Reader Offers Advice to Prevent Spline Wear

June 10, 2016

To solve the problem of the shaft prematurely wearing out in a dredge's vane pump, Loctite was applied to the small pump shaft and two internal splines.

Don Searles

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Until my retirement, my company, Dredging Specialists, designed, built, and operated hydraulic dredges, completing more than 150 projects in 22 states.

The dredges we built were powered by diesel engines that drove hydraulic pumps. The hydraulic systems powered an underwater dredge pump, five winches, and other hydraulic actuators. A gear-drive box got bolted to the flywheel of the diesel engine to drive three hydraulic pumps. Typically, the two lower pumps were of axial-piston design and the upper one was a vane pump.

Each pump had a splined drive shaft that mated with internal splines in the output shafts of the gearbox. The shaft on the vane pump was smaller than those on the axial-piston pumps, so we had to install a splined adapter to mate the vane pump’s input shaft with larger shaft of the gearbox.

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To prevent premature wear of a pumpâs input shaft, apply Loctite to the splines on the pump shaft and to the internal splines of the adapter. Next, apply grease to the external splines of the adapter, install the adapter into the drive box, and then mount the pump to the drive box.

On the first dredge we built, the vane pump’s shaft wore out very quickly. To solve the problem, we applied high-strength Loctite on both the small pump shaft and on the internal splines of the adapter.

First, we applied Loctite to the splines on the pump. Next, we put Loctite on the inner spline of the adapter and applied grease to the outside. After sliding the adapter into the gearbox, we then installed the pump.

This locked the vane-pump shaft to the adapter and prevented movement and wear between them. Even after thousands of hours of operation, the adapter was still locked on the vane-pump shaft, and the problem was solved.

Submitted by Don Searles, who still provides expert witness and consulting services through Dredging Specialists. Visit www.dredgingspecialists.com for more information.

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