the measured parameters to have the
required control action.
Process instrumentation includes all
types of measuring instruments for
all the different operating parameters
among which there are four most
important parameters which are pressure,
temperature, flow, and level. The advanced
on-line analyzers which measure the
process composition is also considered as
one of process instrumentation.
The measuring Instrument consists of
three main components:
A sensor, sometimes called a primary
measuring element, to measure the
required physical property
A transducer which convert the sensor
signal into a standard signal form that suits
the control system such as a pneumatic
signal (3-15 psi), an electric signal (4-
20 mA), a digital signal of Foundation
Fieldbus,….etc.
A transmitter which put the transducer
signal on the form ready to be transmitted
without loss and then transmit it and now
in smart transmitters it also transmits a
meaningful data about the status of the
measuring instrument as a whole.
Measuring Instrument Components
Process instrumentation includes the
control valves, the most common final
control element, and also pumps speed
and stroke control.
The final control element or a control valve
is simply consisting of an actuator which
converts the output signal from the control
system into a signal that can operate
the valve in response, the positioner for
adapting the response and the valve. The
smart positioner is now in use to send and
receive useful data to/from control system
for predictive maintenance purpose.
Main Components of Control Valve
W hy is it important for an end -
user to understand process
instrumentation ?
Let’s first have a look at what is
the purpose of using process
instrumentation; this maybe summarized
in the following five points:
1. Safety. It is imperative that industrial
facilities operate safely so as to promote
the well-being of people and equipment
within the plant and in the nearby
communities.
2. Environmental Regulations. Industrial
plants must comply with environmental
regulations concerning the discharge
of gases, liquids, and solids beyond the
plant boundaries.
3. Quality and Productivity. In order to be
profitable, a facility must make products
that meet specifications concerning
product quality and production rate.
4. Economic Operation. It is an economic
reality that the facility operation over
long periods of time must be profitable.
Thus, one of process instrumentation
objectives is to be consistent with the
economic objectives.
5. Stable Plant Operation. Process
instrumentation as a part of the whole
control system should facilitate smooth,
stable plant operation without excessive
oscillation in key process variables.
An end-user has to understand process
instrumentation in order to assure
that the above mentioned purposes
are completely fulfilled. Process
instrumentation has widely spread
applications and too many vendors.
Local indicators such as pressure gauges
could be considered the simplest process
instruments, however selecting the right
one for your application is a nontrivial
process. Hence, an end-user should
understand process instrumentation
to deal with the existing instruments
in the facility and to know how far the
integrity of each of them. To specify
any malfunction source if it comes from
mal-operation or from instrument fault.
To make the right troubleshooting
and to decide when it is needed for
an instrumented to be corrected and/
or repaired. To make sure that the right
preventive maintenance plan and
predictive maintenance actions are
properly implemented.
For the situation of adding a new
instrument to the facility, it is important
to understand process instrumentation
to know how to select the right process
instrumentation for the right application
to simply achieve an add-value to the
facility.
W hat are the recent technologies
in process instrumentation , and
how does the industry work
towards it .
When having a look on the technologies
of sensing and controlling elements,
one could notice huge subjects to
discuss. In fact some recent technologies
are considered just modifications
and adaptations to suit a wider
range of applications and having
new achievements towards accuracy,
reliability, integrity, and best price.
For example, due to the criticality of
flow measurements, the manufacturers
never stop researches to develop new
features for hard and severe applications.
One who follows the new products of
flow-meters and revise some researches
like that of Flow Research can notice
that types such as Coriolis, Ultrasonic,
Magnetic, and Vortex flow-meters
are considered the fastest growing
technologies relative to other types.
Let’s have a fast look on Coriolis mass-
flow measurement which is considered
one of special type flow-meter that is
used in wide range of industry sectors,
the feature of multivariable metering
may be considered as one of the recent
technologies submitted by some vendors
where multiple process variables such
as mass flow, density, temperature
are simultaneously measured leading
to accurate information about other
process parameters such as volume
flow, concentration,…etc. Some vendors
present Coriolis flow-meters in larger
sizes that may reach 12 inches.
Issue 31 PECM
9