Kruger Inc., with head- quarters in Trois Rivieres, Quebec, Canada, is a global company that manufactures and markets newsprint, specialty grades, lightweight coated paper, directory paper, tissue, recycled linerboard, corrugated containers, lumber and other wood products.

The Kruger Tissue Group includes a mill in Memphis, TN - K.T.G. (USA) LP. The main products at Memphis are bath and facial tissue for the premium private-label segment of the US retail market. Annual capacity is 100,000 tons. There are four paper machines and 10 converting lines.

Northern softwood and eucalyptus are the main fiber furnish. Voith hydropulpers prepare the fibre for the rest of the pulping process. They were at the heart of the mill's maintenance problems.

During pulping, material comes in contact with the rotor and a tremendous shock load is transferred to the shaft, flexing whatever sealing system is being used (contact, lip, labyrinth, etc.). To maintain its integrity, and keep contamination out, among other things, the seal must be able to accommodate shaft movement, which, over time, can break down even the best of seals. On breakdown, water runs past the seal, down the shaft and enters and contaminates the gearbox housing.

According to David C. Orlowski, president and CEO of Inpro/Seal, Rock Island, IL, sealing options tried on hydropulpers include: lip seals (with an average service life as little as 1,800 hours); sealed bearings (which do not seal moisture on water); fibrous packing (which degrades); close-clearance designes(which still allow leakage); contact seals (which stop contacting); flingers (a type of rubber ring that provides only short- term protection).

In time, says Orlowski, with any of these methods, water will get past the seal, causing the gearbox bearings to fail. The hydropulper problem. The Memphis plant's five Voith hydropulpers have been in service for about 40 years. They were retrofitted and modernized in the 1990s, including the gearbox and motors - but breakdown continued.

According to Dave Knox, crew leader of K.T.G.'s maintenance technology group, the main cause of failure was water contamination in the gear-box mounted directly under the hydropulper tank. The problem had been going on for years and was not addressed by the previous owners.

When the mill restarted in 2003, so did the equipment failure. To complicate matters, because of its out-of-the way location, they could not tell when a lip seal failed. The problem continued because the overhaul procedure included the use of lip seals. The water contamination continued until two years ago when they began to install. bearing isolators

Enter the bearing isolator. Orlowski says that to understand K.T.G.'s problem, one has to look at the history of lip seals. At one time, they were the only choice for general- use sealing devices. They are inexpensive and so were the number one choice to seal industrial rotating equipment.

To address the lip seal problem, Orlowski invented the bearing isolator in 1975. The bearing isolator is a non-contact, non-wearing, labyrinth-type device, offering permanent bearing protection. It consists of two parts, a rotor and stator unitized so that they don't separate gearbox. from one another while in use. Typically, the rotor turns with a rotating shaft, while the stator is pressed into a bearing housing. The two components interact to keep contamination out of the bearing enclosure and the lubricant in.

Orlowski says that though the end user has a Inpro/Seal Co., www.inpro-seal.com; choice, the best bearing isolators are made of www.bearingisolators.com metal, usually bronze, utilize a vapor-blocking feature to inhibit the transfer of contamination, are manufactured to exact specifications and shipped the same day as ordered.

Inpro/Seal solves the hydropulper problem. K.T.G.'s Knox related his problem to Mike Perkins at Chesterton who recommended the use of Inpro/Seal brand bearing isolators. Knox met Joe Kline, Inpro/Seal's regional manager who handles the K.T.G. account and, working together, developed bearing isolators engineered to the mill's exact needs and specifications.

During 2005 and 2006, Inpro/Seal model 2200-A-33503-0 and 2200A-33289-0 bearing isolators were installed on two of the five hydropulpers as part of the mill's overhaul program. For the last two years, there has not been a single hydropulper failure. The problem of water entering the gearbox bearing was eliminated. Similar permanent bearing protection is scheduled for the other three hydropulpers.

On rolls, too. K.T.G. also uses Inpro/Seal bearing isolators on the paper machine rolls. The PMR (paper machine roll) bearing isolators are specially engineered for the size, speed, alignment and operating conditions of wet and dry ends of machine rolls. PI

Inpro/Seal Co., www.inpro-seal.com; www.bearingisolators.com