In reality, it’s obviously more complicated, with surveys, structural analyses, finite element modelling and blueprinting leading to compliance with a range of EN and BS standards.

And it gets more complex still when the cranes have to be moved, in spite of which demand for relocation services and associated engineering expertise is increasing, driven by increasing ship sizes and the demand for higher productivity, according to Larry Lam Choon Seng, chairman and managing director of Singapore-based Portek.

His company specialises in port engineering, as well as operating five container ports of its own, with a combined throughput of 680,000 teu last year.

With crane movements in double figures last year, and destinations as diverse as Algeria, Mexico, Cristobal, Valencia and Vietnam, the company has the relocation process down to a fine art. They suggest seven discrete steps:

1) Survey crane structure, loading and discharge locations

2) Select vessel; determine best load and unload methods

3) Complete finite element analysis of crane structure and bracing

4) Design stowage plan

5) Strengthen crane structure, lashing, loading and sea-fastening

6) Sea voyage

7) Unlash, discharge, and re-commission crane Ship selection also needs careful consideration. For sea journeys there are four options. Firstly, there is the tug and barge combination, which gives a large cargo area, is relatively economical, but comparatively slow. Second, consider using a forklift vessel offering fast quayside gantry crane load and unload, but with low vessel availability.

Or thirdly, employ a semi-submersible self-propelled vessel offering fast lift or skid on and off, high cruising speed, but also with low availability. Lastly, there is the option of hiring a ship with onboard heavy lift cranes, which can load or unload anywhere, but once again there is a relatively scant selection.

Selecting the right one involves factoring in vessel availability, time available, distance to be travelled, restrictions at ports at both ends of the journey, crane dimensions, and expected weather en route.

The relocation offers opportunities to complete associated work, like span and height changes, conversion to alternative power supplies, and control and operating system upgrades to build in more speed and efficiency.

Span change can become a factor for rail-mounted cranes, when the destination port has a different rail gauge. Depending on the degree of difference and the individual crane’s geometry, some modification might be necessary, such as lengthening and reinforcing the portal beams, re-positioning the land-side legs, adding to leg sections, or adding triangular trusses to enlarge the portal for cranes with a larger span.

Furthermore, it might be necessary to fit new wheels, or machine the existing ones to a new profile to suit the rails at the new location, and fit supplementary wheels.

If a crane is being relocated, chances are it’s of an older design, and has outdated drives and controls, so it is always worth considering what benefits might accrue from incorporating enhancements. Upgrades to any crane’s drive and control systems are a key route to performance enhancement, with accelerated cycle times adding significantly to its moves per year.

Drive and control refits should be considered because the systems are getting old – after a decade or more, parts may be out of production, and therefore hard or impossible to find. Reliability starts to be an issue towards the end of a system’s service life, as breakdowns become more common, and with them a decline in productivity. Or it might be that there’s a need for higher performance – larger vessels without proportionally-longer time available again. A new digital drive can incorporate productivity tools such as management systems and automation features.

Speed increases can come from increased drum size, fitting a higher-ratio gearbox, on increasing motor speed. Portek cites the example of two rubber-tyred gantry (RTG) cranes in Penang, where a study and subsequent enhancement yielded a 33% increase in hoist speed for rated load and empty spreader alike.

And there are significant software options that can be added as part of the enhancement and relocation package, capable of tracking containers, auto-steering of RTGs, crane diagnostic software which monitors crane activity and conducts troubleshooting and problem identification in real time, and even laser collision avoidance software that continuously detects and calculates the speed of moving and fixed objects in the yard, and reduces the change of them coming together unexpectedly.