Recently, a refinery customer came to use with a level application. Our team determined that it would be a perfect fit for radar level gauges, IF they turned on a Siemens radar algorithm called CLEF, that would let the radar measure accurately all the way to the bottom of the tank.
What is CLEF? How does it work? And why does it matter?
Recently, a customer noticed that the Siemens ultrasonic level measurement system he had installed in a storage bin showed a signficant amount of moisture buildup. At extreme temperature changes (like we’ve seen a lot latele here in the Midwest), there’d be moisture buildup on the Echomax ultrasonic transducer, sometimes so severely, they’d have problems from signal loss.
How could they fix it? One quick trip to the local big-box or auto supply store provided a Siemens-supported solution.
It was bound to happen sooner or later.
I took a call from a customer who needed to replace a garden variety differential pressure transmitter… with one exception: He needed Honeywell’s DE digital protocol for communicating to his DCS. The DE protocol is still great, but since so many installations today use HART or Foundation Fieldbus, all of our in-stock pressure transmitters had a HART communication card – a critical mismatch to what the customer needed.
A year ago, we would have been stuck rush-ordering a unit from the factory, with all the attendant delays and expediting charges, because you couldn’t swap out a comms card without making the transmitter’s hazardous approval invalid.
What could we do?
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Before I talk about the value of a universal 4-20mA analog output on a level controller, let me explain why anyone would care. It’s all about ground loops.
Since the early days of electronic instrumentation, way back when, even before cell phones or PCs, instrument people struggled with ground loops that create an offset error, drive the signal off scale, or burn up an analog circuit.
Lots of people like the pushbuttons on industrial pressure transmitters because the basic settings that every transmitter needs can be set up without a HART communicator. This includes things like the tag name, engineering units, LRV (Lower Range Value, the zero, or what 4.0mA represents), URV (Upper Range Value, the span, or what 20.0mA represents) and damping (an average or filter factor that dampens noise).
On the new Honeywell ST700/ST800 series smart transmitters, the tag name and engineering units are easy to configure and self explanatory, but I seem to stumble when setting up the LRV and URV because I’m faced with a non-descript choice. There’s two sets of options (under Transmitter Setup, not Calibration):
OK, either configures an LRV or a URV value, but which is which? What’s the difference?
Because of the way they operate, all thermodynamic disc traps leak steam. It’s not a question of IF, but of How Much, and how much more over time.
Typically the leakage is two pounds per hour when the trap is new, and increases to about five pounds per hour after just one year in service.
This amount of leakage or wasted steam can be expensive for the steam producer. But before you write it off as an expense you just have to grin and bear, check this out:
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The HART communication protocol has been firmly established as the standard means of configuring field instruments for some years. But talking to a field instrument needs a communicator.
There are the handheld communicators, Rosemount’s x75s and the “budget-priced” Meriam MFC 4150, but at a cost that’s more a capital appropriation than an MRO expense. Even the Meriam, with a 3-year field device description subscription starts at more than $4000.
People continue to ask me if there isn’t a more budget conscious approach to HART configuration.