Tower Crane Inspection Intervals per GB/T 31052.2-2014

GB/T 31052.2-2014 is Part 2 of the GB/T 31052 series on inspection and maintenance procedures for lifting appliances, focusing specifically on tower cranes. Due to their tall structures, demanding working environments, and frequent erection and dismantling, tower cranes present significantly higher safety risks than overhead type cranes, making a more rigorous inspection and maintenance regime essential. Applicable to all types of tower cranes, this standard serves as a key reference for on-site crane safety management. Kelude Heavy Industry provides tower crane inspection and maintenance services in accordance with this standard, covering everything from routine inspection to comprehensive inspection.

Daily Inspection Checklist for Tower Cranes

The standard specifies that daily inspections (per shift) must be carried out by the operator before start-up. Inspection items include: Foundation and base frame — check for settlement or cracking in the concrete foundation, loose connection bolts between the base frame and foundation, and proper grounding. Tower mast standard sections — check for loose connection bolts or pins between mast sections, and verify that the verticality deviation is within the permissible range (no more than 4/1000 of the tower height in free-standing condition). Slewing mechanism — check for loose slewing bearing connection bolts, abnormal noise or oil leaks in the slewing drive unit, and proper operation of the slewing limit switch. Hoisting mechanism — verify that the brake operates smoothly, the wire rope is spooled evenly on the drum, the lifting height limit switch is functional, and the hook safety latch is intact.

Luffing mechanism — check that the trolley travels smoothly, the luffing wire rope is properly tensioned, and both the luffing limit switch and radius limit switch operate reliably. Electrical system — inspect cables for damage or aging, verify that all control grips and buttons function correctly, and confirm the emergency stop button is reliable. Safety devices — ensure the overload limiter (load moment limiter) passes its power-on self-check, the anemometer reading is correct, and the contacts of all limit switches are free from sticking. If a Class A nonconformity is found during daily inspection (a defect that directly compromises safety, such as loose tower mast connection bolts), the crane must be shut down immediately for corrective action and must not be operated with the defect present. Daily inspection results should be recorded in the operation log, and any issues found should be promptly reported to equipment management for maintenance scheduling.

Periodic and Comprehensive Inspection Requirements

Periodic inspections are performed monthly by maintenance personnel. In addition to all daily inspection items, these inspections must also cover: Visual inspection of welds on tower mast standard sections — focus on the weld seams between the main chord members and web members for cracks, using a magnifying glass of at least 5× magnification. Inspection of the slewing bearing gear mesh clearance — backlash must not exceed the specified value, and the tooth surfaces should be checked for pitting or spalling. Measurement of brake shoe wear on all mechanisms — shoes worn beyond 50% of their original thickness must be replaced. Full-length wire rope inspection — check for broken wires, wear, corrosion, or deformation; replace the rope if the number of broken wires within one lay length exceeds 10% of the total wire count. Insulation resistance test of the electrical system — the insulation resistance between the main circuit and ground must not be less than 1MΩ. Pulley block inspection — replace any pulley where the rope groove wear depth exceeds 25% of the wire rope diameter.

Comprehensive inspections are conducted annually by equipment engineers or accredited third-party inspection organizations. In addition to all periodic inspection items, comprehensive inspections include: Precise measurement of tower mast verticality — using a theodolite or total station to measure verticality deviation in four directions of the tower mast. Non-destructive testing of the metal structure — ultrasonic testing (UT) is performed on a sampling basis on weld seams of critical load-bearing components such as the main chord members, slewing turret, tower head, jib, and balance arm, with a sampling rate of no less than 20%. Load test — dynamic load test at rated load and 1.1 times rated load, and static load test at 1.25 times rated load, measuring structural deformation and brake slip distance of each mechanism. Full calibration of safety devices — accuracy calibration of the overload limiter, load moment limiter, and all limit switches to ensure their trip points remain within the permissible deviation range.

Anchorage Device and Jacking System Inspection

The anchorage device and jacking system of a tower crane are critical inspection items that distinguish it from other crane types. The standard specifies that the anchorage device must be inspected monthly—checking the connection bolts or pins between the anchorage frame and the tower mast for looseness, verifying that the embedded parts or through-wall bolts at the building connection points are secure, and inspecting the tie-in struts for bending, deformation, or weld cracking. The building structure at the anchorage points must be capable of withstanding the required adhesion forces, and the user unit should confirm this through calculation in the anchorage plan. The length-adjusting screws on the tie-in struts should be locked to prevent loosening, and the threaded portions should be coated with grease to prevent corrosion. A thorough examination of the anchorage device must be conducted quarterly—inspecting all weld seams (including the connection welds between the anchorage frame and tie-in struts, as well as the splice welds on the struts themselves) for cracks, with flaw detection sampling performed where necessary.

Inspection and maintenance of the jacking system directly affect the safety of tower crane erection and dismantling operations. The standard requires a thorough examination of the jacking system before every erection operation: checking the hydraulic pump station for proper oil level and quality, inspecting hydraulic oil lines and joints for leaks, examining the piston rod of the jacking cylinder for scratches or corrosion, verifying the reliability of pin connections on the jacking cross beam and climbing pawls, and inspecting the welds between the jacking steps and the tower main chord for cracks. The safety lock (hydraulic lock valve) on the jacking cylinder must automatically lock the cylinder in the event of a hydraulic line burst to prevent the tower mast from falling. Jacking operations must be directed by a designated person, and erection is prohibited when the on-site wind speed exceeds Beaufort scale 4. After jacking is completed, the tightening of connection bolts between the new mast section and adjacent sections, as well as the perpendicularity of the tower mast, should be verified.

Tower Crane Inspection Item Comparison Table

The comparison table below summarizes the inspection intervals, executors, and main inspection items across the three-tier inspection system for tower cranes. Equipment managers can use this table to develop their inspection schedules.

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