A few months ago, the Heyl & Patterson blog tackled the competition of the Continuous Barge Unloader vs. the Grab Bucket Unloader, to see which machine was the best for unloading river barges. A grab bucket is a simple enough machine: a clamshell bucket is lowered onto a barge, takes a bite of bulk materials and ascends to deposit its contents into a receiving hopper. However, the Continuous Barge Unloader is far more complex. This article will examine this machine more closely to see what makes it tick.
The Continuous Barge Unloader, or CBU, is a stationary structure to which barges are delivered for offloading. The machines are so prominent on the Mississippi River that they are unofficially known as "HPs." The structure is built in a bridge-like fashion, usually using box girders and anchored to substantial concrete cells. The digging device is comprised of a boom and a string of buckets interconnected by strands of chain, which form a catenary loop. A mechanical engine located at the top of the boom structure powers the chain. The engine drives a sprocket assembly at the head end of the drive train. Two additional sprocket assemblies are located at the bottom, or digging head, of the boom. One sprocket provides proper chain tension, while the other provides transition in lifting the loaded buckets up the boom.
The boom is pin-connected to a rope-driven trolley that provides the boom's ability to traverse the width of the barge.
Located on the trolley is a boom hoisting engine. The hoisting engine adjusts the elevation of the boom to accommodate varying water fluctuations as well as the rise of the barge as it is emptied. The boom hoist is reeved to the boom via a wire rope and sheave arrangement.
The buckets are generally very large in capacity. Therefore, chain speeds are relatively slow. The number of buckets per machine is dependent on the boom length, but 35 is a typical quantity. As the loaded buckets are raised up the length of the boom, they pass over the head end shaft and the contents are discharged into a chute. The chute in turn discharges onto a gathering conveyor, which is appropriately sized to handle the peak unloading rate.
A pair of barge haulage engines are used to move the barge at a slow variable speed to the digging head of the boom. Precise speed control is important to provide a consistent amount of material to the buckets.
The size of the buckets and speed of the chain determine the overall capacity of the CBU. The overall power requirements will vary, depending on capacities, however a typical range is between 225 and 400 kW.
Electrical control for the CBU is provided from the modern digital controllers, and the system logic is via programmable logic controllers. Newer installations are equipped with a comfortable operator's cab featuring the latest in human machine interface systems. Depending on user preferences, the interface systems include touch screen controls, automated operation, digging rate display and fault annunciation.
As evidenced by their popularity along the Mississippi River, Heyl & Patterson has designed and manufactured CBUs for decades. We also offer a complete line of replacement parts and upgrades, regardless of the original manufacturer. Mechanical upgrades include buckets, lubrication systems and trolley wheels, while electrical upgrades include control systems, fiber optics and variable frequency drives.
To learn more about Heyl & Patterson's Continuous Barge Unloaders and other types of barge unloading equipment, click here:
