How does the Triconex system prevent DO contacts from sticking together?
Thread Content
While reviewing the user manual for the Triconex system, I came across a problem that is likely to be common: the DO output circuits of SIS systems are designed to be \"fail-safe\", meaning that power is supplied under normal conditions, and any disconnection in the circuit can be detected when power is lost. However, this design inevitably introduces another issue – if the output relay remains powered for an extended period of time, its contacts may stick together, preventing it from separating when it should. What should be done in such a situation? Does the Triconex system have a similar diagnostic function to check whether the output contacts are stuck? Thank you!
Since you’ve added relays in between, it has nothing to do with TRICON. To avoid the situation you mentioned, it is necessary to use safety relays that are SIL-certified.
In addition to using relays of good quality, another approach is to test the interlock operation as often as possible when the opportunity arises.