Retrofits?

Retrofitting? Does anyone have any experience?

I am working on a retrofit, AIM to replace one PLC, MITSUBISHI (Part of a Microprocessor based control system TURLOOP)controlling a turbine's speed with a TRICON PLC.

Need some guidance as to how retrofits are done, I am also to do a literature review however through internet searches I have realised that not much documentation has be posted or shared or even available on the subject.

Any experience with similar retrofits will be of great assistance, not necessarily as specific to turbine speed control....

Most of my work is retrofits of small sections of control systems. Upgrading from obsolete motor controls to modern replacements, and some PLCs also. I ususally begin by throughly documenting what exists, (here, that is often not what the drawings show!) Get your existing prints detailed and accurate to begin with. When designing the retrofit, carefully compare the specifications of the old stuff and the new to identify potential problems that may result from differences, and to take advantage of new features that are almost always available with newer hardware. It is usually easier and faster to R&R an entire pre-assembled backplane than to try to strip off old stuff and re-install new. Rarely do we replace entire enclosures, but sometimes that is the best option depending on the condition of the old versus cost and downtime requirements. Most of our equipment runs 24/7 and these retrofits have to be done start to finish in less than 8 hours at this plant. I try to schedule them during regular maintenance (PMs as we call them here) which usually only last four hours. In my first two years on the job, I bet I stripped out ten miles of old wiring and threw away 3000 old relays when upgrading 36 machines from electromechanical drum steppers to 7-slot SLC-5/04 racks. Ahh, that was such a good feeling throwing that old, unreliable, unsafe junk in the dumpster. It was also excellent general experience dealing with panel wiring, troubleshooting, and software debugging.
Paul C.

I agree with everything OkiePC said...get your existing documentation up to date, make sure of old and new specifications, and try to do full backplane replacements whenever possible.

If the machine you are about to retrofit is one that is running, take some time to learn how to run it. Find out what it does and doesn't do, what problems operators have with it now and how they correct/bypass them now. Knowing what should and shouldn't happen is invaluable. Furthermore, make sure that you have a crystal clear understanding of what is expected of the "new" machine. Often you will find that someone expects new features. If so, you definitely need to know and plan for those.

I also like to make up a completely new set of electrical drawings of the completed retrofit in advance of starting. This not only gives me a good roadmap, it also helps me identify potential oversights. Usually I end up with even more thorough documentation than existed with the original system. Mainentance guys tend to like this a lot.

Since you are switching from one type of PLC to another, also make sure you really understand every statement in the exisiting PLC logic. If you don't, you could find yourself unable to make your new system work as well as unsure how it was done before. Occasionally, one brand/model of PLC will have a capability that another does not.

Make sure you have a very thorough list of all tools and components you will need before you start. Order your parts early and make sure you have them at hand before you need them. The better organized you are at crunch time, the more time you have to spend on start-up issues rather than running back-and-forth between the parts cage and your machine.

Steve

DOCUMENT, DOCUMENT and DOCUMENT. I third OkiePC's statement. Get EVERY piece of documentation and sort it out. I use a Six Pocket Subject FIle to sort and organize my documents. I keep all manuals and prints in a box CLEARLY marked with the project name. This helps when you have more than one project going on at the same time.

I have a customer file section in my documents. Each customer gets a folder. Each project gets a folder. I keep prints in a sub folder, plc program in a different folder and use as many sub folders under the project as necessary to keep things EASY to open. I also have 2 floppy or CDs with the current information saved there as backup. I like to hard copy the current program and prints for ease of viewing.

Many times retrofits are "supposed to be done in a timely fashion during a usually too short time frame". NEVER let the customer rattle you while doing the install. Do it right the first time and you NEVER have to find the time to do it over. Most every one will agree that the customer or your boss will appreciate it too.