The CSL Innovator is undoubtedly unique in the shipping world. Built for worldwide ocean trade by Canada Steamship Lines (CSL), the CSL Innovator is a Panamax-class self-unloading vessel. (Panamax-class refers to a ship that has a dead weight of between 60,000 and 70,000 tons and is capable of traversing the Panama Canal.) This unloader was designed to handle a wide range of cargos, including such hard-to-handle commodities as moist iron ore concentrates, cohesive coals and gypsum rock. The innovative hopper and gate design and the unloading system, which includes the first double-articulated unloading boom ever built, are largely the result of the extraordinary vision and engineering talents of W. H. (Bill) Johnston, senior vice president of CSL. Jenike & Johanson is proud to have been involved in several aspects of this design.

Historical Perspective

Self-unloading vessels originated on the Great Lakes and handled cargos of free-flowing materials such as grain, road stone aggregates, and iron ore pellets. The hopper angles in the holds were shallow (35° from horizontal), and hopper surfaces were rough carbon steel. Flow from the hopper openings to the tunnel reclaim belts was typically controlled by roller-track gates of the type shown in Fig. 1A.

Due to the shallow hopper angles and the type of gate used, the flow pattern from the hoppers was essentially funnel flow, which was quite adequate for free-flowing cargos. The vessels, capable of carrying up to 35,000 tons of cargo and discharging at rates up to 5,000 tons/hr., gained wide acceptance.

In the 1970s, markets developed for more cohesive commodities, particularly Western Canadian coals. Initial experiences in handling cohesive materials were not promising. Cargo hang-ups were frequent. Arching, ratholing, and inability of materials to slide down slopes—particularly the valley angles—provided the impetus for CSL to look for a new design. In the early 1980s, CSL enlisted the help of Jenike & Johanson engineers, who tested materials and made recommendations for a new hold configuration and gate design. We recommended modifying the hopper configuration above the belts in order to accommodate a new, large, rectangular double-acting slide gate (Fig. 1B). In addition, we recommended lining the side slopes with ultra-high molecular weight (UHMW) polyethylene sheets.

These design modifications solved the problem of hang-ups with many cohesive commodities, and for nearly a decade have been features of most Great Lakes self-unloader designs. In fact, most vessels built today have hoppers that are lined with UHMW polyethylene sheets.

Nevertheless, the slide gates have not been without problems. Mechanically, they are not as robust as the original roller-track gates. They are sometimes difficult to close completely, and they present problems to the tunnel crew in initiating the controlling flow, particularly with cohesive cargos.

It was with this background and the growing demand for self-unloaders in worldwide ocean trade that CSL began work on a third-generation vessel. Jenike & Johanson engineers were again asked to assist in this new design.

Designing self-unloading vessels is one of the most challenging bulk handling assignments because of the broad spectrum of criteria that has to be satisfied. First, the range of potential cargo is enormous, and CSL's new vessel had to be capable of carrying the maximum possible range. Typical free-flowing products include grain, iron ore pellets, and aggregates. Cohesive products include wet ores, concentrates, and cohesive coals. Fine, dry, dusty products include alumina and possibly cement. Products that cake include salt, potash, and sugar. Many products are single sized, but others, like mine-run gypsum, can contain large, slabby lumps.

The configuration of holds and hoppers had to maximize the useable volume in a Panamax-class vessel. In order to maximize useable volume, it was necessary to use a three-belt withdrawal configuration rather than a conventional two-belt system. Also, the hopper slopes had to be kept as shallow as possible, yet be capable of handling cohesive/adhesive cargos.

The vessel was designated with 240 gates. Gate configurations had to take minimal headroom. In addition, each gate had to provide good flow control for a wide range of free-flowing and non free-flowing cargos. Finally, it had to be cost effective, easy to construct, and mechanically robust.

Dr. David J. Goodwill of Jenike & Johanson's office in Toronto, Canada, worked closely with Bill Johnston for a two-year period, designing and redesigning hopper and gate configurations. They used flow property results obtained for a very cohesive iron ore concentrate as the design basis material. They considered many gate design concepts, constructed working models and performed flow pattern tests. Eventually, they developed a new gate of the "basket" or "swing" gate type in conjunction with Consilium CMH Marine AB (Fig. 1C).

The new ship, aptly named the CSL Innovator, has been in continuous service now since September 1988. To date, the performance of the new hold configuration and gate design has been exceptionally good and has far exceeded industry expectations. Raymond Johnston, CSL's Vice President for Customer Services and Transportation, states, "As a result of the significant amount of research and development time and money that went into the CSL Innovator, we now have the most technologically advanced self-unloading vessel in the world. With the vessel's unique capability to handle a wide range of difficult cargos, satisfy environmental requirements with respect to dust and noise pollution, and offer superior discharge flexibility with the articulated boom, this is one R&D project that is certainly paying off."