Loading cement in the heaviest rainfall region of the world
- 01 July 2012
- Company & Industry News
Ship loading systems must be able to deliver the optimum performance even under unfavourable and difficult climatic and geological conditions. Bangladesh is located in the area of influence of the south-west monsoon, and therefore has an annual rainfall averaging 1,500 to 2,250 mm. The difference between the high and low water level of the River Surma is around 8 m. Due to the great demand for cement, there is a great need in this region for efficient unloading and loading systems for the cement industry. As a leading supplier of such systems, coupled with the necessary foreign experience, SMB International GmbH from Quickborn has been awarded the order to construct two ship loading systems for cement on the River Surma in Sylhet, Bangladesh.
The major part of Bangladesh is made up of the delta areas of the Brahmaputra, Ganges and Meghna rivers; a low-lying region interspersed by many water courses, which is frequently threatened by floods, because the major rivers carry increasingly large volumes of water as a result of the continuing deforestation of the slopes of the Himalayas. In the delta area of the Ganges and Brahmaputra, large parts of the coast are covered by the mangrove swamps of the Sundarban.
The climate of Bangladesh is tropical, with the rainfall increasing from west to east. In the east, at the feet of the Tripura-Lushai range, the annual rainfall is 3,000 to 4,000 mm. Here lies the Mowdok Mual, the highest point of elevation of Bangladesh at 1,003 m. More than half of the annual rainfall arrives during the period from June to August. In March, April and October, tropical whirlwinds often sweep over the Bay of Bengal, leaving catastrophe in their wake, since the resulting floods inundate large areas of the country. The native jungle vegetation has been largely destroyed by clearance, while the high population density of 1,023 people per square kilometre (the highest of all low-lying countries) has lead to extensive change of land usage into arable land, where the main subsistence crop is rice.
Ship loading systems
The experts of SMB had to take these climatic conditions into account with two sturdy and robust systems which would withstand the weather conditions for years. Supply interruptions and stoppages would incur substantial additional costs. Various factors play a decisive role in the choice of equipment for ship loading systems, such as the location of the system, the means of product supply and the loading throughput. The system used was a sack loading system, which loads the sacks into the ships by means of a spiral chute. In order to be able to cope with the different water levels and maintain the maximum possible flexibility in ship loading, SMB installed a loading system with a telescopic loading chute. This consists of two parts. A hydraulic cylinder is screwed on like a thread. The cargo comprises cement in sacks.
The bulk density of this abrasive, corrosive and hygroscopic product is 1.2 to 1.5 tonnes per cubic metre at a maximum temperature of 50 °C. "The cement is like sandpaper in consistency. The flow capability on the spiral chute is severely impaired particularly when the cement has hardened. We counteract the material properties of this abrasive product by the use of high-quality components such as a special plastic coating, which protects the system components against wear and enables them to be cleaned easily. The result is high performance conveyor solutions, which are designed for smooth long-term operation and work with minimal energy consumption", explains Dipl.-Ing. Andreas Wolf, Mechanical Engineer of SMB International GmbH.
A conveyor belt of 20 kilometres in length transports the materials for the cement to a local factory. The product is then transported in sacks on a conveyor belt to the loader, and initially arrives at the ship loader on a central rotating plate, which feeds the sacks on to another conveyor belt on the boom. From here the sacks continue on to the spiral chute, where they slide vertically by gravitation onto the rotating plate of a loading head, which transports the sacks on to a telescopic conveyor belt of the loading head. By means of raising and lowering the boom with the aid of a cable winch in combination with a rotating device of the loading head by 360°, most areas of the cargo hold can be reached without warping the ship. Here the sacks are then loaded into the required area of the ship. In this way, and depending on the skill of the operator, 2,400 sacks of 25, 40 and 50 kilograms can be loaded per hour into a ship. The complete loading process is handled by a single operator using a radio remote control. One further person moves the sacks off the conveyor belt of the loading head into the cargo hold of the ship. The sacks are transported on by ships which distribute the product in the country by river.
All electrical and mechanical components of the machine are designed and manufactured by SMB in Germany. The individual assemblies were manufactured in Quickborn, and these electrical and mechanical components, including the control unit, subsequently delivered and installed on-site. In the areas of mechanics, and electronics and programming, the company sends out experts who coordinate the various working groups on-site. "Due to the individual requirements and the interesting environment, our team has once again gained valuable experience. The project has contributed towards consolidating our relationships with the Asian market, and obtaining more comprehensive knowledge of the industry structures.
Further orders are currently in progress for the same market", explains Dipl.-Ing. Andreas Heckel, Managing Director of SMB International GmbH.