GRAPHALLOY^® Bearings for
Pulp & Paper Applications

Summary

Paper making facilities have caustic, acidic, submerged, dry-running, and high temperature applications. These are tough scenarios for most materials. Metal bearings often corrode, and grease is washed out or baked out. Plastic bearings can melt in these environments. When looking for alternative bearing materials, Graphalloy bearings offer a solution for various services.

Why Graphalloy for Pulp and Paper Applications

Graphalloy materials, made from graphite-metal alloys, have the following advantages:

• Self-lubricating: Require no grease or oil
• Temperature Range: Operate from -450°F to +1000°F (-265°C to +535°C)
• Submerged: Operate in submerged conditions and hostile liquids. Will not swell. No lubricant to wash out.
• Non-galling: Will not gall when running against metal rotating partss
• Dampers
• Corrosion Resistant: Graphalloy Bushings resist attack by most corrosive liquids and gases such as sulfuric acid, hydrochloric acid, chlorine water, and caustics. A thin layer of GRAPHALLOY deposited on the shaft inhibits corrosion of the shaft.

Pulp and Paper Applications for Graphalloy

• Hot Lime Conveyors
• Salt Cake Drag Conveyor
• Agitator Shafts
• Header Gluing Machines
• Rope Sheave Bearings
• Dampers
• Screw Conveyors
• Pumps
• Dryers
• Electrostatic Precipitators

Graphalloy^® Case Histories for Pulp & Paper Applications

Electrostatic Precipitators

Temperatures range from 250°F to 400°F depending on the specific process. The fly ash, salt cake, and other process products cover the bearing housings. When the roller bearing fails, it only takes a few hours to do major damage to the drag scraper housing, shaft, drag chain, and scraper blades. Based on customer feedback, Graphalloy bushings run for 4-5 years in this application without issues. The cost savings are easily demonstrated. Customers that have converted to Graphalloy experience a significant reduction in downtime, maintenance and most significantly the head and tail housings are not damaged when Graphalloy is in service.

River Water Pump

The customer required bushings that could operate in pumps bringing river water into the mills. The polymer bushings they used previously had high vibration levels and the life was 12-15 months. We offered Graphalloy GM 205.3 (Babbitt) bushings for the Impeller, Column, and Bottom Case bushings. After 2 weeks the initial results were favorable. The pumps were running with vibration levels of .007 in/sec as compared to .012 for the pumps with the polymer bushings. After 16 months, the pumps are still running well and the customer is very pleased.

Re-Pulper Washer– Auger Pillow Block Bearings

It takes two days of downtime to replace the drive and non-drive pillow block bearings. The pulp washers are located in the most caustic area of the re-causticizing plant. Replacing these two pillow block bearings is a labor intensive and costly expenditure for the mill. The roller element pillow blocks seize up on the shafts approximately 60 days after installation. The failure is due to the very high ph of the caustic. GMC recommended grade 212 with a pillow block bushing assembly. The Graphalloy bushings in this application have lasted over 11 years, many times longer than the original roller bearings, which only lasted 3 months. Furthermore, Graphalloy bearings do not cause any damage to the auger shafts. This mill has 33 of these pulp washers in service.

Rope Sheave Bearings

The ball bearings in the rope sheaves, located one to two feet from the dryers, had a life of two to six weeks. The dryers are natural gas burners that aid in evaporating the water from the paper. The heat generated by the dryers (400°F to 500°F) cooked the grease in the bearing, shortening life. After review the facility decided to put in Graphalloy bearings, which can handle the heat. After six months of operation, the 6" rope cluster sheaves are still going strong. This is a six fold improvement in the life of the bearing.