Today is...
Monday, June 26, 2017
Welcome to, the global online
community of automation professionals.
Featured Video...
Featured Video
Wiring and programming your servos and I/O just got a lot easier...
Our Advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive
Can Siemens PCS7 be considered as a True DCS?
All the Vendors claim their offering is a true DCS and 'can perform the assigned role'...
By Dr. R. Murugesan on 24 March, 2007 - 10:17 am

As a specialist Control System Professional, I am involved in the selection of Industrial Automation Systems for Power Plants of varying capacities.

Against our bid enquiries for Distributed Control Systems (that should have superior features with Optimisation, Hot Swapping, Integral SoE, Compliance to 'Open Architecture or with Fast Ethernet', vendors of all kinds submit their offerings.

All the Vendors claim their offering is a true DCS and 'can perform the assigned role'. It appears the following products are not truly comparable in character and functional capability.

Siemens PCS7, XPadd
Metso DPU4F
Yokogawa CS100
Honeywell Experiod, UC900

I would be very thankful for valuable inputs from professionals on the above products justifying them as true DCS or otherwise.

Thanks and regards

Dr. R. Murugesan

> Honeywell Experiod, UC900

Two different products.
Experion is a DCS.
The HC-900 is a hybrid controller. It has redundant controller & power supplies, but not redundant I/O. I/O limitation is on the order of 2,000 points.

HC is great for what we use it for, but it isn't a DCS.


By Dr. R. Murugesan on 14 April, 2007 - 2:31 am

Dear Mr. Bud,

Thank you for your response with brief but valuable info on Honeywell HC900; truly, HC900 cannot be classified as a true DCS.

Several automation solutions {DCS, PLC, Hybrid or PC-based with packages like WonderWare} can serve a given set of plant automation needs. The overall architecture capability, processing performance, operational convenience and readily meeting future needs like integrating with an ERP cannot be ensured by all such options. A true DCS is expected to cater to all such needs.

In the light of above, will you or other interested professionals post your valuable inputs to my mail posted on March 24, 2007?

Thanks and regards,

Dr. R. Murugesan

Dear Dr. R. Murugesan,

Please add the Foxboro I/A Series DCS from Invensys to your list.

I personally headed a team of Engineers in the purchase/configuration/installation/commissioning of a 1 million dollar I/A system back in the nineties.

As the Lead Engineer I made sure that the team had adequate training at Foxboro (6 weeks), coupled with bi-monthly 1 week visits to our site by a Foxboro Engineer to monitor our progress and answer any queries during the 1 year project.

The I/A system is so robust and intuitive that it was a pleasurable task for all of us involved from start to finish (and a successful finish on time too!).

10 Years later I worked in a team of Engineers in the purchase/configuration/installation/commissioning of a medium sized Siemens PCS7 System.

What a difference, someone boobed and assumed that a PCS7 System is just PLC Step7 and SCADA WinCC. IT IS NOT!!!

The two main logic tools used are FBD (Function Block Diagram) and SFC (Sequential Function Chart) which are configured and compiled before being downloaded to the PLCs (or Automation Stations in PCS7 lingo) consequently there was no budget for training.....

To make it worse somebody decided we should use Siemens PDM (Process Device Manager) for the configuration of the hundreds of Profibus PA instruments/valve actuators and Siemens Simocode motor starters on Profibus for motor control, on which we had little experience.

The software configuration was a real battle and a steep learning curve from start to finish (and a finish 12 months+ late!) which left a bitter taste in all of our mouths.

Thankfully the Siemens hardware was excellent (as usual) with only one major module failure (which was in a redundant configuration anyway) during the 2 years we were involved.

I guess I need another PCS7 project to apply all the knowledge gained from the mistakes we made....

Turning to the "is it a DCS" question, PCS7 Version 6.1 had one noticeable deficiency - Inter Automation Station (AS) signals had to be set up manually as there was no tool in FBD or SFC to select a signal from a different AS when configuring. (Unlike the Foxboro I/A System).

However the latest PCS7 system is at Version 7, so hopefully this has been fixed?


Referring to your point about Inter AS communication the latest version of SPPA T3000 or rather all its latest upgrades provide a facility called peer-to-peer connection which one can use for the same

i have heard that the latest version of T3000 is being developed to have functionality of both T3000 itself and Tec4FDE
Would you please elaborate on this if you have heard the same?

By Anonymous on 15 April, 2007 - 5:26 am

DCS = Distributed Control System
This is the pure definition of a DCS. Your bid inquiry is someones definition on what they want / need for their plant.

Too often engineers get hung up on generic nomenclature (PLC, DCS, PAC, etc.) Today many of the control products on the market can in fact be implemented in a DCS configuration.

