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Instrowest was approached by Western Areas to investigate and rectify the accuracy and repeatability issues they were having with their onsite Thermo Ramsey Weightometers. The weightometers had previously been serviced by another provider. Two technicians flew to the site to report on findings and give recommendations on how to move forward and obtain a requested accuracy within ±1%.

Upon inspection of the three weightometers installed, we found multiple issues, which were rectified by the Instrowest team.

The site metallurgists’ biggest concern was the mill feed weightometer that they had tried multiple solutions on. The mill feed weightometer had consisted of a Thermo Ramsey multi-idler pivoting weigh scale frame that had been installed on the top end of the conveyor. This was later decommissioned after recommendations from the previous service company and a new single idler Thermo Ramsey belt scale was later installed in the middle of the conveyor to negate the old scale. Neither of these scales was achieving the accuracy required.

Instrowest technicians found that the curvature in the conveyor frame was allowing the belt to lift from the weighing area on startup and when running empty. This, along with poor idler alignment and incorrect calibration chain data, resulted in poor weightometer performance.

The Solution

After discussions with site personnel, it was decided that the whole weigh area need to be reinstalled and that the best solution was to start fresh with a new weightometer installation. By raising the weigh area up on the incoming end and installing three lead-in and three lead-out idler frames with balanced and adjustable rollers, Instrowest was able to ensure that constant contact was maintained across the weigh area.

The new weightometer chosen was a Siemens MMI installation.
This was chosen because:

1. The excellent accuracy of ±0.25%
2. The ease of installation meant no cranes were required and the belt could remain in place (lifted with belt lifters) thus reducing the time required to complete the installation
3. Excellent linearity across the range
4. Limited variance caused by horizontal forces
5. Built-in redundancy in having 2 frames and 4 load cells
6. Ease of use & Instrowest’s proven record with the MMI.

Results

Instrowest was able to complete installation over two shifts (one day shift and one night shift) with final commissioning and calibration completed on the morning of the second day.

The new Siemen’s weightometer installation has been installed for only a month and has already proven to be accurate and reliable. Installed in this manner, it has an advertised accuracy of 0.25%. Instrowest’s client has been more than happy with the achieved results.

Melanie Flynn, Senior Metallurgist at Western Areas had the following comments regarding the installation and Instrowest’s contribution.

"Alf Matthews attended the site in July 2012 to inspect and make recommendations regarding a particularly troublesome weightometer, critical to metallurgical accounting. Instrowest provided a detailed and comprehensive report subsequent to the visit which included recommendations for an appropriate scale, its location on the conveyor belt, and cost-effective modifications to the weigh area to improve the overall quality of the installation. The new weightometer is now consistently yielding a <1.0% error. I found the service professional and thorough and would highly recommend Alf Matthews and the team at Instrowest."
 

If you would like Instrowest to assist you with any weighing queries or problems please contact Instrowest.
Email: admin@instrowest.com.au
Website: www.instrowest.com.au
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Tags: Weightometer, Siemens MMI Installation, Siemens Belt Weighing, Siemens Belt Scale