Archive for category Radar
In a coal-fired power plant, the coal is transported from the yard to the silos on a conveyor system.
The process of dumping coal from the conveyed buckets into the silo creates a lot of dust.
Written by: Dan Weise
A couple years ago, Siemens published a great handbook on using radar to measure solids levels, but the $60 price tag limited its readership.
You can now download the book for free as an electronic epub file formatted for electronic readers, which in my case, is the Firefox browser on my laptop. It could be any browser (Internet Explorer or Chrome), or presumably any electronic book reader.
In order to understand level readings, you must first comprehend how the instrument works. Three of the most common level-measuring techniques involve using a displacer, float, or differential pressure instrument.
Here’s the catch.
While each of these instruments can be used to report a level reading, none of them actually measure level.
I know what you’re thinking…
If none of these instruments measure level, how do we end up with a level reading? Read the rest of this entry »
Recently, we’ve run into a few radar level applications that had some startup challenges, mostly because the person installing the transmitter didn’t consider how radar wave transmission would affect the level transmitter’s performance.
One trick to any installation is to reduce the number of obstructions encountered by the transmitter. But you have to take into consideration that radar waves don’t transmit in a concentric circle around the transmitter. And this can create a problem of its own.
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?
A customer who had had lots of experience with Milltronics and Siemens ultrasonics was installing his first SITRANS LR560 radar level transmitter. They had worked with it in the shop beforehand, going through most of the settings. They even tested it by setting it up to shoot against a file cabinet and used a tape measure the check the indicated distance value.
Everything checked out OK in the shop.
When they installed the transmitter on the top of the bin, they changed the transmitter’s sensor mode parameter from the distance mode they used in the shop for testing to level mode. After aiming, the level value shown in the local display was dead nuts on, but the 4-20mA signal going back to the control room was way off.
The bin was a third full. The 4-20mA showed it about double that. Not only that, the 4-20 was going in the wrong direction. The bin was emptying and the HMI reported an increasing level value. Someone realized that an inverse-acting output was typical of a distance value, so they reconfigured the sensor mode to distance. That got the 4-20mA much closer to a distance value, but it was still not exactly what it should be, and besides, the goal was to read level, not distance, in the control room. What was going on?