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Death to the control system; long live the control system

May 19, 2011

If you want to see friction, put a few process automation salesmen together and ask them whether it’s best for a company to support its legacy control system or to migrate to a new platform.

On the migration side, you’ll hear something like this:

Eventually, your system failures will become increasingly critical and frequent. Or you’ll learn that your original vendor is phasing out support for the system. In either case, it’s time to migrate. As a result, you’ll get faster processing time, and easier integration of diverse components and third-party systems. Migration is expensive, and worth it.

Those who make the case for evolution usually say something like this:

Evolution provides improved control of lifecycle costs and technology budgeting. It minimizes downtime and avoids the major diversion of resources to design, implement, learn, troubleshoot and train on a new system. Evolution preserves operator knowledge, plus all the engineering effort, application work, operations knowledge and programming time that have been invested in a control system over its lifetime. It costs less than migration and delivers more reliable results.

Ironically, most companies hear these opposing views and they come up with a middle-ground plan, best described as Evolutionary Postponement of Migration.

The folks in finance approve of this option, because it minimizes short-term spending. But competitively it makes the least sense of all. It institutionalizes the notion that the existing DCS is just temporary – starving it of the full commitment that a company’s critical operations require. At the same time, it puts off the day when the perceived long-term solution is implemented. It’s the worst of both worlds.

There are really only two strategies that result in a full commitment to peak performance: Evolve Always or Migrate Now. Either one is better than “none of the above.”

Is your company stick in the middle, or has it made a firm commitment to a long-term strategy for its controls?

1 Comment

  1. 1 Ingo 24 May

    What I find interesting when observing certain maintenance practices at site is the that a lot more money is spent on items which wear out often rather than on items which age often.

    Let me explain: a pump and motor is mainly a mechanical device with some electric components for starting and stopping. It has not changed fundamentally in design and mechanics for a long time and it can run for 30-40 years with only minor repairs (if any). If this is a rather large device and the bearing on the motor or pump shaft siezes, then it is not unusual for the maintenance team to spend anything up to $150,000 there and then to order a new bearing and have it fitted, given this pump is important to the process. However this pump will only slow but not stop production for a few days.

    On the other hand a DCS controller is a complicated electronic device with software which, arguably, does not wear out as such. But (and a big but here) this item has a short lifecycle of say 10 years. During this 10 years this controller may have had another two version produced that is similar but not 100% the same as the original.

    Now this controller does not break down either and you have some spares. Lets say that in year 12 the controller fails for some reason, the spares you have on hand have never been used (kept in original packaging) and when plugged in also fail as they have never been powered up for over 10 years either.

    This happens again with the last spare and now the vendor of the controller gets called for a new one. Remember that the process is still running at this stage, but the user does not want to run long without redundancy on this critical control section of the process, in case the running controller also fails.

    The vendor explains calmly that they do not have that model anymore, however the new one can be used. But you'll have to upgrade your tools and HMI to make full use of it, plus other items. This will cost about $100,000. The user complains that this is too much and is there nothing else that can be done?

    If nothing else is done or maybe a second hand unit is sourced or maybe the failed units are repaired, there is a high likelyhood the existing controller will fail anyway, or the repaired units only last a short time. Remember no real system faults have been seen to date and therefore little mony has been spent on the DCS. However if this controller was to fail entirely, then the whole process will stop. Then everyone is upset and the user will try to make sure it is the vendor's fault in some way: You did not tell me of the new models, how was I to know it would fail, etc.

    Nothing lasts forever. Electronics as much as mechanical devices. Electronic devices are made up many smaller items not manufactured by the vendor and these are also only produced for a short time. Software is even more volatile as many changes can be easily implemented. A vendor needs to keep up to date in ordre to sell the latest features that everyone wants. If this is not done then think about what mobile phone you were using 20 years ago.

    This scene may seen odd to you and I hope it is not what you practice. But I have had many such conversations in the last 20 years. So not really that unusual.

    But why has this situation developed? A shut at this plant could cost upwards of $500,000 a day. Rejigging (migrating) to a new controller may take upwards of a week. And yet if the controller had been replaced with a newer model at the time the newer model was released (with a planned down time) AND the system was kept up to date, this scenario would not have developed or at least been minimised with less cost and possibly no downtime.

    So why not Evolve Always? The DCS parts themselves are cheap compared to a new bearing or motor or other plant items.

    Maybe we have all forgotten what a DCS does and what it's for: To keep production at maximum levels of output and keep the plant safe.

    What is the cost of not keeping the plant running at maximum production and unsafely? Maybe the controller replacement cost is not so bad afterall. Or what do you think?

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