Computers are now indispensable
in the design and operation of process plant. The great benefits provided
by today's computers to undertake extensive calculations bring with them
the need to recognize that:
- if care is not
exercised, they are also capable of delivering wrong answers to high
degrees of precision
- the detection
of such errors becomes correspondingly more difficult as the extent
of computerized activity grows and the complexity of programs increases.
The
CAPE Subject Group of the UK Institution
of Chemical Engineers therefore established a Working Party which
has attempted to condense more than 150 man-years of their own collective
experience of computing in process design along with that of the numerous
other contributors. This document presents Good Practice Guidelines and
suggestions for:
Process Engineers Using Software in their design
activities
Process Engineering Managers
Model-Building and Program Development
Education and Training
For
Process Engineers Using Software in their design activities
Computer software is now almost universally used in the design of process
plants. These Guidelines address issues such as the following:
- Defining the
problem
- Selecting the
program & preparing the Input data: fitness for purpose
- Checking the
results: sources of errors & their potential consequences
- Sensitivity analysis
& design margins
- Legal & Professional
Aspects
The
Guidelines are primarily concerned with the use of computer tools such
as for flowsheet simulation and equipment design. The principal feature
of such tools is that they are used in a decision support environment;
computer tools can be used to provide information or even advice but,
in all cases, a qualified engineer makes and is ultimately responsible
for all design decisions. The Guidelines do not address issues concerned
with areas such as computer-aided draughting and the three-dimensional
visualisation of plant and pipework layout, or the use of embedded process
control software. Readers should note that these guidelines are in no
way intended to modify or replace engineers' responsibility under the
appropriate legislation (see below): these guidelines must be treated
as suggestions and in the spirit of "necessary but not necessarily sufficient".
The working party accepts no liability whatsoever for any use which may
be made of them.
Summary of Key Messages:
-
It is a professional engineer's legal and professional responsibility
to exercise good engineering judgment in making design decisions and,
therefore, to satisfy him/herself regarding the adequacy of the information
upon which design decisions are based.
-
Much
of this information is today generated by computer-based systems and
so the quality of these systems and the skill and judgment with which
they are applied to a design problem are a critical part of these
responsibilities.
-
The
purpose of these Guidelines is to suggest some simple precautions
which should be taken to help protect the integrity of proposed engineering
solutions and thus to adequately discharge professional responsibilities,
for example:
-- ------
what matters is the quality of the engineering decision: focus on
"fitness for purpose" of both the computer-based system and the data
which is fed into it
-------- assume that everything is "guilty until proven innocent":
you must check and ensure that the computer-based model is appropriate
to your needs and that the data (including any data from databanks,
etc) is correctly specified and adequately covers the expected ranges
(for example, of temperatures, pressures and compositions)
-------- you must check and ensure that the program has worked successfully
and that the results are adequate for your purpose: you must satisfy
yourself that you fully understand any weaknesses and that you apply
them sensibly and with good engineering judgment
-------- sensitivity analysis is a key weapon in identifying where
the critical problems lie and in assessing their likely impact on
your design decisions
-
Do
not hesitate to seek help and guidance from your more experienced
colleagues, from your support services or even from the suppliers
of the systems concerned (and seek it early, not when things have
already gone wrong).
Get the complete guidelines
For
Process Engineering Managers
These guidelines contain suggestions for good practice to those who manage
process engineers using computer software for the design of process plant.
They address issues such as the following:
- Engineering Experience
& Getting Help
- Software Selection
& Validation
- Training
- Networks
- Audit Trails
- Good Managerial
Practice
- Legal & Professional
Aspects
They
are primarily concerned with the use of computer tools such as for flowsheet
simulation and equipment design. The principal feature of such tools is
that they are used in a decision support environment; computer tools can
be used to provide information or even advice but, in all cases, a qualified
engineer makes and is ultimately responsible for all design decisions.
The Guidelines do not address issues concerned with areas such as computer-aided
draughting and the three-dimensional visualisation of plant and pipework
layout, or the use of embedded process control software. Readers should
note that these guidelines are in no way intended to modify or replace
engineers' responsibility under the appropriate legislation (see below):
these guidelines must be treated as suggestions and in the spirit of "necessary
but not necessarily sufficient". The working party accepts no liability
whatsoever for any use which may be made of them.
Summary of Key Messages :
- Modern engineering
computer tools makes it very easy for engineers to appear to carry
out very comprehensive design tasks when, in reality, they may not
fully understand what they are doing.
