The PLC vs. DSC Experience Survey interim report is an ongoing, crowdsourced, open survey for users to share experience and know-how with the automation community.
The PLC vs. DSC Experience Survey interim report is an ongoing, crowdsourced, open survey for users to share experience and know-how with the automation community. Take the survey here. Using a PLC-based system rather than a Distributed Control Systems (DCS) has been a growing discussion for several years. Distributed Control Systems (DCS) have traditionally been the primary solution for process automation, but for a number of reasons, many users implement applications using PLC systems instead of DCS. Some users believe that a single integrated architecture based on PLCs, Industrial Computers, and PACs (Programmable Automation Controllers) is the best approach to total plant automation. More than 10 years ago, some vendors started advocating for a single PLC control architecture for process plants to displace DCS systems. In a 2011 interview of a business manager at a major PLC company pursuing the process business, I asked what distinguishes their offering from a DCS. He responded by rephrasing the question, noting the real question should be what distinguishes their PLC-based DCS from other DCS systems. Most process plants today have both DCSs and PLCs installed for controls. Traditionally, DCS control and manage the core processes (food, pharmaceutical, refining, etc.). PLCs control non-core process functions, including material handling, water treatment, motor controls, balance of plant operations, air compressor controls, packaging, and other functions. At some plants, PLCs or DCSs control all of the plant functions, but at this point these are the exceptions. siemens s5
The Open Process Automation Forum, part of The Open Group, is developing the new Open Process Automation Standard, O-PAS™ , intensifying discussion around PLC vs. DCS. The O-PAS™ Standard aims to develop, publish and evolve an open architecture and specification supported by industry end users, suppliers and integrators. The O-PAS Standard defines an open, interoperable and secure architecture for industrial process automation systems. Starting with the first version of the standard, the edge control and programming is specified as the established IEC 61131 and newer IEC 61499 control engines and programming. For more background, read the Roots of the Open Process Automation Forum.
The PLC vs. DCS Survey is ongoing and designed to promote understanding of process automation and control user issues, tradeoffs, concerns and thoughts. A summary of the crowdsourced results will be published periodically as a resource and refence for users. This is an independent survey not sponsored by any suppliers. The ongoing open survey can be taken here. These are current results based on user experiences with the percentages showing responses to questions. First, let’s look at the demographics of the respondents so far, which are shown in the first two graphs. More than 90% of those who filled out the survey have 8 years of work experience or more. Just under half (46%) of respondents are from the USA, but people in Canada, Europe, South America, China, Australia, Asia (excluding Japan) and South Africa also responded. Survey respondents’ work experience Where the respondents live
Have you used DCS and PLCs for process control applications? Before diving into the survey results comparing DCS and PLC, it’s important to point out that a majority (86%) of survey respondents had experience using both DCS and PLCs for process control applications. The remaining 14% had experience using either DCS or PLC.
PLC vs. DCS: Overall cost comparison in process applications Initial survey results indicate that in 82% of cases, PLC systems cost less than DCS systems in process applications. However, some respondents (8%) reported the opposite, and 10% said PLC and DCS systems presented about the same costs.
PLC vs. DCS: Upgrade cost comparison About two thirds (66%) of survey respondents reported that PLC systems offered a lower upgrade cost than DCS systems. Eighteen percent said DCS has lower upgrade costs, and 16% indicated the two systems shared about the same costs for upgrades.
PLC vs. DCS: Maintenance cost in process applications In yet another cost comparison, respondents were asked to compare the maintenance costs of the two systems. Just over half (56%) of respondents to the survey reported that PLCs have a lower maintenance cost, while 30% said the opposite, indicating that DCS have lower maintenance costs.
PLC vs. DCS: Engineering hours in process applications Cost considerations are important, but it’s also important to think about the manpower involved with managing systems. Just under half (44%) of respondents said DCS requires less engineering time than PLCs, while 20% indicated that PLC requires less engineering hours than DCS. Thirty-six percent said the required engineering hours are about the same.
PLC vs. DCS: Programming flexibility Just under half (46%) of survey responses indicated that PLC possesses more programming flexibility than DCS. 22% said the opposite. The remaining 32% of respondents said the programming flexibility for the two systems was about the same.
PLC vs. DCS: Enterprise & Cloud Communications Options Another important consideration involved the number of options the systems offer when it comes to enterprise and cloud communications. Forty percent of those who took the survey said DCS has more Enterprise and Cloud Communication Options than PLC, while 28% asserted the opposite view. The remaining 32% of participants indicated that PLC and DCS systems offer about the same number of enterprise & cloud communications options.
PLC vs. DCS: Process Applications Controller Field I/O Device Selection Availability (Sensors, Actuators, etc.) Another question asked participants to say whether PLC or DCS offered a wider range of process application control field I/O devices, such as sensors and actuators. Almost half (48%) of survey participants said the two systems offer about the same range of devices. 42% said PLC has more; 10% said DCS has more.
PLC vs. DCS: Process Applications Industrial Network Options (i.e.: HART, ISA100, WirelessHART, Profinet, EtherNet/IP, I-O Link) Survey respondents also offered their opinions regarding the range of process applications industrial network options for DCS and PLC. While 34% reported that PLC controllers have more industrial network options, just 18% said the same about DCS controllers, and almost half (48%) of respondents said DCS and PLC controllers offer an equal number of industrial network options.
Please contribute your experience and opinions by taking PLC vs. DSC Experience Survey which is independent and not sponsored by any vendor. Take the survey here.
Bill Lydon is a Digital Manufacturing Transformation Industry 4.0 Consultant available for consulting and advisory projects. Lydon has 35 years of experience designing and applying technology in the automation and controls industry. He started his career as a designer of computer-based machine tool controls; in other positions, he applied programmable logic controllers (PLCs) and process control technology. Working at a large company, Lydon served a two-year stint as part of a five-person task group, that designed a new generation building automation system including controllers, networking, and supervisory & control software. He also designed software for chiller and boiler plant optimization. Bill was product manager for a multimillion-dollar controls and automation product line and later cofounder and president of an industrial control software company.
Check out our free e-newsletters to read more great articles..
plc controller ©2024 Automation.com, a subsidiary of ISA