PLC versus DCS

PLC versus DCS

PLC versus DCS

PLCs and DCS  play a major role in Industry Automation  controlling Modern manufacturing Plants and Factories. Over the years due to continuous development and functionality  merging  between PLCs and DCS. The border Line of Differences became obscure. This blog post will lay out the differences between the both to facilitate automation Engineer in choosing the best Systems ( PLC or DCS)  for their Project.

Below are just my personal Opinion and Comparison  , it does not Represent any Company

PLC versus DCS Selection

NO Subject Comparison PLC DCS
1 Speed 20ms to 100ms 80ms to 800ms
2 Down Time Recovery Depend on Controller Architecture Design to Switch Interoperability
3 Process Batch Control Can do Batch Control but Specialize in High Speed Process Specialize in Batch Control
4 Flexibility Design  For High Program Modification Rigid not easy for Modification build in static function block  Library
5 Scalability Scalable depends on architecture Design Design for Scalability
6 Cost Cheaper compare to DCS Expensive Compare to PLC
7 Complexity Could be very Simple to very Complex Plenty of Library . Things are design for Simplicity
8 Skills Needed Ladder Logic, Structure Text, Function Block, Sequential Function , C,J Function Block, NT, SQL

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PLC versus DCS ( Control Architecture  /Communication Protocol )

 

Hardware >Allen Bradley >Siemens
ControlLogix CompactLogix S7 1500 S7 1200 Simatic HA Series Simatic RTU
Functionality Configuration PLC / DCS/ Telemetry PLC / DCS/ Telemetry PLC / DCS/ Telemetry PLC / DCS/ Telemetry DCS Main Batch Controller Telemetry
Redundancy Auto Triger User Configured Auto Switch FB User Configured Batch Control Take Over No Redundancy
TCP/IP Yes Yes Yes Yes Yes Yes
Modbus Yes Yes Yes Yes Yes YEs
Profibus No No Yes Yes Yes Yes
Profinet No No Yes Yes Yes Yes
Control Net Yes Yes No No No No
FieldBus Yes Yes Yes Yes Yes No
Hart Yes Yes Yes Yes Yes Yes
Processing Power High Processing Power Medium Processing Power High Processing Power Medium Processing Power High Processing Power Medium Processing Power

 

PLC versus DCS ( Implementation and Utilization )

 

Hardware >Allen Bradley >Siemens
ControlLogix CompactLogix S7 1500 S7 1200 Simatic HA Series Simatic RTU
DCS Utillization PlantPax Connected Enterprise No No No Sinema Server Connect No
Telemetry Yes Yes Siemens Remote

Access

Sinema Remote

Sccess

No Yes
Certification Max Sil2 Sil3 Sil2 Sil3 Sil2 Not Clear Not clear
Utilization Market Leader Onshore Chemical Process Plant High speed Manufacturing Plant Water Treatment Plant & Pharma FMCO Processing Plant Chemical and Food Plant Wind Farm

 

 

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