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What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/20/2017 10:05 AM

Hi,

Our magnetic separator for coal conveyor using unsupported PLC S7-200 (EOL), given the mtbf of PLC was quite good. Thank you.

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#1

Re: What is the right approach to analyze benefit of retrofitting unsupported PLC

07/20/2017 10:16 AM

It depends upon the predicted equipment need for the facility. If, for example, the facility were being superseded by another piece of equipment, or the market were dropping away, then there might not be any need for any retrofit.

The forum cannot make these sorts of judgements as these are determined by local conditions.

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#2

Re: What is the right approach to analyze benefit of retrofitting unsupported PLC

07/20/2017 10:38 AM

Something in a CBA should do it.

Cost Benefit Analysis Template - University of Pennsylvania

You're welcome.

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#3

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/20/2017 1:20 PM

It sounds like the existing PLC is still working, but since it has reached End Of Life, you are trying to justify replacing it.

Problem with that is your trying to sell someone (management) on the idea of spending money to replace something that isn't a problem right now, but could be a potential problem in the future. That is usually a hard sell.

The only approach I have known to work when money is involved, is to show them how much money they will lose in downtime/lost production, due to a failure of the device in question.

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#5
In reply to #3

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 2:36 AM

This exactly what I'm trying to do, you paraphrasing my question a lot better. Thank you.

I'm not in the position of giving a recommendation per se. But want to objectively justify the situation as a new technician and have a better understanding about reliability in overall. Should I approach the analysis from the PLC itself or the overall system/subsystem.

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#6
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Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 8:13 AM

I kind of agree with Mr. James.... "don't fix if ain't broke"!

Given that you are a new technician and this unsupported PLC is the heart of the system which I assume your main responsibility, the best thing or approach I would do at this time If I were in your shoes is to concentrate and focus on learning that system well!

To give an unsolicited recommendation, objective or not, may at this point be viewed as a negative on your part, putting doubt on your technical abilities?? You may also have to get to know first who among the management people is or has any technical background /expertise? He/she may become your future quarterback that may guide you... As I had extended to many in the past but whether in or out is the???

Good luck!

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#7
In reply to #6

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 9:11 AM

You forget the rest of my quote: "...just build a better one."

Always work and on personal projects with an eye toward improving the capacity, capability, and reliability of equipment you are placing in the "field of application."

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#9
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Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 10:05 AM

"Should I approach the analysis from the PLC itself or the overall system/subsystem."

You should approach it from the standpoint of process/manufacturing reliability.

Two things to be aware of: 1. This PLC may already be on someone's plan for scheduled replacement. 2. Depending on what you replace it with, the cost isn't just the cost of the PLC, but the software to program it, and the training of in-plant personnel to maintain it.

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#17
In reply to #9

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/24/2017 7:00 AM

...and

3. The effect of down-time while the change is taking place.

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#4

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/20/2017 1:30 PM

This is no problem at all, until it goes out, and the plant shuts-down until you can retrofit a new PLC.

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#8

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 9:39 AM

It's possible that the IO components could be easily and inexpensively converted to be a remote rack for your main control system. Copy/convert the software into your main automation system, and you know effortlessly the condition of your separator.

That way you get rid of the overhead for orphan PLCs that some mechanical engineer bought as part of a package, and bring some value forward in a single automation platform for your plant.

Or you'll find there will be many people dumping S7-200 parts on the secondary market, and you'll have no trouble keeping parts in stock for many repair cycles for at least 15 years from now, from experience.

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#21
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Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

09/20/2017 10:12 AM

This approach by rwilliams have worked for me. There are many suppliers who buy out surplus after retrofits and may be able to provide parts and supplies to keep your old PLC going.

Another contributor had also hit on an approach which worked for us: show upper management the cost of a failure with extended downtime .....that usually gets them going.

Remember : when the plant is running, no one is interested.

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#10

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 12:46 PM

So the real question should be, is the plant just going to lay everybody off when this thing fails, or just send them home until it it has parts replaced so it can be restarted. Either way, management obviously doesn't care if they have employees living paycheck to paycheck. That is not their problem.

