What is interlock release? Come and take a look
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The company has a coal grinding system, with temperature, pressure, and pressure difference interlocks installed on the grinders. This coal grinding process system is also equipped with a Siemens S7-300 PLC that comes with a touch screen and fault alarm functions. The DCS has already been used to remove all the temperature and pressure interlocks from the grinders; however, the interlocks in the PLC have not been removed. I asked whether, if those interlocks in the PLC remain in place, the system will shut down if the temperature and pressure exceed their limits
Theoretically, it will still stop, because generally equipment like yours is mainly controlled by PLCs; DCs do not directly control the equipment – instead, the PLC issues commands first, and it is the PLC that controls the equipment.
It will trip; generally, the PLCs in such systems are connected to the DCS, and in other words, the trip will still occur if the interlocks in the PLCs are not disabled
In my opinion, it’s about determining which components are sent to the DCS and which ones go to the PLC, as well as what role each of them plays
Look at how the signals are transmitted – why can the DCS disable interlocks, while interlocks can also be used to trigger shutdowns in a PLC? You haven’t explained the signal flow clearly.
The original poster didn’t explain clearly; it depends on whether the parking signal is generated by the DCS or by the PLC. It’s necessary to refer to the original design diagrams. Based on past experience, if a PLC is involved on site, normal control and parking functions are carried out by that PLC, while the DCS and PLC communicate with each other using the MODBUS protocol to retrieve parameters and display them on the DCS screen. In principle, due to its low communication speed, MODBUS cannot be used for logical operations and control. But since you mentioned that DCS has chains, you need to check the original design diagram.
The interlock in the PLC has not been disabled; if the interlock conditions are met, the corresponding interlock will be triggered. Interlocks have already been implemented in the PLC, so there is no need to repeat them in the DCS. The communication from PLC to DCS is used only to transmit important signals to the DCS; generally, the DCS serves solely to monitor field parameters.
Is the electrical stop signal sent by the DCS or by the PLC? You didn’t make that clear