Boom Crane Slewing Bearing Inspection per GB/T 31052.12-2017
GB/T 31052.12-2017, "Cranes — Inspection and Maintenance — Part 12: Jib Cranes," is the dedicated standard governing the inspection and maintenance of jib-type cranes. It specifies the daily inspection, periodic inspection, and maintenance requirements for portal cranes, mast cranes, floating cranes, and deck cranes during service.
GB/T 31052.12-2017 is Part 12 of the crane inspection and maintenance standard series, specifically addressing the inspection and maintenance requirements for the structural components and slewing bearings of jib cranes. The slewing bearing and boom structure are critical load-bearing elements of a jib crane. This article provides an interpretation of the standard's core requirements.
Standard Scope and Inspection Framework
GB/T 31052.12-2017 is the 12th part of the GB/T 31052 series, dedicated to the inspection and maintenance of jib-type cranes, including portal, mast, floating, and deck cranes. Compared to other crane types, jib cranes feature more complex structures, a greater number of mechanisms, and more diverse working environments—ranging from docks and vessels to construction sites. Consequently, inspection and maintenance cycles vary significantly based on operating conditions and usage intensity. The standard establishes a four-tier inspection and maintenance system: daily inspection (each shift), first-level maintenance (monthly), second-level maintenance (quarterly), and annual comprehensive inspection. Each tier specifies detailed inspection items, methods, and acceptance criteria.
Daily Inspection Checklist
Before each shift, the following checks must be performed: Crane rail and foundation (for portal cranes)—verify the rail is free of obstructions, the track gauge is correct, buffer stops are secure, and rail clamps are in the open position. Boom—visually inspect the boom structure for deformation and cracks, ensure the boom connecting pins show no axial movement, and confirm the wire rope is properly seated in the pulley grooves. Hoisting mechanism—verify brake functionality (lift the hook 100 mm off the ground to confirm no load slipping), check that the wire rope is spooled evenly, and ensure at least 3 safety wraps remain on the drum. Slewing mechanism—confirm smooth slewing without binding or hesitation and that the slewing brake operates correctly. Safety devices—perform a self-check of the load moment limiter (LML), functional test all limit switches, and verify the anemometer reading is normal. For floating cranes, additionally check that the vessel's inclination angle does not exceed 5° and that the ballast water system is functioning properly.
Main Structural Component Inspection
The structural components of jib cranes are subjected to alternating loads and are prone to fatigue cracks. Key inspection focus areas include: Boom—use visual inspection and Magnetic Particle Inspection (MPI) to examine the boom root, gusset plate weld seams, luffing pulley support welds, and tie bar connections. Portal base (for portal cranes)—inspect the weld seams connecting the cross beams to the outriggers, with particular attention to the welds on both sides of the portal opening, where stiffness is lower and stress concentration is more pronounced. Slewing platform—inspect the welds and base plates at the hinge point between the slewing platform and the boom. Mast crane—check the straightness of the mast's main chord members (section axis deviation ≤ L/1000) and inspect the guy rope ground anchor connections for wear and corrosion. Floating crane—inspect the vessel structure, particularly the reinforced deck area in the lifting zone, for deformation and weld integrity.
Special Inspections for Floating Cranes
Floating cranes require additional inspections beyond those for land-based units: Hull watertightness—verify that the liquid level alarm devices in all watertight compartments are functioning correctly. Ballast system—confirm that ballast pumps and valves operate smoothly and that piping shows no signs of leakage. Hull corrosion protection—check that the anti-corrosion system for the submerged portion of the hull (sacrificial anodes or impressed current) is operational. Mooring system—inspect the windlass, anchor chain, and bollards for wear. Floating cranes must be dry-docked annually to inspect the underwater hull, including measuring bottom plate corrosion thickness and performing weld repairs as needed.
Jib Crane Structural Component Inspection Reference Table
The following reference table outlines the core parameters for structural component inspection of jib cranes, intended as a guide for selection and operational personnel.
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| inspection item | inspection content | inspection interval | Acceptance Criteria |
|---|---|---|---|
| boom structure | Weld Seam/Deformation/Crack | Monthly | None Crack/Deformation Measure< L/1000 |
| Slewing Bearing | Gear Wear/Bolt Looseness | Quarterly | Tooth Thickness Reduction<10% |
| Connectionpin | Wear/Corrosion/Clearance | Semi-annually | Clearance≤0.5mm |
| Wire Rope | wire break/Wear/Lubrication | Before Each Shift | Per GB/T 5972Standard |
FAQ
• Monthly — Measure radial and axial clearance of the slewing bearing using a dial indicator. Clearance exceeding 0.5 mm warrants attention.
• Semi-annually — Check and re-torque the slewing bearing connection bolts. Sample at least 20% of bolts and verify torque is at or above 90% of the specified value.
• Annually — Perform grease analysis to check for metal particles in the raceway lubricant.
