Radar Technology for Level Measurement

UCML's first silo level control monitoring device was a Sitrans LR460 installed on the first of our two outdoor silos. It is connected to a remote display inside the building. Sitrans LR460 is a non-contacting, 25-GHz frequency-modulated continuous wave (FMCW) radar level transmitter, and it uses a four-wire connection (two for 115 VAC power supply and two for the mA output). After some fine-tuning of the signal, Sitrans LR460 provided reliable operation.

The Sitrans LR460 uses a 4-in. horn antenna with an 8° beam angle. Due to the center location of the Sitrans LR460, the transmitter was detecting the seams of the silo, which were tuned out via the process intelligence feature called "Auto-False-Echo-Suppression." This process required the silo to be near empty. Once configured, Sitrans LR460 provided acceptable readings, except for the lower cone area.  

With the success of the both the Sitrans LG200 and the Sitrans LR460 in mind, United Canadian Malt selected the new Sitrans LR560 for a solution for level measurement of the second silo. The stainless-steel housing was readily adaptable to UCML's preferred way of installation on our silo inspection hatch, and its compact size made it easy to carry the transmitter to the top of the silo for the installation. From our electrician's point of view, the unit's two-wire configuration was also instrumental in saving installation work and wiring costs.

Sitrans LR560 uses a high frequency of 78 GHz and a unique lens antenna to provide a narrow 4° beam. The local display interface has an easy-to-use, graphical Quick Start Wizard that allowed operators to set up the Sitrans LR560 in a couple of minutes using the display pushbuttons. The extreme narrow beam of Sitrans LR560 provides plug-and-play performance, and no additional fine-tuning was required. The seams of the inside of the silo did not interfere with the level readings, and reliable readings are provided all the way to the bottom of the cone area.

Sitrans LR560 is available with HART, Profibus PA or Foundation fieldbus protocols. Programming can be performed remotely with Simatic PDM (process device manager), AMS or PACTware with Siemens' DTM. The local display interface features a backlit display, and can be rotated in four positions. An integrated purge connection is readily available for self-cleaning of the antenna lens if the solids material is exceptionally sticky.The 78-GHz frequency creates a very short wavelength that provides exceptional reflection from sloped surfaces and aiming is rarely necessary. An optional aiming flange is available to aim the antenna away from obstructions or towards the center of the discharge cone for reliable readings in the cone area.

Benefits

Since the Sitrans LR560 was installed, UCML's operators have noticed very stable readings from the transmitter, from completely empty to full. During filling, our operators simply keep an eye on the remote display, monitor the filling cycle and then shut the transfer system off if the level approaches the top of the silo. There has been zero maintenance on the Sitrans LR560 since its installation, and no maintenance is expected.

UCML's silo cleaning schedules have also benefitted from the Sitrans LR560's compact design. Its low profile and lack of extended horn have meant a significantly easier—and safer—cleaning process for the two workers who are on top of the silo performing the required operation. The yearly maintenance cost associated with the previous mechanical level system has been eliminated. In fact, the cost of the new equipment was paid back well within the first year of its operation. 

Overall, as the general manager at United Canadian Malt, I am very happy with all of the instruments we're using from Siemens Industry. We have acceptable performance from the Sitrans LR460, and we were very surprised with the small size of the Sitrans LR560 and how much easier it was to install, set up and operate. Our operators know what is going on throughout our process, and we no longer have any overfilled silos or inaccurate readings from old technology. 

Monte Smith is general manager at United Canadian Malt Ltd.