Winch Drum Spooling and Wire Rope Lifespan

Winch Drum Spooling and Wire Rope Lifespan
11/20/2017 1:23:43 PM

Untidy wire rope spooling doesn’t just look messy. Twisted hoist lines can bring a construction project to an abrupt halt. When that rope gets kinked, crushed or otherwise damaged, it has to be replaced. And you’ve probably learned the hard way that quality wire rope isn’t cheap.

Properly handling wire rope and correctly spooling the winch drum will help reduce block rotation and increase wire rope lifespan. Here we’ll look at one method that accomplishes both:the LeBus spooling method.

First, a little "spooling schooling” …

Most cranes today use grooved winch drums to help the rope wind smoothly. This means the rope rests on the previous wrap rather than alongside it (as is the case with smooth winch drums). A helical (spiral) groove on the winch drum (sort of like the thread on a screw) guides the rope to make it spool correctly. However, when the rope lines up with the end of the barrel and covers the drum completely, the rest of the rope has nowhere to go.

In this video, you can see the winding process of a mining hoist rope onto an original LEBUS winch drum in 2 layers.

Enter the LeBus Counterbalanced Spooling System. Named for its inventor, Frank LeBus, the system uses grooves that are parallel to the flanges (edges) of the drum. When the rope reaches the end of the drum and covers the whole drum in a single layer, the subsequent layers are nestled into the groove pattern created by the layer beneath.

The LeBus method reduces cross-winding by keeping most of the rope parallel to the flanges in the inner layer rope groove. Parallel grooving evenly distributes tension and torque between the individual layers. This will vastly increase the life of the wire rope, improving safety and reducing downtime in the process.

Today, Lebus International, based in Longview, Texas, continues to produce proprietary winch drums and related spooling equipment. Although other parallel groove drums are sometimes incorrectly called "Lebus drums,” a true Lebus system must be designed and produced specifically to meet the application for which it is used.

The groove pattern is always designed to suit the rope’s length, diameter and construction. Improper spooling can be the result of a new rope being installed that is slightly larger in diameter than the groove pitch—that’s why it’s important to check that the rope stays in the grooves in the first layer when you begin spooling.

There are drawbacks to the Lebus system. For one, parallel grooving costs more than helical grooving. The grooves must be cast or machined into separate pieces and mechanically fastened to the drum barrel. It also requires a specific fleet angle (the angle between the rope coming off the drum and the point it meets the first fixed sheave). You’re also limited to one rope size, as only one size cable can be used on a particular grooved cable drum.

These downsides and increased equipment costs, however, are easily offset by the savings in wire rope replacement that the fleet manager typically sees.

One more note on installation: When there are multiple layers of rope on a drum, there’s going to be a lot of pressure on the lower layers. That’s why it is important that the rope is first installed under tension. You want to avoid any slack on inner layers, which can be crushed or nicked against the groove walls by the outer layers of rope. Generally speaking, a tight line makes for better spooling.

For more information about the use and care of wire rope, refer to Python’s technical information page. For any crane with a drum holding more than three layers of wire rope (common with mobile cranes), Python recommends the Lebus grooving system. If you need to know more, or if you have any questions, contact LC Crane, and our technicians will be glad to help.

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