Challenges Sensing Lightweight Polystyrene Flake Regrind in a
Blending Hopper
PROBLEM:
A South Chicago Heights, IL manufacturer of portion packaging,
primarily for dairy creamers, has had much difficulty sensing the
high level in their blending hopper. The hopper contains polystyrene
flake regrind that is very lightweight. They have not had success
using proximity switches due to the low dielectric constant of the
material and dust build-up. What can be used for point level monitoring
with very light materials and in an environment where some dust also
exists?
EXPLANATION:
Materials too light for rotary paddle units (paddle
may just turn and carve a hole in the material) and too light and
dusty for proximity switches are usually problematic. Even capacitance
probes with high sensitivity, such as the TrueCap® family from
Monitor Technologies, may not be successful. Lightweight materials
usually have very low dielectric constants, close to that of air,
making sensing by RF capacitance methods difficult if not impractical.
What will work on lightweight materials less than 5 or even 3lbs/ft³?
SOLUTION:
Many plastic processors have this problem. Those that work
with very lightweight materials, even dust, and any “flake” or “regrind” definitely
can have this challenge. However, vibratory point level sensors
with a single probe design (not tuning forks) tend to work very
well
in these applications, unless there is the possibility of very
heavy
build-ups but this isn’t very likely with very light materials.
In this example the customer solved their problem of sensing polystyrene
flake regrind by using the Model PZP vibratory point level sensor
from Monitor Technologies.
The Model PZP uses state-of-the-art piezoelectric and electronic
technologies to provide the ability to sense materials as light
as 1.5lbs/ft³. The PZP also provides a relay output and is equipped
with a universal power supply for AC or DC operation.
The PZP is a proven problem solver even for difficult challenges
like very lightweight materials. The PZP is available in a wide
range of probe configurations.
Give Monitor Technologies a call
and let us put our creative solutions to work for you!
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.
PROBLEM:
SOLUTION: 
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