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  • PLC Life Expectancy

    What is the general life expectancy of a PLC?


  • #2
    I am sure there is a MTBF documented on most PLC's, but have seen many PLC units of various brands lasting 10 years and more.

    Most units that I change out are still working, just being upgraded for capability.
    Of units that failed, most are voltage transients or relay output mechanical failures.

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    • #3
      I'm with Roger, same here. Had one bad power supply but other than that it's power surges and relay failures. They usually need to built very well to hold up to industrial environments.

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      • #4
        Failures due to bad or weak parts tend to show up quickly. Beyond that it comes down to stress or mechanical wear. If there are no electrical stresses, relays are easily the most vulnerable.

        The only caveat I would offer is related to stress. Newer parts are faster and faster parts usually have lower voltage ratings and are more sensitive to electrical stress. The flip side is that semiconductor processes are better today and chip quality tends to be more consistent.

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        • #5
          Assuming good clean power and room temperature is 30 years a realistic expectation?

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          • #6
            Originally posted by pbw View Post
            Assuming good clean power and room temperature is 30 years a realistic expectation?
            And decent plastic, since most plcs housed in plastic, instead of the metal of yore!
            We have some plcs that have batteries dated in the mid '90s - so well past 20 years.

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            • #7
              Originally posted by kewakl View Post

              And decent plastic, since most plcs housed in plastic, instead of the metal of yore!
              We have some plcs that have batteries dated in the mid '90s - so well past 20 years.
              There are definitely potential issues with plastic terminals. I've seen them get brittle and turn to dust.

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              • #8
                I have an AB in an unheated MCC enclosure that is close to 25. Another AB is 10. All have interposing relays on the outputs. AB PICOs are still at it as well. Time will tell on the CLICKs.

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                • #9
                  I have several 305's from 1996 in a sawmill environment. Think lots of vibration and dirty.
                  Several AB micros and SLC from the late 90's.

                  I'm with BobO, if it doesn't die new or my other circumstances, chances are it will last awhile.

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                  • #10
                    We have several Siemens S5 in our plant that are from mid 90s. Where I used to work we had some machines with Idec PLCs from the 80s, still running.

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                    • #11
                      I have a Cutler-Hammer D100 from 1986 still working and running in my home garage.
                      If you've done the very best you can, worrying won't make it any better - Walt Disney

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                      • #12
                        Originally posted by pbw View Post
                        Assuming good clean power and room temperature is 30 years a realistic expectation?
                        I've seen mine and others go 20+ years with no issues (in fact I was just telling a guy this morning about taking out a functioning 1980s Toshiba in 2004, with relay outputs driving stuff that cycled every 10 seconds, in an application that sometimes ran two shifts!!), but I would use 10-15 years for planning purposes.

                        Besides, in 10-15 years, there will be a PLC 200 times better than will do all sorts of cool new things and cost 10% of what the original unit did.

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                        • #13
                          Originally posted by Ridgeline Mach View Post
                          I have a Cutler-Hammer D100 from 1986 still working and running in my home garage.
                          Is that the relabeled Toshiba stuff? The Toshiba I mentioned in my other post was an EX28, and on some other machines they had some C-H branded units.

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                          • #14
                            Originally posted by ControlsGuy View Post

                            Is that the relabeled Toshiba stuff? The Toshiba I mentioned in my other post was an EX28, and on some other machines they had some C-H branded units.
                            Yes.

                            When I first saw them they were a Cutler-Hammer product. My guess is Cutler-Hammer had a contract with Toshiba to not offer the Toshiba version after about 5 or so years. A friend of mine, whose since retired, was a C-H distributor, but also sold the Toshiba versions when C-H had problems with delivering the D100. They were exactly alike, except the C-H's were black while Toshiba's were tan. That was my go to PLC for the longest time before the SLC500 came out and forced us to move away from it.

                            I get a chuckle now out of that D100. I have it operating contactors in the workshop of my garage. It is so slow, it's hard to believe it was once considered high tech. I flip a switch, and denote a perceivable delay before a contactor is energized or de-energized.
                            If you've done the very best you can, worrying won't make it any better - Walt Disney

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                            • #15
                              Oh, and the replacement for the Toshiba applies here, too. It was a DL250 and it's still humming along just fine after 14 years; I was in the plant just the other day. Oh, and it's very hot in there, probably up to 125-130 sometimes.

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