adccommunitymod (AutomationDirect) asked a question.
Created Date: September 22,2009
Created By: sjstein
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Hello all, At our facility, we have begun to see what I'm afraid is the start of a disturbing trend - failure of the "Upper " bank (A) of the 16 bit output module (p/n D2-16TD2-2). This is starting after over 5 years of run time in a system which sources current to pull in a coil on a remote relay (~70ma pull-in current). Typically only three or four of the outputs are energized during the running time, so the overall current is quite small. Within the last six months we 've had 3 separate module failures - all in unique systems (although all identical designs). Each module shows the same failure mode - the PLC controller doesn't realize anything is wrong; the front panel indicators (LEDS) work fine (this is to be expected). The outputs all seem to "float " at 24Vdc (which is the common voltage connected to the module), even if the controller is not commanding the output to energize. Note that this failure only seems to affect one bank (A), the other bank (B) seems to operate fine (although is unused presently in my design, so is not exposed to field devices). This failure mode is unfortunate in that the output module is still able to source enough current to energize the remote relay - even if the PLC program is commanding the output to de-energize; so I now have a remotely controlled device that can no longer be shut down under PLC control. I suspect somehow an opto-isolator is being blown, but the characteristics of this failure are hard to nail down given the typical use of isolation (e.g. it seems prudent to design output sections in a fail-safe matter in that a failure of isolation component would induce a low/de-energized state on those outputs). So my questions are as follows: * Are there schematics available for the output/isolation section of this module? * Has anyone else seen this failure mode? * Any suggestions on mitigating the problem or designing it away? Thanks in advance, --Josh Stein
Created Date: September 22,2009
Created by: Szarman
Try a different slot in the base, or try a different base. Also, you might have some sort of inductive load problem. I would suspect that the outputs are blown not the opto-isolator, but I am no expert. I am sure plenty of people will have more troubleshooting ideas for you.
If the unit you have no longer works at all (the outputs are damaged) and you have to buy a new one. Try a F2-16TD2P. It has fault protected outputs and can source .25A per point instead of 0.1A.
Created Date: September 22,2009
Created by: sjstein
It is definitely the module itself as the problem happens back on the bench in a different base with a different controller.
Created Date: September 22,2009
Created by: a agnone
I did not see where you mention one of the outputs fails or all 8 of them fail. Most likely the output is shorted. I can not remember if they use FET's or a Bi-Polar transistor but they do short if overloaded. We just had a simular case a few month back with the same module. It turned out one of the coils on a vacuum generator was failing, but it would still work. It drew too much current and over time blew the output. We even had a coil wire short itself to the valve casing and short out the output, it was intermittent. These things are hard to find sometimes. You might want to just try and replace what ever is connected to that output and see what happens. You are right to see the led's work. They are on the control side. It is sometimes hard to believe several systems can have the same problem, but it happens. You said the systems are 5 years or more in age. It is possible things are starting to go bad. I would get one system to work then go after the others. Some would even recommend fuses on the outputs to prevent any accidents. I know this is not a lot of info, but something to check.
Created Date: September 22,2009
Created by: sjstein
I did not see where you mention one of the outputs fails or all 8 of them fail. Most likely the output is shorted. I can not remember if they use FET's or a Bi-Polar transistor but they do short if overloaded. We just had a simular case a few month back with the same module. It turned out one of the coils on a vacuum generator was failing, but it would still work. It drew too much current and over time blew the output. We even had a coil wire short itself to the valve casing and short out the output, it was intermittent. These things are hard to find sometimes. You might want to just try and replace what ever is connected to that output and see what happens. You are right to see the led's work. They are on the control side. It is sometimes hard to believe several systems can have the same problem, but it happens. You said the systems are 5 years or more in age. It is possible things are starting to go bad. I would get one system to work then go after the others. Some would even recommend fuses on the outputs to prevent any accidents. I know this is not a lot of info, but something to check.
All eight in a single bank fail together - bank 'B ' in unaffected.
Unfortunately I don't really have an opportunity to swap or diagnose the issue on the load side as the solenoids are buried within an exclusion area and are under control of another group; it's almost impossible for me to "prove " a catalyst since none of my guys work on the field devices.
I'm going to try the 'F ' model with the protected outputs as a first attempt.
Created Date: September 22,2009
Created by: FACTSTech
sjstein
Sounds like the failures are wiring and lack of suppression on inductive loads (coils).
You can also change to "F2"16TD2P, DC Output with Fault Protection ", however always suppress all coils.
Created Date: September 22,2009
Created by: a agnone
FACTS did he say what CPU he is using? I think those modules are only supported in the DL260.
Created Date: September 22,2009
Created by: stimpsonjcat
I agree...the coils need suppression.
Created Date: September 22,2009
Created by: FACTSTech
a agnone is correct, the F2-16TD1P and F2-16TD2P are only supported by the 250-1 and 260 CPUs.
Created Date: September 22,2009
Created by: milldrone
All eight in a single bank fail together - bank 'B ' in unaffected.
From the original post
The outputs all seem to "float " at 24Vdc (which is the common voltage connected to the module), even if the controller is not commanding the output to energize.
My vote is for a ziplink surge supressor ZL-TD8-24 if the added coil dropout time can be tolerated. It would be hard to believe that the "shorted outputs all happened from an overload. But an inductive kick, say from several coils at the same time is my guess.
Unfortunately I don't really have an opportunity to swap or diagnose the issue on the load side as the solenoids are buried within an exclusion area and are under control of another group; it's almost impossible for me to "prove " a catalyst since none of my guys work on the field devices.
I did not see any mention of fast blow .1 amp fuses for each output either.
Created Date: October 19,2009
Created by: pslapshot
Pslapshot
I think there's a small fuse for each bank. Did you check that.
I went through 3 card's before I found out.
Pat