Less Load During Load-Out

Graham Bros. Construction, Canada

With a new Sitrans LR560 level measurement solution, Graham Bros. Construction now has reliable level measurement over the full range and operation of the asphalt load-out silo, and operators can continuously monitor the asphalt level from the comfort of the control room.

Graham Bros. Construction, located in Brampton (near Toronto), Canada, is a typical asphalt facility. It mixes aggregates with liquid asphalt cement (AC) in a ratio of approximately 5% AC to 95% solids. This hot and sticky mixture is conveyed to load-out silos where it is temporarily stored until delivery trucks transfer the material to road crews or other construction sites.Level measurement in these silos has been extremely difficult. Material build-up and destructive forces of aggregate material cause problems for contacting probes. The intense heat creates temperature stratification, causing errors for ultrasonic systems.

High and low point level switches do not provide continuous monitoring, so the plant operator has no idea where the level is. Near the end of a shift (with five trucks waiting in line for asphalt), this could leave the last truck without product or leave excess product in the silo. Various grades for different purposes are produced on different days, so leftovers are not desirable. Unreliable level measurement has led to inefficiencies and headaches.

Readings into the lower cone area are possible with Sitrans LR560’s narrow 4-degree beam (Photo: Siemens AG)

A level solution reduces workload

Until the fall of 2010, Graham Bros. Construction had been using the Sitrans LR260 radar level transmitter on the asphalt load-out silos. This transmitter was performing well but readings in the lower cone area were not accurate, due to the wider 8-degree beam of the Sitrans LR260 25 GHz horn antenna. Also, reliable operation required a couple of site visits from Siemens field engineers to adjust special parameters when the silo was empty.

Graham Bros. Construction agreed to upgrade the Sitrans LR260 in October 2010 to the newest technology from Siemens, the high frequency 78 GHz Sitrans LR560. The installation was very simple with the smaller, more compact Sitrans LR560 and its easy 2-wire connection. The programming was accomplished in less than one minute with the Local Display Interface pushbuttons.

The Sitrans LR560’s small lens antenna is less than 3” and yields a very narrow beam of only four degrees. The 4-20 mA loop that powers the radar transmitter is also connected to a remote display in the plant’s control room for easy monitoring by the plant operator. Reliable level readings have been provided from the beginning and no maintenance or fine-tuning has been required.

Excellent performance

Graham Bros. Construction now has reliable level measurement over the full range and operation of the silo, and operators can continuously monitor the asphalt level from the comfort of the control room. The narrow beam of the 78 GHz Sitrans LR560 allows for more precise readings into the cone area – not possible with the previous radar technology. This accuracy ensures that trucks are properly filled, optimizing the facility’s operation. The non-contacting technology means little maintenance or cleaning is necessary.

“Sitrans LR560 is a robust, reliable level monitor well-suited for this environment,” said Randy Moores of Graham Bros. Construction. “It was easy to install and configure and hasn’t required any cleaning. It has improved plant efficiency significantly.”