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Repairs that are better than new
Next Pitch Lines Article:
A bimonthly publication dedicated to sharing solutions to gearing problems and tips on avoiding them in the first place. Your comments and suggestions are welcome - let us hear from you.
The Gear Works 500 S. Portland St. Seattle WA 98108 |
Some people try to keep things stirred up in their lives, but for those in the pulp products business, that takes on a special meaning. It's essential that a pulp plant's carefully-mixed ingredients stay that way in order for subsequent processes to take place. And sometimes the only thing between success and failure is a set of gears in an agitator drive. A case in point is the Longview Paper Facility of the Weyerhaeuser Paper Company in Washington. This large plant produces more than 400,000 tons of paper products a year that go to the industrial and consumer markets as "whiteboard" food packaging material (largely for milk cartons) and brown board corrugating medium for shipping containers and fine paper products. More than 10 of the plant's 200 acres are filled with large tanks, each holding about 30,000 gallons of pulp mixture.
The "formula" varies according to its
intended use, but generally consists of wood fiber, water, resins, and additives required for strength, absorption, and other qualities. With 10 tanks on line, approximately 300,000 gallons is being stirred 24 hours a day. Actually, "agitated" is the more accurate term, and each tank has an agitator unit suspended inside. They run
constantly, their heavy-duty gear boxes turning large "paddles" at about 25 RPM to keep the pulp ready for processing. Reliability is important because, once agitation stops, the mixture settles and becomes unusable in less than an hour. When Weyerhaeuser first had a gear box failure in one of these units, they were surprised to find that the manufacturer didn't provide repair service for it. Searching for an alternative, they brought their problem to The Gear Works. Since the gear box was similar to a number we had successfully repaired previously, we made a proposal and soon began work. As you can see from the photos, what we found inside was severe gear and bearing failure, apparently caused by contamination of the lube oil. After many years of service, the seals on the unit failed, resulting in corrosion and excessive gear wear. Once our inspection had revealed all this, we reviewed the findings with Weyerhaeuser and recommended repairs, including cost and delivery estimates. With their approval, we initiated a detailed program that solved their immediate problem and also prepared for future needs. We began by making manufacturing parts drawings to allow for re-orders. Then we re-manufactured the gears andmade modified pinions to maintain the existing ratio and center distances. Alignment and the diameters of the bearing/seal bores in the case were checked, repairs were made as required, and the case was cleaned and painted with an anti-corrosive coating. The new pinions, made from a stronger steel than those they replaced, were checked to assure that they would equal or exceed the originals in load carrying capacity. The gear set was then re-assembled with new bearings and seals and a contact check run in the box to assure maximum full-face gear contact and proper alignment. Next, a no-load spin test was run to check for vibration, gear noise, and proper functioning of the recirculating lube oil system. The oil was then flushed and inspected; units are shipped dry to allow the user to install the lubricant of choice for the specific application. Finally, the entire unit was painted with red primer, ready for the customer's finish color, and a quick-reference job number tag was attached. From start to finish, that first job took about ten weeks.
Now, after doing more than 100 of them for many customers, the average turnaround is about six weeks, or as little as ten days in an emergency. Weyerhaeuser likes to keep a spare of each type on hand so their on site repairs can be done "instantly," which they define as a complete change-out of an agitator drive in about 24 hours. The Gear Works then gets the failed box, and we "make 'em better," as our repair shop motto says. And as Pete White, Maintenance Supervisor of the Longview plant's Paper Products Division says, "The Gear Works provides reliability of repair on our equipment with quick turnaround. They're always there when we need them, and we've been working with them for 20 years." That's our goal, whether it's a complex gear set or a single part ... to save the customer the time and costs of replacement. And as the folks at Weyerhaeuser have discovered, that's one less thing to get "stirred up" about.