Journal Enhancement for the Pulp & Paper Industry
The SIFCO Process® is commonly used for on-site repairs in the Pulp and Paper industry.
Typical applications include:
- SUCTION ROLLS: bearing diameters
- DRYER ROLLS: bearing diameters, heads, surface defects caused during maintenance
- PUMPS: bearing housings, impeller bores, shaft bearing journals and seal areas
- ELECTRIC MOTORS: bearing housings, rotor journals, commutators, bus bars
- POWER GENERATION EQUIPMENT: steam turbine bearing journals, flange faces, diesel engine cylinder liners, connecting rod bores, crankshaft journals
A Case History
Problem: Steam heat was applied too rapidly while starting up a 4.5 m (15 ft) long, 4.5 m (15 ft) diameter Yankee Dryer. The inner race on a roller bearing cracked, which damaged the journal. Approximately 95% of the journal area required build-up material and the amount of material required on 65% of the area was 25 microns (0.001 in.) to 508 microns (0.020 in.) per side. Approximately 30% of the area required 508 microns (0.020 in.) to 2250 microns (0.090 in.) on a side where broken up fragments pressed into the journal. The tapered journal had a diameter of 330 to 356 mm (13 to 14 in.) and a length of 203 mm (8 in.).
Solution: Selective plating was the best solution to repair the journal. The plating of the journal began with mechanical preparation of the surface using flap and polishing wheels to remove sharp projections, oxides, baked on films, etc. Afterwards, the area was cleaned with solvent and masked off. The area was then cleaned, etched, desmutted, nickel flashed, and copper-plated 625 microns (0.025 in.) thick over the entire surface. There was some surface roughness at this point, so flap and polishing wheels were again used to improve the surface. The journal was measured using a micrometer, and areas where there was sufficient stock were masked off so that additional plating could be applied only where it was required.
The remaining area was cleaned, etched and copper plated with an additional 625 mm (0.025 in.) thickness. A total of 4 layers of copper were applied in this manner. This provided sufficient stock over the entire journal. The process took a total of 40 hours up to this point.
The journal was machined with a single point tool, approximately 50 microns (0.002 in.) undersize. Nickel was finally applied at a thickness of 25 microns (0.001 in) to give a harder, anti-galling surface.
Result: 10 years later the bearing was still in use