Self-unloaders for US stone import traffic
Self-discharging bulker technology has an important new reference in the US-owned, Chinese-built ‘Ireland’, for Gulf of Mexico trade. David Tinsley reports.
Houston-based Vulica Shipping is boosting its fleet of panamax self-unloading bulk carriers with two newbuilds constructed in China to a design that marries heightened efficiency in the handling and transportation of aggregates with future-proofing in terms of environmental standard.
As a wholly-owned subsidiary of Vulcan Materials Company, the largest US producer of construction aggregates, Vulica is responsible for the parent’s blue-water shipping needs, including exports to the US market from the group’s large quarry and marine terminal on the Yucatan Peninsula of Mexico. This entails shipments through a range of ports on the US Gulf Coast, where quality stone cannot be mined locally.
At the time of writing, the 67,150dwt Ireland was due for delivery from Jiangsu Hantong Ship Heavy Industry Co by the end of July, with second-of-class Donald M. James to follow in November this year.
Ireland encapsulates the B.Delta68 SUL design developed in Finland by Deltamarin, drawing on the larger B.Delta82 type’s fully-tested hull, but with a shallower draught, and tailored to the customer’s specific requirements. The consultancy’s contract award from the shipyard embraced approval design, both basic and detail, plus procurement handling and on-site assistance.
The B.Delta series comprises a bulker design family spanning the 25,000-210,000dwt band, and derivatives such as chemical tankers, and a multiplicity of newbuilds from the range have been built or ordered from Chinese yards. Trademark Deltamarin features are highly competitive fuel consumption performance, EEDI compliance, low emissions, high deadweight intake and optimised lightweight.
The stern shape has been optimised for efficient water flow into the propeller, while the design of the propeller and the rudder, and the use of a pre-swirl stator, help achieve the requisite, low fuel consumption. The bow stem is straight, with no rake, and there is minimal flair.
The self-discharging boom pivotally-mounted at the after end of the weatherdeck, just forward of the superstructure, is a visually commanding aspect of the vessel as well as a technically outstanding element, encapsulating Canadian engineering expertise in self-unloading systems honed on Lakers and deepsea bulkers.
Bulk material handling specialist EMS-Tech of Belleville, Ontario, designed and supplied the gear for the Vulica newbuilds, conferring the means of delivering aggregate ashore at a rate of 4,500 tonnes per hour, or 5,300m3 per hour. The gravity-fed, self-discharging system comprises two tunnel conveyors fitted with EMS-Tech patented feeder gates and a 27m lift, C-loop elevator-conveyor, culminating in the 79m-long discharge boom.
The continuous discharge system is more productive and more efficient than crane unloading and loading. Furthermore, according to Vulcan Materials, it also helps preserve product quality, as the gravity fed, conveyor-based handling concept only minimally degrades the stone, a factor which is especially important for concrete aggregate.
Each ship embodies seven cargo holds, with individual hold volumes ranging from 8,633m3 to 11,516m3, catering to different grades of aggregate, and affording a total capacity of nearly 71,000m3. The construction incorporates topside tanks and hopper side bottoms, and the hold bottom is W-form in longitudinal profile, by virtue of the two gravity-feed channels and tunnel conveyors running parallel through the cargo spaces. Due to the hopper bottoms, the holds are unsuitable for conventional grab discharge.
In the stowed position, the boom extends over the length of three aftermost holds. Its pivot point is 41.3m from the stern and 187.7m from the bow, and the unit is designed for a maximum slew from centre of 105 degrees and a minimum luffing angle of 0 degrees.
An all-electric solution, in the shape of the MacGregor MacRack system, was selected for the hatch cover outfit. The side-rolling covers employ a combined rack-and-pinion drive and lifter system, with automatic cleating. Each hatch cover panel has one drive unit actuated by one electric motor, located at the mid-point of the longitudinal coaming, and which both elevates and rolls open the panel.
Electric drive offers benefits with regard to speed and ease of operation, simplified maintenance, and energy savings due to no need for continuous running of powering machinery, and also eliminates the risks of pollution and deck fouling from hydraulic oil leakage. In a shipbuilding context, an important advantage is the easier implementation due to the absence of hydraulic pipes, pump and associated work.
MacRack employs variable frequency drive (VFD) technology, allowing for the optimised use of electric power. At the start of the opening process, high torque is required for lifting the hatch panel at low speed. After this phase is complete, lower torque is sufficient and the panel can be rolled aside at full speed.
Limited deck hydraulics
Except for the unloading boom, there are no hydraulics at all on deck, obviating risks of hydraulic oil spillage and pollution through leaks and system failures.
The Vulica newbuild project provides a further reference for MAN’s electronically-controlled, G-series generation of two-stroke propulsion machinery. In each case, the chosen model is a five-cylinder, G60ME-C9.5 Tier II diesel. Although the design’s nominal, maximum continuous rating is 13,400kW at 97rpm, the engine was specified at a derated, contractual MCR of 8,600kW at 80rpm, close to the L2/L4 line in the power/speed layout diagram.