I'm not a big fan of the Siemens product line but the ability for controller to communicate with each other and HMI's allows you to distribute control among many controller working together to run your plant. Thus multiple PACs / PLCs can be setup in a distributed control architecture.

The other items you mention are by definition "other" features of the control system. Some systems work better at distributing control and I/O, while others work better at a single task. Every system has strengths and weaknesses so you should utilize the system that best accomplish what you need in a system.

By Victor Bast on 16 April, 2007 - 11:04 pm

Dear Dr. Murugesan

The PCS 7 system from Siemens is a DCS. All the features and functions needed to be a DCS are designed into the product. We compete head-to-head with the other major vendor's DCSs, including Honeywell's Experion PKS, Emerson's Delta V, Foxboro's I/A Series, Yokogawa's Centum CS 3000 and ABB's System 800xA.

Some of the components of PCS 7, for example, S7-400 series controllers and WinCC software, are also sold separately and compete directly with other vendor's PLC and HMI products. This can cause confusion.

I'm interested in learning why you're considering PCS 7 for a power application, though. PCS 7 is designed for the chemical process industries (chemicals, refining, oil and gas, pharmaceuticals, industrial gases, glass, cement, etc.)

Siemens latest DCS for power applications is the Siemens Power Plant Automation T3000 (SPPA-T3000). The System has been designed to perform power plant automation tasks: turbine control, boiler control including boiler protection, balance of plant (BOP), etc.

Victor Bast, Application Engineer
Siemens Energy & Automation
Process Automation Systems

By Dr. R. Murugesan {India} on 18 April, 2007 - 12:32 am

Dear Mr. Victor,

Thank you for your clarifications.

Being associated with Siemens, veritably you chose to highlight the aspects of Siemens system in comparison with or superior to contemporary offereings of other system Vendors in question.

For reasons best known to Siemens India and their System Integrators (through whom only Siemens systems are offered in India!!), only PCS7 platform is offered even for Power Plant applications.

Would appreciate your detailed comparative product feature tabulation with Siemens PPA T3000 for Power Plant Automation (comparing with ABB 800xA, Honeywell ExperionPKS, Foxboro IA and Yokogawa CS3000 platform solutions).

Thank you for your support in our quest.


Dr. R. Murugesan

By Shahid Waqas on 21 April, 2007 - 10:55 am

Is the SPPA-T3000 a new brand label for the Teleperm-XP?

Best Regards,
Shahid Waqas

By Victor Bast on 28 April, 2007 - 5:35 pm

Good guess, almost right! TELEPERM XP (TXP) system was renamed SPPA-T2000 by Siemens PG in April 2006. 'T' is for Teleperm. There's an SPPA-T1000, T2000 and T3000.

Dear Victor,

Within the Siemens family (I am too a member) we have different DCS systems. One is the PC based automation system for TPP/ Combined/ Gas turbines/ plants- TELEPERM XP Add (T3000)

The other one, 'PCS7' system apart from chemicals, refining, oil and gas, pharma, ind. gases, glass, cement, it is also used for Hydro Electric Power Projects. This system is capable of SoE, machine monitoring & control & other central functions.

Thus both of the systems finds place in Power Plant applications.


Samit Mathur

By Durgesh Jha on 12 May, 2007 - 10:11 am

Dear Samit
I feel you are not aware that Teleperm XP add and T3000 are two different product and based on two different technological platform. Teleperm XP add is named as SPPA T1000.
Siemens PCS7 is 100 times better as compare to T1000 or Teleperm XP add. Teleperm XP add uses Simatic I/Os with CP 5613 interface.
Power Generation has presentley 2 systems SPPA T2000 earlier known as Teleperm XP and SPPA T3000. These two systems are german made system. T 1000 i.e. Teleperm Xp add is Indian made system with virtual controller. A PC loaded with softwares. It has a soft controller not the microprocessor or Embedded electronics based.

Durgesh Jha

Dear Durgesh,

I want some technical details for SEIRUG-P hardware, which is used for SPAA-t1000.

Please let me know where can I get docs related to SPAA-t1000.



By sum_developer on 28 March, 2008 - 11:20 pm

SPPA-T1000 is Indian system - it's sold only in India - no ref. outside (at least none till I was there). Actually my previous job was in Siemens Gurgoan where the development of this system is done. SIERUG-P (full name is Sierug Power) is name given by Siemens India for PIP controller which they buy from MPL company. In Sept. '07 Siemens India announced another controller called Microbox PC. This is a Siemens Germany product (you can read about it on Maybe this is more powerful, I'm not sure - it is a PC after all and with same Windows OS as earlier controller - so stability will still be an issue.

