Two resometric belt weigher systems, supplied by process weighing specialists Procon Engineering, are playing a pivotal role in the handling of coal at the rapidly expanding Tianjin Port on China’s north eastern sea board .

The belt weighers have a throughput capacity of 7000 tonnes per hour with belt speeds of 4.8 m s -1. They have been supplied to contractors Voest-Alpine Material Handling GmbH (VAMH) and form integral parts of two of their giant mobile coal reclaimers (VARL) and stacker-reclaimers (VASR). These have been installed as part of the Phase One and Two extension project at the Nanjiang Terminals for the Port Equipment & Facilities Import Company of Tianjin. For Phase Three of the extension project at Terminals No. 9 and 10, VAMH has ordered two more belt weighers for a stacker and a reclaimer, identical to Phases One and Two. Currently the stacker has been successfully commissioned and the reclaimer is scheduled to be in operation by summer 2004.

Tianjin is China’s second largest container port and fourth largest coal-handling port. The ports play an important role in transporting goods around the country, particularly in the absence of adequate road and rail facilities. Approximately two-thirds of all sea-borne cargo is domestic, of which 29 per cent is coal.

The coal is transported to Tianjin Port via a dedicated rail link from the Shenfu Dongshen Coalfield. With a proven coal reserve of 223.6 billion tonnes and a coal bearing area of 31,200 square kilometres, the Shenfu Dongshen Coalfield ranks among the top eight coalfields in the world. Situated in Yulin Prefecture of Shaanxi Province and Yike league of Inner Mongolia, it is denominated as China's reserve energy base. Tianjin Port alone is capable of handling 20 million tonnes a year and the planned growth will increase this to 50 million tonnes by the next decade.

Throughout the projects, Procon engineers have worked closely with the VAMH development centre in Zeltweg, Austria, which is the hub for their worldwide activities in the fields of open pit mining and bulk material handling. From VAMH's beginnings in 1851 the company has developed from a local maintenance workshop for the Austrian Steel & Mining Industry to become a leading global supplier of specialised mining equipment and bulk material handling plants. The company is a fully owned subsidiary of the Sandvik Materials Handling which in turn is part of Sandvik AB's Mining and Construction Division.

The Inflo Resometric Belt Weighers are ideal for such arduous applications and provide a unique combination of features that ensure the key factors influencing belt scale performance are maintained in service over long periods of time. At the heart of the scale is the Digital Resometric force transducer or resonator which provides unequalled levels of measurement performance that are repeatable for extended periods. The resonator has no moving parts and is pre-loaded to a standard level by the applied force from the weigh carriage. As the force varies with the load passing over the carriage rollers, the resonant frequency changes in proportion to applied load. This change in frequency is processed by the electronics and combined with the belt travel speed to provide an accurate weight reading per unit time. Periodic calibration checks can be carried out simply and expediently by utilising the built in calibration weights. Lateral chains are fitted between the weigh carriage and the rigid conveyor to prevent any unwanted side forces being introduced by factors such as poor belt tracking or material asymmetry. As a result, once the weigh carriage is installed and aligned, it only sees the vertical forces produced by the material being weighed.

Unlike fixed inclination weighing applications, the belt weighers on the stackers are subjected to constantly changing angles of operation. This would normally introduce significant cosine weighing errors due to the apparent change in the suspended weigh carriage mass. To automatically compensate for the changing angles of operation, the weighers are fitted with Inflo’s proprietary Astatic Mass Zero Compensation system.

As VAMH’s senior project engineer, Johann Tielitz concludes: “The belt weighers are a critical part of our equipment and we need to know they will provide long term reliability and accuracy. We have developed a strong working relationship with Procon Engineering and experience shows that their equipment exceeds our expectations.”

The contract for the belt scales follows on from the successful installation of a total of three Inflo belt weighers supplied to VAMH for Tianjin and a further nine belt weighers for stackers and reclaimers at the Baoshan Project in Shanghai. Procon have also supplied a further six Inflo belt scales on fixed conveyors at Tianjin.