Bulk-Handling Grabs

German manufacturer Orts GmbH produces a complete range of bulk-handling grabs for operators using mechanical-rope, electro-hydraulic and diesel-hydraulic equipment in either orange-peel or two-clamshell designs.

Bulk-Handling Grabs

"Bulk grabs are suitable for all types of dry bulk cargo. Of course, each type of material has its own physical characteristics, which could mean having to design a grab for specific products. However, in most cases, shipping and stevedoring companies need an "all-round" grab, which they can use to handle different types of cargo efficiently," explains sales director Sigvard Orts (junior), adding that scrap metal, pig iron and large stones also fall within the range of such equipment too.

In terms of productivity, Orts emphasises that this is dependent on three key factors: kinematics, the closing force of the knives and on the overall skill of the crane-driver. In fact, a 12m³ electro- or diesel-hydraulic grab could theoretically achieve average loading rates of around 250-300 tonnes per hour. "The reliability of the grab is also extremely important when discussing productivity. It is pointless to buy a cheap grab, if it then breaks down during vessel handling, effectively prolonging the length of the port call.

The grade of filling is also crucial; the better the grade of filling of the bulk-handling grab, the shorter the loading/discharge time," stresses Orts. Challenged to define the exact role grabs play in the dry bulk industry, he points out that not all bulk materials can be handled with a vacuum, screw or belt unloader. Indeed, if the on board load becomes compressed, as can happen during heavy seas, belt or vacuum unloaders can struggle to cope.

"It is true that grabs do not have such a high discharge rate as alternative technologies, but they do have more universal applications and are certainly more flexible, not to mention robust. Furthermore, some shore-based terminals are just not equipped to handle large rates of unloaded bulk.

While other bulk discharge equipment manufacturers stress their ability to contain dust emissions, Orts underlines the fact that a well maintained grab will produce less spillage and that, in reality, most dust emissions are made when discharging dry bulk consignments into hoppers. 

In fact, Orts GmbH developed a 100% covered grab in the 1980s, specifically to address environmental concerns. Quizzed as to whether purchases of grabs are driven by price or technology, Orts unhesitatingly replies that both are important.

"Technologically, the knives on our grabs offer a high closing force and have optimised kinematics. Add to this a high discharge rate and all round reliability with a reduced need for parts replacement and you have a very cost effective piece of equipment, especially when you consider the price over the whole life time of a grab," Orts points out.

Mechanical Rope Grabs

Neither leasing nor maintenance is commonly bundled into purchase agreements. Outright purchase is still the preferred acquisition method, while maintenance can be relatively easily undertaken by a competent mechanic, argues Orts, adding that in emergency cases the company is nevertheless prepared to despatch its own engineers worldwide. In Singapore, Dubai and the US are also partner companies, which can help and support with know- how and service- personal.

As for the future, Orts notes that some grab manufacturers are trying to bring down the overall weight of their products enabling handling capacity on the crane to be increased.

However, it is Orts' belief that on mechanical rope grabs there are limits to how far this can go. Nevertheless, he does see potential improvements forthcoming in further reducing dust spillage.

The grabs with enclosed clamshells from ORTS have unique construction inside to avoid compression of the bulk material and an overfilling of the grab.

No overfilling means, that the crane driver does not have to open, release bulk material and close again. Such manoeuvres are time extensive and lowering the rate t/h.