My personal advice is use T3000 system from Siemens Germany. It is for coal-fired power plants and very good. And don't believe what Siemens India tells you about T3000 system... contact Siemens Germany direcly for true story. Maybe you'll get lucky. I don't have any contact - maybe somebody could give it.

Other good systems are ABB and Yokogawa. Of course be careful with ABB - they have lot of systems to offer, so slection is impt. Max system and Emerson Ovation may be good, but they have no supporting setup in India.


SPPA-T3000 is a German made system, but around 25 Indians have worked in developing this system since March, 2001. The developement of this system is still being carried out in India (Gurgaon) as well as Germany. There are 25-30 Indians still working in this project and directly involved in software developement, integration, testing and training of the Control system.

By Durgesh Mhatre on 23 April, 2008 - 11:06 pm


The most critical difference between Teleperm XP & T3000 is that TelepermXP is Unix based, while T3000 is Windows base user interface, thus Teleperm XP is more powerfull but was difficult to use, but T3000 is more user freindly.

Well but both can be remotly placed on a server & accessed from any other remote location.

T3000 is basically latest version of Teleperm XP.
Both are exclusive products of Siemens AG.

T3000 have more features than TelepermXP, like if you are using Tec4FDE as an hardware tool, then you can easily generate YDR in T3000 automatically. Some more quick features like Spreedsheet engineering, have made task more simpler.

Both have in build HMI so we donot have to link the tags from two different softwares like one of WinCC scada and the PLC S7 300 or other, it automatically links parameters once path is given.

Best difference which makes T3000 better than PCS7 for power plants is that, T3000 have pick & drop menus for all possible control devices, like Motors, valves, controllers... and all we need to do is to provide the block the feedback & protection conditions & get the output.

Also it provides best documentation.

Durgesh M

By Jeff Gare on 2 July, 2008 - 12:40 am

This is not strictly true. Recently we chose PCS7 over T3000 on 1200mw power plant, all the drop menus are available through EON Germany (Grey logix). Remember all the bottom end is manufactured by Siemens A&D, it is only interface that is Siemens PG. The biggest advantage is that the end user is not locked in to long term contracts and the equipment is available from almost anywhere. PCS7 is increasingly used in the power industry. Commercially it is also a third of the price for the same functionality.

By themacallan on 11 March, 2008 - 12:39 am

I wouldn't recommend PCS7 with Power Solutions library for large power plant, especially if using tec4 and failsafe systems. OK, maybe for a plant with only 2 redundant S7-417s and a small S7-414 for small safety system it is OK, but not for 5+ redundant S7-400 systems plus a large BMS safety program.

T3000 is designed for power plants and is much better and can use both FUM and ET200M modules in the same system. You can also get firewalled communications between units, which I believe you can't get from PCS7.

I have used both systems and would certainly recommend T3000 for a large power plant, although the system set-up for T3000 really does require a specialist from either Germany or India and the configuration, committing and activation of changes needs changing as there are too many mouse-clicks for me.

By Josef Fischl on 19 April, 2008 - 4:14 am

Dear Dr. Murugesan
Dear Mr. Bust,

PCS7 is not only design for the chemical process industry. A various number of references in the field of power generation are available. The difference for use in chemical industry or power application you find the used library.

There are some good libraries for the power field
e.g. premium plant library, SWB Synor or PS library from Siemens PG. Siemens power generation have up to 200 references with PCS7 + PS library.
In my opinion, PCS7 is a good choice for power application < 100 MW.

Josef Fischl

By Andrey Zolotavin on 28 April, 2007 - 5:36 pm

For some reasons from the list disappear famous Emerson Ovation, which is truly DCS, specifically developed and installed in Power Generation applications.

Andrey Zolotavin

Dear Dr. Murugesan,

This is to highlight that the METSO DPU4F is the real DCS with the Built in SOE and High Speed Closed loop control (less than 50msec). We have used in our 500Mwe NTPC Project and it is running satisfactorily without any difficulties. HC 900 is controller, and it cannot be compared with the true DCS. Regarding the CS 100 and other ABB versions, I do not have work experience.



By Anonymous on 7 June, 2007 - 12:50 am

Dr. Murugesan,

You are interested in comparisons even though you have many years of working experience. The kind of job that you are into should have made you an eminent personality and should have refrained you from drawing conclusions. METSO DPU4F for your information is not a DCS but the controller of maxDNA DCS.

Please stand corrected.

By Anonymous on 9 June, 2007 - 12:08 am

Dr. Murugesan,

maxDNA DCS has the largest market share (over 65%) in the INDIAN POWER INDUSTRY (as per ARC report. This has built-in features like SOE, etc. as listed in your mail.

