Jib Crane Inspection & Maintenance Intervals and Acceptance Standard

GB/T 31052.4-2014 is Part 4 of the GB/T 31052 Inspection and Maintenance Procedure series, specifically covering jib-type cranes. This category includes portal cranes, mast cranes, cantilever cranes, railway cranes, and floating cranes — all crane types that use a boom to achieve luffing and slewing motions. Because jib cranes are equipped with luffing and slewing mechanisms, their inspection priorities and challenges differ significantly from those of overhead type cranes: the luffing rack, slewing bearing, and boom structure demand the closest attention.

Daily Inspection Requirements

The standard specifies that daily inspections of jib cranes are performed by the operator at the start of each shift. Inspection items include: Jib system — visual check of the boom structure for deformation, cracks, or abnormal vibration; condition of the boom connecting pin and cotter pin; free rotation and lubrication of the pulley block at the boom head. Luffing mechanism — surface condition and lubrication of the luffing rack or screw; wire breaks or wear on the luffing wire rope; proper operation of the luffing limit switch; reliability of the luffing brake. Slewing mechanism — abnormal clearance or noise around the slewing bearing; pitting or tooth breakage on the slewing drive gear; proper operation of the slewing limit switch. Hoisting mechanism — proper brake operation; even spooling of the wire rope on the drum; integrity of the hook safety latch. Safety devices — power-on self-check of the load moment limiter (LML) or overload limiter; accuracy of the radius indicator; proper display of the anemometer.

Daily inspection of jib cranes also includes a special item — the condition of the crane rail and foundation (for rail-mounted jib cranes). Check for rail settlement or deformation, loose connection bolts, rail joint gap and misalignment within allowable limits, and the condition of end stops and buffers at both rail ends. For outdoor jib cranes, also verify the operational flexibility of the wind rail clamp or anchor device, and check that the clamping surfaces and anchor pin holes are free of debris. If a Class A nonconformity is found during daily inspection (e.g., a crack in the boom chord member, loss of a critical connecting pin, or failure of the load moment limiter), the crane must be shut down immediately for rectification. Kelude develops daily inspection checklists and provides training for customer equipment in accordance with GB/T 31052.4.

Periodic and Thorough Inspections

Periodic inspections are performed quarterly by maintenance technicians. In addition to all daily inspection items, the following are added: Weld seam inspection of boom chord and web members — inspect critical welds (at the boom root, luffing hinge points, and boom head) using a 5× or higher magnifying glass; if a suspected crack is found, confirm with magnetic particle or dye penetrant inspection. Luffing rack inspection — measure tooth flank wear; if tooth thickness reduction exceeds 10%, evaluate whether replacement is needed; measure the backlash between the rack and pinion; check wear on the rack guide rails and sliders. Slewing bearing inspection — measure axial clearance with a feeler gauge or dial indicator and compare with factory data; torque-check connection bolts (sampling rate no less than 20%). Full-length wire rope inspection — disconnect the rope end fittings to inspect the full length, focusing on rope core condition and internal corrosion, at least once per quarter. Accuracy calibration of overload limiter and load moment limiter — calibrate accuracy at typical working radii using standard weights; error must not exceed ±5%.

Thorough inspections are performed annually by equipment engineers or accredited inspection agencies. In addition to all periodic inspection items, the following are added: Full non-destructive testing of the metal structure — perform ultrasonic testing (UT) on critical welds (boom root, luffing hinge points, slewing platform, main girder, portal legs) with a sampling rate of no less than 30%. Load test — at maximum radius and an intermediate radius, lift the rated load and 1.1 times the rated load through a full operating cycle. Static load test — hold 1.25 times the rated load at maximum radius for 10 minutes. Anti-overturning stability verification — verify overall stability through comparative verification of calculations and field measurements. Comprehensive electrical system inspection — verify insulation resistance, grounding resistance, and each protective function individually. Full calibration of safety devices — calibrate and functionally verify all limit switches, overload limiter, load moment limiter, anemometer, and emergency stop button. Inspection reports must be kept in archival storage until the crane is scrapped.

Special Inspections for Specific Jib Crane Types

The standard adds special inspection requirements tailored to the characteristics of different jib crane types. For portal cranes, the gantry structure—specifically the weld seams at the connections between the portal legs and the lower cross beams—requires particular attention, as these joints are the most susceptible to fatigue cracking in the crane's metal structure. Ultrasonic Testing (UT) must be performed at these locations during every thorough examination. For mast cranes, the guy rope system demands focused inspection: the tension of each guy rope must be measured and logged, the tightness of wire rope clips and turnbuckles verified, and any displacement or settlement of ground anchor foundations checked. Floating cranes require inspection of the pontoon's watertight integrity and ballast system, the connection structure between the crane and the pontoon, and the effect of wave action on overall stability. For cantilever cranes, the torque values of the connection bolts between the column and the boom, as well as the boom's side bow and deflection, must be verified. The inspection frequency and methods for each crane type are detailed in the standard's annexes; inspectors should develop targeted inspection plans based on actual site conditions.

Inspection Records and Reporting Requirements

The standard sets forth standardized requirements for inspection records and reports for jib cranes. Daily inspection results are recorded in the equipment operation log and must be retained for at least one year. Periodic inspections and thorough examinations require formal inspection reports, which are filed in the equipment's technical documentation and retained until the crane is scrapped. Each inspection report must include: basic equipment information (model, serial number, years in service, cumulative operating hours), a detailed results table for each inspection item with the assessment conclusion (pass / fail / needs follow-up), a description of any issues found and corrective actions taken, items requiring special attention during the next inspection, and the inspector's signature. The report must also document the closed-loop status of rectification measures identified during the previous inspection. For Class A nonconformities—defects that pose an immediate safety risk, such as cracks in the boom's main chord members or failure of the load moment limiter—the inspection report must be submitted immediately to the equipment management department along with a stop-work rectification notice. Class B nonconformities must be noted in the report with a rectification deadline, and equipment management personnel are responsible for tracking follow-through.

Jib Crane Inspection Interval Comparison Table

The comparison table below outlines the core parameters and configurations for jib crane inspection intervals, for reference by selection and operation personnel.

Frequently Asked Questions