What makes self-unloaders special?

HISTORY

Beltship Management Limited (BML) is a joint venture company between Globe Master Management and Gypsum Transportation Limited (GTL) and has been involved in the self unloading and transshipment market for over 20 years, writes John McMillan, Technical Director, Beltship Management Limited.

However with its partners BML has roots stretching back to the late 1800s with the first Gypsum Queen loading gypsum in Canada in the 1890s. In 1947 GTL was the first company to build ocean going self-discharging bulk carriers and as such as a group there is a vast knowledge of the industry, the self unloading concept and the cargoes carried.

Moving forward to the early part of this century, BML embarked on developing a new generation of self-unloaders for its partners and clients GTL — not only to suit the particular requirements of GTL’s in-house trade, but also to be able to meet the commercial demands of other identified clients, particularly in the coal and aggregate trades.

The GTL in-house trade transporting gypsum from the two quarries in Nova Scotia each posed their own particular problems. Little Narrows involves a long pilotage with very narrow turning points and berthing without the aid of tugs. Hantsport has the largest tidal range in the world, some 12 metres, allowing only a three-hour window for the vessel to berth, load and depart, all with minimal tug assistance. These factors influenced the choice of bridge and navigation design, main engine, thrusters, propeller and rudder. Additionally the short loading time, which equates to a very fast loading rate and a very short deballasting window, was a major factor in the design of the vessels ballast system.

Requirements from USG’s production plants were that the new vessel should discharge quicker and avoid rapid changes in product flow, i.e. slugs of cargo. The additional requirement to carry a diverse range of bulk cargoes for other clients requirements led the owners to look at many options before finally deciding on a completely new discharge system to the marine field, the moving hole feeder, from designers Kamengo, a Canadian engineering company.

To enable the vessel to be in and out within the three-hour window at Hantsport, the vessels load at a rate of 10,000tph (tonnes per hour). This enables the vessel to load the stipulated 40,000 tonnes within the two and a half hours available for the actual loading operation. The vessel has a maximum draught at any time during the loading period of 9.75m whilst keeping an under keel clearance of only 0.3m. This scenario has required the installation of a sophisticated ballast system controlled with the aid of a loading computer interfaced with an on-line ballast monitoring and control system.

Due to the short time available for loading and the constant danger of grounding, the vessel’s main engine is left running. This, together with the Lips CPP, Kawasaki 1,100kW bow thruster and the Becker high lift rudder, enables the vessel to very quickly depart the dock. Using the forward thruster and the Becker rudder the vessel can crawl sideways from the berth with virtually no forward movement and without tug assistance. The choice of a high lift rudder over a stern thruster was an easy decision as the Becker rudder not only provides enhanced docking and undocking manoeuvring but also provides better control at low speeds during pilotage, and favourable consumption figures during normal passage. The first vessel of the class Gypsum Centennial is powered by a Sulzer 6RT-flex58T-B main engine, which has a maximum continuous output of 11,275kW at 93 rev/min. It is the world’s first large low-speed engine in service with electronically controlled common-rail fuel injection. Due to the success of this ground breaking decision the sister vessel Gypsum Integrity was outfitted with the same engine.

The Gypsum Centennial has four cargo holds, with the traditional self-discharge shaped sloping bottoms that lead the cargo by gravity flow through the MHF and onto the two hold conveyors. The hold conveyors incline in the aft part of the cargo handling area and discharge the material onto the cross conveyors.

The combination of the MHF with the application of low coefficient of friction glass flake paint on the sloping sides of the cargo whilst holding a high angle within the cargo holds ensures difficult cargoes will be discharged quickly and effectively albeit with the loss of some cubic capacity. The longitudinal conveyor belts have been engineered oversize, at 2m, meaning the belts can operate at relatively slow speeds whilst still providing the 3,000tph discharge. This translates to lower maintenance requirements over time, reduce spillage (experience has shown that spillage is almost zero) and a reduction in dust generated.

The telescoping boom is designed to reach as diverse a scope of onshore receiving arrangements as possible. The BMH Marine designed boom has a telescopic length of 36m, which is exceptional considering the boom length is 76m and the minimum length retracted is only 40m. It is this flexibility that makes it easy to distribute the material directly to stockpiles onshore or to transfer to other receiving arrangements, such as barges, hoppers and ship-to-ship transshipments.

The entire cargo discharge operation can be controlled by one person operating a terminal located in the vessels central control station. From this station the operator, via various monitors and operator panels can control ballast and cargo discharge whist viewing the entire operation through the vessels fully integrated CCTV system.