Many of the large installations in India and abroad are working satisfactorily (including many NTPCs in India).

You are working for a reputed consulting company and are still struggling to find out the comparisons is strange. At the first place most of the DCS names listed by you are incorrect and you intend to draw conclusions on suitability, credibility and worthiness of the System.

Request you to refresh your basics before drawing conclusions.


Well, Dr. R. Murugesan, the most important thing nowadays is what exactly is your requirement, because the systems are very flexible. For example, you want to have hot swapping, as you have mentioned. It is available in Siemens with hotswap backplane buses, which means if a card is defective you can replace the card online, but similarly if you need a system where you can add new cards, then you need additional online configuration software.

So it is important that you know what exactly you need. You can get support and help by contacting the vendors, they will give you presentation of their system acording to your requirement.

Hope my reply helped you.

minhajie @ hotmail. com

Try Siemens SPPA-T3000 if you want a fourth generation Control System.

My industry colleagues tell me that some controllers cannot be updated with fresh (i.e. additional) controls (e.g. say 20 new PID controls plus associated logic) while in live mode. This may also include other items like new operating displays or even the addition of controllers and operator stations.

A true DCS supports full on-line expansion at almost all levels and does not require system or controller shutdowns to achieve this.

I suggest you get detailed information from the various vendors and then decide what are your minimal requirements and then determine which vendors meet those.

Not all DCS systems (or those that claim to be DCS systems) are equal!


By Dr. R. Murugesan on 29 December, 2007 - 12:36 pm

With the implementation of some versions of Advanced Process Controls (APC) using the DCS infrastructure, it is widely reported that fiscal benefits can accrue.

If we can justify the benefits in terms of ROI in months, DCS with best features can be selected.

I would appreciate elite readers to send in valuable information on APCs implemented with specific optimization packages for concerned process units and the benefits reaped in terms of ROI.

Best regards

By Y.K.JARIWALA on 3 April, 2008 - 11:38 pm

Dear Dr. Murgesan,

You must have finalised the order of your DCS.

I just want to know if you have bought DCS
or Non DCS.


We have probably forgotten the concept of design
of DCS system & hence this discussion would go

According to us system specified by you all are
not true DCS systems & strangely you have missed
Ovation system from westinghouse/Emmerson.



Go for Emerson Delta V for small sizes (60 MW & below) or for Emerson/ Westinghouse "Ovation" for big power plants. You will get all answers, if you go for the above brands.

Siemens, by the way, is a PLC. It is us, the engineers, should evaluate that and not listen to what manufacturers say.


I beg to differ. Siemens PCS7 is as much of a DCS as Delta V is.

A DCS architecture like Delta V, PCS7, Rockwell's FactoryTalk, GE's Proficy, ABB's 800xA, or Honeywell's Experion C300, are all very similar. They all consist of proprietary field controllers, an Ethernet LAN, and a proprietary software suite running on COTS PCs.

You can debate the various features, but not the fact that they are all DCS systems.

By the way, John (no last name) you wouldn't happen to work for the company you were touting, would you?

Just sayin'...

Walt Boyes
Editor in Chief
Control magazine
blog:Sound OFF!!

Putman Media Inc.
555 W. Pierce Rd. Suite 301
Itasca, IL 60143
630-467-1301 x368

By Sastry MRKS on 30 January, 2008 - 12:28 am

I would love to agree with Walt Boyes.

In fact, I am a small person in Control Systems Integration. However, I had the privilege of working with Siemens S7-300, 400, PCS7 systems, Delta V from Emerson, Honeywell Experion PKS. I work with Rockwell ControlLogix currently.

I have done the integrations, programming myself at times.

My experience is that: Delta V, Experion, PCS7 are all DCS systems. They have Hot swapping, Online Redundant, Fault Diagnostic Modules, Ethernet/IP communication processors in the Hardware section.

These systems have high end graphics, SoE modules, highly reliable historians, Security Management modules, Asset Management software, Condition Monitoring Modules and other software modules needed for connectivity to ERP.

However, I would like to differ with a comment of someone who said everything can be done by anything. If Siemens PCS7 can do everything, there would have not have been a system like Teleperm DCS. If Delta V can do everything, there would not have been a system like Ovation.

The point is: Siemens/Emerson, when they work sincerely for Power Domain, they must have had a tough time in building logic for Boiler control, Turbine control, BOP, etc., which is very specific to Power Industry. So they must have done enough work & research on Power systems domain in terms of standardizing the software modules required for Power Industry.

Hence, it make some sense in going for Teleperm or equivalent/Ovation, or for that matter any system which is very much proven for a particular domain.

Hope I am right.


