While there are managers in the process industry that see
training control engineers as a no-brainer, these
are very much in the minority. They may send staff on courses
covering configuration of the distributed control system (DCS)
and implementation of multivariable predictive control (MPC),
but some managers seem to miss the point that engineers also
need to develop expertise in basic control techniques.
It appears to be a case of not knowing what they dont
knowi.e., there is a lack of appreciation of what a fully
trained engineer can achieve. Without an injection of
expertise, so-called experienced staff lack the
knowledge to pass on to new recruits.
Of the engineering disciplines relevant to the process
industry, process control is probably the least well-taught at
universities. Often handled by lecturers with backgrounds
having little to do with chemical engineering, the courses are
laden with complex mathematical techniques that have little
relevance to the industry. While all graduates need additional
training to advance their careers, this is particularly true
for those destined to work in the field of process control.
Process control engineers have an immediate impact on the
process. Todays systems permit the engineer to move from
idea to commissioning with little involvement of other staff.
Most other engineers develop recommendations that are reviewed
with others, move on to designs that are also reviewed, and
work with others during commissioning. Control engineers are
more akin to process operators in the way they work. Operators
are well-trained, so why arent control engineers?
Questions to consider
The following 10 questions are designed to expose common
gaps in a readers knowledge. If you are a control
engineer, be honest in answering them:
1. Have all of the controllers been configured with the
best choice of a proportional/integral/derivative (PID)
algorithm? For example, am I aware that most systems support
the option to have proportional action based on the process
variable (PV), rather than on error? Do I believe that this
algorithm is inferior because it gives a slow response to
setpoint (SP) changes, or do I know that, for many controllers,
applying this option with the correct choice of tuning can
reduce, by a factor of three, the time that it takes the
process to recover from a disturbance? (See Fig.
Fig. 1. Response to a load
2. Am I using trial-and-error as the main tuning method?
Am I aware that this increases, by a factor of around 50, the
time taken to properly tune a controller? Do I know that,
because of the time required, the controller is unlikely to
ever be properly tuned? Am I aware that there are over 200
tuning methods published for PID control, and that mostif
not allof them have some major deficiency? Does my chosen
method properly compromise between a fast return to SP and the
movement of the manipulated variable (MV)? (See Fig.
2.) Is this method designed to be used with the chosen
version of the PID algorithm?
Fig. 2. Taking account of MV
3. Do I know that applying derivative action can greatly
improve controller performance if the process deadtime is large
compared to the lagtime? (See Fig. 3.) Am I
reluctant to use it because it makes tuning more complicated?
Do I abandon its use if the measurement is noisy, or do I know
how to solve this problem? Do I know how to resolve the spiking
problem that derivative action causes with regard to
Fig. 3. Use of derivative
4. Is maximum use made of the surge capacity in the plant?
(See Fig. 4.) Are vessel levels maintained
close to SP, or are they allowed to approach alarm limits to
minimize downstream flow disturbances? Are level gauges ranged
to maximize vessel working volume? Do I know that nonlinear
algorithms such as error squared and gap
control can be used to more fully exploit surge
Fig. 4. Use of surge
5. Are filters being used mainly to reduce the visual
impact of noise on trended variables? Filters can significantly
reduce the controllability of the process and may not be
necessary in all cases. Do I know that I should instead check
what impact the noise has on the final control element (usually
a control valve)? Do I know of other readily available
filtering techniques that cause less distortion to the base
signal? Am I aware of the importance of eliminating noise at
the source, particularly with level measurements, and how this
can be achieved?
6. Am I aware of other algorithms that can outperform
even an optimally tuned PID algorithm? Do I know that these can
be easily implemented in most DCSs?
7. Do I know that most MPC packages provide
bias rather than ratio feedforward? In many
cases, performance can be substantially improved by
implementing ratio feedforward at the DCS level. Do I know how
to properly tune the dynamic compensation in such controllers?
Do I know of the benefit that ratio feedforward gives in
automatically maintaining optimum PID tuning in all of the
units controllers as the feed rate is changed?
8. Do I apply density compensation to fuel gas flow
controllers to display flowrates in standard volumetric units
(e.g., Nm3/hr or standard cubic feet per minute)? Do
I know that this worsens the disturbance caused by changes in
gas heating value?
9. Are my inferential property calculations
automatically updated using laboratory data? Am I aware that,
in most cases, this can cause the inferential to become
10. Have I been persuaded to locate my compressor
controls in specialist hardware rather than in the DCS? Do I
know that, if I apply the correct tuning method, this may not
How did you do in the test? If it has exposed even one area
where your knowledge is incomplete, then chances are that there
is an opportunity to improve process performance that will
capture benefits far exceeding the cost of effective
What does it cost to train a control engineer, and what are
the economic benefits? In addition to the time spent on
learning how to configure the DCS and how to apply the chosen
MPC, a control engineer will need around three weeks of further
training. This training should cover basic control techniques,
conventional advanced control, process-specific
techniques, inferentials, etc. Such courses can cost $1,000 per
day. Factoring in travel and living expenses, the total price
of training could be $20,000. A manager might view this as
costly, but it is insignificant compared to the benefits to be
achieved through additional training.
