Can Siemens PCS7 be considered as a True DCS?

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

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

Regards

Jari
[email protected]
 
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.

Regards....
 
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
www.controlglobal.com
blog:Sound OFF!! http://www.controlglobal.com/soundoff
_________________

Putman Media Inc.
555 W. Pierce Rd. Suite 301
Itasca, IL 60143
630-467-1301 x368
[email protected]
 
S
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.

Thanks,
Sastry
 
S

September, Clyde

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.

Regards,
Clyde September
 
T
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.
 
S

sum_developer

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 http://www.automation.siemens.com/Industrial-PC/html_76/products/box/microboxpc427b.htm. 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.
 
V

Victor Miles

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.
 
M
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
Asia-Pacific
Synergy Intl.
 
Y

Y.K.JARIWALA

Do you have documents regarding this?

We would really appreciate it.

There are dedicated cards for SOE in every DCS.

Regards,

Jariwala
 
G

Gregory Halbert

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.
 
J
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
 
D

Durgesh Mhatre

Hi;

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.

Regards,
Durgesh M
 
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.

Vikas
 
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...
 
D

Dr. R. Murugesan

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.

Regards
 
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