STEMM has managed to close an international agreement with shipowners and stevedores of the main European ports to manufacture clamshell grabs for cereal handling in the unloading of bulk carriers.
The manufacture of this type of grabs requires highly qualified personnel and technical equipment, especially boilermakers and welders duly approved, according to ASME and ISO standards.
Physical characteristics of the Grain Handling Clamshell Grabs
It is a clamshell grab option that can be installed especially on cranes type ITALGRU, LIEBHERR, GOTWALD, with a capacity of 55 tons at maximum boom outreach.
A clamshell grab of this type is an indispensable tool with an own weight of about 18 tons and an installed electric motor with a power of 55 kW.
It is driven by four robust, special high-pressure hydraulic cylinders with a diameter of 160 mm, which are fitted with shock absorbers.
The mechanically welded construction uses high strength steels (TRENX 700) and anti-abrasive steels (HARDOX 500), both in the central body as well as in the shells and in the sealing and penetration lips.
Method of operation
These grabs are operated by a powerful and well-designed electro-hydraulic unit with an internally installed Manifold Block.
This Manifold Block concentrates all the components and valves inserted in a single piece or steel block. It is quickly dismountable, allowing easy interchangeability for control and maintenance operations.
Grab Connect Remote Control System
The GRAB CONNECT system designed by STEMM engineers is a highly developed and highly experienced system that allows remote control of a grab located at any port in the world.
The control of the grab is displayed either on a computer, a tablet or a Smartphone providing all kinds of parameters and technical data, such as pressures, temperatures, current consumption, number of manoeuvres carried out, etc...
In addition to its control, it allows diagnostics and preventive maintenance treatment by carrying out a check of the machine's condition. Thus, before the arrival of ships at the port all corrective or updating operations can be established, so that when unloading operations begin everything is totally controlled and there is no possibility of unforeseen events, ensuring that ships are unloaded without stoppages or incidents.
Quality systems that attest the result
The entire clamshell grab manufacturing process at STEMM's facilities is subject to continuous and intensive quality controls:
- Laser, plasma or water jet cutting of laminated sheet metal.
- Full surface treatment of all surfaces, with maximum shot blasting level SVENSK grade SA 2.5
- Primer treatment before 4 hours have elapsed.
- Subsequent C5 marine treated paint finish in RAL 1007, with a minimum dry film thickness of 300 microns.
During the manufacturing process, in order to ensure the excellent quality required, continuous and constant technical controls are carried out, both by STEMM's internal personnel and by the duly approved technicians who are contracted by BUREAU VERITAS engineering.
All the final tests, control and supervision were carried out with the support and intervention of the technical specialists of the company LLOYDS who issued a Final Certificate of Tests and Approval of the Provisional and Definitive Reception.
How we were awarded the contract
The buyer was a maritime consortium of international shipowners and stevedores, operating in various European and Indian Ocean ports.
The technical committee in charge of the selection of the most suitable option, 11 engineers and doctors of great prestige and experience, was appointed by the consortium's top management.
This Committee appreciated almost unanimously the high technical performance of great value and design offered in the technical report presented by STEMM engineers, who in addition to providing technical reports with designs and profile calculations by means of Finite Elements of the profile of the shells, enriched the presentation with 3D designs.
They also valued a proven kinematic development ensures and adequate drag with a constant penetration force in the special PROGRESSIVE PROFILE LIPS and suitable to guarantee a filling coefficient in the order of 95%.
This optimum filling degree was fully corroborated and confirmed in the unloading operations of the first 300,000 ton bulk carrier that arrived in port and had caused great expectation.
