Regarding the sequential recording of SOEs in the dark horse SIS, what are the principles for recording and what is the content of the recordings?
Thread Content
1. How do SOEs record interlock actions? How is the recording function implemented? 2. What is recorded? Is it the time of the incoming and outgoing DI/DO signals, the time when the solenoids on site are powered on or off, or the time at which the valves open and close (with feedback from the on-site valves via MICROSwitch)? 3. What do the start time and end time represent respectively? If the signal is sent instantaneously, why is there a gap between its start time and end time? 4. In front of the tag number, there is E0204+ the instrument tag number. What does this E0204 represent? Is it a code value? Automatic control instruments
SOE’s interlock action recording function
The SOE function of SIS is for accident cause analysis. SOE collects and displays the time and security events of FCS.
E0204=EVENT 0204
The application systems vary from place to place; it’s the first time I’ve heard of this system
As a technology used by a few manufacturers to make huge profits, the specific implementation methods of SOE are not made public. However, although we need not know or understand the underlying principles of its implementation, we do need to be aware of our requirements, that is, what can be used for tracing in the event of an accident. Since the variation of signals in DCS/PLC systems is related to the program scanning cycle – which is essentially the sampling rate – the values of external signals obtained using conventional methods and ordinary cards are very likely not to correspond to the values at the actual times when those signals occur. In other words, although a series of related and consecutive events occur one after another, conventional methods are unable to distinguish between them, which results in insufficient accuracy. As a consequence, it becomes impossible to determine which event occurred first after an interlock is triggered, or which event caused another, and thus it is impossible to trace back to the root cause of the problem. Therefore, it can be inferred that to implement such functions, the ability to report immediately whenever there is a change, and to do so proactively, is essential. It is not waited until its scanning cycle arrives to carry out detection; rather, any change at any time is sent directly to the system, with a timestamp being recorded.
1. HIMA’s SOE is the third-party software WIZCON (which is also related to Yokogawa’s control software); variables are defined at the control layer and come with time stamps；
2. The content recorded by SOE is first a boolean value, which can be customized；