Control relay contacts
Control relay contacts get burned and/or oxidized over time and may loose contact after being closed for a prolonged period. Cycling control relays off and back on "wipes" the contacts clean and then they start working again until the next failure.
Condensation and water leaks can cause permanent damage from corrosion that's not easy to detect, even on new equipment. Not only can it cause relay contact problems, minor condensation on a motherboards may result in hidden corrosion across sensitive circuits which are intermittent depending on the humidity. There are several relay and socket problems here. The condensation may dry out but the problems still remain - bad connections. Terminals and copper wires should be bright and shinny. Dull green, gray and black discoloration may be condensation, it's worse on DC controls than AC, like the + battery terminal on your car batter that always goes bad first.
PLCs later added on older industrial facilities "hickup" all the time because of power related problems like I mentioned earlier above, especially on older buildings with newer VFD ect that have been added over time. Sometimes failure to properly isolate analog sensor wiring in conduits and even the controls themselves (plastic wireways) may result in a false input triggering, especially with modifications here and there. One output may result in triggering another falsely.
Condensation and water leaks can cause permanent damage from corrosion that's not easy to detect, even on new equipment. Not only can it cause relay contact problems, minor condensation on a motherboards may result in hidden corrosion across sensitive circuits which are intermittent depending on the humidity. There are several relay and socket problems here. The condensation may dry out but the problems still remain - bad connections. Terminals and copper wires should be bright and shinny. Dull green, gray and black discoloration may be condensation, it's worse on DC controls than AC, like the + battery terminal on your car batter that always goes bad first.
PLCs later added on older industrial facilities "hickup" all the time because of power related problems like I mentioned earlier above, especially on older buildings with newer VFD ect that have been added over time. Sometimes failure to properly isolate analog sensor wiring in conduits and even the controls themselves (plastic wireways) may result in a false input triggering, especially with modifications here and there. One output may result in triggering another falsely.
