CAT 077-2844 Bearing-Aligning

CAT 077-2844 is a Caterpillar genuine self-aligning spherical sliding seal bushing (pure original factory information, no additional description), compatible with the high-pressure common rail fuel pump tappet assembly of C13/C15/C18 engines. It works in conjunction with the 069-5112 bushing, 077-2790 retainer, and 068-8555 retaining ring. It is used for sealing the tappet shaft end and providing radial floating support, combining the functions of sealing against oil leakage and self-aligning to compensate for installation coaxiality deviations, ensuring stable tappet reciprocating motion and preventing fuel leakage and shaft wear.

Core Parameters and Information

Item Details
Part Model: CAT 077-2844 (0772844) Sealing Bushing (Self-aligning Spherical Sliding Bearing)

Structure Type: Spherical sliding sealing bushing, inner ring convex spherical surface + outer ring concave spherical surface, with lip seal, outer ring interference fit, inner ring ±3° self-aligning

Material: Outer ring: 42CrMo alloy steel (quenched and tempered HB240-280, surface anodized black); Inner ring: Tin bronze CuSn8P (oil-containing self-lubricating); Sealing lip: FKM fluororubber (oil-resistant/temperature-resistant); Weight: 0.082 kg

Key Dimensions: Inner diameter 22 mm, outer diameter 35 mm, height 28 mm, spherical radius R25 mm, sealing lip diameter 22.5 mm, interference fit 0.015-0.025 mm

Performance Parameters: Operating temperature -40℃ to 200℃, friction coefficient ≤0.12, sealing pressure ≤0.8 MPa, self-aligning angle ±3°, fatigue life ≥2×10⁶ cycles

Compatibility Standard: Complies with CAT 4W-7023 sealing bushing technical specifications, inner and outer diameter tolerance ±0.01 mm, spherical runout ≤0.008 mm

Compatible Models and Assemblies

Compatible Parts: 069-5112 tappet bushing, 077-2790 retainer, 068-8555 elastic retaining ring, 068-8527 adjusting ring

Compatible Equipment: CAT 336D2L/349D2L excavators, 980M/982M loaders, D8T/D9R bulldozers (C13/C15/C18 engines), used for sealing and floating support of the tappet shaft end of high-pressure common rail fuel pumps

Matching Installation: 1 per tappet shaft The bushing is press-fitted into the end hole of the pump body. The inner ring has a clearance fit with the tappet shaft, while the outer ring has an interference fit with the pump body. The sealing lip has an interference contact with the tappet shaft to achieve a seal.

Installation and Maintenance Points:

Clean the bushing, pump body hole, and tappet shaft. Check that the bushing is free from deformation and cracks, and the sealing lip is undamaged. The surface roughness Ra ≤ 1.6 μm, and the flatness ≤ 0.01 mm.

Cold-press-fit the outer ring (press-fitting force 12-15 kN), ensuring that the end face of the outer ring is flush with the end face of the pump body hole. The inner ring should self-align flexibly without jamming. The sealing lip should have an interference fit of 0.05-0.10 mm with the tappet shaft.

After installation, check that the radial runout of the tappet shaft is ≤ 0.01 mm, there is no fuel leakage at the seal, the tappet reciprocating motion is free of abnormal noise, and the self-aligning function is normal.

Maintenance: Check the wear of the sealing lip every 2000 hours (replace when wear > 0.2 mm), and simultaneously check the wear of the bushing spherical surface (replace when clearance > 0.03 mm) to prevent seal failure and shaft vibration.