Manitowoc 31000 Crawler Crane Showcases Advanced Cable Testing Technology
It’s big by any measure. The largest capacity crawler crane ever designed and built by Manitowoc has a maximum lifting capacity of 2,535 U.S. tons. Powered by two 600-horsepower Cummins diesel engines it sports a 1,543-ton fixed jib and a 1,212-ton luffing jib.
The Manitowoc 31000 crane is equipped with two independent load hoist drums grooved for 50 mm wire rope. Its standard line pull is 110,230 pounds.
The crane, which can be outfitted with a maximum 2,126,000 pounds of counterweight, also features a unique self-supporting Variable Position Counterweight (VPC) system. The patented VPC system minimizes footprint and ground preparation needs by automatically positioning counterweight between fully retracted and fully extended positions.
“On a crane that big, the wire ropes are necessarily large, long and expensive,” said B. Tad Dunville, managing director at Lifting Partners, agents for Unique Group, the U.S. importer for AMC Instruments. “Where many fleet owners typically replace wire ropes on a time or usage basis, in this case it pays to have another solution, one that lets you understand the state of the cables, including and most importantly the core because that is typically where most faults occur.”
For testing the hoisting, boom and whip lines on a Manitowoc 31000, Maxim Crane Works hired Certex Rigging who brought in Unique Group to supply the Rope 65 system from AMC Instruments and two magnetic resonance testing (MRT) tools.
For the test, which included evaluating the crane’s three 50 mm cables for the hoisting line and 34 mm cables for the boom and whip lines, the Rope 65 MRT tool was affixed to each line. The lines were run across their full length while the Rope 65 tool remained stationary.
The Rope 65 system evaluates the wire in the cable from jacket to core by inducing a micro-current in the rope and analyzing changes in the property of the current, which can indicate breaks or corrosion anywhere in the cable. The results are displayed on a laptop or tablet at the site, or a skilled technician can remotely diagnose issues. A single rope of 300 feet can be surveyed using Rope 65 in half a day.
Overall, the Manitowoc crawler testing was finished in about three days. Because there was scientifically sound data regarding the state of each rope, the crane owner was able to retain three 50 mm cables that were well over 3,280 feet long, resulting in a six-figure savings.
“The owner also understood just how deteriorated the boom cable was on the crawler crane,” Dunville related. “Typically, ASME B30.30 or ISO 4309 standards describe the minimum criteria for scrapping a cable, but often customers with high value ropes or high value applications – where downtime is costly – find that they are willing to replace the cable before ASME or ISO require it. This might be at the next scheduled downtime, because planned maintenance is usually much less expensive than unplanned repairs.”
Because MRT testing offers cost and time savings, Dunville noted, the budget to perform testing in a remote location is much lower. Advances in MRT technology like that used on the Rope 65 tool have also allowed for running the lines faster during testing and ensuring that it is truly non-destructive.
“The test results are also repeatable, partially because the device records information in both time and distance indices simultaneously,” Dunville said. “And technicians and owners can find faults later, without stopping the rope, and compare data over time to see if a process, operator or physical piece of rotating machinery such as a sheave is possibly causing damage.
“With the cost to replace cables in the hundreds of thousands of dollars, it doesn’t make sense to automatically replace them on a time or usage basis,” Dunville added. “On this project for Maxim Crane Works, we were pleased to have a great partner like Certex Rigging.”
The Rope 65 MRT tool has proven itself at some of the highest profile construction sites in the United States. It can also be fitted with Ropewatcher, a permanently installed option, on various mobile and overhead cranes where downtime or ropes are costly.
