Hogg
Fuel & Supply operates concrete batch plants in Ontario,
Canada. Hogg Fuel has been a quality supplier of ready mix
concrete for over thirty (30) years. They use a blend of Portland
cement and slag. The “slag” is actually GGBS or
ground granulated blastfurnace slag. GGBS is sometimes used
as an additive to concrete to provide benefits in the areas of durability,
quality, strength and finish. Typical batches include about
10-15% slag but this can vary depending on the need of their customer.
Maintenance Supervisor Bob Knarr was looking to replace the older
weight & cable units installed on their 20ft (6.1m) cement and
slag storage silos. Although the weight & cable based technology
provided accurate distance measurements, they required maintenance
several times per year. Bob and Hogg Fuel wanted a measurement
system that would be would not require maintenance, would provide
true continuous readout, provide the accuracy they require, while
retrofitting into the existing mounting portals on top of their silos.
This
plant was designed as an auxiliary plant to their main facility and
therefore was built with smaller capacity silos than their main plant. However,
this auxiliary plant has become increasingly busier in recent years.
This makes tracking the level critical as loads are required more
frequently than in the past.
Flexar has met all of their expectations and system requirements. As
with all complete systems, Hogg Fuel has a rotary paddle point level
unit top mounted with a two foot extension for indication of high
level to alert the cement delivery to shut down when the vessel is
full. As an added bonus, Flexar provides the batcher in the
control room the ability to track the progression of the fill cycle
right to its completion! The Flexar sensors were installed
in late April 2006.
Flexar is a guided wave radar continuous level sensor. Distance/level is
measured by the time-of-flight of the reflection of a microwave signal (transmitted
down the wave-guide, which is a heavy-duty 0.3” SS cable with 3.9 ton tensile
strength) off the material surface. Cement and GGBS slag both have relatively
low dielectric constants and Flexar’s direct measuring mode
was successful in providing real-time continuous updates of the material
level during filling and draw-down.
Global Flour Processor Uses Flexar® Guided Wave Radar
A large global flour processor and food products company recently began using the Flexar® guided wave radar in a total of eighteen (18) silos and bins to manage their finished product inventory. Readings from these continuous level sensors is reported as being reliable and accurate, even during pneumatic filling, contrary to their previous measuring system. A previous non-performing ultrasonic system was replaced by the Flexar level sensors. Flexar guided wave radar level sensors were chosen as the best for pneumatically filled dust laden flour silos.
Eight (8) Flexar level sensors are installed in load-out silos that fill bulk trucks with processed and finished flour. These silos are 12ft in diameter and 35ft tall. The finished flour is pneumatically conveyed into these silos. During filling the internal environment of the silos is very dusty and turbulent. The finished flour in these silos is used for loading bulk transport trucks for distribution. In addition, ten (10) Flexar level sensors are installed in 40ft high bins that contain bran. This material is also sent by bulk transport to end users.
All of the Flexar level sensors are equipped with an RS485 digital communications output that is connected to a PC with a graphical user interface for inventory management purposes. Monitor’s SiloTrack™ inventory management software is used by the facility to monitor and manage material inventories of both the finished flour and the bran. SiloTrack allows for multiple user viewing and data access via LAN and this is how the facility will be using the software that provides a flexible, graphical user interface, alarms, report generation and history analysis functions.
Guided wave radar is especially well suited to level measurement applications of dusty powder materials even when measuring during pneumatic filling. Flexar guided wave radar utilizes TDR (time domain reflectometry) technology. Radar pulses are continuously transmitted down the sensor’s probe and guided to the material surface where they are reflected back to the electronics along the wave guide. The time-of-flight of the pulses is measured and directly related to the distance to the material surface and its level.
This
plant was designed as an auxiliary plant to their main facility and
therefore was built with smaller capacity silos than their main plant. However,
this auxiliary plant has become increasingly busier in recent years.
This makes tracking the level critical as loads are required more
frequently than in the past. 
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