By adopting a scrubber system, the shipowner has ensured compliance with stringent existing and future emissions legislation, while enabling continuous operation on IFO 380 intermediate fuel oil of 3.5% sulphur content, both at sea and when in coastal waters and manoeuvring in port. Anticipated consumption at a laden speed of 13.5 knots is in the order of 24 tonnes per day.
Among the technical highlights of these new US-owned vessels is a direct drive, permanent magnet (PM) shaft generator, delivered by Finnish specialist WE Tech Solutions. With its active front end (AFE), low harmonic drive technology, the proprietary WE Drive enables the generator to efficiently feed electrical power into the ship’s network across the full operating range of the main engine, irrespective of speed. By harnessing the rotational energy of the propulsion engine, with the added, variable-speed capability, the 1,750kWe shaft generator promises a drastic reduction in running hours for the auxiliaries, yielding through-life savings both in fuel and maintenance.
Ireland is a new showcase for Hyundai Heavy Industries’ ever more popular HiMSEN four-stroke engine marque, selected as the prime movers for the diesel generator outfit. Two of the three auxiliaries are nine-cylinder models of the H21/32 design, each yielding a maximum output of 1,980kW, and the third aggregate has a six-cylinder version, rated at 1,320kW. The three sets thereby apply a combined power concentration of 5.28MW for electrical energy generation, complementing the capacity available from the shaft generator when the ship is under way.
Efficiency at port
Such is the intensity of cargo handling and the associated electrical load on a large self-unloader that IFO 380 consumption in port can be expected to be around six tonnes per day during loading, and as much as nine tonnes when discharging at the maximum rate. Waste heat from the auxiliaries as well as the main engine will be recovered through a gas tube boiler.
To facilitate manoeuvring, the vessel has been specified with 1,750kW and 1,000kW tunnel thrusters at the bow and stern, respectively, sourced from Rolls-Royce Marine. The thrusters are of fixed pitch propeller type, direct coupled with VFD-controlled electric motors. Fixed pitch propellers are considered by the owner to reduce the risk of oil leaks compared to the controllable pitch alternative.
VFD is also employed for all deck machinery, the self-unloading drive motors, main seawater (SW) and low-temperature (LT) cooling system and the engine room ventilation supply fans, so as to ensure more efficient energy usage.
At the behest of Vulica, the shipyard contracted DuPont Sustainable Solutions to supply scrubber systems for both newbuilds in China. Developed by DuPont subsidiary Belco Technologies, each shipset comprises one single-inlet scrubber dedicated to the main engine and one multi-inlet scrubber to treat the exhaust from the three auxiliaries.
As well as achieving virtually wholesale SOx emission removal, the systems reduce particulate matter (PM) and also fulfil US washwater requirements.
The design is of in-line type, formed as a slim, open tower, and does not have fans or a by-pass. The DuPont “run-dry” capability suits operations where the trading pattern involves regular trading into and out of an Emission Control Area, as will be the case for the new ships. A single-stream, Belco-designed DuPont hybrid scrubber has also been nominated for retrofit to one of Vulica’s existing self-unloaders, the 45,800dwt H A Sklenar.
“This investment allows us maximum fuel flexibility to meet current ECA requirements as well as prepare for the IMO 2020 global cap on SOx emissions,” confirmed Vulica Shipping’s general manager Atul Sabarwhal. Within the North American ECA, the sulphur limit is 0.1%, while the upcoming worldwide cap has been set at 1.0%.
Vulcan Materials’ Sac Tun limestone quarry in Mexico is served by an adjacent, company-owned terminal, just south of Playa del Carmen. The harbour is connected to the quarry by a 5km, high-speed, 60-inch (1.52m) wide conveyor system, transferring up to 12m tons per annum of various grades of limestone, fines and related products to waiting ships.
Ireland and Donald M.James will augment the existing owned fleet of three panamax self-unloaders, the W.H.Blount, Bernardo Quintana, and H.A.Sklenar. Capacity used in the traffic from Mexico is supplemented by a contract of affreightment with Canadian bulker specialist CSL International.
Technical husbandry for the fleet is outsourced to the US arm of Wilhelmsen Ship Management, located in Pasadena, Texas. Supervision of the newbuild programme in China is being jointly handled by Vulica and Hong Kong-domiciled Fleet Management Ltd (FML).
Depth, to main deck
Draught, scantling (summer load line)
Cargo discharge rate
4,500t/h or 5,300m3/h
Main engine power, specified MCR
2 x 1,980kW + 1 x 1,320kW
+100A1 Self Unloading Bulk Carrier, ESP, ShipRight (SDA, FDA, CM), ESN, *IWS, LI, ECO (BWT, EEDI-2, IHM), LMC, UMS, ShipRight (BWMP<S,T>,SCM, SERS)
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