Challenge The paper mill experienced a failure of a grid-type coupling hub on the main drive of their coal conveyor. The problem was found to be a wallowed keyway and spinning of the coupling hub on the gearbox input shaft. Since there wasn’t a spare gearbox for this conveyor drive in the plant, the maintenance team determined that there were only several operating hours worth of coal left in the bunkers to feed their boilers. After that, the paper machines would be shut down in order to switch over to natural gas.

Coupling hub repaired with Loctite® Quick Metal

Solution

A millwright who had been attending the Loctite® Manufacturing Reliability Training Process at the plant suggested a method of repair for the coupling to gearbox input shaft that he'd learned in one of the training sessions.

Loctite® Quick Metal® Retaining Compound is a creamy, non-running adhesive that can be used between machinery parts to repair worn areas and restore correct fits. It fills gaps up to 0.020" and has a temperature range of -65°to +300°F.

As the shaft was worn substantially more than 0.040" diametrically, the millwright decided to make a "Loctite® Sandwich" constructed of shim stock and Quick Metal. The coupling hub was then reinstalled.

Results

The coal conveyor was back in operation before the bunkers were completely emptied of coal. The machine shop manager said that this saved the paper mill substantial outage on the paper machines and allowed them to run the coal conveyor on a 24 hour-a-day basis, 7-days-a-week, until they could get a new gearbox and install it during a scheduled shutdown. The cost of downtime for this paper mill can exceed $50,000 per hour, avoiding a shutdown that could cost a million dollars.