Water & Wastewater Asia September/October 2019

32 | INSIGHT
Communicative trends in
process automation
By Peter Lindmueller, Industry Manager, Water & Waste Water, Endress+Hauser
The current standard for
signalling the measured
values generated by the
instrumentation (measurement
line) is the analogue current
interface. This method maps
the measured value to a loop
current. 0 or 4mA corresponds
to the lowest, 20mA to the
highest reading that you
want to transmit. Current
interfaces offer the advantage
of high interference immunity, a
starting motor does not bother
them, for example, but they only allow the
representation of measured values within
very narrow limits. The user does not get any
information on the status or other conditions
of the measuring point. Sometimes the
information is enhanced by having an alarm
relay for the status, but the overall content
is very limited.
In the end, it’s difficult to talk about
communication at all.
Why are operators and users interested
in the details of instrumentation
statuses? Where are the propellants for
communication, where does the desire to
know more about the process come from?
Essentially, there are two reasons behind
this:
• There are more and more remote
installations (satellites) that need to run
24/7 but are staffed only at certain times
or not at all.
• Less staff with deep process and
instrumentation skills is available.
Due to both reasons, plant operators
need to get deeper insight into the plant
in the future and must be able to assess
its functioning and the potential of
defects from a distance.
There are further trends that drive the
need for deeper process knowledge:
• Cost pressure: Plant operation and
maintenance in the context of limited
financial budgets.
• Information needs: A city mayor might
be asked in a budget round discussion
if a facility is used to capacity, how
effective and how efficient it is. Here,
a qualified answer is expected which
means that the above mentioned KPIs
(Key Performance Indicator) must be
ready at hand.
• Planning needs: Deployment of expert
emergency services is expensive. All
assignments that can be moved from the
non-plannable to the plannable zone
allow a more favourable cost calculation.
• Greater linkage between professional
and private aspects: Although
professional and private life do not
merge into symbiosis, they are getting
closer. Operators are, for example, able
to do a remote evaluation
of the system from
their home while caring
for their children. In
other words: The digital
twin of the system is
available on their
smartphone, tablet, or
computer displaying the
real conditions of the plant.
It is not just about a measured
value and a status, but about
much more information on
the measuring point.
“How are you?” Describes an information that
goes much deeper than the pure measured
value and describes the state of the measuring
point. This can range from “everything ok”
to “cannot do any more”, it can contain
references to the status of consumables
(e.g. 20 per cent of the bottle’s detergent
has been used up) and it can of course
contain information about the measured
value quality, e.g. my last calibration was
60 days ago and must be renewed in
30 days.
Regular calibrations can be:
• forced by authorities
• necessary to optimise process flows
Very often we can distinguish between
process-optimising measurement
(operational measurement) and product
quality determination. While processoptimising
measurement supports optimised
usage and dosing of excipients for example,
the second measurement describes the final
product quality, or the quality of the raw
materials used.
Water & Wastewater Asia • September / October 2019