If Mark V TC failes, for example one of the exhaust TC fails, what electrical (mV) value does the card reads? and is there any setting in Mark V software to detect open ckt? is there any way to set the TC for Fail_Hot or Fail_Cold? I mean, e.g. if the TC is scaled for 0-2000 degF and if it fails (open ckt due to wire break or TC broke) does it reads OL and goes out of range or does it reads max value 2000 degF or does it reads 0 degF? What is the range of mV on the Mark V TC card (TBQA)?

 

If T/C fails (open Circuit), it will read the minimum value in the scale code for the thermocouples, basically open circuit is 0 mv. The thermocouple will be rejected from the system and you will get an alarm indicating a failed thermocouple. There is no way to set failed hi or low, it will fail to Open Circuit. Check your Scaledata file (I don't have a copy here) and it will tell you in DEG. F what the scale reflects as Max/Min temps. the mv scale is set by selecting the thermocouple type selected (Type J,K,etc).

 

generally if TC cable opens or tc broke u can get minimum temp as a reading (in 9FA machine our exhaust TC value shows -18 deg. cen when TC cables opens). during GT running there wont be any change in spread value. i think this may not effect the turbine to trip. but if TC came out of the well and exposed to atmosphere and cable was not have any break, this will leads to GT trip due to spread trip. this case will applicable when 2 TC have the same problem.

 

Thank you very much for your responses.

I thought scaledata.dat is for HMI, I could be wrong.

I believe IO_CFG program pulls the TC table that relates the mV to degF, so in case of open ckt it will show the corresponding reading to 0 mV.

but, in case of failed condition, there must be somewhere they set fail condition whether to fail cold or fail hot? and maybe for some super critical condition it can be dynamic based on unit current temp.

Anybody knows where they set this in Mark V?

 

The configuration is preset by what type of TC used. As set in the io configurator, i.e. type J or typically type K. If you want to know the mv values check out the standard chart here:

http://srdata.nist.gov/its90/download/type_k.tab

you can see that 0C is 0mv and 1000C is 41.276, non linear. I don't think you set the range.

 

Ki_ran_r,

GE sets the failure mode for the thermocouples in the PROMs on the cards that handle thermocouple inputs. The failure mode is NOT configurable in most Speedtronic turbine control panels.

What you see in the I/O Configurator is what you can change. Having said that, there is always the remote and unlikely possibility that the card I/O Configuration file might be edited to effect some kind of change, but that would require extensive knowledge of how the configuration file parameters work and what the limits of modification are, and that's not documented anywhere publicly that I'm aware of.

If you would describe the problem(s) you are trying to solve it would help us make better recommendations. Most every time I've been asked this very same question it's because someone is trying to mask failed exhaust T/Cs using I/O Configuration settings--which is not appropriate for the Mark V or for GE-design heavy duty gas turbine control and protection.

So help us help you by describing the problem or issue you are trying to understand or resolve and we may be able to suggest some alternative(s) or work-arounds--if any exist.