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Gas Turbine Trip Due to Damper Open Signal Loose
HRSG at the rear of the diverter damper fallen.

MFT trip due to broken support of the HRSG location is the just before the entrance of exhaust in HRSG. Then ST trip within a 10 second after that GT trip on that time. Although GT exhaust site damper is ok mechanical movement is ok. I want to know proper explanation why it is TRIP. If possible please describe through Mark 6e logic.

2 out of 3 members thought this post was helpful...

mrabby,

What is an MFT, please?

I also realize the English is probably not your primary language. I understand you are asking why the unit trips when [something happens], but I'm really struggling with what the [something happening] is.

GTs will NOT perform well when the back-pressure on the exhaust is too high. In fact, they can be severely damaged if the exhaust back-pressure is too high.

I have seen sites that used a single limit switch on the HRSG damper mechanism to initiate an alarm and/or a trip when the damper was out of position. And, most often when only a single limit switch is used there are "reliability" issues (that switch or its mounting bracket) often gets damaged, and that causes the turbine control to trip the unit and/or prevent a START.

But, other than that, I can't offer any more (because I really can't understand the scenario).

And, the question about the "Mark VIe"-based explanation is unclear, also. Are you trying to find the logic signal associated with the limit switch? Generally, that is often listed on the HMI Trip Display (the logic signal name associated with each trip condition).

Hope this helps!

1 out of 1 members thought this post was helpful...

>MFT trip due to broken support of the HRSG location is the
>just before the entrance of exhaust in HRSG. Then ST trip
>within a 10 second after that GT trip on that time. Although
>GT exhaust site damper is ok mechanical movement is ok. I
>want to know proper explanation why it is TRIP. If possible
>please describe through Mark 6e logic.

Is MFT Master Fault Trip? Is HRSG is getting the exhaust from one GT or more? Is there only Exhaust damper installed on your site?

On our site HRSG is getting the exhaust from the two GTs. We have the option to run on the OPEN cycle (when GT exhaust is going towards the atmosphere) and combined cycle (When GT exhaust is going towards HRSG).


atmosphere
| |
| | | |
-------------Damper1-------------------------------- ------
GT1 - - - > |Damper2 | < - - - GT2
--------------------------------------- -----------------
| HRSG |
| |

Our site arrangement is shown above. We have two dampers for each GT. Lets call them Damper 1 and Damper 2. The basic idea is that when the exhaust air comes out of GT it should have a path to flow out either directly to the atmosphere (Open Cycle) or through the HRSG to the atmosphere (Combined Cycle). If both ways are closed then the turbine will trip on High back pressure. The high back pressure condition will occur if both damper1 and damper2 are close(There is no way for the air to go anywhere). It is the security of the turbine. If there is no way for the air to go it should trip. If it does not trip on that it will trip on high back pressure. So the limit switches are installed with each damper. One limit switch is for OPEN position and other is for CLOSE position. Either of the dampers must be open for turbine to work.

If both dampers are closed the turbine will trip.

I can discuss the MarkV or MarkVIe logic if you provide the details about your site. Hope it will help.

1 out of 1 members thought this post was helpful...

If the stack damper comes off the "open" switch, the logic has to assume the damper is on its way closed. Ergo the MFT, (Main Fuel Trip), which among many other events, within milliseconds, slams the IGV's closed so the humongous air compressor no longer has air to push. Were you maybe thinking of sending a tech out to the stack and try to "save the unit"? 30"~40" WC back pressure prolly wont hurt the CT, if it's a GE, but should be more than enough to bulge the sides of the HRSG, then watch gravity do the rest.