Assessing Non-Nuclear Production Instrumentation; Ert Technology As the New Standard for Dredging
Type:
Presented during:
CEDA Dredging Days 2021
Authors:
F. Bosman, M. Williams, K. Primrose, K Wei, and A. Boer
Abstract
For decades, nuclear density meters have been the principle method of measuring density within dredging and mining, however utilizing radioactive sources implicates operational, safety and cost issues. In anticipation of new regulations and societal opinion on sustainability, alternative measuring principles have to be adopted.
This paper and presentation provides an assessment of different non-nuclear density techniques, Damen's choice for Electrical Resistance Tomography (ERT) based technology, and the results of a full scale validation test on board of a hopper dredge. Furthermore, the ongoing development program of the technology and life cycle costs are addressed.
State of art
Acknowledging the market needs, Damen have followed developments at suppliers closely in past years, and tested multiple sensors in their pump test loop. What we found is that all systems on the market have their advantages and disadvantages, but also require higher initial investment compared to conventional nuclear measurement.
From an operator's perspective, a sensor and its processing instrument needs to have a wide application, must be robust, reliable and accurate, and have a low OPEX. Since all of the available products are still under development by manufacturers, Damen has the stance to opt for technologies and suppliers which possess the potential to increase performance on all aspects.
ERT technology and its suppliers
The ERT technology is offered by UK based company ITS (Industrial Tomography Systems), and by Krohne from the Netherlands, the latter applying ITS's technology in their sensors. Krohne's sensor combines the ERT method with their renowned magnetic inductive flow technology in one single spool piece.
ERT is a non-intrusive measurement method that utilizes the electrical properties of flowing material for understanding, measuring and controlling processes. An ERT sensor typically involves an electrode array that is equally distributed around the circumference of a pipe. A low frequency alternating current signal is then injected into a pair of electrode which results in potential differences on the remaining electrode pairs. These voltage measurements contain the electrical conductivity information and by obtaining all the possible independent voltage measurements from the electrode array, a conductivity 'tomogram' can be reconstructed, which represent a complete cross sectional conductivity distribution within the sensing area.
One of the benefits of ERT technology is the quality and processing speed of signals. An additional feature of this instrumentation is, that it provides real-time visualisation of solids concentration through a pipe-cross section. It is possible to show the flow profile of solids, which can be used to estimate possible deposition of solids. This may be an important aspect for operators, however it requires horizontal installation.
The ERT combimeter
ITS and KROHNE have recently developed instrumentation to combine a magnetic inductive flow meter with ERT to produce an integrated production meter, called the combimeter. By integrating both measuring systems in a single spool piece, this offers practical savings in manufacturing costs and more efficient utilisation of space.
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Keywords: Electrical Resistance Tomography, Magnetic Flow, Non-nuclear instrumentation, Production Measurement.