Co-lifting: when two cranes lift the same load

Some loads are too long, too heavy or too skewed for a single crane to lift them alone and keep them stable. The solution can be tandem lifting – two (or more) cranes or winches lift and move the same load at the same time. It sounds like a simple extension of a normal lift, but the Labour Authority's guidance on tandem lifting with cranes describes it as an exercise with markedly tightened requirements because the risk of the cranes pulling against each other or loading the load unevenly is real.

§When is tandem lifting used

Co-lifting is typically used for long elements such as bridge elements, masts, large machinery parts or steel structures where the centre of gravity is far from both ends, or where the load's own weight exceeds what a single crane on site can handle. You don't choose co-lifting because it's easy — it's used when it's necessary and because it makes significantly greater demands on planning than an ordinary single lift.

§Planning and operation

A combined lift must only be performed after thorough planning and under the leadership and control of a designated expert. Everyone involved — crane operators slingers and others involved — must be carefully instructed in how this particular lift is to proceed who leads it and what is done if something deviates from the plan.

§Weight distribution must be calculated — not estimated

The weight distribution for each crane or hoist for the lift and transport must be calculated in advance. It is not enough to estimate how much of the load each crane bears — the calculation must be ready before the lift begins, and it is checked against the 75 percent limit each crane must comply with.

§The cranes should match

The requirements that make care safe and dignified

§Special rigging: yoke

For combined lifting, if necessary, special lift gear must be constructed such as a spreader bar or similar which is arranged so the weight is distributed correctly and so only a vertical lift of the load occurs with each crane throughout the process. Standard lift gear designed for a single lift cannot be reused for this task without further work because the requirements for distribution and vertical pull are stricter.

§Certificate and communication throughout the lift

Co-lifting may only be performed by certified crane operators and communication between the involved crane operators and the competent leader must be agreed and stable throughout — typically via radio where everyone hears the same commands simultaneously. If communication is lost or doubt arises about how the load is hanging, lifting is halted until conditions are clarified.