Control.com - Nerds in Control

From your experience, what are the most problems you face with control system in gas turbines? How do you tackle it? And what is recommendation to eliminate such problems?

Dear jhon,

I guess you are new to gas turbine operation. Actually there are many types of problems faced by operation people in this field among which some are common, some are strange and some may look very much complicated. It's better you leave your problem here, if you are facing any; so that someone who have knowledge about it or is familiar with that particular problem can answer to your query.

MM Ahsan

Speaking from a different perspective than the operator or the instrument technician or the operations supervisor or the maintenance manager, my biggest problem with gas turbine control systems is their lack of documentation and the amount of assumptions people make about how a turbine is supposed to operate and what the control system is supposed to do or not do.

Having said that (about the lack of documentation), the programming in today's modern control systems *IS* the documentation. That's right; it's all there. Is it easy to understand? For the beginner, probably not. Is it bloated (excessive what with the "unlimited" memory of some of the systems)? Yes. Are there adequate comments in the code? Usually not. Are the signal names easy to understand? Again, for the beginner, probably not.

But the rest of the documentation generally blows. The written descriptions of what's supposed to happen when with some appropriate comments and history where appropriate are just lacking and in some case just plain wrong, not to mention missing.

And what does this lead to? Lots of confusion about what's supposed to happen when and whether or not the control system is working properly. Which leads to lots of unnecessary down time, and lots of unnecessary troubleshooting; and lots of unnecessary component and instrument replacement.

In particular, the servos of GE-design heavy duty gas turbines get improperly blamed for all manner of problems, and quite frequently replaced when there's nothing wrong with them. And worse, when they are replaced people don't know what has to be done and what doesn't. LOTS of assumptions are made about how they work, how they are to be "adjusted", and what should be done when they are replaced. And this all costs money: lost production and lots of people standing around. The servos ain't cheap, but their cost pales in comparison to the money wasted changing them out while people stand around not to mention the lost production.

And why? Because of the dearth of documentation. And the assumptions that people make because of the lack of documentation and explanations.

I'll never understand how anyone can operate or troubleshoot or maintain a gas turbine without ever referring to a set of P&IDs, or, as GE calls them, Piping Schematic Diagrams. They are key to understanding how the devices interface to the control system, and how the systems work together, and what devices *aren't* controlled or monitored by the control system. So, this is a huge piece of control system documentation that most operators and technicians have access to but just ignore. And why supervisors allow their charges to get away with not understanding or referring to the P&IDs is just beyond comprehension.

So, for me the biggest problem is the lack of understanding of how the unit (turbine and driven device and auxiliaries) is supposed to operate. Unfortunately, there aren't many easy ways to resolve this problem. Training is key to understanding how turbines operate, but most power plant managers rely on "experienced" operators and technicians to train new personnel, occasionally providing some training, usually after some catastrophic or near-catastrophic event.

Fortunately, you have found this site which, for GE-design heavy duty gas turbines is about the best the World Wide Web has to offer. GE seems to be offering some training and even question resolution to Customers who have purchased long-term service agreements and/or contractual service agreements, but there isn't much else for everyone else (except for control.com).

A properly designed and configured turbine control system shouldn't really exhibit many problems; after safety, reliability should be very high on the list of desirable attributes for any turbine control system.

So, if you have questions, ask them here and we'll do our best to help.