I would like to ask whether it is possible to control the PLC and on-site valves via communication
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A newcomer has a question for everyone: A set of equipment has been installed in an explosion-proof area; it comes with its own PLC, the control station is located on-site, while the operation station is situated in a control room several hundred meters away. Party A wishes to use fiber optics or other communication methods to display process parameters and operate the on-site automatic control valves, as well as to implement interlock and shutdown functions. Previously, for safety reasons, we would usually place both the PLC cabinets and the control stations in secure locations, connecting them to the field using hardwired connections, which ensured no problems with detection and control. Are there any national standards, industry standards, or other guidelines that specify whether it is possible to control devices such as PLCs or actuators on-site via communication? Please give me some advice. Thank you!
This is a very common setup pattern for control stations and operation stations. Connected via redundant optical fibers. Other communication methods cannot be used.
Thank you. I have another question: usually, the operation station and the control station are placed in relatively secure cabinet rooms and control rooms, allowing fiber optic connections to be used. If one of them is located in a less secure area, would security considerations regarding routing prevent the use of fiber optics or communication for control purposes? Are there relatively clear standard specifications, or are there no restrictions?
Communication technology is now very advanced, and redundant communication methods (two switches, two optical cables) are used, so the building owner needn’t worry about this issue. During implementation, the two communication optical cables do not follow the same path to prevent simultaneous damage. The wired method can be considered when there are few points and the distances are short.
In other words, it isn’t explicitly stated whether this can or cannot be done, right? Then choose according to the actual situation. Thank you!
No matter where it is placed (of course, relevant specifications must be met, which is outside the scope of this discussion), fiber optics are used for long-distance connections. Generally, it follows a redundant fiber mode with two routes; it is best to have one location per day. If that’s not possible, then it shouldn’t be in the same path either; for example, using the same slot box is definitely not appropriate.
Controling a valve via communication means that the control system outputs communication signals (Modbus, TCP/IP) to directly control the valve. This approach is generally not recommended, but since fieldbus systems output digital signals, there is no problem with it. At Shanghai SAIKO, fieldbus systems were in use over 10 years ago with no problems. What the original poster is referring to is the use of fiber optics for communication between the host computer and the control station; in both cases, the communication between the host computer and the control station certainly takes place via network protocols. I haven’t seen any others.
This is quite normal; in the future, the workload will be reduced in this way. Distances of several hundred meters can now be controlled via 485 Ethernet, allowing remote operation from the on-site host computer. Implementing redundancy enhances safety, with the key aspects being the safety of the control programs and the ability for emergency shutdowns