BELTSHIP IN SIERRA LEONE

BML was contacted by African Minerals Limited (AML), in 2010. AML is a minerals exploration and development company with significant interests in Sierra Leone. It is listed on the Alternative Investment Market (AIM) of the London Stock Exchange, and is headquartered in London, United Kingdom.

In 2010 however the project was in its infancy and AML required a transshipment solution to move 8mtpa (million tonnes per annum) of iron ore from the Port of Pepel, inland from Freetown, to an offshore transshipment location where the iron ore was to be loaded onto Capesize ocean going vessels (OGV).

The loading port has a draught restriction of 9.5m, the channel is narrow with tight bends, and currents in the channel can run in excess of four knots. We could see immediately that the environment almost completely reflected the operating challenges that the vessels were designed to overcome at the loading ports in Nova Scotia, Canada. Additionally, the advanced manoeuvrability meant that the vessels were ideal for the challenges of ship to ship operations, and with the flexibility provided by the vessels telescopic boom, efficient loading of an OGV with a minimum of TS vessel movements would be possible.

AML export cargo consists of three grades of DSO, lumps, fines and AL32.The AL32 is a product which contains a certain amount of clay which can make handling difficult, however the vessel’s hopper shaped holds with their high slope angle combined with the MHF discharge system (negating hog backs) and oversized conveyors and transfer points was designed to handle ‘sticky’ cargoes.

These technical advantages, inherent in the design of the vessels, together with an early start date and attractive freight rates, secured the contract for Beltship in the face of stiff opposition from other specialist transshipment companies and Beltship kicked off operations in October 2011.

Since startup the transshipment operation has been very successful and, after a short ramp- up period, the vessels have consistently over- performed relative to the requirements of the contract. This success resulted in a contract amendment to increase the transshipment exports to 20mtpa for which Beltship brought into the project a third vessel and embarked on a major upgrade of the two existing vessels to increase design discharge capacity from 3,000mtph to 3,500mtph.

The improvement can be easily seen in fig. 1. An average rate of 2,800tph is required to meet the 20mtpa contract requirements whilst the actual average is now nudging 3,400tph. Beltship worked closely with Bedeschi on this upgrade. Bedeschi is one of the oldest companies in Europe for heavy clay, bulk handling and crushing equipment manufacturing and they provided the equipment in a containerized solution enabling quick outfitting on board each vessel, over a five- day period, by Beltship and Bedeschi engineers.

As continuity of service is extremely important, Beltship has entered into a number of contracts with service providers to provide expert advice and immediate backup support in the event of equipment failure.

Among these are Techomar, based in Switzerland it provides performance evaluation of the vessels’ main and auxiliary engines via on-board interfaces connecting directly via satellite and the internet to its offices. This allows constant evaluation of performance providing forward looking maintenance practices which can be planned in advance and in co-ordination with the client 

and avoid unnecessary downtime. Another is MacGregor’s marine bulkhandling division based in Enkoping, Sweden, this company is connected directly into the vessels’ computers that control the discharge equipment allowing immediate interrogation of the system and online support to the vessels’ crew when required. For belt maintenance Beltship has contracted QBM, a well-respected Canadian company providing services to the self-unloading and transshipment fleets. QBM is on a rapid response contract and have engineers on constant readiness, with all required visas in place, to attend in Sierra Leone at a moment’s notice. To back up this response, Beltship holds a complete set of belts in Dakar at the Lisnave facility, Dakarnave, where craneage and dock space is available only a day’s steaming away. A further set of all smaller belts is held on site in Sierra Leone.

Beltship has a commitment to Sierra Leone and has

undertaken a cadetship scheme to provide education and employment opportunities for the youth of the country. Promising young men and women are sponsored and supported by Beltship to attend the Regional Maritime University in Ghana and regularly join the Beltship fleet for practical training and experience. Beltship also provides employment for over forty local employees in positions both ashore and afloat and are proud to support the local children’s charity ‘All as One’, which provides orphaned and destitute children of the country with a home, education and medical care.

During June of this year, after major phase 1 investment by AML, Beltship expects to transship approximately 1.8mt of iron ore, thereby proving the 20mtpa run rate required by the client and making Beltship one of the world’s largest transhippers by volume as well as one of the most experienced ship-to-ship operators worldwide.

Besides the noteworthy projects mentioned on p69 of this issue, EMS-Tech Inc. has also been busy on the marine front, having delivered material handling systems for installation on five Panamax and four Great Lakes self-unloaders, all of which are being constructed by Chengxi Shipyard for CSL and Klaveness.

At the time of writing, six of these ships have been successfully delivered to their owners, one of which, the Baie St. Paul, is pictured. These systems incorporate the latest in efficient, high performance self-unloading systems with the EMS-Tech Feeder Gate forming the basis on which these systems are built.