- For this reason,
the use of such tools has to be managed very carefully, both by the
individual engineer and by their line management
- Management has
the overall responsibility for developing appropriate standard procedures
and practices and for ensuring that they are followed.
- If an employer's
practice is faulty, or the individual is not adequately trained in
good practice, then the employer would be held liable.
Get the complete guidelines
For
Model Building & Program Development
Sooner or later, a case will be encountered where the existing/standard
tools (ie. those available either within the organization or from vendors)
are not adequate and where some model-building and/or programming will
be required. Common examples include modeling a novel reactor or tray
design, adding a model to a flowsheet simulator, developing a special-purpose
thermophysical property model and so on.
These Guidelines present some suggestions for a methodical and professional
approach to engineering program development and draw attention to key
aspects of what is involved.
These Guidelines address issues such as the following:
- Writing a program
is a project, just like an engineering project, and should be handled
in broadly the same way:
- define objectives and end-user requirements
- design program to satisfy requirements
- build program and test that it works correctly
- validate
program to ensure that it correctly represents the physical system
- deliver program with full supporting documentation
- provide necessary training and support
- Observations
on various aspects of software project & quality management, such
as:
- Estimating and Planning
- Cost Control
- Change Control
- "Fast Track" Short-Cuts
- Support and Maintenance
- Liability/Legal Issues.
They
are primarily concerned with computer tools such as for flowsheet simulation
and equipment design. The principal feature of such tools is that they
are used in a decision support environment; computer tools can be used
to provide information or even advice but, in all cases, a qualified engineer
makes and is ultimately responsible for all design decisions. The Guidelines
do not address issues concerned with areas such as computer-aided draughting
and the three-dimensional visualisation of plant and pipework layout,
or the use of embedded process control software.
Readers should note that these guidelines are in no way intended to modify
or replace engineers' responsibility under the appropriate legislation:
these guidelines must be treated as suggestions and in the spirit of "necessary
but not necessarily sufficient". The working party accepts no liability
whatsoever for any use which may be made of them.
Summary of Key Messages:
- Program development
is not a trivial job: to do it well requires special skills and experience
and you should consider such a development only as a last resort
- It is your duty
to exercise professional care, just as it is when you take on any
engineering task.
- The adoption
of good practice from the beginning (and the beginning is especially
important) will not only be consistent with your duty of professional
care but will also save you time, effort and problems.
- Engineering decisions
will be based upon the results generated by these programs. The program
must work correctly and proper records must always be kept (which
will become a part of the audit trail).
- The end product
(ie. the program) must enable end-users to do their job professionally,
as described in their Guidelines. If it doesn't, then you have failed
to discharge the responsibilities which you assumed when you took
on the program development task.
Get the complete guidelines
For
Education & Training
The increasingly widespread use of computer-based systems in design activities
means that it is increasingly important that all process engineering personnel
should have at least a basic appreciation and understanding of such systems
and techniques.
These guidelines contain suggestions for those responsible for the training
of engineers, managers and developers, either in academia or the providers
of industry-based training.
Suggestions are presented for fundamental topics (such as mathematical
modeling, numerical methods, modeling of thermophysical properties, fluid
flow, etc) which might be covered at a basic or advanced level, whether
as part of undergraduate, post-graduate or post-experience training and
whether this training takes place within a higher education institute
or within a company.
Readers should note that these guidelines are in no way intended to modify
or replace responsibilities under the appropriate legislation: these guidelines
must be treated as suggestions and in the spirit of "necessary but not
necessarily sufficient". The working party accepts no liability whatsoever
for the use which may be made of them.
Summary of Key Messages:
- The basic training
of process engineers should prepare them for work as users of engineering
software.
- Engineers should
be taught the use of models as an aid to the design and investigation
of engineering systems and should have an awareness of the assumptions,
approximations and limitations of such models and their potential
consequences within the context of the particular question being addressed.
- Students should
also be acquainted with the legal and ethical framework within which
they will operate as professional engineers and its implications for
the use of computer tools.
- Computer applications
for engineering are in a continuous state of development, with new
concepts and techniques appearing on an increasingly frequent basis,
and so even experienced engineers will, therefore, benefit from regular
supplementary training, in order to keep up-to-date or to explore
more specialized or detailed aspects.
- Managers are
responsible for the development of engineering procedures and practices
but most modern engineering software is very complex and the pace
of development is such that many managers (especially senior managers)
may have little recent direct experience in its use.
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