Ab plc5 to ab clx or siemens s7?

makopa5

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We are currently running a PLC-5 system consisting of 12 PLCs with a lot of I/O per PLC and inter PLC comms and need to upgrade. What would you suggest is the best upgrade route: Control Logix or Siemens S7?
 
Try to provide much more detail about your system. What it does. What is the inter PLC comms for. If you want to upgrade, can you do it in small steps, can you do it one go, or must you do it in small steps, or must you do it in one go.
What HMIs do you have. What SCADA.
etc. etc. etc.
 
It Consists of 5 x 5/60 and 7 x 5/40 processors with average 3 x 16 slot chassis connected via Remote I/O adapters. They control a Concentrator and is divided into eg. Milling, Floataion, Crushing and Tails handling sections. Inter PLC comms consists of Drive Statuses and analog values needed by the next process and is communicated over the DH+ network via a ControLogix Gateway consisting of DH/RIO modules as well as a ENBT module which connects to a Citect V6.0 I/O server and ART server. Production is of paramount importance and minimal downtime is available (Max. 24HRS) per month. i know with Logix it's possible to do it in small steps but i'm not so sure about Siemens.
 
Your description sounds as if it is actually one big plant, and the division into several PLC5 CPUs is because the task is too much for one PLC5 CPU, or because of the limitation of how many racks you can connect to one PLC5 CPU.
If that is the case, it is clearly an advantage to collect everything into ONE CPU. Both S7 and ControlLogix are powerful enough, but only ControlLogix can connect the old PLC5 chassis via RIO. That may be the only realistic way to upgrade in small steps that can be done within 24 hours. In the long run I suggest that the old PLC5 racks are completely substituted for something newer.
 
If the plant personal are familiar with the PLC5 code then the change to Contrologix will be minimal.

(Besides I'm not sure PLC5 to S7 would really be considered an upgrade...) lol
 
You mean if you could freely do everything in the time needed.

Well, we have some experience in upgrades. At the moment we are doing several upgrade projects. We try to keep the hard shutdown period and the subsequent running in as short as possible. It is one of the reasons why we can attract customers for such upgrades.
At the moment we are working on a project where we totally have to replace 9 S5-115U racks with a new S7 based system. From shutdown to startup there will go 3 weeks (*). And then there will be 1 week of running in. All programs will be simulated in advance to keep the running in time this short.
*: This bit is merely a question of manpower. We will do the job with just 2 electricians. But if we set in 1 electrican per rack, I cant see why the 3 weeks couldnt be cut down to 2-3 days.

The same discussions are typical for upgrade projects.
In small steps, or all in one bold jump ?
Small steps means you can keep the shutdown minimal, maybe within weekends so that the production is the least affected.
One big jump, means the overall costs will be the least, and you can implement new features that the old system does not have.

The reasons for us chosing S7 over ControlLogix are many, and a big part of it is inertia. You dont switch unless there are some very good reasons.

In your case, I would go for ControlLogix. You already have some ControlLogix experience, and the ability to connect the old racks via RIO gives you some flexibility that isnt possible with S7.
 
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If the plant personal are familiar with the PLC5 code then the change to Contrologix will be minimal.
That is yet another discussion. Port the old code or start all over ?
I say, start all over. If you port the old code, you will forgo some of the big advantages of doing the upgrade. Old PLCs are written in a totally different way to how you program new PLCs.
And that means again that it is not in itself an argument to stay with AB.
Just my opinion.
 
I recently did a project smaller than yours but with many of the same challenges: many DH+ messages between controllers, large numbers of Remote I/O chassis, and a very short switchover time. We also had a third-party HMI communicating with the controllers.

The conversion and testing all took place before we switched even one wire; we spent about 20 man-weeks on planning, analysis and testing.

When we finally "threw the switch", it was 20 minutes to rewire the RIO scanners and about 5 hours to find the last of the program bugs and start back up.

The heart of our approach was the Allen-Bradley 1756-RIO module. It has a unique "Shadow Mode" that allows it to be connected to a RIO network and listen to both the Input and Output data on the network. Because of this, we were able to convert our PLC-5 ladder logic to ControlLogix code and compare the results of the ControlLogix program to the results of the PLC-5 program in realtime, while the PLC-5 remained in control.

The 1756-RIO module is based on a design from a Florida company called Quest Technical Solutions. Their EtherNet/IP to RIO and DH+ modules are essential to this sort of fast-switchover migration to ControlLogix while retaining RIO networks and I/O adapters.

Also important to our work was the DH+ protocol analyzer from Frontline Test Equipment (www.fte.com).

These devices are moderately expensive and require quite a bit of in-depth A-B knowledge to use. In my case, that was money very well spent because we were able to keep production running at the plant and have a very short shutdown.
 
The heart of our approach was the Allen-Bradley 1756-RIO module. It has a unique "Shadow Mode" that allows it to be connected to a RIO network and listen to both the Input and Output data on the network. Because of this, we were able to convert our PLC-5 ladder logic to ControlLogix code and compare the results of the ControlLogix program to the results of the PLC-5 program in realtime, while the PLC-5 remained in control.
Very interesting. Didnt know that.

A comment to the kind of upgrade that you described: This exchanged the old CPUs for a new ControlLogix CPU - but the old i/o hardware remained. Despite that PLC5 i/o is quite reliable, it will not last forever, and the inevitable complete switchover should be planned for.
We had one upgrade project that came suddenly, not because the customer was dissatisfied by the existing functionality, but because the old hardware started to give in - not the CPU, but modules, power supplies and even backplanes.
 
That is yet another discussion. Port the old code or start all over ?
I say, start all over. If you port the old code, you will forgo some of the big advantages of doing the upgrade. Old PLCs are written in a totally different way to how you program new PLCs.
And that means again that it is not in itself an argument to stay with AB.
Just my opinion.


Perhaps I misstated that I should've said if the plant personal are familiar with PLC5 coding the change to CL5K would be minimal.
I would find it a difficult decision to justify a change of that much hardware from AB to Siemens or Siemens to AB. Big job but the machines will run either way.
--
The change over Ken described is an interesting one and I agree the IO would need to be change as much as the processor. Perhaps the CPU change could be the first stage a project and another IO network(modern) could be installed in parallel and implemented over time.
 
Think about that if you do a total switch, then you will be free to do whatever you can imagine.
If you change over in small steps, you will typically keep everything as it is, apart from the PLC.
Often there is new technology or methods that has appeared in the 15-20 years, and by implementing these the endcustomer gains this as an extra benefit over just the PLC upgrade. We find that it is easier to sell an upgrade if we sweeten the deal with improvements. Often the management simply dont want to invest a penny in an old plant if it doesnt mean that some other benefit is gained.
 

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