High Angle Conveying Revolutionizes Shiploading and Unloading

Courtesy : Trans Tech Publications - Bulk Solids Handling Journal

1. Introduction

The important advancements in ship loading and unloading span more than 100 years. However, the technological strides of the last 20 years have revolutionized this essential endeavor into a highly efficient and economical process [1]. These new technologies are spreading rapidly in this fully globalized industry and are destined to benefit all shipping interest; from terminal operators to terminal users-to say nothing of the positive effects on the industries they serve.


Fig. 1: View aboard a continuous "automatic" self unloader down the unloading boom toward the enclosed HAC

Terminal operators benefit directly from these new technologies with optimum utilization of their facility. Terminal users benefit also from reduced lay times and increased route cycle frequency [1]. Plus, the industries served by the worlds shipping industry are no doubt poised to enjoy improved transportation economics and, thus, improved competitiveness in more distant markets.

2. Grab Methods to Continuous Systems in Less Than a Decade

In a study published as recently as 1971, the argument between discontinuous and continuous ship unloading persisted. At the time, discontinuous grab methods were still considered superior to continuous mechanical systems such as screw conveyers, ladder unloaders, and pneumatic systems [2].

In shiploading a similar discussion has focused on the merits of various systems ranging from dual-linear methods to 2-quadrant and traveling concepts [3]. However, in the last ten years, exprimentation and operational histories of the various options along with significant technological advances have turned many of these discussions into debates.

In ship unloading, continuous systems have clearly proven to be both reliable and flexible in the full range of bulk materials handling-including free-flowing materials like cement, grain, etc.; and non-free-flowing material like coal, bauxite, iron ore, etc. Even comparison of pneumatic versus mechanical options have been largely resolved in favor of mechanical solutions [1].

In shiploading, traveling loader systems - although the oldest of current shiploading options - have distinguished themselves as both the most economical and most flexible with the exception of their historic requirement for long piers to accommodate slope conveyors [4]. The need for long piers to accommodate slope conveyors has been virtually eliminated with the advent of proven high angle conveying systems.

3. High Angle Conveying Proves Ideal for Loading and Unloading

In recent years, continuous "automatic" self-unloading systems using high angle conveyors have proven to be the most economical method of clearing both ships and barges (Fig. 1). Currently, there are several designs of high angle conveyor systems. Some systems on the market use a pocket type belt which, unfortunately, is quite expensive relative to standard belting [5]. There are, however, successful high angle conveyers in use today in "automatic" self-unloading applications which employ relatively low-cost, standard conveyor belting to accomplish the materials handling task (Fig. 2). These conveyors are provided by Continental Conveyor & Equipment Company, Winfield, AL, USA, under the tradename HAC and they use a state-of-the-art sandwich belt principle.

In addition to the obvious economies of utilizing standard conveyor belting, the sandwich belt principle offers the added benefit of moving materials with virtually zero degrade. This is compared to degrades of more than 10% on equivalent pneumatic systems which are also known to consume significantly more energy to accomplish their task than comparably-sized high angle conveyers.

One of the secrets to the high performance capabilities of the Continental design is its use of proprietary, patented, pressing components (Fig. 3) which ensures easy conveyance of all types of bulk solids, offering tremendous flexibility to the ship or barge operator.


Fig. 2: An elevation view of a Continentai HAC system incorporated into a continuous "automatic" ship unloader


Fig. 3: The continental HAC features proprietary, patented, pressing components to ensure easy conveyance of all types of bulk solids

The fully-equalized pressing mechanism secures material toward the center of the belt while gently, but effectIvely, sealing the belt edges together. This minimizes the number of problem-prone inflection zones [6].

In shlploadlng, the Continental HAC is capable of eliminating the need of long slope conveyers and greatly enhances economies and flexibility of traveling loading systems (Fig. 4).

4. High Angle Conveying Delivers High Volume Productivity

Unlike high angle conveying systems typically in use in the last decade - such as screw, bucket and pocket belt designs -the HAG systems of the 1990's are ideal for tOe handling of large volumes at rates which exceed 6,000 t/h. This allows for dramatically increased productivity in both the loading and unloading process and will, in all likelihood, revolutionize the economics of the industry positively for all bulk solid shipping interest. Continental has over 80 of these type installations in successful operation worldwide.

5. Conclusion

The trends are clear - shiploading and unloading are rapidly evolving into considerably more cost-effective processes, using advanced technologies which are highly automated and require a fraction of the space, both on board and on the dock of the typical systems of just a decade ago.

Simply, high angle conveying, and especially so when using the Continental HAG configuration, is revolutionizing shiploading and unloading by dramatically reducing key materials handling cost factors such as cycle times and operational cost and capital outlays.


Fig. 4: An elevation view of a Contrnentai HAC system incorporated into a continuous "automatic" ship unloader


[1] Hofmann, W.C.: Mechanical and pneumatic continuous ship unloading; bulk solids handling Vol. 11 (1991) No.1, pp. 313-331.

[2] Severn, D. Knnen beim Erzumschlag andere Gerte mit grerem stndlichen Durchsatz den heutigen Oreifet--Schiffsentlader ersetzen?; Krupp factory reports, Vol. 29 (1971), Issue 3/4.

[3] Carmichael, A.: Shiploaders for handy-size and Panamax vessels; bulk solids handling Vol. 13 (1993) No. 3, pp. 519-524.

[4] Horak, P.M.: An economical shiploading system for the 21st century; bulk solids handling Vol. 17 (1997) No.2, pp. 205-211.

[5] Paelke, J. W.: Progress with continuous steep angle and vertical conveying; bulk solids handling Vol. 16
(1996) No. 1, pp. 21-30.

[6] Continental Conveyor & Equipment Company, High angle conveying to 90 degrees: Company brochure.

HAC is a trademark of Continenta Conveyor & Equipment Company.

J. Ray Mcgaha and James L. Smothers, Continental Conveyor & Equipment Company, 
P.O. Box 400, winfieid, AL 35594, USA.
Tel.: +1 205 487 64 92: Fax: +1 205 487 42 33
E-mail: rmcgaha@continentaiconveyor.com