The real problem is that they have failed to plan. They did not plan to fail, but that is exactly what will happen when it breaks down. Too many people are comfortable with this idea. Run it into the ground, until it breaks, and then we will bitch and moan about how expensive it is to start it back up.

Downtime cost is a function of how prepared one happens to be. The less prepared one is, the more it costs. I believe that some managers would drive a car with flat tires until the rims collapse. Perhaps you should talk to a controller or account who understands the future value of an asset.

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#11
In reply to #10

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 1:12 PM

You cannot translate into beancountus lingo.

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#14
In reply to #10

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 8:13 PM

Too many people are comfortable with this idea

That is why, I need to learn a better analysis of reliability. Thus for this situation/plc I want to study it for learning purposes given I'm not in the position to give a recommendations.

I've found this paper "Analysis of PLC System Based On Markov Model" what do you think? is it good approach using markov model?

Thank you

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#12

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 4:22 PM

Adpabd,

Many good suggestions already. Let me add a few questions and comments.

  • Do you have access to the programming software for this S7-200 and do you know how to use it?
  • Do you have a printed copy of the entire program as well as good as-built prints on the I/O wiring?
  • Do your operators have a very good understanding of how the system is supposed to operate?
  • Do you have an electronic copy of the entire program?
  • Do you have access to people who have the proper software and programming cables? (Such as outside contractors)

I was involved in a replacement of a similar PLC which had failed. The people had no copy of the program in any format. The plant had a VERY knowledgeable operator who had been using it (the PLC had operated a sewage sludge incinerator that had to meet EPA regulations and documentation). We put in a new one from a competing brand (AB), wrote the program "from scratch" and did all the computer and SCADA programming needed to interface it with the plant's operation. Took about a month before they were back on-line.

Depending on the answers you have or get, to the questions I have posed along with others from others on this forum, you can talk to contractors who would give you a quote if they were hired to make the change. If you have the needed software and programming skills, you can do it "in-house", which normally gives a substantially reduced cost. I have not worked extensively with Siemens, but I believe they have software that can "port" an S7-200 program into a current version of processor, so if you have an electronic copy the problem gets much simpler.

--JMM

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#13
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Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 4:53 PM

Are you a relative of the Special Counsel investigating the POTUS/Russian meddling malarky? Put a bug in his ear about shutting it down, before the whole country goes down the tubes, this thing is getting more ridiculous every day.

BTW - extremely good advice you offered to Mr. Adpabd.

If they don't follow through with your advice, they are suckers.

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#15
In reply to #13

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/21/2017 11:13 PM

No known relationship other than human.

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#16
In reply to #13

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/23/2017 1:19 AM

This "thing" isn't ridiculous, or malarkey. Your failure to accept reality is.

Peace bro.

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#19
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Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/24/2017 9:52 AM

Yeah, you're real loud behind that curtain of anonymity, nice try "Lyn".

That dog won't hunt. It is a dead dog.

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#18
In reply to #12

Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/24/2017 8:15 AM

Only to expand upon jmm's comments, to properly support the old PLC, you also will need a computer with the software needed to edit or re-write the PLC code or even to read it from the PLC. That might also require that your computer runs an older version of Windows or some other operating system that may be hard to find. And that can also be the very thing that drives an upgrade because most of the computers that ran that old software have died from old age.

Proper documentation, including complete drawings are critical to keeping an old system going. A good understanding of the details of the existing software is really important as well. Newer PLC's have advanced capability and replacing an old one provides the opportunity to add diagnostic code that helps to reduce downtime because of some component failure. Downtime reduction is a very good selling point to upgrading because it produces profits above budget. Some of the diagnostic code may consist of using spare contacts of relays to verify that they are working. That can make the task of finding a burnt out relay or some other problem very easy to find, and the reduction in downtime can be dramatic.

Other benefits of retrofitting might include productivity increases by speeding up some process. One really has to understand what the PLC is doing in order to determine if it might be possible to make efficiency improvements. In short, there is no "right approach" short of knowing everything there is to know about the old system and understanding what is possible with newer (perhaps less expensive) hardware.

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#20
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Re: What is the Right Approach to Analyze the Benefit of Retrofitting Unsupported PLC?

07/24/2017 10:29 AM

This is awesome. Thank you so much for the advice and all other's advice here.

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