By September, Clyde on 5 February, 2008 - 11:17 pm

Dear Sastry,

I think you've hit the nail on the head - industry tailored solution - this to me really spells the difference between DCS in application as opposed to the general description, which would include any remote box and some link technology plus an interface of sorts.

For example - redundancy is a big thing and has to be correctly implemented and designed from the field to the controller, yet some PLC manufacturers ignore the field interfacing aspect, and focus solely on the PLC I/O design for hot swapping.

The donkey is in the details and unfortunately these discussions very rarely get into them - possibly too much detail?

Whatever happened to proper research? or is this a coffee table discussion, in which case... pass the sugar please.

Clyde September

By Victor Miles on 2 April, 2008 - 12:16 am

In recent times, we have come across Profibus and Profinet based controls systems. Most customers (and consultants too) generally accept Profibus. But not many know that Profibus DP comes in different versions. Each version has its own special features. For example, for process automation, you must insist on Profibus DP-V2 status. "V2" standard was introduced in 2002 and is absolute essential for critical features like SOE (Sequence of Event), Safety System (e.g. Furnace Safeguard System), fast response times.

A system which uses Profibus DP-V0 or DP-V1 can never provide accurate and precise time stamping. If you are looking for 1 ms time stamp accuracy, your system must be configured for DP-V2 which uses a real-time master to send out a time stamp to all slaves - this synchronizes all stations to the system time with a deviation of less than a millisecond. This allows for the precise tracking of events.

Similarly, if your application calls for low response time then "V2" enables you to have direct slave to slave communications - thereby eliminating the time overhead caused by need of having a master (necessary in case of V0 or V1). This reduces response time on the bus by up to 90%.

Finally, you must now that the "Profisafe" profile uses Profibus DP-V2 protocol. Profisafe is an open solution for safety applications. It defines how fail-safe devices, emergency stop pushbuttons, Light arrays, overfill cutouts, etc., can communicate over Profibus with a failsafe controller so safely that they can be used for safety systems up to AK6 or SIL3. So, if you are ordering a safety system for example a burner management system or protection system for turbine - then the controller and I/O must communicate over Profisafe and not simple DP-V0 or V1.

As per my analysis, only ABB 800xA and Siemens SPPA-T3000 provide the full DP-V2 functionality. Other systems like Centum's R3.08 or Ovation are primarily V1 systems. So, be very careful while selecting a control system for your plant - and ask a simple yet important questions: is the network V0 or V1 or V2?

Dear All,

Today I read all the stuff above. I have worked on two systems:
1- ABB's Industrial IT
2- Honeywell Experion PKS

I found Experion very much better then ABB's system, as Experion is very reliable system. Can anybody compare it with a different product (DCS)? I mean to say if anyone has worked on different systems then they should simply grade them all with reason, so that we can have a better picture.
I have one other question too: does PCS7 have a redundant (embedded) controller like Honeywell has C200, or Siemens has many controllers to control one process?

According to me, if PCS7 has more than one redundant controller for control distribution, then it should not be called DCS. According to the basic definition of DCS: A SINGLR CONTROLLER SHOULD PROCESS ALL THE LOOPS PARALLEL AND EACH LOOP SHOULD BE INDEPENDENT.

By Mike Davis on 3 April, 2008 - 12:53 am

Dear Victor,

It was a delight to read your article. Continuing the discussion, we should also discuss the reliability of a control system. Now reliability is a commonly used but poorly understood term - in my interaction with consultants and customers (particularly in Asian market like China and India), I discovered that everyone puts a great emphasis on the hardware architecture of the system. They demand features like dual redundancy, triple modular redundancy and so on - little realizing that this is not the end of the story. Unfortunately, they never ask questions on MTBF (Mean Time between Failures) of the system components. Without this basic information, any reliability calculation is incomplete. By system components, I mean both the hardware and software components. You must also pay attention to your maintenance set-up and the support you have from your control system supplier - based on this you will calculate the MTTR (Mean Time to Repair), which is the second basic information.

If you are familiar with probability theory, you would know that if failure probability P(f) of a component is 1/p then P(f) of a dual redundant component would be 1/p * 1/p = (1/p)^2. Hence, the consultant's craze for dual redundancy. In making a comparison between two different systems - say a single element system from vendor A against a dual element system from vendor B, the consultant takes a simplistic view that the dual element system must be naturally more available than a single element system. Sounds logical - but wait a moment and think - one crucial assumption here is that the MTBF value of both the elements is identical. But how do you presume this to be the case?

Let's say - the single element system from vendor A has a P(f) = 1/100

In case of vendor B let's say the P(f) for one single element = 1/8, so in case of a redundant or dual element P(f) would be 1/8 * 1/8 = 1/64.

