Upgrade PLC vs DCS vs Hybrid system?

On 3 Jan 2007 18:18:46 -0800, dxh22@bigpond.com proclaimed to the
world:


Are you doing the install or hiring the work out?

Paul M wrote:


That decision is one of the outcomes of what I am looking at! A lot of
the config/installation will have to be contracted out of course but
how and why etc depends on what kind of conclusions I reach. Hopefully
I can get a clearer more unbiased view of the issues involved from
someone who has been there before me.

This is clearly a major exercise, it needs close involvement all the way
through of people with specific experience of every stage involved, from
basic architecture design, through platform selection, design, installation,
integration, cutover, commissioning and training. If you want to keep it
platform-vendor independent up front, then you'll need the involvement of an
outfit that can handle all the front end engineering. Building your own
implementation team without having a fair amount of experience yourself is a
chancy business in its own right. Good luck.

On Thu, 4 Jan 2007 19:00:59 +0900, "Bruce Varley"


I have a lot to say about this having been involved several times in
cleaning up the mess left over after everyone involved in a project
gets mad and goes home, leaving the people left to try and operate the
plant, dazed and bitter.

If I don't get the chance to say anything else about this, I would
urge you to hire someone with a history of sucessful projects of this
type and make sure that a single firm has the finacial responsibility
of seeing it all work.

I hate to push my own barrow, but you will need to engage a firm of
Consulting Engineers to help you though this.  Our job is to give you
answers to exactly the questions you pose above.

Norton Consultants has been involved with similar projects (for ACI
Minerals) in the dim distant past and is currently engaged on similar
upgrades for the major Oil Companies.  You can find us on the web at
www.nortonconsultants.com

There are many others around who can help you, some good, some bad.
Maunsell have a control systems division in Melbourne (called 'Mamic' last I
checked) and I could give you a contact name if you like, there's Patterson
Flood Engineers and countless others...

We look forward to being of assistance.  A small hint in passing -
ControlLogix is not all it's made out to be and if you are not *really*
careful with your systems design, you could find yourself in very deep
poo...

HTH,
Cameron:-)

Cameron Dorrough wrote:


Thanks to all the posters who answered. The replies were pretty much
what I was aware of. The answer to the technical issues will drop out
following deeper investigation and in the mean time I am gleaning small
nuggets of wisdom from a myriad of sources.

The small hint above intrigues me. Have you had a specific problem in
the past or is that a general observation? I have been getting more
information from Rockwell on possible obsolescence of their product
line and as a consequence will probably install more
ControlLogix.......?

Paul and Jake have spelt out the complexities of control systems design far
better than I could. We have used and continue to use ControlLogix (and
Yokogawa and others as well) for a variety of different clients and
applications and no two systems are ever exaclty alike.

The biggest issues I, personally, have with ControlLogix are (1) that it is
marketed as "the solution for everyone", (2) it is heavily software-based
and each update brings new "undocumented features" which you are left to
find yourself and hence (3) none of the Rockwell people I have ever met have
even the faintest idea of it's limitations (and there are some) and how they
might affect your plant.

If I'm going to recommend a system to a client, particularly one connected
to another system hybrid fashion that they can blame when stuff goes wrong,
I'd want to be extra careful defining the interfaces..

I hope this helps,
Cameron:-)

dxh22@bigpond.com wrote:

There is no magically "good" answer.  There are only issues of
usability, maintainance, expense, stability, security, short term costs,
long term costs, and so forth.

Manufacturing hype can be cut through by understanding what these folks
are really selling.  I suggest taking introductory courses to find out
how the systems are configured, how they work, and what networks they
support.

Also, you should consider what these systems offer in the way of
maintainance features, and where you might need to improve your own
maintainance staff.  Consider what tools they'll need.  Consider what
record keeping you want them to do, and what system features might be
helpful.

Finally, consider where you may need to go with your regulatory
environment.  Look at what reporting features they offer.  Figure out
who is supposed to do those things and how hard they are to implement.

Cameron's suggestion of retaining an engineering firm is a good first
step toward making these decisions.  You will need someone's help
getting started.  The fact that you have to ask these questions at all
shows that you really need this sort of help.

