Difference between local operation and remote operation of PLC
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During the project’s equipment procurement phase, the placement of PLC cabinets is a concern. I would like to ask about the advantages and disadvantages of on-site operation panels, PLC control, and DCS control, as well as what distance requirements exist The pictures show two options sent by the design institute. I’m not sure what criteria should be used for making a choice – whether it’s based on process requirements, site conditions, or the characteristics of PLC and DCS remote transmission. I hope experts can give some guidance! Thank you so much!
If an explosion-proof area is involved, it is recommended to place it in the cabinet room; otherwise, it should be placed on-site. The distance depends on circuit evaluation and voltage drop. Generally, there is little need for hardwired connections for PLC and DCS signal points, but hardwired connections are required for communication and control signals. For ordinary equipment, PLCs are usually used, while more complex systems can employ DCS; in a DCS system, a separate set of controllers is typically allocated. For small-scale DCS systems, PLCs are recommended.
This post was last edited by myface on 2018-12-12 at 09:48. The images are not visible. If it’s just monitoring data, using communication channels can help save on cable costs and DCS node expenses; it’s worth considering whether this is cost-effective. However, if interlocking is involved, it’s better to use hardwired connections.
Are you considering local operation of the centrifuge or operation from the DCS room? Remote operation can be carried out over a distance of no more than 500 meters. On-site operation: On-site operation should be as close to the unit as possible. A PLC cabinet is installed on-site to enable local operation; the cabinet has a communication interface (a communication protocol needs to be agreed upon), and the signals are sent to the DCS, which only displays the information without the ability to control it. There are two options for remote operation: either not use a PLC and transmit signals to the DCS configuration, or use a hardwired shutdown system ； Place the PLC in the cabinet room; there is an interface on the PLC cabinet through which data is transmitted to the DCS using a predefined communication protocol, allowing for the control of the DCS ； Remote operation signal transmission can cover a distance of no more than 500 meters (communication cables are now much better shielded than in the past). In engineering applications, for distances of over 500 meters, on-site signals are sent to the intermediate cabinet room (located between the site and the Chinese and English control rooms), and from there they are transmitted to the central control room for processing.
The content of the image is this text, written by the design institute
How to achieve explosion protection for PLC cabinets? Is the cabinet itself explosion-proof? Positive pressure explosion protection? Do you mean the DCS cabinet room when you talk about the cabinet room? It’s over 200 meters from our location to the DCS cabinet room
I’m not quite sure what you mean by “less hard wiring” It seems you understand quite well. Could you explain it in more detail? Thank you
Few signal points – use hard wiring