Siemens' radar level transmitters help grain storage facility improve inventory control | Automation.com

Siemens' radar level transmitters help grain storage facility improve inventory control

Siemens' radar level transmitters help grain storage facility improve inventory control

June 11, 2016 - In the Northwest United States there’s a grain handling facility with almost 100 silos. They store and ship grain globally. The facility receives grain via rail or river barges from various states, or seasonally from local farmers. Often, the grain requires cleaning and, in other cases, pre-blending before it is moved to the shipping silos. From the silos, it is transferred to ships for export. It is critical for the facility to know how much inventory they have available in order to effectively fill the various compartments in the ships.

Challenge

For this reason, they need reliable level measurement in their storage silos, as well as in their shipping silos. The conditions in the silos can vary depending on the condition of the grain. Sometimes, the grain can be extremely dusty and sometimes, due to the humidity in the environment, the dust becomes like a paste. This can lead to build-up on the level measurement sensors.

Using the plumb bob technology, the operators measure the level of most of the silos once each morning and then, on demand in groups or individually as needed by the operators in the control room. The level readings are then displayed on their PC-based HMI system that the operators can view in the control room. The operator’s preference is to have a real time level measurement from all silos, not just on demand.

When the conditions are ideal, the on demand contacting device works well, however, the cable does not always function properly when buildup is present, and it requires additional maintenance. This means that the plant personnel must to go on top of the silo and pull on the cable. Occasionally, the cable gets buried and when this happens, it requires two people to work the cable out of the grain. This can take several hours to correct, and if the cable breaks retrieving a broken cable is an even more involved endeavor.  This puts the operation at risk and delays moving the product to shipping or other storage silos. Lost production, additional time lost in port for the ships, and the associated labor for such an event potentially adds thousands of dollars to the overall costs.

Solution

The plumb bob technology currently in place does a good job when silo conditions are not challenging. Having a reliable level measurement instrument, regardless of the internal silo conditions, is a must. For this reason, the facility decided to install and test a non-contacting radar level transmitter.
They chose the most active and problematic silo to evaluate and compare the radar transmitter performance against the contacting cable technology that was currently in use. The activity in the silo is due to the constant movement of product. This particular silo is used as an intermediary step between the storage silos and the shipping silos. It is also used for pre-blending of grains. Dust is more prevalent here than in the other silos. The evidence can be seen by the dust accumulation around the vent area when compared to the rest of the silos.

Most grain silos have a cylindrical geometry. But, they chose a narrow interstice silo (or star-bin silo) to test the radar level transmitter. This type of silo is generally a more challenging application for traditional level radar transmitters because of the multiple curved internal walls, and their close proximity, which can cause signal degradation.

They had a plumb bob type instrument installed in the same star-bin silo as the radar level transmitter test unit. The level measurement is within a couple inches of the contact level measurement. More impressively, when the grain is depleted, the level instrument reads the level down into the cone, 118.5  feet  away. The level transmitter operates at 78 GHZ, resulting in an extremely narrow signal. It can read down into the cone of a narrow silo and yield a reliable and consistent level measurement. The control room operators can see that the level transmitter can provide the type of output that they want and need, on a continuous basis.

Benefits

Because the radar transmitter is a non-contacting instrument, the risk of product contamination was eliminated and the facility had no costly extended delays due to stuck or broken cables. There is no longer the need to climb the silos and manually stick them.  This eliminates a huge safety concern for personnel.  Continuous level measurement is a real time indicator of what is in the silo at all times. Once the transmitter was set up using the quick start wizard no further tuning or maintenance was required and the level transmitter provided the control room operators with the type of output they wanted on a continuous basis. 

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