For example, a control engineer typically will be
responsible for control applications that are capable of
capturing in excess of $500,000 per year. Commissioning a project of this value just two weeks
sooner would be enough to justify the training. If maintaining
existing applications (for example, over a two-year period),
then a 2% increase in their utilization would generate the same
savings. Also, if the company relies on external specialists
during implementation, then reducing the involvement of a
top-grade consultant by two weeks would yield similar
While such benefits apply to operating companies, similar
benefits can be achieved by those companies offering advanced
process control (APC) implementation and process engineering
services. With only minor differences between competing
technologies, the main criterion in selecting an APC
implementation company is the expertise of the engineers it
offers. Winning even one more contract by demonstrating a
higher level of expertise more than justifies the cost of
developing that expertise.
Similarly, plant owners are increasingly expecting
engineering contractors to be more aware of the importance of
good basic control design. Too many processes with inherent
control problems exist, along with missed opportunities that
could have been avoided at negligible cost, if considered at
the process design phase.
Which course should an engineer choose?
More than any other engineering subject, process control
training requires practical, hands-on exercises.
Most engineering disciplines work with steady state. It is
relatively easy to demonstrate steady-state behavior in a
computer slide presentation. However, it is not so easy to show
parameters changing over time.
Student-friendly, dynamic simulations take far more time to
build; it can take 50 hours or more to develop the material
covered in one hour on the course. The ratio for the
preparation of more conventional teaching material is likely
less than 10:1. More effective courses are necessarily more
costly. This is particularly true if they are presented by the
more experiencedand, therefore, usually more highly
paidengineer. The value of a course should be assessed on
what impact the participant can have on process profitability
upon returning to work. He or she should return with several
ideas that can be put into practice immediately.
Presenting the course on a manufacturing site provides the
opportunity for practical exercises to be carried out on real
controllers. The resulting improvements have a noticeable
impact on process performance, and they greatly increase the
confidence of the engineer to implement other ideas.
Who should present the course?
It might be easier to answer this question by identifying
potentially poor choices. The DCS vendor is best placed to
instruct staff in the use of the system. However, vendors are
generally more effective at explaining the how than
the why. For example, they can describe the
multiple versions of the PID algorithm available in their
systems, but they are generally less adept at explaining when
each algorithm should be used.
Similarly, the MPC suppliers will be able to describe how to
effectively design, implement and monitor their technology, but they will not go
into detail about the basic controls that should be in place
before step-testing is undertaken. While MPC suppliers are
concerned that such controllers operate well, they generally
place less demanding criteria on their performance.
With a few notable exceptions, most academic institutions
treat process control as a highly theoretical subject. Their
courses tend to be cheaper because the tutors time and
the facilities have already been paid
for; however, their usefulness is often questionable.
Should the course be held in-company?
There is the temptation, particularly if only one or two
engineers need training, to send them on an open-access course.
It costs the supplier more to run these types of courses than
it does to run in-company courses since open-access courses
must be marketed to a wide client base, there is a greater
administrative load, and the course facilities must be rented.
For the customer, an open-access course may be the less
costly option, even with the inclusion of travel and living
expenses. Also, engineers may have the opportunity to develop
valuable contacts in other organizations. However, the
following points should be considered:
- An in-company course opens up the opportunity for others
to attend; the most successful APC projects are those in which the
entire staff is involved.
- Plant supervisors, process engineers and production
planners normally do not attend open-access process control
courses; however, they will usually sit in on at least part
of an in-company course. An in-company course provides a
valuable opportunity for these personnel to develop an
awareness of technology and the role they can
play in its successful implementation.
- An in-company course can be customized to closely match
the companys needs.
- Some material included in an open-access course may not
be relevant; it may assume less previous knowledge, and its
timing may be inconvenient.
When should training take place?
Training budgets, like many expenses that are perceived as
optional, are often the first to be cut when the economic
climate is poor. However, this is precisely the time when
control engineering expertise should be developed. The
likelihood is that no major APC projects will be approved, and
so releasing engineers for training does not disrupt their
Furthermore, engineers will have time to identify and
exploit the many zero-cost improvements revealed by the
training. Also, when major investments are again considered,
the basic process control layer will already be ready to
receive APCtherefore, substantially shortening its
Myke King is the author of
Process Control: A Practical Approach, as
well as the director of Whitehouse Consulting.
Previously, he was a founding member of KBC Process
Automation. Prior to that, Mr. King was employed by
Exxon. He is responsible for consultant services,
assisting clients with improvements to basic
controls, and with the development and execution of
advanced control projects. Mr. King has 35 years of
experience in such projects, having worked
with many of the worlds leading oil and petrochemical companies.
He holds an MS degree in chemical engineering from
Cambridge University, and he is a Fellow of the
Institution of Chemical Engineers (IChemE).