You see what I mean - even though the vendor B has a dual redundant system, still the single element system from vendor A has a lower probability of failure and in turn a higher MTBF.

The same principle also applies when you calculate the MTTR.

So, the next time try asking your vendor to confirm the MTBF of all the hardware and software components - better still ask the vendor to provide a availability calculation.

Mike Davis
Business Development Manager
Synergy Intl.

By Y.K.JARIWALA on 3 April, 2008 - 11:40 pm

Do you have calculation for availibilty of system?


By Dr. R. Murugesan on 15 June, 2008 - 11:53 am

Dear Mr. Mike Davis,
Thank you for your suggestion to consider carefully the impact of resultant MTBF. Your inputs of failure probability calculation is quite useful to evaluate the MTBF.

I guess the total DCS Availability Factor calculations from each system vendor needs to be evaluated considering both mtbf and mttr.

I would appreciate views of other professionals to consider DCS Availability Factor.


1/p * 1/p = (1/p)^2
- in case of series connection.

Dual redundancy - parallel connection.

Dear Mr. Mike Davis,
Thank you for your valuable contributions to this topic. I agree fully with your views on the treatment of the subject on 'reliability'.

The availability of the system is of paramount importance, especially in view of harsh operating conditions. Most DCS vendors confuse this term only relating two parameters, vis: MTBF and MTTR.
In my view, the availability of the total DCS needs to be addressed considering contribution from each of the following factors:
* system failure
* control for one critical closed loop
* control for one non-critical closed loop
* control for one critical open loop
* control for one non-critical open loop
* all functions of one operator station
* one type of operator request function
* main data bus failure, back-up in operation
* main communication controller failure, back-up in operation
* main processor in one DPU failure, back-up in operation
* process I/O module in one DPU
* one complete DPU failure

Each system vendor would have in place as part of QIP to test above features with assignable weightage factors so put together, a total system availability of 99.7% or more can be guaranteed.

I would be very grateful to receive inputs from you or other professionals on the above.

Dr. R. Murugesan
Consultant-Industrial Automation & Change Management

By Y.K.JARIWALA on 3 April, 2008 - 11:35 pm

Do you have documents regarding this?

We would really appreciate it.

There are dedicated cards for SOE in every DCS.



By TimeStamp on 23 June, 2008 - 11:49 pm

From where came the requirement for 1ms time stamp for alarms?

To me the true definition has been lost in the DCS systems which used to be RISC based architectures. But now we have followed the direction of the misguided and have fallen into the Windows trap set by Gates. Not to say that Windows is bad but it is not made for real time or close to real time control. I feel that the companies Honeywell, ABB, Foxboro and others reduced the true capabilities had they stayed away from the Windows environments... Having worked for all three of them and seen what others called DCS systems but were more of an OCS open control system with a basis in the PLC platform world on the market... The true differentiation of a system will be those that program and design the system. Some programmers will have access to better tools than others on different systems only due to the markets that they serve. The key indicator will be who can survive from a company management standpoint...

By Gregory Halbert on 5 April, 2008 - 2:19 am

You forgot to mention one of the companies that has also "DCS like" solutions: Schneider Electric.

They provide a solution named CPC which is similar to some system you mentioned with more openness.

Dear Dr. Murugesan,

It would be better if you can list how is system classified as a true DCS. As for me the concept of a true DCS is an old one, and people keep on following their own understanding of what exactly a DCS is. Sometimes when I ask these details to customers/users they are at a loss to explain what they mean by a true DCS. Maybe you can throw some light so people in this forum are in a better position to understand and select.


By Muhammad AlHawamy on 13 September, 2008 - 12:37 am

I have been working in a consultancy firm. I have happened to evaluate bids for my clients. Based on my experience I would say Siemens PCS7 is not a reliable solution as DCS. ABB 800xA can be regarded as true DCS.


What are the key factors according to which you concluded that ABB's 800xA system is truly DCS? I'd like to see what your evaluation table looks like.

Thank you.

Dear Mr. Muhammad,

Would you please tell us your technical reasons behind evaluating PCS7 as not reliable?

I can understand if you say PCS7 is not a true DCS but not a RELIABLE solution makes me wonder how you judge a solution as not reliable! Would you please tell us what kind of customers you have? I mean Oil & Gas, Pharmaceutical or power plants or what?

One last thing, what is it that you could find in ABB 800XA and couldn't find in PCS7? I'm really curious to know your answers.

I have also been working in a consultancy firm. Even i have been stuck on the same issue to final DCS. will u plz evaluate why Siemens PCS7 is not a reliable solution as DCS. plz give technical specs.

