When it comes to extensive use of CAD-based drawings, I sometimes wonder whether this comment is true: ‘What we call progress is the exchange of one nuisance for another nuisance’ (Havelock Ellis). My good sparring partner, Dermot Kennedy (CEO of the firm I&E Systems – systems engineers) will perhaps forgive me for perhaps misquoting him below on an area he is passionate about – fixing our broken drawing systems, with some great suggestions, based on his work over the past 40 years:
Modern control (and related electrical) systems are some of the most complex of man’s works. They deliver economic gain and improved environmental conditions all around us. Their hardware cost follows Moore’s Law ever lower.
A complimentary chapter on Symbols and Equipment numbering from our drawings manual is at the end of this note…
Their documentation is growing in size in an effort to describe the complexity. System documentation is so costly and slow that it is usually curtailed by budget and schedule.
Is this surprising when you consider that we still use techniques over 100 years old?
We ‘draw’ circuits and ‘schedule’ cables and ‘write’ documents. To ensure that these all agree with one another we wait until the last one is complete and then ‘check’ them. We have numbering systems for drawings, documents, equipment tags, cables and panels etc. Information is only accessible to those who can navigate this mess.
Normal drawings have the underpinning of scale but electrical and control drawings do not. So the allocation of information to individual sheets is left to tradition; no help with modern systems. An individual item may be partially described on 50 or more drawings and then, as a consequence, when an equipment number is changed the physical change may cost less than 1% of the document revisions. The usual result of this is that the drawings are never kept up to date.
Some control systems perform safety related activities and are subject to a mandatory requirement for accurate information. Traditional documentation is never adequate to show compliance. And the real answer is not to add another check list. We can thus continue with the traditional CAD based ‘hard-wired-everything-locked-in-place’ approach or venture into use of better techniques and software.
An obvious solution (which is mostly ignored) is to build a multi-faceted model of the system – a prototype in virtual space with all the characteristics required of the planned installation. And the activities emulate the real work of building the system:
1. Select the equipment and create the individual components required
2. Locate and assemble them appropriately
3. Connect them together
4. Configure circuits and application code to give the desired functionality
5. Check the end result
6. Now the model can be published to give MTO’s and any printed documentation required for the final implementation
Add me as a friend on Facebook to download chapter two on Symbols and Equipment Numbering from our drawings manual.
Attend a thought provoking debate and presentation (‘Why our drawings systems are broken and what to do about it’) on the best way forward in terms of bringing our drawings systems into the twenty first century. In order to establish credibility, we will use a number of drawing packages to illustrate some of our points with real examples from engineering projects; but I hasten to tell you that we do not endorse them.
Yours in engineering learning