediately upon entering the after weathertight door (within the sheltered area between the funnels) a wet-gear area and WC is located.
The accommodation/mezzanine level beneath the raised forecastle contains further accommodation comprising a single cabin for the engineer and three double cabins: all are en-suite with individual shower/WC areas. Furnishings throughout the five-tug series conforms to high standard premium quality commercial specifications. Aft of the accommodation to port at this level is the switchboard room while to starboard there is a laundry room and HVAC area. The area forward of the crew cabins contains the anchor hawse-pipe pockets and forepeak.
Moving finally down to the lower level and starting forwards, stairs leading down from the mezzanine level provide access to various areas including winch electrical panels, chain lockers, dry stores, fi-fi locker and a linen store. Aft of this area is the engine room itself, dominated by the two Wärtsilä 8L26 engines. The three Volvo 6XD7TA auxiliaries are located between the main engines, one on the centreline forward and two abreast of each other and level with the rear of the main engines. The ‘off ship’ fire-fighting pumps run off the forward end of each main engine via PTO shafts and gearboxes and clutch with a sea chest for each pump located below. Outboard of each engine are the box cooler arrangements.
Another off-set stairway leads up to the mezzanine deck while at the aft end of the engine room space there is a slightly raised engineer’s workshop containing among other things a work bench and column drill. A watertight door in the workshop leads aft to the spacious Z-drive compartment, aft of which is the aft peak tank. Various tanks are located in the lowest part of the vessel. From aft moving forward these include: fresh water, fresh water ballast, Z-drive lube oil, fuel oil (main and day tanks), oily water and used oil and finally untreated, and treated sewage and grey water tanks.
By Peter Barker
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