The productivity paradigm

In these times of reduced capital expenditure, terminal operators need to make the most of their existing equipment. But if your portfolio of equipment includes mobile harbour cranes (MHCs), can they really compete with gantry cranes, for instance, and can anything be done to increase their productivity?

MHCs were originally developed for different kinds of applications than quayside gantry cranes but as MHCs have developed over the last couple of decades, their efficiencies have increased.

Although MHCs do not always beat gantry cranes on handling rates in all types of operation, they may offer other benefits, such as lower cost, operational flexibility and the ability to handle multiple types of cargo, argues Peter Klein, marketing manager at MHC manufacturer Gottwald.

There are also differing opinions about the productivity that can be achieved with MHCs. Some anecdotal evidence suggests that MHCs can be as productive as gantry cranes. One former terminal executive, for instance, points out that there are stevedores in Rotterdam that can consistently do 30-33 moves per hour on ships ranging from 2,000teu to 4,500teu using MHCs, whereas some US terminals can manage only 24-26 moves per hour with quayside gantry cranes.

There are also claims that the difference depends on vessel size and that MHCs can outperform gantry cranes on small ships. "As vessels have got bigger and the outreach has increased, operating from a MHC cabin has become less efficient overall," says the same source. "Of course, with MHCs, operator competency and shoreside management have a greater impact on productivity than in a conventional STS operation," he adds.

Most comparisons of gross moves per hour in the same operational conditions suggest MHCs are less productive than gantry cranes. "My experience of working with these terminals tells me that MHCs produce 15-20% less than that of gantry cranes," says Rakesh Patel, senior officer at DP WorldÕs Nhava Sheva International Container Terminal in Mumbai.

Apart from outreach, there are many other factors [to consider] like the MHC can work with small parcel vessels, has restrictions with tides, limitations with the spreader and SWL.

"It can be useful at small sized ports where there is no competitor and where volumes are low. All these limitations of MHCs are overcome by gantry cranes and hence they give more productivity."

Captain Adeeb Sartawi, chief commercial officer at Aqaba Container Terminal in Jordan, says: "All modern terminals now are using STS gantry cranes due to the advantages of better and faster reach across container ships, better visibility and control for the driver, and thus higher productivity.

"In my experience the MHC average production is around 20 moves per hour. In my last terminal, RAK in the UAE, the terminal achieved 35-plus moves per hour using single lift STS gantry cranes. In general we use 30 moves per hour as an average good productivity rate for STS gantry cranes which is widely accepted by major global container carriers."

Klein says: "In container handling, [MHC productivity is] 25 boxes per hour on average. We are told by customers that experienced crane drivers have managed to handle more than 40 containers an hour, depending on site and operation conditions.

"Bulk handling is a quite good example for MHC development. Back in the 1980s, Gottwald built the first ever four-rope MHC with two hoists based on the conventional two-rope versions invented in 1956. Today, we offer not only MHCs but also portal harbour cranes and floating cranes based on MHC technology.

"With all three types of cranes, operators achieve up to 1,800 tonnes per hour, depending on site and operation conditions. The average through-the-ship rate can be calculated with over 1,100 tph as a rule of thumb. It goes without saying that handling rates are dependent on a range of conditions, such as hoisting height, slewing angle, and landside infrastructure."

Scott Schoenfeld, an executive responsible for ports mergers and acquisitions at SteelRiver Infrastructure, has worked in two ports that utilise both MHC and STS cranes. "In both cases the production for STS gantry cranes was much higher, 30%-plus," he says.

But he says that MHCs have merits including: "speed of deployment adding capacity quickly without major civil works; lower cost; compatibility with multi-use facilities allowing project or heavy lift capacity; ability to cover multiple quays or finger piers; and relative ease of training."

He says that there are drawbacks such as: "lower productivity; the need generally to have more than an eight bays separation Ð both for traffic and boom swing if working more than two; they are usually powered with a diesel plant; they can destroy quaysides over a long period of use; and there are higher instance of damage especially aboard ship".

He adds: "Large specialised container terminalsÕ obvious choice is a STS gantry crane, but for smaller multi-use ports in developing areas, MHCs can add much needed cheap capacity."

An executive at a major global terminal operating company, who wants to remain anonymous, says: "The extensive deployment of MHCs in African and Latin American markets, even where one terminal operates a combination of gantry and MHC, attests to the speed of deployment and flexibility of this type of equipment.

"One major detractor is that the operational cost of MHCs can be considerably higher than a gantry crane. It rather depends on the local union/port labour agreement, but I have seen costs be as much as 50% higher for MHC as a result of an imposition of greater gang numbers."

However, Klein argues that Gottwald MHCs can be powered with shoreside power as well as new alternative drive options and also offer flexibility and versatility. "Contrary to STS cranes they are able to handle long and bulky materials without problems since they have a 360-degree operating angle," he explains. "Whereas STS cranes are built with a specific application in mind e.g. for container handling Ð their capacity is quite often limited to 60 tonnes. MHCs have much higher lifting capacities which allow them to handle even heavier cargo such as wind turbine components, steam and gas turbines and other heavy investment industry products.

"If a customer operates more than one MHC, he is also able to offer tandem lifts to achieve even higher loads.

"A further advantage, which should not be underestimated, is that MHCs cannot only travel from terminal to terminal in a given port but can also be relocated from one port to another elsewhere in the world."

So, can terminal operators increase the productivity and uptime of their MHCs? Joachim Dobler, marketing manager MHC manufacturer Liebherr, another, says that terminals can improve their logistics by, for instance, optimisation through simulation of processes. He also recommends: experienced crane drivers; avoiding overloads; regular crane inspections; preventive maintenance; and use of reliable machines.

By way of example, he says: "Two LHM 500 MHCs at APM Terminals Apapa, Nigeria, have over 9,000 operational hours each. Installation was in November 2008, which means both cranes have a daily working average of over 19 hours."

One terminal operator points out that many developments that STS gantries have gone trough such as twinlift, tandem lift, higher trolley and hoisting speeds and more automation Ð are all aspects that can and have not been developed for MHCs.

Klein responds: "We have introduced cranes with higher lifting capacity, more powerful lifting curves, significantly improved hoisting speeds and higher classification. It goes without saying that Gottwald MHCs can be applied for twinlift operations at the largest vessels.

"Gottwald has also enhanced its cranes with innovative features such as crab steering for ideal manoeuvrability and automation of frequently repeated crane movements such as propping. A further example for the innovative touch of Gottwald mobile cranes is the load guidance system to ensure even safer and more convenient operation with such features as linear load motion, load anti-sway, point-to-point handling mode and hoisting height limiting system."

Dobler says that many advanced developments have also been applied to Liebherr’s MHCs and technological improvement remains at the top of the company’s agenda. For instance, he says, for container handling the company offers the ’Cycoptronic’ anti-sway system for direct, sway-free load positioning. For bulk handling the ’Teach-In’ feature is available, a semi-automatic system that pilots the crane on full speed, without sway, to a pre-assigned position.

Dobler also points out that that the LHM 500 has a capacity of 50 tonnes under the spreader at an outreach of 42 metres and is, therefore, suitable for full twinlift operation up to the 13th row.

"The new generation of cranes will all be equipped with the ÔPactronicÕ hybrid drive system," he adds.