RESPECTED SIR,

i am new to this website. but i found lot of information and it is very useful to me. plz help the following question. it will help my future.

I am working in poer plant there 4gt and 4 hrsg and two st. last week one of the STEAM TURBINE tripped (2726rpm). the alarm is:

TEMPERATURE TURBINE JOURNAL BEARING REAR 2 OUT OF 3 ANALOG VALVE FAILURE.

We are using Siemens PCS-7

At 2726 rpm one by one bearing thermocouple getting channel fault. any two combine together, turbine trip. (2 out of 3 logic).

we are using BACK PRESSURE type.

 

Hello Ali;

You are describing a situation on a safety protection (2oo3 voting) through a PCS7 system controlling a genset. What is your question: do you think the thermocouple alarms are false? Do you think the temperature readings in the S7 CPU are incorrect (therefore the 2oo3 logic is invalid)? Do you feel that at the specific rpm you mention you should not have a trip? Did this trip happen more than once, at the same (or almost) rpm?

Please specify the reason you are asking for our help. Then maybe we can be more useful.

Hope this helps,
Daniel Chartier

 

did you check your T/C? was it OK? it seems that your bearing temperature (minimum 2) got failed and it tripped the Turbine. Nothing to do with your speed. if your only one T/C is failed it should not have tripped the turbine unless otherwise yourlogic has made to trip the turbine if there is any "BAD VALUE" on Input. send me detail mail to [email protected]

 

Dear Sir,
You mean to say two thermocouple failed at a time, in normal cource failure of two field sensor at a time is very very remote. If it happens really, it means there was some problem with the 24 v dc / 230 V AC supply to these sensors. Supply to these sensors was either from common source of supply or some jumper/ short link arrangement in the field. For proper analysis of fault you can have sequence of event recorder for all critical safety & alarm discrete inputs. SER will do the stamping of all alarm / trip @ 1 m sec. SER can handle shower of alarm in easy way, same will be helpful for tripping analysis.

Kapil
[email protected]

 

I had a problem like this with our RTO. It would operate fine then lose the avg temp generated by two thermocouples through a plc. The problem turned out to be the input module card of the plc.

idtmemberdoug