Belt weighers stay stable on the quayside

Edited by the Engineeringtalk editorial team Jun 13, 2005

More than 20 Inflo belt weighers are continuing to provide accurate and trouble free weighing on equipment operating in the tough working environment at the EMO terminal at Rotterdam.

More than 20 Inflo belt weighers supplied by UK based Procon Engineering are continuing to provide accurate and trouble free weighing on equipment operating in the tough working environment at the EMO terminal at Rotterdam.

The weighers are fitted to stacker reclaimers and in belts on several locations at the terminal.

EMO (Europees Massagoed-Overslagbedrijf) has been located on the Maasvlakte Rotterdam since 1973 and its terminal is the largest dry bulk terminal in Europe, specialising in the unloading and storage of iron ore and coal from around the world.

Offering direct access to the North Sea at a draught of 23m, EMO can handle panamax size ships and the largest dry bulk carriers.

The company, which operates 24 hours a day, 360 days a year, unloading about 35 million tonnes of raw materials annually, plays a vital role in the supply chain of iron ore and coal needed for the European steel and power generation industries.

Procon Engineering has a long-standing relationship with EMO, stretching back more than 25 years, and the weighing equipment has proved to have outstanding reliability and long term accuracy.

EMO operate five Krupp/PWH stacker-reclaimers fitted with Inflo Weighers rated up to 7kt/h, four PHB/PWH/MAN ship unloaders and three barge loaders.

EMO's Project Assistant Ab van Doorn is more than satisfied with the Procon equipment and as he explains: "The weighers operate in one of the most arduous environments imaginable and they have to withstand extremes of weather with little time for maintenance".

"Although the weighers are a relatively small part of the giant equipment working at the terminal, their importance cannot be underestimated".

"Any downtime is costly and very inconvenient, and as a result, reliability is vitally important".

The Inflo Resometric belt weighers have proved to be far more reliable than conventional load cell based units and are ideal for such arduous applications.

They 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.

Lateral chains are fitted between the weigh carriage and the rigid conveyor to prevent any unwanted side forces being introduced through 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.

Periodic calibration checks can be carried out simply and expediently by using the built-in roll-over calibration weights fitted across the weigh carriage.

These have a cam at each end and under normal operating conditions sit free of the weigh carriage on the outside frame.

When calibration is carried out, they are simple rotated round so that the weight rests on the live weigh carriage.

Unlike fixed inclination weighing applications, the belt weighers on the stacker reclaimers 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.

The belt weighers are checked for calibration on a regular basis against two weights and measures approved Inflo belt weighers at permanent locations on site and also a Pfister train loading scale.

During the last calibration in 2004, correlation of better than 0.5% overall was recorded showing just how stable the weighers are in this harsh environment.