An improved inspection process coupled with an innovative design change is driving down crane maintenance costs for one intermodal operator. Content courtesy The Timken Company; based on a recent collaboration with one of the nation’s largest rail carriers.
Rail-mounted gantry (RMG) cranes are the unsung workhorses of the intermodal transport system. Day after day, these specialized structures place countless containers on railcars bound for distant drop-off points, where gantry cranes will again place the containers on trucks for final delivery. With so much riding on every lift, railroad operators demand optimal reliability from RMG cranes and are always looking at ways to control costs, including smarter strategies and stronger engineered solutions that reduce maintenance spending.
Recently, one large railroad was paying too much for chain and replacement components for its aging gantry cranes. The railroad was purchasing crane aftermarket parts through the OEM as it always had, but costs were starting to creep higher due to reductions in chain performance, requiring more frequent maintenance. These costs included the cost of the new chain, time lost from interruption to operations, as well as labor costs each time the maintenance team had to pull the RMG out of service prematurely. Determined to find a more competitive chain supply channel, the railroad’s regional maintenance manager struck up a conversation with engineers from the Drives® chains division of Timken.
Improving Routine Inspection
One common problem crane owners experience is that leaf chain can be difficult to inspect. In a drive application, each joint of a standard roller chain will see the same number of articulations, whereas leaf chains experience articulation (and hence, elongation) quite differently depending on which section of the chain must bear the brunt of the load while articulating.
ASME standard B29.8 dictates leaf chain should be replaced at 3% elongation (at which point the tensile strength of the leaf chain is reduced by 18%). However, the Drives team determined many of the railroad’s chains had exceeded this mark despite regular inspection efforts. As well, there was frequent confusion among maintenance staff about the proper method used to measure chain elongation. In response, the Drives team developed two improved methods for chain inspection for the railroad.
As part of its recommendation, Drives created a sturdy metal wear gauge that gives maintenance workers a quick and easy way to inspect chains, with clear indicator marks on the gauge showing 1%, 2% and 3% elongation.
Drives also demonstrated a better way to measure the exact amount of chain elongation by using a caliper’s longer lower jaws (opposed to the shorter upper jaws specified by the OEM). By sliding the longer jaws down the chain link plate, greater stability and an exact reading can be achieved (whereas the small prongs of the shorter jaw tend to be slightly angled, making it difficult to get an accurate reading where pins protrude only slightly from the link plate).
With stronger inspection procedures in place, the railroad still required an upgraded product solution to increase crane uptime. Again, Drives delivered a heavier-duty leaf chain in place of the OEM chain and has provided direct assistance in tracking the performance of the new chain.
Minimizing Friction and Wear
Leaf chains designed to industry standards—regardless of lacing combination (e.g., 4×4, 6×6, 8×8, etc.)—use two outside link plates to hold pins in place and prevent them from rotating. However, as chains get wider (as the number of shear points between the inner and intermediate link plates increases), the friction between the plates and pins also increases, particularly as more load is applied to the chain. This puts even more torque on the pins, resulting in pin rotation that enlarges the pinhole to the point the chain comes apart or breaks completely.
To complicate matters, the weight of a cargo container may not be evenly distributed, meaning that at any time one strand of chain can see dramatically more loading than another, again leading to pin rotation. In leaf chains, pins are staked horizontally—if a pin has started to turn toward a 45 degree angle, it’s a sure sign rotation is occurring.
To meet the railroad’s need for a more reliable leaf chain, Drives modified an existing design to dramatically improve pin retention. To achieve this, engineers developed a special middle link plate for select sizes of chain that provides the improved pin retention required for challenging hoisting applications, but without creating stiff joints or inhibiting the movement of the chain.
After several rounds of testing, the railroad was satisfied with the performance and durability of the new chain and placed a large order for all transloading facilities in the Southwest region. And with this recent success under its belt, the railroad continues to look for other opportunities to improve the reliability of its cranes using upgraded drivetrain components.
In Drives, the railroad found a partner willing to solve problems and no longer needs to buy from its OEM, now that many of its cranes are out of warranty. Drives not only impressed the railroad’s maintenance team, it also convinced the corporate purchasing office to proceed with a larger contract for crane upgrades.
For intermodal operators, it’s evidence that smarter, stronger solutions often come from component suppliers with an intimate knowledge of the inner workings of critical equipment, and in this case, it was just the lift the railroad needed.
Richard Neuhengen is a Product Manager for Timken Drives LLC.