Variable density flowmeter for loading road tankers using process tomography

Abstract

Montell Carrington Limited produces polyethylene and polypropylene nibs, which are sold in bulk form to companies who use them to make products for the consumer market. The nibs are stored in 30 storage bunkers, each with a capacity of 500 tonnes. The external distribution of nibs is achieved using 40 tonne road tankers that are filled from each of the bunkers using gravity feed.Work has been undertaken at the Manchester Metropolitan University, in collaboration with Montell, to develop a Variable Density Flowmeter using Process Tomography that will enable the mass flow of nibs to be measured with an accuracy of ±2% and hence control the loading of the road tankers. The flowmeter (260mm diameter) was situated between the bunker discharge outlet valve and the tanker. Measurement of the density distribution across the pipe, using Process Tomography, enabled the mass flow into the road tankers to be determined. The Montell Process Tomography (MPT) system was a PC based system incorporating Texas Instruments C40 parallel processors and a 12 electrode capacitance measuring system with a driven axial shield. The capacitance detector was an AC bridge detection circuit working at 100kHz, a demodulator and a back projection algorithm were used to obtain the process images.