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Flow Measurement

What Is the Overriding Consideration in Flow Measurement?

| Author / Editor: Sabine Mühlenkamp / Dr. Jörg Kempf

Taking User Expectations on Board

Ralf Haut is responsible for the chemical industry at Krohne. He argues that close contacts with the user base are the secret to success in the measurement business. “What really matters is staying within critical limits and complying with the process control specifications. In high-precision applications, for example catalyst dosing in chemical reactions as well as in alarm systems and safety instrumented systems, the specifications are inherently more stringent. Accuracy errors under operating conditions can only be reduced by performing calibration under exactly the same conditions, assuming that the customer is willing to invest the effort.”

However, operational availability of the equipment is the top priority for Krohne because system availability ultimately depends on it. Entrained Gas Management (EGM) on Krohne Coriolis meters was developed for precisely this reason. Even when entrained gas is present in the medium, the devices continue to operate and they indicate the two-phase flow. “Especially at startup when air is still present in the lines, EGM is very useful because having to restart the measurement instrument could possibly bring the entire system to a halt or introduce unnecessary delay in the startup sequence,” explained Haut.

In addition, unusual process situations such as entrained gas must not be allowed to interrupt production. Extensive maintenance needed to prevent performance degradation causes downtime and extra cost.

“Using diagnostic functions such as our Smart Meter Verification, users can assess the health status of the system without interrupting production. This ensures that users can rely on the measurement results at all time,” added Kramer.

Emerson argues that the ability of the Sales force to draw attention to possible effects and explain them is a sign of quality. “With the introduction of the flat spec in 2002, Micro Motion made it easier for users to select the right sensors, because zero stability is already included and does not have to be added in. We can say the same about density accuracy. We offer training which teaches users how to recognize these effects and optimize the commissioning process to minimize them,” said Kramer.

Advanced Technology Released to the Field

Despite the fact that many of the companies surveyed said that they were satisfied with the flow meters currently available, some changes and enhancements have been introduced since the last Achema. Endress+Hauser cites two new developments, namely a 2-wire flow meter range and new device test procedures for simple, thorough periodic checks without the need for dismantling.

At Krohne, Haut reports that EGM for Coriolis meters has now been released for field use. “Initial customers have now started using 2-phase indication. Besides indicating cavitation at upstream pumps, EGM is also used for process control, for example in forced evacuation of stacked containers, to raise a warning when gas is released into a liquid medium or to indicate state transitions.”

Flexim has noticed increased use of Coriolis meters, but Jahn is an advocate of ultrasonic meters. “Our clamp-on ultrasonic flow meters are becoming increasingly popular, and SIL-certified versions are now available, which further extends the applications horizon. In contrast to Coriolis meters, there is no need to interrupt ongoing operations for installation, they are not susceptible to wear caused by the medium flowing through the tube and there is no drift,” reported Jahn.

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