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Advanced DP Level Instrumentation Improves Performance and Safety

 What has a bigger effect on reliable level measurements? The instrument itself, or the infrastructure carrying the data?

Let’s face it, to get consistent, reliable measurements, you must have both. The most sophisticated level instrument trying to communicate on cabling installed 30+ years ago might not always get the signal through, and bad things can happen as a result. Similarly, an unreliable instrument won’t help you, regardless of the infrastructure.

Getting the two to work together is the main point of our article in the April 2020 issue of Flow Control, Advanced Level Instrumentation Improves Performance and Safety. Usually most articles treat these topics, instrumentation and communication infrastructure, separately. We’re connecting them because new capabilities now available with advanced instrumentation can provide diagnostics for the infrastructure, and we apply it to measuring level.

But this doesn’t apply to just any level instrumentation, we’re talking about using differential pressure (DP) measurements built on Emerson’s Rosemount 3051S Pressure Transmitter. Here’s how it works:

For many years, owners of the large storage tanks typically found in manufacturing plants, terminals and other tank farms depended on mechanical approaches such as float-and-tape setups. More sophisticated plants might use differential pressure (DP) instruments with sealed or vented tanks. DP offers significant advantages over mechanical alternatives when used in ways that utilize its capabilities well and take its limitations into account. The following sections concentrate on specific considerations associated with DP level applications and how the technology has been refined for better performance.

So that’s a key point—use the best instrumentation, but it has to be in the right context where it can deliver its best data. That’s where the sophistication of the Rosemount 3051S makes the difference.

 Even if the tank connections and impulse lines are working flawlessly, level measurements can be corrupted by instrument wiring problems. Getting a signal from a DP transmitter on a tank to the automation host system may involve sending it hundreds of feet, with many wiring terminations in between. A broken or short circuit will cut off the signal entirely, but more subtle problems can interfere in ways that are not drastic enough to be immediately recognizable but are still able to mislead operators.

So bad wiring equals bad data. The Loop Integrity Diagnostic functions of the Rosemount 3051S can recognize and warn of problems with current leakage and increased electrical load which can degrade loop functionality and accuracy. If you have instrumentation techs who can go around the plant and test loops, you’ll find these too, but who has extra techs? Let the automation do the work.

New advanced transmitters, such as Emerson’s Rosemount 3051S Pressure Transmitter, have loop integrity diagnostics, which perform tests for these conditions automatically, monitoring electrical integrity on a continuous basis to ensure accurate measurements. Should current leakage or voltage sag be detected, the 3051S can send alarms to operators and maintenance as directed.

Let’s hear about your experiences. Are you getting reliable level measurements? Are you having problems with loop integrity and your instrumentation networks? Have you solved the problems, or are you still trying to figure out solutions?

You can find more information like this and meet with other people looking at the same kinds of situations in the Emerson Exchange365 community. It’s a place where you can communicate and exchange information with experts and peers in all sorts of industries around the world. Look for the Level and Advanced Instrumentation Groups and other specialty areas for suggestions and answers.