Turbine Compartment Hazardous Gas Detector 5A


Thread Starter


Dear all

i have problem in my site. we have gas unit GE frame9FA and inside the turbine compartment one hazardous gas detector (5A) give a negative reading. we stop the machine and change the detector and calibrate also. during calibration it pass and give a "0" reading. but after we start the turbine, we notice at base load and about 260 F turbine compartment temperature the sensor start to give a -ve reading -1, -2, -3 to -8 and give fault alarm. for rack and hazardous gas system. we stop the machine and check the flowing check.

1- check lube oil compartment gravity damper. it is ok.

2- check turbine compartment fire damper. it is found ok open and no stuck.

3- check and meager the cable from terminal block for sensors to panel. it's found ok.

please can you guide me and tell me how to solve this problem

thanks and regards
What happens when you exchange the wiring at the monitor with that of another sensor--to see if the problem is the monitor/card?

Who manufacturers the sensors/monitor used at your site?

Most of the sensors are extremely sensitive to dirt and oil--even from human hands. So, great care must be used when replacing sensors so as not to damage them by contaminating them with hand-prints/never-seize/oil/grease.
Thanks for your interesting. after changed i went to calibrate the sensors. it is going to calibrate smoothly and accept the calibration. after calibrate while unit shutdown it give "0" reading. after calibrate the sensor, i admit CH4 from calibration cylinder to check it's healthy. i found the sensor was sensing the ch4 and give alarm in HMI and Rack also. we use general monitor sensors P/N :11159-2L Atex temperature rating 180 C.

I <i>guess</i> this means everything is working as it should now??

It's not really clear what you did to resolve the problem, but if it's working that's good news.

> I <i>guess</i> this means everything is working as it should now??

the problem was not solved till now. the sensor still give -ve reading while turbine in service. but when turbine shutdown the reading is "0" can you help me by your experience what is the cause of the -ve reading for the Hazardous gas sensors.
I know that I am late because the request was opened at 2015 , however I would share a small experience on this subject. Well, the nevative reading obtained after running the machine is obtained by turning on the ventilation system، so I would suggest to do the calibration (especially the zero adjustment) while the ventilation system forced on . And you will see the result .