Jetty-and-barge export facility for Moma mineral sands

The export facility at Kenmare Resources PLC’s Moma mineral-sands project in Mozambique, currently nearing completion by a 50/50 joint venture between Bateman Engineering and Multiplex Ltd, is a highly cost-effective solution to transporting product to the bulk carriers, given the topography of the sand shelf off the coast at Moma.

With the shallow-sloping sea-bed at Moma, a jetty that permitted direct berthing of bulk carriers was not feasible. Therefore, the export facility selected comprises a 450 m long jetty from which the mineral-sands products can be delivered to a self-unloading barge that shuttles between the jetty and sea-going bulk carriers moored about 7 nautical miles off shore.

The jetty

The jetty is a steel structure resting on 92 piles, each 600 mm in diameter, arranged 4.5 m apart in 2-pile lines spaced at 9 m intervals along the length of the jetty. Each pile is driven between 12 m and 18 m into the seabed, which is about 6 m below the water level at the end of the jetty. The piles rise about 12 m above the ocean surface at high tide.

The conveyor, moving 1,000 t/h of material from the covered product stockpile inshore, rises at the end of the jetty and discharges the product into the feed chute of a loading-boom conveyor that transfers the product to the barge moored alongside the jetty. Three additional piles support the off-loading platform which is also provided with six mooring dolphin piles, 1,200 mm in diameter, fitted with fenders and bollards.

The jetty was constructed by driving each succeeding bent of piles into the seabed using a crane and pile driver standing on the end of the progressing jetty. Work on the USD7 million subcontract for the jetty commenced in June 2005 and was completed at the end of November 2006.

The barge

At the off-loading platform a luffing and slewing loading-boom conveyor transfers 1,000 t/h of product into a receiving hopper on the barge. The boom accommodates the movement of the moored barge relative to the jetty. On the barge two conveyors take the product to the barge’s two enclosed 2,000 t capacity silos.

When the barge moors alongside the bulk carrier, two withdrawal conveyors will extract the product from the silos, deposit it on a cross conveyor to the elevator leading to the barge’s luffing and slewing discharge-boom and conveyor. The product will then be discharged at a rate of 1,200 t/h into the hold of the bulk carrier.

Cross-contamination of the titanium products, comprising ilmenite, rutile and zircon, loaded into the barge will be minimised by handling the products separately and providing the means to clean out the system between the batches. The product will be covered throughout and kept dry in all weather conditions with a dust-extraction system to minimise dust pollution.

Fully laden, the self-propelled 1,400 t barge has a draught of 2.9 m to permit it to navigate the shallow sea shelf at Moma. Azimuth thrusters at each corner enable the barge to manoeuvre into loading positions as well as achieve 7 to 8 knots in the open sea.

A crew of 10, with full on-board accommodation, will operate the barge around the clock. It is designed for operation in international waters, not only to make the trip from Indonesia to site, but also to make periodic calls to Durban, the nearest harbour with a dry dock sufficiently large to service it.

The subcontract price for the barge is USD11 million. Work started in January 2006 and, when construction is complete, about 40 days will be required for the voyage from the shipyard to Moma.

The export facility is part of a USD265 million engineering, procurement and construction contract for the mineral-sands processing plant at Moma and its associated infrastructure.

More information on Moma’s export facility is available from Eddy de Beer, MBJV Engineering Manager (Jetty) and John Scott, MBJV Engineering Manager (Barge) on +27-11-899-9111 or email industrialminerals@BatemanEngineering.com.

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