MillMaster

Greenbank’s MillMaster® uses unique patented light sheet technology to determine the size of particles being conveyed in a lean phase pneumatic conveying environment.  The size of particles that can be measured ranges from 0.5 micron to 500 microns for the standard device. 

The device works by illuminating the particles using a laser and generating a light sheet through a specialist optic. The illuminated flow is then captured using a high speed charge-coupled-device (CCD) camera.  The speed of the camera shutter “freezes” the image of the illuminated flow which enables various image processing algorithms to be applied.

The key to the uniqueness of the MillMaster® is the application of algorithms for removing in and out of field particles and determining the true size from the image. As the light sheet illuminates the particles it also alters their size in relation to the image, and being able to determine their true size from the image and known camera parameters is what makes this device most effective. 

Capable of performing several different measurement operations, the MillMaster® counts and sizes the particles in the sample and this size distribution can be arranged in a number of ways to the user. As a default it is arranged into bins of various sizes, indicating the approximate size distribution.

The system can alternatively arrange the information as a Rossin-Rammler distribution, which is more familiar to engineers operating milling groups and classification processes. The programme also calculates and trends the average particle size, the maximum detected and the minimum detected.  In fact, through the use of Greenbank’s in-house programming engineers, the exact design of the outputs can be altered to suit specific customer requirement.

The device itself operates on an iso-kinetic extraction system. The iso-kinetic method allows a representative sample to be taken at any point and the MillMaster® is designed so that this sample is passed through the system in such a way that no obscuration takes place.  Usually the sampling point is positioned in an area of good particle diffusion, well away from significant roping or clustering of particles. If such a position cannot be found then Greenbank can utilise computational modelling to select a position that would contribute the most representative sample. 

The system is such that in probe sample mode it can deliver a reading every 5 minutes. On continuous mode it will deliver an updated reading every minute. However the time between samples can be configured by the end user via a touch screen panel. The results issued are averaged from several images taken of a particular sample and this is then further averaged over the time, improving the accuracy of the information supplied.