Level Detection...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!
Spotlight: True Fail-Safe Level Switch
SafePoint®
"True" Fail-Safe Level Switch
The
SafePoint rotary paddle level switch with a self-validating design
detects material presence plus continuously monitors its own ability
to function. The analysis includes sensor health and system power
failure, which makes the SafePoint truly “fail-safe”.
The SafePoint incorporates patented use of Hall-Effect technology,
dual outputs to indicate both material presence and unit health,
and microcontroller technology to continuously protect bulk solids
processing and storage from the consequences of unknown sensor
failure by providing immediate indication of a sensor failure
and confirmation of proper operation.
Other practical features of the SafePoint include rugged construction,
motor shut-off when paddle becomes impeded to maximize motor life, twist On/Off
cover for bolt free removal, and local status indicating light (except hazardous
location models)
A practical application for the SafePoint would be to use this "true"
fail-safe product if undetected sensor failure could result in a
catastrophic process problem.
PROBLEM:
SOLUTION: 
