Why do it?
Crane modifications are often required to service larger vessels, increase productivity, allow for a different terminal operation, or reduce maintenance costs.
Modifying existing cranes is quicker and often a more economical alternative than purchasing new cranes.
Modifications to the crane’s geometry allow an existing crane to service larger vessels. The most common geometry modifications are increasing the lift height or increasing the outreach, backreach, or both. Occasionally, taller yard vehicles require more clearance under the portal beam.
Crane upgrades are often implemented in conjunction with relocation to another terminal. When cranes are relocated, they usually need some modifications. Common modifications include strengthening the structure for increased storm winds, adding or strengthening stowage hardware, crane gage changes, and changing the power supply system.
Common quay crane structural modifications
Increase lift height
Cranes are commonly raised about 6 m, but larger raises are also possible. Raises of up to 9 m have been completed. Lift height can be increased by inserting a new section of leg, inserting a sill beam cap, or extending the main equaliser brackets below the sill beam. For raises greater than about 3 m, a leg insert is the most practical raise method.
Figure 1 shows the leg insert crane raise method. The truss work is the temporary lifting frame. Figure 2 shows a sill beam cap and local leg reinforcing. This method raises the crane and provides added strength and stiffness to the O-frame. Figure 3 shows a main equaliser bracket extension. As mentioned above, this is the most economical crane raise method for raises of about 3 m or less.
These methods of crane raises can usually be accomplished relatively quickly and with limited disruption to the terminal operations.
Frequently, it is necessary to strengthen or stiffen the raised frame for lateral loads. The strengthening can be accomplished by the addition of cover plates on the legs, and knee braces between the legs and support beams (see Figure 4).
When a crane’s lift height or outreach is increased, it is necessary to check the main hoist system for its capacity to handle additional hoist rope length. Depending on the size of the existing main hoist rope drum, it may be necessary to extend the grooving or double wrap the hoist rope. Double wrapping the main hoist rope may be problematic and should be avoided.
Elevators, stairs, and platforms will also need to be modified for raised cranes.