Hi Everyone,(@CSA)
Please what is the different between Dcs mark vle and mark vle gas control turbine and why GE company used two controllers for DCS and three controllers for gas control turbine

 

@ali kareem shybany,

I think you'll be waiting a long time for @CSA to respond....

Generally speaking, there isn't much difference. The gas turbine control version has many gas turbine-specific input/output cards and functions which are more useful for gas turbine-related field devices, while the DCS version has input/output cards more dedicated to field devices and instruments used primarily in balance-of-plant applications.

As for why the difference between the number of control processors between the two applications. It's mostly about GE's gas turbine control philosophy, redundance and reliability. To GE, running reliability is everything--keeping the machine running when a single failure occurs is of prime important to them and they believe that TMR (Triple Modular Redundant) control systems are the best way to achieve that. In addition they value control and protection very highly and feel that TMR control systems give them a high degree of stability and machine protection.

GE also feel that for DCS (balance-of-plant) applications DUAL REDUNDANT systems (two control processors sharing control and capable of quickly switching to a single control in case of problems) is adequate for equipment control and protection. So, the decision between DUAL REDUNDAT and TMR is basically a function of control philosophy and reliability. For their equipment (turbines and driven devices) they want TMR control and protection; thoe machines are very high dollar and full of state-of-the-art technology and they have to warrant the equipment.

While it seems like a very good idea to have Mark* VIe for BOTH turbine and balance-of-plant control systems, the reality is that the two systems are programmed and configured using very different programming methods--so plant engineers can and do have a very steep learning curve to learn both programming methods in order to understand, troubleshoot and maintain the equipment. Also, while it would seem that both Mark* VIe systems would share many input/output cards--in reality they don't share as many as one would expect. So, in reality it takes at least two engineers/technicians to learn and quickly diagnose and troubleshoot problems (real and perceived) because going back and forth between them quidkly can be a real test of composure, skill and focus. So, while it seems to make logical sense, in practice it is much less logical and sensical than would be expected.

They are both very good, purpose-built control systems. That means they are not general purpose programmable logic- or programmable action controllers capable of being used in a papermaking plant or a chicken processing facility. In fact, they wouldn't be very good at either application because the Mark* VIe was designed to be a turbine control system and by extension a fossil fuel power generation balance-of-plant control system. It's just that sharing spares and having one, or two, people who are knowledgeable and capable and competent in both applications of the same control system is not easy to achieve or practical for that matter. The number of spares--which would logically be expected to be somewhat lower because of a common control system actually becomes higher because of different programming and configurations.

 

@ali kareem shybany,

I think you'll be waiting a long time for @CSA to respond....

Generally speaking, there isn't much difference. The gas turbine control version has many gas turbine-specific input/output cards and functions which are more useful for gas turbine-related field devices, while the DCS version has input/output cards more dedicated to field devices and instruments used primarily in balance-of-plant applications.

As for why the difference between the number of control processors between the two applications. It's mostly about GE's gas turbine control philosophy, redundance and reliability. To GE, running reliability is everything--keeping the machine running when a single failure occurs is of prime important to them and they believe that TMR (Triple Modular Redundant) control systems are the best way to achieve that. In addition they value control and protection very highly and feel that TMR control systems give them a high degree of stability and machine protection.

GE also feel that for DCS (balance-of-plant) applications DUAL REDUNDANT systems (two control processors sharing control and capable of quickly switching to a single control in case of problems) is adequate for equipment control and protection. So, the decision between DUAL REDUNDAT and TMR is basically a function of control philosophy and reliability. For their equipment (turbines and driven devices) they want TMR control and protection; thoe machines are very high dollar and full of state-of-the-art technology and they have to warrant the equipment.

While it seems like a very good idea to have Mark* VIe for BOTH turbine and balance-of-plant control systems, the reality is that the two systems are programmed and configured using very different programming methods--so plant engineers can and do have a very steep learning curve to learn both programming methods in order to understand, troubleshoot and maintain the equipment. Also, while it would seem that both Mark* VIe systems would share many input/output cards--in reality they don't share as many as one would expect. So, in reality it takes at least two engineers/technicians to learn and quickly diagnose and troubleshoot problems (real and perceived) because going back and forth between them quidkly can be a real test of composure, skill and focus. So, while it seems to make logical sense, in practice it is much less logical and sensical than would be expected.

They are both very good, purpose-built control systems. That means they are not general purpose programmable logic- or programmable action controllers capable of being used in a papermaking plant or a chicken processing facility. In fact, they wouldn't be very good at either application because the Mark* VIe was designed to be a turbine control system and by extension a fossil fuel power generation balance-of-plant control system. It's just that sharing spares and having one, or two, people who are knowledgeable and capable and competent in both applications of the same control system is not easy to achieve or practical for that matter. The number of spares--which would logically be expected to be somewhat lower because of a common control system actually becomes higher because of different programming and configurations.

Many thanks @WTF? for your information, please can you provide me main of the deferent between each one for all of the things software, hardware, etc?

also I have another question, what is the different between dual controller and redundancy controller In Dcs GE ?

also what is the concept of redundancy control that is mean the first one as service and another one as live or what exactly please?

