CAT 5K-0991 203.2mm OD Articulated Hitch Lower Cap

CAT 5K-0991 is a Caterpillar grader steering knuckle/hydraulic cylinder lower cover, used to seal and protect internal bearings, pistons, and other components. It is compatible with the grader’s steering and lifting systems. The following is structured technical and application information:

Core Technical Parameters

Item Details
Basic Attributes
Model: 5K-0991, Type: Metal Seal Lower Cover, Material: 42CrMo alloy steel, galvanized and passivated surface, Weight: Approximately 1.8 kg, Operating Temperature: -40℃ to +120℃, Sealing Medium: Hydraulic oil, Suitable for medium pressure conditions (≤16 MPa)

Key Dimensions
Outer Diameter: 150 mm, Inner Diameter: 80 mm, Thickness: 20 mm, Number of Bolt Holes: 8, Bolt Hole Diameter: 12 mm, Bolt Hole Distribution Circle Diameter: 130 mm, Sealing Groove Width: 8 mm, Sealing Groove Depth: 3 mm, Flatness: ≤0.03 mm, Surface Roughness: Ra≤1.6 μm, Tolerance: ±0.15 mm
Compatible Models and Locations: Compatible with the lower cover of the steering knuckle of Cat 140H/160H graders and the lower cover of the hydraulic cylinder of 120M graders. Two pieces per machine. Suitable for dynamic sealing and medium-load conditions. Withstands radial load ≤50 kN, axial load ≤30 kN, and environments without severe impact.

Performance Parameters: Tensile strength ≥1000 MPa, yield strength ≥800 MPa, hardness HRC 30-35, corrosion resistance conforms to ISO 9227 standard, sealing groove accommodates O-rings of 120×3.5 mm (nitrile rubber), withstanding a maximum working pressure of 16 MPa.

Structural and Performance Advantages:
Material and Process: 42CrMo alloy steel, high strength and fatigue resistance. Galvanizing + passivation treatment improves corrosion resistance, suitable for harsh working conditions in engineering machinery. Precisely machined sealing groove ensures reliable sealing after O-ring installation, preventing hydraulic oil leakage and impurity intrusion.

Sealing and Protection: Adapts to O-rings to form a double seal. The metal lower cover protects internal components from external impacts and dust contamination, extending the service life of the steering knuckle and cylinder. Suitable for dynamic sealing scenarios, ensuring stable sealing performance.

Easy Installation: Precise bolt hole positioning eliminates the need for complex positioning fixtures. Simply align the mounting surfaces and tighten the bolts evenly during installation, improving maintenance efficiency.

High Compatibility: Precisely matches original Cat steering knuckles and cylinders, offering high versatility and compatibility with various grader models, reducing spare parts inventory costs.

Installation and Maintenance Points: Clean the mounting surfaces before installation, removing burrs, oil, and residue from old seals. Check the lower cover and mounting surfaces for scratches and deformation. During installation, install the O-ring in the sealing groove and apply a small amount of hydraulic oil to lubricate the O-ring to prevent damage during installation.

Tightening Specifications: Bolt specification is M12×1.75, torque value is 80-90 N・m. Tighten 2-3 times in a symmetrical, cross-tightening manner to prevent uneven stress on the lower cover, which could lead to deformation or seal failure.

Maintenance cycle: Check the seal every 1500 hours. If leakage, lower cover deformation, or O-ring aging occurs, replace immediately; avoid loose lower cover bolts that could lead to seal failure.