Dr. R. Murugesan,

Please add one Chinese brand: Hollysys MACSV
This is a DCS product from Hollysys, a listed company in NASDAQ.

Jerry Zeng
DCS Application Engineer
zengshaojie at hollysys. com
Hollysys Asia Pacific, Singapore

My experience is with ABB legacy system and I am new to PCS7. My first reaction was that this was not a true DCS as I as accustomed to. The reliability one person mentioned probably is referencing redundancy of the system. More later...

By Dr. R. Murugesan on 17 January, 2009 - 1:09 am

Dear Mr. Jerry Zeng,

Thank you for your response and for your inputs.

Veritably, there are interesting additions across the globe to the increasing family of DCS for industrial automation.
I had the opportunity of evaluating Supcon make DCS of Chinese origin.

Can you please provide salient features of the brand Hollysys MACSV)with a list of successfully implemented installations?

I am grateful to all the contributors to this valuable topic.

Dr. R. Murugesan

To respond to the original question, I believe the PCS7 is not a DCS. My point of reference is the ABB InfiNet90 system. On the regulatory logic, the PCS7 system may have copied a DCS pretty well. However, when you start looking at batch control it becomes pretty obvious that the PCS7 system still very much a PLC like running Wonderware.

Rading all the comments to the original question I must say something based on my 18+ years of expereince with the process industries.

Way back in the 90's. Yes there were clear demarkation between a DCS & PLC system simply because both were built to serve different funtions & applications. However nowadays this clear line no longer exists as we can use the power of telecommunication to distribute the PLC & I/O's too over greater disctance thus making them distributed & using powerful controllers all operation are possible in all controllers today.

To say PCS7 is not a True DCS would be wrong as it truly has evolved into a Hybrid DCS system capable to handle almost any task with the Application library. Based on the strengths of this library would make it better suited to certain industries than other & vice versa.

Eg: The Power Plant library is not so great thus, to use PCS7 over T3000 on a huge power project is not what Siemens would recommend. Remember the group within Siemens responsible for Power Generation has always made their own CS over the past 25 years and thus know what is required & made the Teleperm family into what it is today. Great for Power Plants not other plants.

Similarly, the group responsible for PCS7 works with all other industrial segments expect power and thus have evolved the SIMATIC family into PCS7 combining the strengths and developing funtionalality of a DCS in the Engineering tools & HMI interface. It is totally different to the SIMATIC PLC tools & HMI.

I also would like to mention today there are only 2 vendors who truly can offer an Integrated Control & Safety System (ICSS), they are ABB (800xA) and Siemens (PCS7). If you need to know more we should start another thread.

So to all out there if you need a new modern furthure proof, cost effective and low spare part inventory system try PCS7.

Dear Jerry,

Thank you for introducing Hollysys.

Please share with us some special features that Hollysys MACSV can offer. Any project references in S.E. Asia?


Francis Tan
TRIPS Automation Singapore Pte Ltd
(a division of TRIPS Group, Germany)

i believe this "real dcs" issue is something made up by vendors and consultants to justify their overrated and overpaid work. this is a discussion from the past. nowadays 50 or 250 mw does not matter, you can do anything with any system. if you need more IO than standard, you may just add another cpu.

boiler and steam controls are one of the most basic algorithms known to industry and almost every vendor will have them as ready packages. furthermore, there will always be a contractor if major revamps or expansions are implemented. i have seen plenty of power plants operating and very seldomly came across plant engineers trying to modify the system all by themselves. there's always specialised DCS subcontractors for these jobs and you don't need to worry about whether the system is "open" or whatever. they will find a way to do the job.

sequence of events logging is another nonsense function, which became fashionable (together with sil-rated designs) in recent years. plant operators are convinced to have this functionality to justify the wasted money on control systems.

as advice for your situation, there's two options:

1. if you're working for the actual plant operator, go for the cheapest solution. avoid the vendors' traps to misguide you towards overspecification of the system. all you need to check is whether you can add/modify/swap components and software on the run. if so, any system will do the job, go for the cheapest.

2. if you're working for the engineering company, produce a material requisition document copied from several sources (must be at least 100 pages and inconsistent within). make sure nobody understands what you're defining, and treat the vendors as if they're making a system totally new for you, rather than a configuration of standard components. also on the client side, prepare another massive document to justify buying the full monty, with analysis of situations which are nonexistent in real life. this way you will have a better impression on the client. they will think you're under the burden of a very difficult engineering work, and selection of a control system is a very complicated task.

Hello All

I went through all the entries to this question.

None of it is convincing.