 

@ali kareem shybany,

It's really difficult to say without knowing what your interest is. Are you trying to specify a control system for a plant with GE-design turbines and needs a DCS control system for balance-of-plant control and monitoring? Or are you trying to understand what you need to study/learn in order to get a job working on Mark* VIe control systems, either as turbine control systems or balance-of-plant control systems.

I outlined most of the differences in my earlier post between using Mark* VIe as a turbine control system and using Mark* VIe as a DCS/balance-of-plant control system. The biggest "difference" is that two different groups in GE use the Mark* VIe as turbine controls and DCS/balance-of-plant controls. And those two groups have very different philosophies and methods of programming and configuration.

Also there are many turbine-specific modules and I/O packs and many balance-of-plant specific modules and I/O packs. So, keeping spare modules and I/O packs requires purchasing and warehousing many different types of modules and I/O packs which aren't shared by both turbine controls and DCS/balance-of-plant controls.

Redundancy control is basically application specific, and even I/O specific--some monitoring applications don't require redundant sensors and some control and protection applications require redundant sensors. GE decided a long time ago when selling computer-based control systems was difficult because there were all kinds of concerns about reliability and availability that using TMR (Triple Modular Redundant) control systems was going to be their way of convincing skeptical people to buy this new-fangled computer-based turbine control system. (And even then, it was a VERY difficult to convince people and get them to commit to buy computer-based control systems for their power generation assets--high-speed, rotating equipment--because most of the purchasers back then were utilities who valued reliability and standardization over new, and in many cases, unproven, technology which isn't as big a concern today as it was back in the late 1970s and early 1980s--when it was really a big deal. Back then it seems everyone knew someone who'd gotten a water fill for $60,000.00 which was issued by a computer when computers were just beginning to be used by large companies (and even some small ones). It caused some people to very nearly literally have a heart attack, and there was no way that somone was going to buy a computer-based control system with their new turbine-generator because who know WHAT it was going to do and what it WASN'T going to do!!! So, TMR was the answer: a "voted" system where two-out-of-three processors had to agree to start a pump or de-energize a solenoid or have some basic agreement about how much fuel or steam should be flowing into the turbine. Seemed like a very good idea. If one of the processors was out or service or had to be shut down for maintenance or repair or replacement the turbine-generator could continue to run--also a very good idea and benefit of TMR control systems. It would require two out of three processors to trip a machine (though there was a small bug in that scheme because the assumption was that it would be the same condition that all three processors would be voting on to trip the turbine, but if one turbine though the Lube Oil pressure was low-low and one processor though the vibration on the #1 bearing was high-high the turbine would be tripped--with NO Process Alarm to indicate why the turbine tripped.... oops!). Turns out it didn't happen very often--but it did happen, and no one was ever hurt or killed by the bug and it was eliminated in the next version of the turbine control system.

TMR requires, basically, three control processors, which means a lot of additional hardware and wiring and ribbon cables are necessary--which means a lot of blinking LEDs (which scares a LOT of people). Dual redundant control systems had already been around for decades, but the problem with them was that only one of them was really doing the monitoring and control and protection of the equipment and the other one was on "standby" or "back-up" and if there was a problem with the first control system there was always a slight delay in switching over to the standby/back-up control system which meant the equipment was running "blind" for a split second--which is a LOT of time with high-speed rotating equipment. So, GE came up with the idea of having both control systems doing different parts of the control and protection all the time and if one component of one system failed the other control systems matching component would take over within milliseconds. It works pretty well but it's very poorly documented and not very well understood. GE will use it for some turbines (gas and steam) but almost NEVER for new turbines (especially gas turbines with DLN (Dry Low NOx) combustion systems).

So, redundancy and how it is implemented is in the eye of the programmer and his/her bosses. It's not always well understood and is usually poorly documented. But, when it works--it works very well.

That's all I can say. The Mark* VIe is a very good, purpose-built turbine control system. Purpose-built means it was designed primarily as a turbine control (and protection) system and it does that as well and even better than just about any other control system that is adapted for use as a turbine control system. PLCs are really good for many process control applications (oil refineries; chemical plants; chicken processing factories; warehouses; etc.)--BUT they are not as well-suited for adaptation as turbine control and protection systems. For the same reason, one wouldn't use a Mark* turbine control and protection system (it's not really a PLC even though it functions like one in many respects) in a chicken processing plant or a warehouse--it's not well-suited for those types of applications. With the addition of many balance-of-plant I/O packs and modules the Mark* VIe is a fine DCS/balance-of-plant control system. BUT, one can't expect the turbine control technicians who work on the Mark* VIe on the turbines and generators to just walk up to an HMI of the Mark* VIe DCS/balance-of-plant control system and sit down an immediately be able to troubleshoot or analyze what is happening--because the two division of GE that provided the two different Mark* VIe control systems don't agree on programming and configuration methods and practices. They even use entirely different visual display methods for the logic and controls. And, again, many of the I/O packs and modules of the two applications of the control system are different and are specific to the applications (turbine-generators and DCS/balance-of-plant). It's a great idea, and the salespeople are reasonably good at selling the concept of using "the SAME" control system for both the turbine-generator(s) AND the balance-of-plant applications. But the actual implementation is VERY DIFFERENT than what the salespeople promise. GE even has two different groups of people who can service the two different applications of the control systems. The promise and the reality are two different things.