SPACER 7T4809 - Caterpillar

Blast Preparation
Caterpillar recommends the use of a siphon (gravity) fed blasting machine or a pressure blasting machine system with the following specifications:
Air pressure regulated to 552 kPa (80 psi) to 621 kPa (90 psi).Note: During the blasting process the air pressure must hold to 552 kPa (80 psi) to 621 kPa (90 psi). If not, a larger air supply must be used. 25-30 cubic feet per minute of air is recommended. Dry air is required to operate a blasting system that contains Aluminum Oxide.
127 mm (5/32 inch) tungsten carbide blasting tip.
Recommended blasting media is 14-16 grit Aluminum Oxide.
Blasting cabinet that accommodates all sizes of inverted style shafts.
Illustration 5 g02339469Sand Blast Procedure
Protect the shaft
Cover the stopper hole and both oil cross-holes with duct tape to prevent dust and blasting media from contaminating the oil cavity.
Illustration 6 g02339484
Tape over cross hole and stopper hole
Slide the recommended sleeves (refer to Tables 2 and 3) over the bearing surface and the mounting diameter of the shaft to protect the shaft from blasting tip overspray.
Illustration 7 g02339498
Protective sleeves
Illustration 8 g02339509
Installation of protective sleeves
Blasting
Place the shaft on the rolling device (refer to Table 4) inside the blasting cabinet and confirm that the shaft will roll without interference.
Illustration 9 g02339538
Smoothly roll shaft
Set the air pressure to 552 kPa (80 psi) to 621 kPa (90 psi).
Illustration 10 g02339556
Regulator at 85 psi
Use 14 - 16 grit size Aluminum Oxide.
Ensure that the feed line is outfitted with 127 mm (5/32 inch) tungsten carbide blasting tip.
Ensure that the Aluminum Oxide and the blasting tip retain original diameters. Aluminum Oxide breaks down with use and must remain a constant 14 - 16 grit size in order to gain proper surface finish. Over time, the blasting tip will wear and become larger causing lower velocity of blasting particles and a drop in air pressure.
With all safety devices in place, hold the blasting tip above the ramp area 25.4 12.7 mm (1 0.5 inch).
Begin blasting perpendicular to the ramp surface while rotating the shaft using fluid motions for 1.5 minutes (5 to 7 revolutions). A uniform surface roughness should be observed.
Illustration 11 g02339598
Blasting tip 1 inch perpendicular to ramp area
Although protective covers are in place on the shaft, concentrate the blast spray on the exposed seal ramp area only. Blasting the protective covering will cause deterioration of the cover. Deterioration of the cover may lead to damage of the thrust face and bearing surface finish, in which case the shaft cannot be reused.
Clean up, Final Inspection, Validate Surface Finish
Remove the shaft from the blast cabinet.
Inspect the bearing surface and thrust face for blast pitting after the protective sleeves have been removed.
Illustration 12 g02339617
Smooth bearing and thrust surfaces
Peel the tape away from the cross-hole and stopper hole.
Validate the surface roughness of the seal ramp area using a profilometer (roughness indicator). The Roughness Average (Ra) value of the seal ramp area should be 5.00 - 8.75 µm (197 - 345) µin. A cut-off length of 0.8 mm (0.03 inch) should be used.
Illustration 13 g02339658
Profilometer on seal ramp area
Clean the shaft thoroughly