You can term any automation solution as a DCS if and only if it satisfies following points, irrespective of the manufacturer:

1. Automation system is distributed in design, meaning to say, no single node on the system is the universal DATA-OWNER. Elaborately, the data on the system is distributed on various nodes, and hence failure of one node will not hamper system operation.

2. Redundancy is a built-in feature of all the data owners on the system.

3. The communications backbone network is deterministic.

4. The tag database is global in nature and can be reference anywhere and everywhere.

5. PLC and DCS are demarketed by a simple thumb rule.... PLCs are PROGRAMMED. DCS controllers CONFIGURED with the built-in tools and as an advancement user defined algorithms can be programmed. Like GE-Fanuc 90-30 or 90-70/Contrologix have their built in algorithm library but again, you need to program them with register assignments for their working. I dont think we have any DCS controller where you need to assign registers and bits for their working. All we do in DCS is configure with right values. It is like FILL IN THE BLANKS of an existing algorithm with meaningful values and assignments.

6. PLCs never have a parameter called OVER-RUNS. Because, PLCs just scan the LD/IL/FLD and the scan time depends on how long these programs are.
While in DCS, it is real-time where the scanning must be completed in a fix scan period, or else overruns of the processors are announced.

There are many other points that can be considered while comparing a DCS and a PLC.

Request the readers to argue and debate on this, if anywhere i am going wrong.

The author is purely speaking from his "hear / say" experience it seems. No international Vendor can or will float a product if it is inferior to the standards in market. It is just an added advantage that SIEMENS have gone with uniformity in Hardware for giving better support to industrial community.

Engineers using PCS7 are really delighted by the true DCS experience & options it gives. It is only little tough for a novice to choose a siemens DCS for engineering purposes.

Before using a product none can comment on it. Every international vendor does produce a good product. It is the brand name which sells plus the quality of support they give by services & resellers which decide the favour. Almost all features of a product will be available in another.


Experion especially the R400 version is a very open system and truly going to be a DCS. But, having worked in PCS 7 recently and comparing it to Experion I have come to some very interesting conclusions. Ironically to the myth that Honeywell made the first DCS, theirs is really one of the recent OCS. The CEE (Control Execution Environment) is very much similar to a 1990 S5 system. Siemens have had 10 yrs to perfect their OCS architecture, by evolving PCS 7 from S7 controllers.

1. The CM in Experion is said to have been derived from a TDC 2000 Box so that they can be independently loaded and run, the same is in PCS 7 with a chart concept that was mapped to an FC.

2.Online download is possible in both controllers, but separate download and activation of Chart/CM is only possible in Experion.

3. If you have to create a custom block in Experion an engineer will have to actually write it in VB.NET, the same can be accomplished in PCS7 by STL,LAD,FBD or IEC standard SCL.

4. Batch application are relatively easy to engineer on the PCS 7 without the requirement of a Batch Server(Even though they have one) because of the Exquisite 'SFC Type' concept, that has a lot of power, unlike SCM in Experion which I guess is only equal to SFC in PCS 7

5.PCS 7 has very good Asset planning with its Plant Hierarchy, where browsing of charts is possible with respect to area,controller in Plant View and also component view. The Experion asset basically is used only for alarm management from my initial experience.

6.Graphics in PCS 7 are light years better than Experion. The faceplate in PCS 7.1 are all exceptionally operator friendly and readily available to use. Experion graphics suck big time, I think they really need to change/rename PV for solenoid vlave to 'feedback'.

7.Considering foot print of the C300 controller they have really beaten Siemens, but the same design has been maintained for their I/O's that finally give an I/O density for a 2000X1400X600 panel in siemens about 700 while Experion is about 200.

I wouldn't like to be biased, but the facts(almost i hope) are kinda true, considering still i'm still learning, I don't say one is better than the other, I just stated some point I think makes sense for a Commissioning Engineer.

Hi every one

(I am fresher fellow)

I read all the above posts but still i could not conclude the PCS7 is DCS

Now can any one tell me what are the basics requirements for DCS, i mean what are all basic features (For all industrial process domain) one DCS should have to say it as DCS System? like all
above terms used in the posts MTBF, MTBR, Time stamp, Redundancy, reliability etc.

please do not post the generalized answer.

Everyone can consider there own idea of DCS. Mine is a control system domain where numerous controllers are operating in different factory situations or locations, with none being in overall control.

Any DCS system can be configured by various single PLCs networked together, and have done so in the past with Rockwell, Mitsubishi and Siemens. The tricky area is SCADA - should this have overall (operator) control or be itself split into many logical areas.

PCS7 is literally Process Control using S7 PLC family - is it DCS ? - not really but IMHO can be. However understand PCS7 is being phased out so nowadays the point may become seemingly irrelevant.