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Belt Scales Meet High Demands of Custody Transfer

February 20, 2013
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What do football stadiums and motorways have in common? First, they are some of the UK’s most massive construction projects. Second, one of the UK’s largest quarrying companies and building materials suppliers has been a part of both.
    The company provides products and services related to the materials it quarries, such as sand, hard rock, and gravel. It uses these minerals to produce products like ready-mixed concrete, asphalt, cement, and lime.
In addition to the UK’s largest construction projects, the company’s products also help meet the need for infrastructure like roads, schools, hospitals, homes, and offices, as well as consumables used in steel, pharmaceuticals, food, clean water, and sewage treatment.
    Throughout the production of these products, Siemens weighing technology plays an important role for this prominent company.

Weighing Large Loads on the Move
The point at which England’s Thames River spills into the North Sea is termed the Thames Mouth, or estuary. The company’s machinery dredges sand and gravel from the estuary, and boats deliver the materials directly to processing sites.
    Each dredging boat has cargo of approximately 5100 tons, and the site unloads 25 to 30 boats per month at a rate of 1800 tn/hr. The processing site handles the dredged sand and gravel, breaking them into sized aggregate by washing and screening.
    After processing, the company loads up to three trains per day, each with 16 to 20 railcars full of aggregate at Murphy’s Wharf in Greenwich, London. Each railcar can hold anywhere from 67 to 75 tons. This application is called custody transfer, and requires a scale approved by the Measuring Instruments Directive (MID).
    The European Union created the MID to ensure that measuring devices throughout the EU are all part of a common market. For example, belt scales approved by the MID are suitable for use in all corners of the EU – from the UK to Romania to Finland, and in any member country in between.  

Out with the Old, in with the New for Increased Accuracy
To keep operations running smoothly and to stay in line with MID regulations, the company needed to replace an old belt scale that was no longer reliable or accurate. It selected Siemens Milltronics MMI belt scales and Milltronics BW500 integrator, which are approved by the MID for use in custody transfer applications.
    The company installed the Milltronics MMI dual idler belt scale on a conveyor that transports 500 tn/hr of sand at 1.56 in./sec). Aggregate fed from large product bins via vibratory feeders move onto a belt conveyor. The belt conveyor then moves material onto an inclined 35-inc.-wide belt on which the Milltronics MMI is installed. This conveyor then feeds onto a longer belt conveyor that loads the train cars.
    The Milltronics MMI was approved Class 1 OIML/MID, and features triple beam parallelogram stainless steel load cells, which have been proven in thousands of applications around the world. The direct loading of the material onto the scale without the use of pivots, bearings, or counter balances ensures the quickest response time for high-speed continuous weighing.
    The Milltronics BW500 integrator features individual load cell inputs for all four load cells on the belt scale so that off-center belt loading does not affect accuracy. Sitrans WS300 speed sensor completes the belt scale solution and offers four different resolutions for any belt speed.

Improving the Bottom Line during Custody Transfer
The company selected Siemens belt scale weighing system based on its competitive price, as well as its ease of installation and maintenance. The new belt scale has greatly decreased maintenance requirements.
    As well, the local support from Siemens Process Instruments Technology Partner, Support Instrumentation Ltd (SIL), is a definite benefit for this company, since it ensures that this critical field instrument can be kept in good working order.
    High accuracy has also benefited the company, as the scale is producing at ±0.25% of the nominal flow rate for the system.
    The company states it has had a positive experience with Siemens belt scales, saying they provide operators with the high precision and reliability needed for custody transfers.
    Siemens weighing solutions are ideal for even the most demanding applications. They are easy to use, calibrate, and maintain. Custody transfer applications put customers’ bottom lines on the table and Siemens is there to meet these high demands.
    For more information on Siemens, visit www.siemens.com/weighing.

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