Emergencies on Gas Turbine

Hi CSA, et al,

I am actively looking for a Job change and i have a interview scheduled after 1 week, can you please help me with the following.

1) Any emergencies that you have handled at site on Gas Turbine Operations?
2) What kind of Maintenance work will be der on Gas Turbines and how frequently?

Would be more happy to see your response on this , which means a lot to me.

Thanks & Regards,

There are hundreds of threads on Control.com about issues on gas turbines and with gas turbine operations. And many of them have some very good descriptions of issues and also of solutions. Some have very little descriptive information, and even when several possible causes and solutions are recommended we never hear back from the original poster about the root cause of the problems.

Since you asked about maintenance work, I'm presuming you want a job as a technician and not as an operator. However, in my personal opinion a good technician has to be a good operator--because it's necessary to know the start-up sequence, and understand synchronization (from an operator's perspective) and know what happens during a shutdown. Operators (untrained operators and those with little experience) will always be saying [this] or [that] happened, which didn't, or [this] or [that] should have happened (when it never should happen). That's were being a good operator makes for a good technician--because they can spot a percieved problem and provide instruction to the operator making the questionable claim.

Anyway, as for maintenance work, most gas turbine maintenance work is performed on a basis that follows the number of hours of operation, and the number of starts and emergency trips. There are three basic types of maintenance outages (for GE-design heavy duty gas turbines): Combustion Inspecitions (CIs); Hot Gas Path Inspections (HGPIs); and Major Inspections (Majors, for short). There are often two or three CIs performed between HGPIs, and Majors are often done after several CIs and HGPIs have been done. There are GE Operations and Service Manuals available on line which have some very good information about what is done during each type of outage.

Add to that that most well-run plants also perform instrument operational checks (often (mistakenly) called "calibrations"). These checks are done to make sure that devices such as temperature switches and pressure switches and level switches and limit switches operate to change contact states when they should be operating (for example, that a High L.O. Temperature switch operates at 165 deg F, for example, to indicate a high L.O. temperature (alarm), and High-High L.O. Temperature switch operates at 175 deg F (to trip the turbine on excessive L.O. temperature). Pressure transmitters, some of which are very important to proper turbine operation and protection are checked to make sure they provide the proper analog signal for the proper measured signal (for example, a 0 psig the output of the transmitter is 4.0 mA, and at 150 psig the output of the transmitter is 12.0 mA, and at 300 psig the output of the transmitter is 20.0 mA). The as-found conditions are recorded on device data sheets, and if they are not within specification the appropriate adjustments are made, and the device is re-tested to prove the new adjustment is within specification, and then the as-left condition is also recorded. (If no adjustment is necessary, the as-left will be equal to the as-found!).

This is important to ensure protective devices operate as they should and when they should. Also, so that control parameters (such as P2 pressure or axial compressor discharge pressure) are sending the proper feedback signals for important control and protection functions.

These are just some of the controls-related things which are performed during the various scheduled maintenance outages. If there is a forced outage (because the unit tripped because some protection function was triggered, say, a high-high vibration, it's possible the vibration sensors may be tested to ensure they are working properly, or replaced if necessary.

There are LOTS of emergency conditions which can result in a trip (automatic sudden stoppage of fuel to protect the turbine and/or auxiliaries), and some units have more trip conditions than others (depending on the type of fuel(s) the unit can burn, or the type of combustors (conventional or DLN (Dry Low NOx)), etc. While many of the trip conditions are similar for many GE-design heavy duty gas turbines, some are very specific to certain types of units and their auxiliaries--so it's not possible to give a list of some because it may or may not be appropriate for any gas turbine.

Use the 'Search' feature of Control.com; you will lots of threads about gas turbines, and in particular, GE-design heavy duty gas turbines.

Best of luck in your endeavour! Write back to let us know how you fare!!!
Thank you CSA for spending a good amount of time to respond on my thread , this is really helpful.

BTW , interview is for Operations engineer , but thought of having a knowledge on Maintenance as well.

Happy Thanks Giving.