Hi friends;

I have a Gas turbine which compressor are axial type 11 stage and maximum pressure ration is 9.8:1

Its 9 10 and 11 stage is damaged i think due to surge. Some guys said that it is damaged due to FOD. I understand that FOD means Foreign object damage which i meant that something is going from outside into the compressor which is not possible in our case. if this occur which i understand then 1 to 8 stage also damaged.

Actually i want to understand FOD theory

how it damaged the compressor and what are the possible reason of surge on axial compressor?

Regards

 

Hi Mark,

Did you done any power argumentation regularly during GT on BASELOAD? any sign of pitting in the 1 -8 stage of compressor blade? what kind of damage of your compressor blades in stage 9 -11? Melting? Pitting? Cracks? Corrosion failure( unlikely)?

One more thing, how long did you done your Compressor offline washing?

regards
fai

 

Hi guys,

The 9 to 11 stage are bend not melt, no crack and no corrosion and u ask about compressor washing its run only 400 hrs after overhaul. I explain further that the 2nd bearing is free and its lybrith seal are stuck or freeze.

I want to know the theory of FOD.

Regards

<b>[moderator's note: not sure what "lybrith" is]</b>

 

<b>Note to our friendly, local moderator:
"lbyrith" is likely text-speak for labyrinth, or labyrinthe.</b>

Now to the original poster's query. People love to use acronyms and mnemonics all the time, many times in the wrong context. You are essentially correct in saying that foreign object damage is usually caused by something un-natural, or foreign, entering the compressor. And the "entrance" to the compressor is through the compressor inlet so you would be essentially correct in saying that if something un-natural (foreign) entered the compressor inlet that it should cause damage to all stages of the compressor, not just some stages.

Surge and stall have been covered many times on control.com, and can be researched on the World Wide Web using your preferred Internet search engine. One of the failure modes for surge/stall is for some compressor component to be broken off, or "liberated", during the event and then make its way downstream wreaking havoc and destruction in its path. This can occur anywhere along the compressor, not just at the inlet. Some machines have a propensity for failures at certain stages under certain conditions, though I <b>am NOT</b> stating or implying or indicating that this is the case with the machine at your site, just that machines have different operating conditions and idiosyncrasies (just like people!).

Some people like to refer to this as FOD, as well. That's something of a literal stretch, since the component was "inside" the compressor but didn't stay where it belonged after it was broken off.

So, it's a matter of semantics, actually. And a negative aspect of the English language and those who speak it that terms and words can be loosely used and interpreted (though it's not only the English language that suffers from this malady).

As for resolving your issue with your unit, you have not provided sufficient information and likely cannot provide sufficient information to a forum like this to receive specific assistance with the event and its aftermath at your site.

If you haven't already done so, you should contact the OEM (Original Equipment Manufacturer) or their representative or someone authorized by the OEM or knowledgeable about that OEM's equipment to assist with your analysis of the situation on site, providing access to the machine, the control system, and operating information that would take too long for you to obtain and post to a forum like this. Only by having someone on site to view and observe the system and make some educated presumptions about what might have happened, or even point precisely to the exact cause, can you hope to achieve some form of understanding about the unfortunate event at your site.

Remember, you are working with a piece of rotating equipment, and they do fail. Some earlier than others, and some just run and run and run with nary a bobble for their entire useful "life". There may have been some vibration indicating a potential problem, or some pressure fluctuations, or some other indication or ambient stimuli we can never know about without actually being on site, observing, and talking to site personnel in order to make some analysis and recommendation.

Best of luck with your situation!

 

> <b>Note to our friendly, local moderator: "lbyrith" is likely text-speak for labyrinth, or labyrinthe.</b>

I kinda thought that's what it was, but with my luck I figured I could be wrong. I only fix stuff I know is either misspelled or text speak that I know.