cpp – Process technology for the chemical industry 01.2019

Typical compressor map: electric actuators enlarge the operating area
Advantages of electric actuation vs. pneumatic actuation in terms of speed
and control accuracy
stance if precise control must be reconciled
with speed. Driven by a desire to satisfy all
possible requirements, Festo extended its
product portfolio for factory automation
from pneumatic components and solutions
to also include electric automation.
The requirements of the O&G industry must
likewise be met by all new products, namely
operational reliability and of course fail-safe
behaviour, in other words if all auxiliary
power breaks down, the valve must move to
a predefined position if it is relevant for system
safety. The prototype is essentially based
on standard components with all the
necessary certifications. The fail-safe component
integrated into the prototype is currently
a mechanical system that is traditionally
based on normally biased springs,
which relax in the event of a malfunction
and open the valve. The spring is stretched
once initially and then mechanically
blocked, so that continuous consumption of
electrical energy is prevented during normal
operation.
Advantages in operation
One major advantage of electric actuators is
the ability to operate systems closer to the
design limits. Measurements have shown
that electric actuators open an ASCV much
faster in case of failure compared to pneumatic
solutions. As a result of this, systems
can be operated closer to the surge limit
and operating states that would normally
cause the ASCV to open in a pneumatic application
are no longer a problem. The
avoidance of disturbance-related downtime
results in increased productivity and greater
economic efficiency. The control speed and
accuracy are also significantly higher with
electric actuators as opposed to pneumatic,
enabling near-optimal plant operation.
Another advantage of electric drive technology
over pneumatic concerns the simplified
diagnostics. Changing conditions in the system,
such as increased friction in specific
positions over the entire opening path of
the valve, are detected in addition to the
usual operating parameters of individual
components. This data can be transmitted
using standard protocols such as HART and
transferred to a higher-level asset management
system, where it forms the basis for
condition monitoring and predictive maintenance
concepts. The elimination of unplanned
downtime due to failures and the
proactive maintenance of anomalous components
during planned shutdowns extend
the life of the plant and result in higher
productivity.
Outlook
Each compressor generally has a separate
controller, which is independent of the
higher-level DCS, to enable fast and direct
control in the field and rule out signal delays
via DCS bus structures. The integration
of the above-mentioned advanced diagnostic
capabilities and parameters linked to
the plant operating status in dedicated compressor
controls can provide even more
benefits. The goal here is to detect an impending
surge even earlier than is possible
today and allow operation even closer to the
design limits. In the future, AI functionalities
will further support this objective. At
present, though, these are still in the early
stages. The fail-safe function, which is currently
mechanical, could also be implemented
with the help of electrical storage
technologies, meaning that the complete
unit would have to be evaluated according
to SIL requirements. In the search for ways
to reduce plant complexity and hence operating
costs, this is where the future lies.
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Online search: cpp0119festo
Hall 15, Booth D11
AUTHOR:
FOLKERT HETTINGA
International Key Account
Manager O&G and Turbine
Industry,
Festo NL
AUTHOR:
DR. ECKHARD ROOS
Head of Global Industry and
KA Management Process
Industries,
Festo
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