“Creating flow control systems can be a complex issue,
IMPROVING
FLOW CONTROL
IN PNEUMATIC
CONVEYING SYSTEMS
especially if you are dealing with the pharmaceutical
or the food and beverage industries. The standards
that need to be met when designing and constructing
processing infrastructure can be very stringent.”
For many industries, pneumatic conveying brings a number of advantages, not least the lack of moving parts
and system flexibility. However, it is essential that such systems are properly controlled in order to maintain
efficiency and the quality of the product in transit. Delivering effective process control systems requires an
understanding of both the technology and the industry itself.
ony Brennan, Field Segment
Manager, Gas and Micro
for Bürkert, looks at the
advantages of pneumatic
conveying and how it can be maximised.
T
Modern industrial processes are
under increasing pressure to reduce
costs and improve reliability and
productivity. Where these processes
involve pneumatic conveying there are
opportunities to improve the design
and flexibility of both existing and new
installations.
The most significant advantages of
pneumatic or vacuum conveying over
mechanical conveying include:
Reduced maintenance due to the lack
of moving parts. Improved operational
environment with no dust due to the
fully enclosed design. High flexibility
of the transfer route. The possibility to
carry out physical or chemical processes
during the conveying process. The ability
to convey air-sensitive materials using
an inert gas, such as nitrogen, to prevent
oxidation Optimising the transport flow.
The process of transporting materials
often requires the destination to change,
for example when a storage container
is full and the product is diverted to the
next container. The volume of air in the
transport system is crucial to maintaining
the product in suspension and making
changes to the required volume must be
matched by a suitable adjustment to the
airflow in order to keep the product in
suspension and avoid unnecessary wear
to the pipework or degradation of the
conveyed material.
The same applies to making a change to
the product itself; this will also require
an adjustment to the airflow to ensure
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PECM Issue 26
the correct air velocity and product
quality are maintained. However, the
way in which the air is introduced to the
conveying system can have a significant
effect on the system design and the
power requirements to operate it.
More traditional ‘blow pot’ solutions
are giving way to systems that use
multiple air injection points to provide a
uniform air flow throughout the system.
Increased levels of computer control
and monitoring allows new installations
to be delivered with much lower power
requirements, which form a significant
proportion of the operating costs.
Improving productivity
microprocessor control have been
heralded as Industry 4.0 and the Internet
of Things (IOT). Advances in design
technology and the reduction in costs
have resulted in a huge increase in
the amount of technology available
to measure and control industrial
processes.
When applied to pneumatic conveying
it enables the continuous measurement
of material mass flow rates and the
adjustment of air flow rates using
computer algorithms to both within an
optimum range. Furthermore, this data
can be collected and analysed centrally
to ensure that the plant continues to
operate at the best efficiency.
The key to managing these power
requirements, and the subsequent costs,
is to implement a control system that can
react to changes in the internal volume
of the transport system, maintaining
the optimum airflow. This approach has
resulted in the industry shifting from
steady state systems towards non-steady
state systems. The ability to operate
a plant with product quality variation
without stopping the process due to
plugged pipes can greatly improve
the productivity of the plant and help
to reduce the operator’s total cost of
ownership.
To implement such a system requires an
airflow controller that can continually
assess the demands of the system
and provide feedback signals for the
compressors. Integrating such an air flow
controller with a pneumatic conveying
system that has had little or no control in
the past, can be challenging.
However, recent developments in
data networking, connectivity and
The Type 8750. Bürkert specialises in
developing solutions for customers
in a diverse range of industries, delivering
flow control systems for a wide variety of
applications.