x I
INDUSTRIAL PROCESS CONTROL
system configuration, information theory,
and
sampling
theory
are a
direct result
of
the
application
of
systems theory.
I had the
opportunity
to
evaluate more than
a
dozen control
and
safety
systems
for a
large
offshore
oil and gas
project
in
1992-1993.
The
systems belonged
to
suppliers
of
international repute
and
various
countries (e.g., United Kingdom, United States, Germany, Japan,
and
Sweden).
Although
all of the
systems were
powerful
and
could
satisfy
the
control
and
monitoring requirements
of the
project, only
two
systems could
offer
all the
features
highlighted previously.
The
control system
specification
of
requirements that
I
prepared asked
for
the
aforementioned features.
All of the
vendors claimed
that
their systems could
meet
the
specified requirements. During discussions
in
which
the
requirements
were explained
in
more detail, however,
it
became apparent that most vendors
do not
understand
the
requirements. Some vendors stated that
the
features
were
not
necessary
for
offshore
platforms
and
that their system
had
been used
suc-
cessfully
in
similar applications.
If
end-users accepted such claims,
we
would
still
be
installing
the
large case instruments
of the
1950s
and
1960s
with thousands
of
air
tubes around
the
plants.
When Honeywell introduced
the TDC
2000
in
1975,
most instrument
vendors claimed that
the TDC
2000
did not
provide single-loop integrity,
and
consequently
was not
reliable
and
suitable
for
process plants: End-users
did
not
listen
to
such
a
biased claim,
and
Honeywell
captured
more
than
50
percent
of
the
market
in the
early
1980s.
Recognizing
the TDC
2000's
success, other
vendors introduced their microprocessor-based
control
systems
and
multiloop
control units.
At
present,
I do not
know
any
vendor
who
mentions
or
offers
single-loop integrity.
This situation equally applies
to the
present-day control systems with regard
to
open system technology, universal operating system, integrated system
config-
uration,
and so on.
Although
few
systems
can
offer
such
features
at
present, most
vendors will
likely
provide systems with such capabilities
in a few
years.
If
they
do
not,
then they
are
bound
to
fail
and may
cease
to
survive because many large
instrument suppliers
faced
a
similar
problem
during
the
last decade
and no
longer
exist
as
independent companies.
Although open system technology
is
well understood
and
widely applied
in
business
and
administration systems,
the
same cannot
be
said about control
systems,
for
three reasons:
(1)
most
C8tl
vendors
do not
offer
such systems;
(2)
most
C&cl
engineers
are not
conversant with systems theory, sampling theory,
and
information theory because these subjects
are
taught
in
special postgraduate
courses only;
and (3)
most end-users resist changing, mainly because
final
deci-
sions
are
made
by
mature mechanical
or
electrical engineers rather than control
systems engineers.
This
book
explains,
in
simple terms
and
without
applying complicated
mathematics,
the
systems theory
and its
associated theories, together with
the
benefits
of
employing systems theory
in the
selection
and
design
of
C&I
systems.
I
use
examples
from
my own
experience
and
projects
in
which
I was
responsible
for
the
design
and
specification
of the
control system.
My
intention
is to
con-
