Page 3 of 3 FirstFirst 123
Results 21 to 27 of 27

Thread: sticking contacts on a safety relay

  1. #21
    Join Date
    Jul 2006
    Location
    San Francisco Bay Area, CA, USA
    Posts
    7,620
    I believe the error was in the safety relay, not the PLC. Maybe your point was that an error on the PLC program is what was triggering the error in the safety relay, and that may be something worth looking into. As far as I knew, the SLCs never had a qualified Safety PLC format, so it's entirely possible that there could be something that doesn't happen correctly inside the PLC that is then triggering the safety relay, then in the process of cycling power every time to clear it, the safety relay eventually gets its own internal failure and has to be replaced.
    __________________________________________________ ____________________________
    Many people are shocked when they discover I am not a good electrician...

  2. #22
    Jaref yes exactly as you surmise.

    Candidly there are theory that the back mounting plate when it is not stainless steel it can get magnetized if it is one in a large relay cabinet and the inductance of many coils in there causes or proximate distance to magnetized coil adjacent to some other ones that is why I mentioned min separation clearance between electrically pilot coils in close proximity and or the back plate.
    I kind of do follow your post occasionally so I thought oh well explain about getting in late to this thread.

  3. #23
    Quote Originally Posted by nec_addicted View Post
    One option you have is determine the latest update to the program then move the key switch on the controller and reload the latest version to the kernel (AKA firmware) inside the controller to set the logic controller straight which one has the lead.
    Couple slides supporting the bench diagnostics before attempting and chnages
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	basics-of-plcprogramming1-61-638[1].jpg 
Views:	33 
Size:	89.5 KB 
ID:	20068   Click image for larger version. 

Name:	basics-of-plcprogramming1-49-638[1].jpg 
Views:	34 
Size:	55.3 KB 
ID:	20069  

  4. #24
    Join Date
    Feb 2009
    Location
    Durango, CO, 10 h 20 min without traffic from winged horses.
    Posts
    9,436
    Quote Originally Posted by nec_addicted View Post
    Jaref yes exactly as you surmise.

    Candidly there are theory that the back mounting plate when it is not stainless steel it can get magnetized if it is one in a large relay cabinet and the inductance of many coils in there causes or proximate distance to magnetized coil adjacent to some other ones that is why I mentioned min separation clearance between electrically pilot coils in close proximity and or the back plate.
    I kind of do follow your post occasionally so I thought oh well explain about getting in late to this thread.
    I'm calling BS on this.
    If you go and decide to dance with a gorilla the dance ain't over till the gorilla decides it's over.

  5. #25

    Magnetized Rail Road Electric Relays

    I always HAVE admired your statutory sign-off line "if you dance with a gorilla......"

  6. #26

    Magnetized Rail Road Electric Relays

    I have allways liked your stautory sign off line "If you dance with a gorilla......"

    Railroad Traffic Control and relays...

    www.railroadsignals.us/support/relays


    sometimes the truth is harder to believe and sounds more fantastic to comprehend than a fishing expedition.

    My only actual experience with this type relay control phenom was a traffic control system for a bridge single lane with lights om both ends. The idea postulated was to use a relay termed for ,Tailgate logic. It was a relay that picked up back bumper when crossing past-over a coil of large conductor buried in the ground after having started on the remote end of a bridge elevated.

    The lights worked but the reset did not. So my PLC guy in the middle of a deep sleep was called out to fix the reset from turning both lights on both ends from red to green so traffic could continue to cross.

    cheers

  7. #27
    Join Date
    Sep 2017
    Location
    Jefferson Wisconsin
    Posts
    10

    There really is a god!

    Well the coworker paged us back to the robot cage after the brand new in the box Allen-Bradley Safety relay was just installed and low and behold what do you think happened Friday? You guessed it. The band-new-in-the-box relay that replaced the original one (to the tune of $1700 bucks for the two of them) failed on the code 11 "internal fault" after I told them all to pull up the program and find out whats latching that bit, but "NO", the co-worker didn't want to listen to me and kept listening to the robot/pallet wrapping machines tech. Now we are so far at three relays changed. First one replaced by them, now this one, and I will venture a guess they are going to tell the co-worker to replace this one to make it a grand total so far at three.

    Yup, instead of finding the root cause of the problem we keep throwing parts at it.

    So far, stay tuned

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •