Should we use laser-based sensors? A reader wrote: We are doing system automation work to install equipment in a metering plant based on weight and flow characteristics. For some very expensive liquids, paying for the accuracy of their metering is not worthwhile. We have already sought opinions on upgrades for next year's tender. What can we do to improve the flow metering, metering, and pressure sensor system? Tightly Coupled Coriolis We have been using two- or even three-stage flow metering, metering expensive liquids through the outputs of small Coriolis flow meters sequentially in the metering cycle. The smallest “trick” is completed after a larger flow rate, and the larger flow rate accelerates the cessation of the measurement event before completion. …Close monitoring of the specific gravity information of the liquid provided by the Coriolis flow meters can stop metering the liquid when gas-contaminated liquid flow is detected and send a warning message to the operator. …Each metering chain should have a “return tank to purge” option, allowing gas-contaminated liquid flow to be recirculated and purging each meter until the correct specific gravity of the process liquid is obtained. Karl Holz, from Instrumentation and Control Design Engineering at AEP Pro Serv in Dallas, explains: Simpler Designs, Greater Consistency. Current practices in raw material feed control often lead design engineers to trade speed for accuracy, or vice versa. Besides reduced performance, these designs cause companies to waste significant funds on raw materials (trading accuracy for speed) and invest heavily in complex piping and/or variable position valve systems, as well as the automation hardware and software required to drive multi-speed feed designs (trading speed for accuracy). …Our Adaptive Predictive Control (PAC) solution (globally patented, the only licensed by Procter & Gamble) demonstrates its advancement by increasing the accuracy of automated raw material transfer by up to ten times and reducing metering cycle time by 30 percent. …By using model-based adaptive predictive control embedded in our Qi platform, measurement and distributed control systems can predict future events and then accurately add the calculated raw material quantities based on this information. PAC enables simple applications and inexpensive on/off control devices, reducing system installation costs and long-term system maintenance costs. …While the process industry offers numerous adaptable strategies for continuous systems, metering feed transfer systems have until now had very limited options. Figure 1 illustrates four examples of how PAC technology reduces the variability of transfer systems. Optimized control, improved quality: Results from consumer goods manufacturers' practical applications… PAC technology enables manufacturers to achieve higher accuracy in feed transfer systems using simple and inexpensive on/off control devices than most industries use traditional drip/flow control elements, as shown in Figure 2. Increased speed, enhanced use of invested capital: Increased throughput of production batches by 30%, reducing costs by $10,000 per feed transfer line. …The predictive part of PAC continuously monitors the process, constantly determining the actual flow rate of the feed during feed transfer. Based on the flow rate and PAC's learning of the transfer system's previous performance, PAC can continuously predict the optimal point when the transfer system should pause (stop) and the desired quantity to be transferred. …The adaptive part of PAC monitors performance during each transfer and updates the factors to be used by the predictive part. This allows the PAC to adapt to and compensate for normal process handling deviations, enabling feedstock transfer characteristics to change at any time (e.g., moisture affecting dry feedstock, or viscosity affecting liquids). …By utilizing the feedstock flow rate and monitoring batch deviations from the set point, the PAC can determine the desired amount of “dynamic overflow.” Dynamic overflow is the amount that continues to be delivered after a stop command has been executed. Rodger Jeffery, Business Development Manager, and Tom Tait, Marketing Manager, Process Control, at Mettler Toledo in Columbus, Ohio, explain the rapid response of Coriolis. Errors in metering processes using flow meters typically occur at the start and end of metering…Coriolis technology is undoubtedly ideal for measuring valuable liquid flows due to its inherent accuracy and the fact that it measures mass rather than volume. However, the fluctuating rise and fall of liquids necessitates a slow enough response time to accommodate the rather sluggish response time of many existing Coriolis flow meters. Traditional Coriolis flow meters also cannot handle situations where they start empty, requiring more sophisticated methods to ensure the flow meter is full at the start and end of metering. This often wastes some liquid and increases metering time. …Our newly manufactured CFT50 digital Coriolis system offers improved response times, at least 10 times faster than previous Coriolis systems, and reduces the number of metering fluctuations. The new flowmeter technology also handles situations where the fluid tube is initially empty, eliminating the need for precision and expensive workspaces. The performance of these digital Coriolis systems enables accurate metering of even small quantities of expensive additives and ingredients. Wade Matter May, Senior Fluid Consultant, Invensys/Foxboro Measurement and Instrumentation Group, Foxboro, Massachusetts, asked: Should we use a laser-based sensor? We are considering using a laser-based sensor in a triangulation solution requiring high accuracy (10 µm) with a 2-foot range. It seems to be a boundary case, and there may be a cheaper LED-based solution that makes more sense. I would appreciate suggestions from both sides, or just one side, if only one.