And, as it is with so many things in life, taking time to select the right product and perhaps paying a little extra for it at the outset will pay off in the long run – especially against the background of a grab’s working life of up to 15 years, during which it will load and discharge millions of tonnes of material.

Dispelling myth number one, manufacturers Verstegen and Nemag, among others, claim that the weight of the grab doesn’t necessarily indicate its strength.

Such specialist grab manufacturers use high-tensile steels and extremely low-friction bearing systems, allowing them to build grabs with low deadweights and excellent capacities and digging abilities.

The best grab designs are developed using CAD and finite element modelling systems, which can be used to indicate all the stresses and strains on the equipment in use before the first step is taken towards manufacture in the workshop.

Nemag says it’s vital to integrate its grab and the port crane that will be using it: “Computer simulations integrate grab and crane on the crane designer’s drawing board, and this means the grab is no longer the poor relation in the financial budget, because returns can be optimised on the entire installation.”

They cite the use of their 50 m3 coke grab on the world’s largest mobile grab crane, and a scissor grab of 50 tonnes on the world’s largest floating crane.

With the increase in the number and size of bulk cargoes showing no sign of slowing, the future is clearly about how quickly those cargoes can be unloaded – and that, in turn, is a function of grab capacity and speed of crane operation.

No matter what its form, what was once just a humble grab is an ever-more sophisticated piece of equipment, growing simultaneously stronger and lighter. In its turn that requires a clear vision of emerging technology being used to make a quality product designed to deliver the best financial return from crane and grab alike.

That’s an approach that will build in reliability, absolutely crucial to sound financial returns, according to Sigvard Orts Jnr, second managing director of German manufacturer Orts GmbH.

“The reliability of the grab is extremely important when discussing productivity. It is pointless to buy a cheap grab; breakdowns during vessel handling effectively prolong the length of the port call.”

Mr Orts Jnr says each grab-unloadable cargo has its own physical characteristics, which points to having to design a grab specifically for each one. “But in practical terms shipping and stevedoring companies need an ‘all-round’ grab that’s equally at home handling a variety of dry bulk cargoes, and I include scrap metal, pig iron and large stones in that category.”

Nevertheless, he advocates considering three major factors in selecting a grab – its kinematics (the way it moves), its closing force and the crane driver’s skill.

He acknowledges that grabs don’t have the same high discharge rates as alternative technologies, but believes their application is more universal, and they’re more robust, making them more flexible. “Not all dry bulk loads can be handled with a vacuum, screw or belt unloader. If a load on board becomes compressed, as can happen in heavy seas, then belt or vacuum unloaders can struggle to cope.” Furthermore, maintenance can be relatively straightforward, and can be undertaken by a competent mechanic, he adds.

With a variety of designs, from mechanical to those with their own power source for bringing the jaws together, perhaps recent sales point the way to the best option for a grab purchase.

Taking that view, the four-rope option seems the way to go at the moment; Gottwald Port Technology sold 22 four-rope grab mobile cranes last year, accounting for almost 27% of orders. Earlier this year, it sold a further eight to four terminals in Turkey.

Gottwald believes this route is so popular because, compared with purpose-built equipment, the initial capital outlay is relatively low, delivery and assembly times are short, and there are reduced overheads for quayside infrastructure. Operating and maintenance costs can be kept yet more tightly under control by having the cranes driven by shore mains.

Furthermore, the cranes’ flexibility is a further asset, since they can easily be integrated into existing workflows, and relocated to alternative quays or ports to suit changing conditions – which also enhances their resale value.

With ever-larger ships and barges requiring unloading, Gottwald recognises that more is required from a grab. It’s often the addition of more power, and they’ve delivered that by adding second hoist motors, second slewing gear, and adapting the rope pulleys.

All of that supports the use of a mechanical four-rope grab. The company says this offers advantages over motor-driven grabs because there’s less deadweight, even though the grab’s construction is beefed up, the payload-per-move is higher, and the operating speed is higher too.

A spokesman for the company says: “The overall handling performance is dramatically improved, and these cranes can out-perform a motor grab on a two-rope mobile harbour crane by up to 30%.

“An additional benefit of the four-rope grab is its rigidity, which makes it far less susceptible to knock and damage when used in this tough, non-stop operation. This results in reduced maintenance requirements, so crane downtime is kept to a minimum.”

With the right grab in place, how do you know it’s working as efficiently as possible? That’s another chapter in the grab story, and one that Nemag tells. They offer a system that measures grab unloading data, tracking all movements of a grab during work, including the number of cycles made and the cargo it has moved. A discrete identification number allows the accompanying software to identify which crane the information is from.

“By collecting and recording all this grab related information in a database, an accurate overview of grab performance is created,” says Nemag. “By extending the database, or by integration/connecting to existing maintenance software every grab can have its own specific performance history.”