The term ‘crane modernization and modification’ refers to steps taken to upgrade a port’s cranes to enhance their performance, reliability and safety. It can encompass the alteration of crane dimensions as well as upgrades or replacement of old or worn electrical and mechanical systems. In most instances, this work is performed on quayside gantry cranes (QCs) that perform container or bulk-handling duties, rubber-tyred gantry cranes (RTGs), and rail-mounted gantry cranes (RMGs).
Since the late 1980s, ship sizes have more than doubled, from 4000 – 5000 TEUs to 9000 – 10,000 TEUs and beyond. Yet the time allotted for ship unloading/loading has not increased proportionately.
Older cranes typically exhibit the following limitations:
- Insufficient lift height
- Insufficient outreach
- Outdated drive and control systems
- Slow operating speeds
Thus, crane operators must decide what to do with their panamax cranes.
Essentially, the choices are:
1. Dispose of the old cranes and replace with new cranes
2. Modernize and modify to post-panamax dimensions or customize in accordance with customer needs
In preparing panamax cranes for duty on post-panamax vessels, the following improvements are popular from both an engineering and economic standpoint:
A. Dimensional modifications
1. Height increases that range from 6 to 8 metres
2. Outreach increases of 3 to 7 metres
3. Span change or other changes related to crane relocation
B. Performance improvements
1. Crane drive and control enhancements
2. Increased crane speeds
3. Introduction of crane automation and intelligent systems
4. Resolve issue of lack of spares for older cranes
Dimensional modifications
Increases in height
For QCs, a lift height of 30 to 33 metres is needed to clear the height of containers stacked on the decks of large panamax and post-panamax vessels. Most panamax cranes have lift heights that range from about 22 to 26 metres.
It’s often possible to raise crane height by about 6 metres to achieve the 30 -33 metre target without major changes to the hoist machinery, thus making this a very cost-effective option.
For RTGs, a popular modification is to increase the height of one container – 2.5 metres. For RMGs, it’s quite feasible to increase the height by up to 2 containers – for a full 5 metres of additional lift.
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| RTG modification underway in Dubai |
RTG height-raise project in Panama. Ten RTGs were modified from '1 over 4' to '1 over 5' high |
Increases in outreach
Panamax vessels were limited to a beam width of 32.2 metres, permitting 12 to 13 container rows. Post-panamax ships have 18 container rows. With new ‘super post-panamax’ vessels, 22 rows of containers are anticipated.
In extending the outreach of quayside cranes, extensions of two container rows are often possible without extensive changes to the structures and mechanisms of the cranes. Increases beyond two container rows are also possible, but will depend on technical feasibility and economic considerations.
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| Crane before boom modification |
Newly-fabricated extension |
Extension hoisted place |
Connection process begins |
Case in point :
Penang Port, Malaysia
The port decided to modify and modernize one panamax crane.
Height modification process:
1. Crane structure is jacked 9 metres.
2. Four 8-meter support columns are inserted.
3. Crane is lowered onto the four support columns and welded into place.
4. Total time taken: Two weeks onsite preparation plus five days to execute.
For all modernization and modification work, we follow a rigorous set of procedures:
- A survey of crane structures and mechanisms is performed to assess the integrity of the crane structure and its systems to determine the scope of work involved.
- Using finite element analysis methodology (FEM), a structural analysis is conducted to calculate stress levels and identify areas where stresses will be concentrated due to increased dimensions and wind loads.
- Design the optimum structural modifications. Our process is computer-driven but is augmented by years of ‘real world’ experience. Structural modifications are identified, verified by computer simulation, and blueprints are generated. Throughout, the goal is to ensure low stress levels to minimize structural fatigue and extend the service life of the crane.
- Final blueprints of all items – from leg sections and additional beams to access ladders and walkways – are sent to our fabrication teams. All critical welds undergo Non-Destructive Tests (NDT) such as UT/MPI (Ultrasonic Testing and Magnetic Particle Inspection).
- Activities comply with industry standards such as EN 13001, FEM 1.001, ISO 4301 and BS 2573 for cranes. In practice, we routinely exceed industry standards to provide additional margins of safety, performance, and longevity.
Height and outreach increases may necessitate attendant modifications due to increased hoisting path, higher wind load, etc.
- Rope drums may need to be machined with more grooves or be replaced. Rope reeving system to be checked and modified if needed.
- Wheel loads and stability need to be re-analysed.
- Motor and drive system, gearbox, and brakes are checked for duty ratings and replaced if required.
If additional upgrades are contemplated, such as crane drive and control retrofits and other performance improvements (covered elsewhere), these can be accomplished quickly and cost-effectively if performed concurrently with structural modifications.
Recent extension projects
A. Penang, Malaysia: Boom extension of 4.5 metres on Samsung QC
B. Ensenada, Mexico: Boom extension of 2 metres on two QCs.
C. Tuticorin, India: Boom extension of 3 metres
D. Port Cristobal, Panama: Boom extension of 1.9 metres to QC
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