Tandem Lifting boosting productivity and reducing energy consumption

By Patrick Draper, Ram Spreaders, Special to the AJOT

Energy efficiency is one of the most common phrases used in the container handling industry these days. Mega ships have been built to reduce energy per box but also to help improve carbon footprint with more containers being carried by less journeys. 

The same can be said when we think what happens when the containers arrive at the container terminal. It would seem logical to follow the same idea by a method of moving more containers with fewer journeys when unloading a ship. This too would increase volume and help towards ports or terminals to reduce their carbon footprint by being more energy efficient. 

Tandem Increases Load Rates & Saves Energy 

Single hoist Tandem, capable of lifting two 40 feet containers has been designed to increase port performance with an emphasis on energy reduction as key design criteria. 

A lightweight single hoist tandem system which uses essentially the same crane design can reduce energy at the port significantly more than other green system that just shift the source of emissions. While physics dictates that energy used to move a box can’t change moving of 100 boxes in 50 moves vs. 100 moves will significantly reduce the total energy needed per TEU by reducing trolley moves and reducing moment of inertia per move. 

How Much Energy Does It Save? 

The quick answer is 15%. The example of moving 100 empty containers in 50 moves vs. 100 moves reduces the energy consumption significantly. 

A recent study has shown by comparing the crane’s energy consumption between a single spreader operation and tandem spreader operation; the results are impressive. 

The power consumption of a crane is on average 10.7kW when lifting single 20ft containers. Using a tandem head block that lifts more containers per lift cycle consumes only 5.1kW of power per TEU, as it lifts more containers per lift cycle; saving 5.6kW of power, per container. 

So over the course of a year, a typical 100,000 TEU capacity terminal can save 5,600,000 kW of power using a tandem head block. 

What are the Cost Savings? 

The cost of energy is a significant overhead cost for terminal operators which is generally fixed and with little control over unit costs. Terminals can however take measures to control the amount of energy consumed. Take for example a typical EU tariff cost of 0.16 Euros per kW. A terminal with a capacity of 1 million TEU’s when using a tandem head block, can save Euro €450,000 Euros, compared to using single lift. 

Moving more containers in a lift cycle provides an opportunity for the terminal to increase productivity and increase revenue. By reducing the amount of lift cycles per hour also increases the longevity of the crane and spreaders because they work less for the same TEU output of a standard single lift cycle. 

Ports and terminals are under pressure to reduce their carbon footprint under various regulatory bodies and governmental guidelines. Measures such as better energy efficient lighting, improvements in motor technology, streamlining operations and using lightweight spreaders all contribute towards improving a terminal’s carbon footprint, but the introduction of tandem lifting is showing significant reductions in energy and costs helping terminals towards improvements towards their energy management plans. 

The Innovation Behind Tandem is Achieved at a High Percentage

Producing a machine that helps ports and terminals save time, energy and cost was particularly at the forefront of RAM Spreaders research and development team and the foresight to meet the demands for future port operations. 

Also by understanding the needs of the crane operator, RAM has produced an innovative system that maximises the ability to do tandem moves. 

RAM provide a tandem head block system which allows the crane operator to change from single to twin spreader or vice-versa in less than 2 minutes, without calling on additional ground staff assistance. More importantly, it can handle all the vessel and yard exceptions that would result in a need to change; meaning the crane operator can stay in tandem mode for much longer. 

The innovative docking station supplied with RAM’s tandem head block providing a change-over speed of spreaders in less than 2 minutes, without the assistance of ground personnel increase speed and reduce energy consumption. 

Popularity is Growing 

With more than 80 units of single hoist tandem delivered in the last few years, ports and terminals in Asia, Africa, South East Asia, North Africa, United Kingdom and Dubai, using RAM SingFlex™ tandem head block now have that competitive edge; by increasing their TEU capacity and reducing their carbon footprint by being more energy efficient.