Multiple crane lifting—also known as tandem lifting or dual crane lifting—is a high-risk lifting operation that involves using two or more cranes simultaneously to lift a single load. This method is typically employed when lifting an oversized, long, or heavy load that exceeds the capacity or stability limits of a single crane. While necessary in specific engineering scenarios, multiple crane lifting introduces complex challenges related to load distribution, synchronization, structural coordination, and safety. In Hong Kong, such operations are subject to stringent control measures under the *Factories and Industrial Undertakings (Lifting Appliances and Lifting Gear) Regulations (Cap. 59J)*, the *Code of Practice for Safe Use of Tower Cranes*, and the *CIC Guidelines on Safety of Tower Cranes*.
The first and foremost requirement for multiple crane lifts is meticulous planning. According to Section 11 of the *Code of Practice*, tandem lifts must be authorized by a competent person and based on a method statement and risk assessment that specifically address the use of multiple cranes. The lifting plan must detail the roles of each crane, the sequence of operations, lifting points, load center of gravity, communication protocol, and emergency procedures. The plan should be approved by the supervising engineer and reviewed with all involved personnel in a pre-lift briefing.
Load distribution is the most technically sensitive aspect of a multiple crane lift. The load must be shared between the cranes in such a way that each crane operates within its rated capacity throughout the entire lift. This requires precise calculations involving not only the static weight of the load but also dynamic factors such as load sway, slight misalignment, ground conditions, and wind. The lifting gear must be identical or properly matched, and the rigging configuration must be symmetrical. The *CIC Guidelines* recommend using load cells or equalizer beams to monitor and balance the load in real time, minimizing the risk of overload on any one crane.
Synchronization between cranes is another critical concern. When two cranes hoist a load together, even a small difference in speed or timing can cause one crane to bear more than its share of the load. This can result in mechanical strain, tipping, or failure of one or both cranes. To prevent this, both cranes should ideally be operated by experienced operators trained specifically in tandem lifts. Operators must maintain constant radio communication with each other and the lifting supervisor, and hand signals should be standardized and clearly understood. In certain cases, crane movement may be controlled by a single point of command through synchronized control systems, though this depends on the crane models and site conditions.
Site conditions must be carefully assessed before conducting a multiple crane lift. Cranes should be positioned on level, compacted, and load-bearing ground, with adequate clearance for jib rotation and counterweight swing. The exclusion zone around the lift should be expanded to account for the larger operational footprint and increased risk. According to the *Code of Practice*, operations must be halted during adverse weather, and anemometers should be installed to monitor real-time wind conditions. High wind loads on extended or irregularly shaped loads can cause torsional forces, increasing instability.
Regulatory compliance is essential for multiple crane lifting. Regulation 2.3.16 of the *FIU LALG* prohibits the use of lifting appliances beyond their rated capacities. In a tandem lift, even if each crane is within its limit, incorrect load sharing could inadvertently cause overload. Therefore, the lifting plan must include engineered calculations verified by a competent examiner or structural engineer. The entire operation must be supervised by a competent person with experience in complex lifting, and certification for each crane involved must be up to date, including Safe Load Indicator (SLI) functionality and maintenance logs.
Special attention must also be given to the lifting gear used in tandem lifts. All slings, shackles, hooks, and spreader beams must be thoroughly examined and certified in accordance with FIU LALG Regulation 6. The use of non-matching gear or uncertified equipment significantly increases the risk of imbalance or failure. The lifting supervisor must confirm that all gear has valid inspection certificates and safe working load markings that are appropriate for the shared load conditions.
Documentation and traceability are required throughout the planning and execution process. A written record of the lifting plan, risk assessment, crane capacity calculations, communication protocol, operator qualifications, and post-lift inspection must be compiled and kept on-site. In the event of a Labour Department inspection or incident investigation, these documents serve as proof of due diligence and compliance. The *CIC Guidelines* recommend photographing the setup and monitoring key data points such as load distribution and crane movement to support review and learning.
After the lift, a debriefing should be conducted with the lifting team to review performance, note any deviations from the plan, and document lessons learned. If any part of the lift revealed unanticipated stress or instability, the lifting supervisor must initiate further inspections of the cranes and gear before resuming standard operations. According to the *Code of Practice*, post-lift inspections are especially important when the operation involves near-limit loading or unique rigging setups.
In summary, multiple crane lifting is a high-risk but sometimes necessary operation that requires specialized planning, precise coordination, and full regulatory compliance. The responsibilities span across engineers, competent persons, crane operators, riggers, and site supervisors, each playing a critical role in ensuring the lift is conducted safely and efficiently. By strictly adhering to the requirements of the *FIU LALG*, supported by the guidance of the *Code of Practice for Safe Use of Tower Cranes* and the *CIC Guidelines*, construction teams can execute tandem lifts with a high degree of safety, reliability, and professionalism.
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