Many analysers are affected by stray currents or transients. If a fitter does some welding upstream on the pipe, how robust is the unit against electrical damage?

No electrical path exists between the optical scanner head and the MQi’s electronics. In addition, the electronics are isolated from the mains supply according to IEC/EN 60950, UL 60950, UL 508, EN 50178, EN 60204, EN 61558-2-8.

What about lightning protection?

The systems meet the requirements of BS 6651:1992 Appendix C for Lightning protection (medium exposure).

Surge protection is tested to IEC1000-4-5 and IEC1000-4-6 and provides RFI attenuation as well (maximum 73 dB at 5 MHz). The technology is designed to repeatedly handle surges of up to 6000 V and 3000 A.

Do we need to stop the plant to change the light source?

The optical scanner head is mounted directly into the process pipe line and a cover plate is supplied to cover the opening if it is removed. It is thus only necessary to stop the supply pump briefly to remove the scan head and fasten the cover plate.

Are they robust enough to work in the sun at +40 degrees Celsius?

The optical processor unit is fully covered in a grey metal casing, blocking direct sunlight. The data processor unit is also protected by a grey metal cover, shielding it from direct sunlight. The units withstand the high temperatures and harsh environments of heavy mineral separation plants and can handle an operating temperature of 0 to 50 degrees Celsius.

What type of analysis techniques can be used for analysing the samples used to calibrate the MQi?

There is no preferred technique. The following methods have been successfully applied. Grain counting entails counting the individual grains of each mineral species under a stereo microscope. The result is used to calculate the composition, and takes account of the relative density and grain size encountered.

XRF will provide good elemental analysis and, if the particular element occurs in one specific mineral only, the method can be useful.

XRD is a method that is good for qualitative identification of the mineral species present. However, accuracy is not always up to the required level.

AA is similar to XRF, SEM and Qemscan. This method is very good for determining the mineral species. It can become expensive where good composition accuracy is required.

In general, any method is acceptable.

As the reference samples form the basis of the calibration, it is important that adequate attention be given to the number, concentration range and composition values of the calibration samples.

Are there any specific earthing requirements needed?

Normal single-phase earthing is required.

But can minerals be identified by its colour alone?

In the broad sense, no. Minerals are named on the basis of their chemical composition and their crystal structure. The mineral’s history, stretching over millions of years, determines its general appearance and colour. The same mineral, in terms of its name, can therefore have dramatically different appearances and colours in different ore bodies and even in the same ore body. However, in the same ore body, experience has shown that there is limited variation in the appearance of a specific mineral species and remarkable consistency in the spectral profile of each variant. The Blue Cube MQi exploits this consistency with great success.

In-line instruments can be affected by pipe vibration. How do you deal with that?

If the unit is mounted in a pipe section where vibration occurs, the unit containing the optical processor and electronic parts is mounted onto a nearby vibration-free structure. The scanner head, mounted directly into the slurry transfer line, contains only rugged components that are not affected by vibration. Rubber mounts provide limited shock absorption and are used to mount the enclosures.

What does MQi stands for?

MQi stands for Mineral Quantifier in-line.

How do you calibrate the MQi?

The calibration sampling method is described in detail in the operating manual. A standard feature of the Blue Cube technology is the provision of a GPRS (cell phone data transmission) link between the field units and the Blue Cube Systems office. The link enables easy diagnostics and remote calibration of the system.

How does the MQi technology work?

The Blue Cube MQi captures reflected light from a large number of ore particles presented to the scanner. It measures the relative amplitude of the different wavelengths received. This is referred to as the spectral profile.

In a specific mineralisation, each mineral species exhibits its own spectral profile. A mixture of minerals will show a combined profile that will contain a proportional summation of all the various mineral profiles.

This combined spectral profile is referred to as the ‘fingerprint’ of the particular mineral mixture. By comparing the fingerprint of a mixture of unknown mineral composition with the fingerprints of other mixtures with known mineral compositions, its composition can be determined.

Why not multiplex?

  • Sampling from streams often causes line blockages
  • Data frequency reduced with each added stream

Why not rather use on-line XRF?

XRF can only distinguish between elements and not between different minerals. Diffuse reflective spectroscopy can distinguishes between minerals and also measure light elements.