North Star Port

TOOLS TRADE OF THE North Star Port: What are listometer lights and how do you read them? Do the colors have any significance? Richard Stewart: They 're usually called loading lights, and they're fitted on Great Lakes vessels wherever they can be easily seen by mariners on the main deck working cargo. In the case of the William A. Irvin, for example, you can see them on the stack. On some vessels, there may be a repeater on the bridge. The lights indicate the vessel's list (tilt) and trim (fore and aft bal- ance) while loading or unloading cargo. They're controlled by a mercury switch and consist of five lights: two red, one white, and two green. The white light illuminates when the vessel is upright. If the vessel takes a half-degree list, the inner red or green light will illuminate and the white light will be extinguished. Maintaining the vessel in an upright condition is very important and lists more than 1 degree must be corrected. Port: One degree of tilt doesn't sound like much. What could go wrong? Stewart: On a Great Lakes self-un- loader, it could cause faults in the belt tracking. Also, the boom slewing system hydraulics may exceed the design pressures, and the relief valves will lift, stopping the boom. This costs time and money, which is annoying and expensive, but it's just a slice of what can go wrong with even small degrees of tilt. Oceangoing vessels take this into consideration, too. Containers can't be unloaded from the guides on a con- tainer ship if the list exceeds 6 degrees. A vessel that sails with an uneven trim may have trouble steering, exceed draft limits even if the vessel is not over- loaded, and cargo may shift in heavy seas. Slightly more comically, but still Listometer Lights 8 | NORTH STAR PORT | SUMMER 2023 PHOTOS / Jayson Hron; John Rudolph Zweifel and William F. Roleff; Univ. of Wisconsin-Superior Jim Dan Hill Library Archives ichard Stewart began his maritime career in the late 1960s as a merchant mariner in the Vietnam war zone. After graduating from the U.S. Mer- chant Marine Academy in 1973, he sailed oceans and coastwise as a deck officer, eventually commanding ocean vessels through the late 1970s and early 1980s. Stewart then shifted into an academic career during which he eventually directed the University of Wisconsin-Superior transportation and logistics program. In May 2023, the U.S. Maritime Administration commemorated his remark- able career by awarding him the Merchant Marine Medal for Outstanding Achievement. R LISTOMETER LIGHTS, LIKE THOSE SEEN HERE ON THE STACK OF THE WILLIAM A. IRVIN, PLAY A CRITICAL ROLE IN PROPER SHIP-LOADING AND SAFE NAVIGATION. WE ASKED DR. RICHARD STEWART TO TELL US MORE ABOUT THEM.

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