7EA fire damper caused trip


We had a trip yesterday on our DLN1 7EA. Everything running normal, running just above our turndown limit of55MW (up in Alberta Canada, GTG is indoors). When suddenly we got a trip from our CO2 chemtron unit. The co2 let go to zone 2, load compartment, at investigation there was no fire and temperature in the load compartment seemed fine, so we manually isolated the CO2 from the tank. No evidence of an actual fire, the load tunnel temperatures are not trend able so I dont know what they got to. But they alarm at about 220C, and trip the GT at 257C. The heat detectors are not set to go off till 385C, but they did activate. Our first thought was an issue with the fire detectors, seemed unlikely since you need 2oo4. But never the less we meggered the wires back to the chemtron PLC, found zero issues. Everything looked fine with the detectors themselves as well. We had the chemtron unit fully checked out in May 2018 and no issues were found, everything worked great. So we talked to the service man from Firecheck and he had mention he seen in the past the fire damper on the load compartment exhaust line can slam shut because a little hook can vibrate loose. This will then lead to no airflow through the compartment and it will get hot enough to set off the heat detectors. We checked the damper and yes it was closed, but when the CO2 system activates it also closes the damper. So we dont really know what came first, did the damper close because the hook came out and gave us high temps. Or did something else set off the heat detectors and CO2 closed the damper? We dont believe we had a board issue with the chemtron unit since everything reset fine. Has anyone had a similar experience? We put the hook back in since we did find it on the ground and pinched it with a pair of pliers so it cannot vibrate out if that is what actually happened.

Thank you
Yes, no question the system is old and needs to be replaced. We had a trip last year due to a failed power supply. Next MI in 2023 we are replacing the Micro 1-EV.
I use a heat detector test kit. http://www.skinnerinnovations.com/fenwal_hst.html to test our heat detectors. Be sure you purchase the optional 6m cable. We also purchased a pocket multimeter http://www.extech.com/products/DM220 to make testing less cumbersome.

I assume you checked your trip log for indications of alarm status for the load tunnel temperatures.

Contractors used to test our fire protection but we found they were using a torch to heat the detectors which degrades them causing premature detection. We had to replace several detectors because of that.

I believe you have a faulty detector. The micro 1-ev can be placed in a test mode to allow you to check the detectors without causing a release of co2.

Pinching the damper release mechanism is a very bad idea. You should repair or replace that.
My only comment is that often there are limit switches on the load compartment dampers which will alarm when they are not in the correct position.

But, looking back at the Alarm Log would show that, if they are not rusted in place.
Thank you for the links, you are correct the contractor just uses a torch to test our heat detectors, I was not aware this would degrade them. The trip log never showed any alarms related to the tunnel temp. Also this is now after the fact since we are up and running, but 26VG-1 high load compartment temp set at 400F never came in. I am not sure where it is physically located in the compartment in relation to the heat detectors. But I am now concerned as to why that didn't come in?? Unfortunately we do not have limit switches on our dampers.

Thank you both CSA, and Curious_one. This is my first time posting on here and am very impressed with the speedy response!
No trouble alarms before the trip, first out is "45FTX-1 Fire". Next alarm is "speed ratio valve open >15% during start up", these two alarms show the same time stamp, but the fire alarm is listed first. I suspect the speed valve trip alarm is just the result of the trip itself.

In 2018 we switched from a Mark V controller to an Allen Bradley, went from TMR or single redundancy (that's a whole story in itself). Interesting about the testing of the torched detectors. This is something we are going to have to look into for sure. I am looking into the heat detector test kit you sent, will be good to get one on site so we can test these any time we want.

Another thing we are planning is to get indication as to which heat detectors go off, so in the event this happens again at least we can pinpoint which detector to go look at.

Thank you both!

Okay. The Fire Protection P&ID (GE typically calls them Piping Schematic Diagrams) should give you a good idea of the relative location of the fire detectors in the load compartment of the turbine at your site.

The Device Summary should list the settings of the fire detectors in the various locations, as well as the temperature switch.

On some units, the FIRE PROTECTION SYSTEM TROUBLE alarm was a start-check permissive, and because the Micro 1-EV circuity was SO sensitive to grounds (usually the result of poor installation and construction practices) the alarm would be in virtually continually. So, people were either forcing the signal to logic "0" all the time, or putting a jumper/lifting the wire for the alarm at the Micro 1-EV to get around the start-check permissive because they couldn't stop the ground alarms in the Micro 1-EV. (I literally have spent months of my life standing in front of the Micro 1-EV trying to stop ground alarms. I could be standing in dry shoes, on dry cement or pavement or rocks, take a dry small screwdriver and touch it to one of the screws for the fire detector inputs and then touch the bare metal blade of the screwdriver--and the Micro 1-EV would annunciate an ground alarm. As soon as I pulled the screwdriver back from the screw and hit the RESET button on the Micro 1-EV ground alarm would clear--most of the time. I watched a Kidde Fire Protection employee troubleshoot ground alarms for a full week on two 7EA units. He replaced the Micro 1-EV cards twice in each panel, and only slightly improved the situation.)

Anyway, I would be surprised if the sequencing in the PLC was exactly like the Mark V. But, the wiring of the fire detectors should not have been changed. The wiring for the Micro 1-EV should be configured such that any -A fire detector AND any -B fire detector IN A ZONE (a GE fire protection zone). It's not usually just 2-out-of-4--it's more specific than that: any -A and any -B fire detector would result in a fire detection, trip and discharge. So, two -As and NO -B fire detectors would usually only result in a FIRE PROTECTION SYSTEM TROUBLE. (But something in the back of my mind is telling me that that only happened on one of the GE fire zones, because of one shortcomings of the the Micro 1-EV. But, it's been over a decade since I've had the responsibility for commissioning a Micro 1-EV.)