In the long run, however, I'm a big believer in the do-it-yourself
philosophy.  While you get your act straightened out, train some new
engineers.  Pay them reasonably well to keep them on staff.  With a
knowledgeable engineer on staff you can make changes to the system on
the fly.  They'll have good information on what is and isn't working
well for the company.  They'll be able to help you build the next
generation of control systems too.  You may still need assistance from
an outside consulting firm at that time, but you'll be a much smarter
consumer at that point and you'll be able to control costs of the
upgrade much more effectively.

One thing is certain, however: If you install one of these systems, tie
a ribbon around it, and say this is it, we're never going to change
anything here --then you'll be missing out on one of the very best
features of modern control systems:  You can make changes rapidly at
very little expense.

That's what separates the kids from the adults in this business.

Jake Brodsky
(I'm a control systems engineer for a water utility, so what I'm posting
here is free advice, unencumbered by a consulting business or the need
to sell anyone's product)

On Sun, 07 Jan 2007 23:45:05 -0500, Jake Brodsky


This is good advice. I too do control systems engineering and until
recently owned and operated a company that maintained and upgraded
water treatment and industrial instrumentation & control systems. My
last job was as an independent consultant in addition to the
engineering firm hired to design and let out contracts to upgrade a
regional waste water treatment system. My full time job for over a
year was to cut through all the hype and make sure they had a
sustainable and flexible system for the next 25 years. I had a long
history with this customer. The system installed in the 1080's when
the plant was built was failing and the company that installed it no
longer had anyone who knew anything about it. Many times parts were
unavailable.

They spent a lot of money hiring me, but they saved more from having
someone like me, working in their best interest and the only way to do
this is to remove any incentive to sell you something. Even the firm
you hire to design the system have some motives that may end up
costing you time and money. A mistake I have seen engineering firms
make is to spec equipment based on how neat the engineer thought it
was. Another is trying to integrate the system too much. Keep it
simple and provide points in the system that provide easy interface to
new systems. It makes upgrading to new equipment easier.

You have a fantastic opportunity here to make your plant a much nicer
place to work while increasing the profit or you can find yourself
cursing the new system and wishing for the good ol days were back.
Making the first option come true requires the controls engineer talk
with the operators and look at the processes to see if a better way is
possible.

On 3 Jan 2007 18:18:46 -0800, dxh22@bigpond.com proclaimed to the
world:


While Allen Bradley has a good record for supporting their equipment,
the RSView lacks a lot. I would only use RSView for local interface if
needed.

Use a common networking protocol.

Use an HMI that can do supervisory control for DCS and PLC.

I cannot advise what combination of DCS and PLC you should use. This
depends on the process. While both can do the other's job, one does
some thing better than the other. Sometimes it is best to have a DCS
supervising several PLC.



Pitfalls I discussed in another post. Relative costs between system
types is not very much. There can be a lot of cost differences in
brands.


A lot of effort should go into making sure the system can be
maintained with the resources you have there. You need to decide how
you will do this. It is possible to keep it in house.


What they offer will vary between here and there. It's possible to
save a bunch of money by using generic equipment. The "open source"
approach also makes it easier to change brand and/or model in the
future. Again, it all comes down to how well the system is designed.
Hybrid has a lot going for it. You can pick out each system's strong
points and combine them into your system.


Depending on you expectations, this can be done. Don't expect not be
running a 10 year old system in ten years. There will be better stuff
available and the PC interface and protocols will evolve and change.
Expect some changes to the system over they years, but it should be
supportable and most of the equipment should last that long. Mineral
processing can be pretty nasty on equipment.

 What are your processing and how? We have a lot of mining and
processing plants around here (Virginia USA) and I have done a lot of
work for them in the past. Most of the stuff is closed down now but we
had gypsum, lead, zinc, salt, iron and limestone all have been mined
here and we have coal and natural gas production and lots of power
plants. We also have hydroelectric plants that have supplied cheap
power for mining since the turn of last century. Worldwide
availability of the former mentioned minerals closed most of the
production down several years ago. What part of Queensland are you in?
I am not familiar with what natural resources are found down there?
Most of the rock contact I have seen in pictures appear to be
sandstone.


Paul Montgomery, President
Progressive Gauging & Controls Inc.