Issues with connecting complete sets of equipment or frequency converters to the SIS system

Since no one has answered, I’ll provide the answer: 1. The fact that the rotation speed of the reactor’s mixer and the current supplied to it are fed into the SIS system is already a problem; this relates to the selection of appropriate points for monitoring. The rotation speed and current of the reactor’s mixer are generally control signals, but they should rather be part of safety interlocks. Safety interlocks typically do not use signals from the equipment itself; instead, they use direct variables – for example, if the temperature rises after the mixer stops working, that temperature value is used as a trigger for the safety interlock. Signals related to the operation of the equipment themselves are usually not used in such systems. Additionally, it is possible for a point to enter both the SIS and the DCS; a one-input two-output safety barrier will suffice, with the point first entering the SIS and then the DCS. 2. The equipment used to control the temperature of the jacket in the reaction vessel is part of a complete set; however, the valves require SIS interlocking. Since the valves need SIS interlocking, is it necessary to also use a PLC for control? If not, then such valves can be excluded from the complete set of equipment and not connected to the PLC. If control is also involved, the common practice nowadays is to use two solenoid valves, one connected to the PLC and the other to the SIS. The SIS cannot send signals to the PLC.

First of all, thank you very much for your answer. According to Document No. An Jian Zong Guan San [2009] 116, the control requirements for hydrogenation reactions are as follows: The person who prepared the report at our safety assessment agency was very persistent and included all possible control methods, among which was the interlock related to the stirring current of the reaction vessel...

There’s nothing to do about it; in that case, you’re doomed. It’s obvious that decisions were made arbitrarily when setting up the safety circuitry, without considering feasibility at all, and those decisions were even included in the report. As required, inverters with SIL certification are indeed necessary. I checked and found that inverters with SIL2 certification do exist; if such certification is not available, an empirical approach could be used, but that would be problematic, and it’s not certain whether it will work.

1. This can be achieved by using two safety barriers; one barrier is installed in the SIS cabinet, while the signal goes to the DCS either through the SIS or via a cross-panel cable. 2. The pneumatic valve can be equipped with a solenoid valve to control the air circuit; the SIS interlock solenoid valve activates to achieve emergency shutdown. Under normal conditions, the solenoid valve remains powered, the air path is unobstructed, and the PLC can control it freely; in an emergency, the SIS sends a signal causing the solenoid valve to lose power. The fault switch of the valve must be set correctly.

Well, there are frequency converters with SIL certification available. There’s nothing to do about it – the safety assessment agencies, the experts on these assessments, as well as the leaders of the relevant departments all lack practical experience on site; they rely solely on theoretical knowledge...:L