Many sites outside of North America use one of several dedicated F&G systems (Fire & Gas). These systems, not widely available for some reason in the USA, are combined hazardous gas- and fire detection systems. (Which solves another long-term problem with the General Monitor haz gas equipment.)

Hope this helps!
Another thing we are planning is to get indication as to which heat detectors go off, so in the event this happens again at least we can pinpoint which detector to go look at.

Unfortunately, the Micro 1-EV does not have the capacity to monitor each detector. The detectors are typically wired in a OR loop.
Dear ALC, I am part of a group that maintains two GE 7EA's commissioned in 2005 and now nearing 100K fired hours. I have several comments in addition to CSA and Curious_One.

I, like CSA and Curious_One, would suggest that the testing company not use torches to test the heat detectors. I have pushed this several times to our maintenance department, but the fire testing company pushes back saying they don't have equipment that can generate specific temperatures needed to test the heat detectors in the different compartments. I say then we need a different company to test, but that's above my pay grade.

We upgraded our panels from the Micro-1 EV controllers to Kidde Aegis XLT about 2 years ago due to age and availability of spare parts. The Aegis XLT has a similar footprint and is the migration path setup from Kidde when they acquired Chemetron. We experienced one false release indication only that tripped our machine while online, but did not cause a release of CO2. We never had any false releases while the Micro-1 controllers were in service. I have heard of several experiences like yours from other users on the 7EA users group that did have a false indication of a fire that also resulted in a release of CO2 into a compartment while using the Micro-1 EV panels. This seemed to be an intermittent issue with several users as the panels aged. As CSA mentioned system ground faults etc. may have played a role but I can't confirm that.

I would find it hard to believe that your fire system dampers closed due to a latch failure and that is what caused the load compartment temperatures to rise high enough to trip the heat detectors. I have to premise some of my comments on ASSUMPTIONS that my settings are similar to yours, so please take that into account.

You should have 3 thermocouples in the load compartment (TTIB1,2,3) that are ~6ft into the load tunnel so not necessarily indicating actual temperature of the load compartment. The load tunnel is cooled by air discharging from the exhaust frame blowers into the load tunnel area around the #3 bearing wrapper. Typically, a failure of the load compartment vent fans will lead to an increase in the load tunnel temperatures, but not always. I have seen cases where excessive leakage from distressed panels and broken bolts for the exhaust collector have caused very high temperatures in the load compartment, but had a lesser effect on load tunnel temperatures. On my system there is a single temperature switch 26VG-1 that is supposed to alarm if the load compartment temperature is above 400 degf. I believe I have heard that some of the never 7EA machines have actual thermocouples that monitor the load compartment temperature, but I can’t confirm that either. Load tunnel temperature alarms for my unit are set to alarm at 415 degf, runback the unit at 430 degf, and trip the unit at 500 degf.

The thermal heat detectors for the load compartment are supposed to close at 725 degf, which is significantly higher than the temperature switch setting of 400 degf. In my opinion applying a torch to see if the heat detector switch closes is not a proper testing procedure.

If you were asking, and based on the information you provided, I would suggest that your trip was due to an intermittent false output from the Micro-1 EV panel that protects the load compartment. And not an actual high temperature in the compartment. But this statement is based on a lot of assumptions and past experience.
Due diligence would suggest confirming the calibration of 26VG-1 and that it properly alarms in your system. Actual verification and testing of all 4 load compartment showing at what temperature they change state.
Many years ago I added additional output relays from the fire protection panel into the control system that generate an alarm if only 1 channel heat detector picks up. This so the operator would be better informed if an event was in progress and clarifying if the event was in the turbine/Acc compartment or the load compartment.

As Curious_One stated, getting indication of which individual heat detector picks up would require significant effort, and may not be possible at all since the current wiring setup has all heat detectors for a specific channel and zone wired together in parallel. And the Micro-1 does not have enough input channels to monitor all the heat detectors individually.

Our control system is still from GE. They never provided a historian with their system. Several years ago I purchased a historian product from Canary Labs that I am very impressed with. I have all the analog transmitter values logged along with many digital signals. It has proved valuable and quicker than what we have being sent to our DCS.

Is the Canary Labs product using OPC (DA and/or UA) to get the data from the Mark*? Or????

I presume the data is getting Mark* time stamps....

Any other details you could share would be great!
Hi CSA, the canary Logger connects to the HMI GeCssOpcServer application which is an OPC-UA server as I understand it. I run the Canary services on one of the control room Win10 GE HMI's so I don't have to deal with computer DCOM concerns. I also added a NAS to the same machine for the Canary historian files. The configuration and UI are pretty simple even for someone as dense as myself, the hardest part for me was configuring the NAS as a network drive.

I presume the data is getting Mark* time stamps.... That I can't really answer. My desire with the Canary historian was just be that, a decent historian to let me look at historical analog data, and include digital signals as well. I don't use it for issues that are time sensitive. I use the TripLog, WorkstationST Alarm Viewer, or specifically configured Dynamic Data Recorders(I can't believe I went for years without leveraging this very powerful tool) to catch high speed events as needed.

Pricing at the time was ~$4600 for 2500 tags, an excel add-in, and 2 user license for their "Axiom" user trend interface.