Positive Material Identification

[JosexEmir]

Hi all,

I work in Power Plant with 3 Gas Turbine "GE7EA" and 1 Steam Turbine (Fuji) totaling 304MW and I'm beginning a activity to identify the material's chemical composition, espeficaly the parts (capital parts) that have "coating".

I'd like to know if anyone have experience about PMI without removal the coating (Is it possible?). I'm concerned in damaging the parts if I remove the coating (few parts are new e other are repaired.


Any feedback will be very appreciated.

Emir Martins
Termonorte S.A.
+55 (69) 8115-8147

 

[rothwem]

The answer is that "it depends". Do you know what the coating is?

The XRF alloy analyzers used for PMI have an interaction volume that they sample from. I've found that thin samples, for instance, will pick up a little excess iron from the table that I test them on. In the end, it comes down to interpretation. PMI is not an exact measurement of chemistry, it is just there to make sure that some dummy in receiving didn't swap the carbon steel barstock with the stainless barstock.

If you want a perfect chemical analysis, its going to be a destructive test, and you will have to remove the coating.

 

[racookpe1978]

What parts of the "capital plant" are you trying to test?

The manufacturer of the turbines and generator casings will give you exact chemical/alloy requirements for their pressure casings.

 

[EdStainless]

Don't be tempted to reverse engineer parts thinking that you can save money. The alloy is only a small part, the manufacturing methods and the coatings are all integral to these parts working correctly.
If you really want to know what they are you have to destroy a part to find out.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[metengr]

PMI is not the method to determine chemical composition of turbine parts.

 

[arunmrao]

Concept of PMI has been oversold to the gullible. Certainly do not recommend use of PMI for the turbine parts.


"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[EdStainless]

The concept of PMI is based in API. It is for checking in-service piping and fittings in refineries too verify that they are the material that you expect them to be.
All other field testing and such needs to be done knowing that there are no codes or rules.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[JosexEmir]

Hi All,

First of all, I'd like to thank all feedback received (were very useful).

The Capital Parts that we want to test are Nozzles, Buckets, Liners, Transition Pieces, etc. and we have materials' "spec" of, practically, all parts (GE's Manual) and, in gerneral, these Capital Parts use GT-33 coating.


So, we'd like just check (to make sure) if the material the parts that we buy (or send to repair) are the same.



Best Regards,

 

[metengr]

I would simply code the new parts you purchase from the OEM and have them recorded so that when you send them out for repair, you have the information cataloged, and spares in inventory can be used. Trying to use PMI for this effort will be a waste of your valuable time.

 

[JosexEmir]

I thank (understood) your comments and our supplier knows about "material spec" but, as I said early, this (to check always the parts when arrive in the company) is a recommendation (order) of our Insurance.

The Insurance wants to make sure (for warranty effect) that we are assembling the parts according spec GE.

 

[EdStainless]

If you are worried then your option is it audit the supplier and verify his methods for assuring that parts meet the specifications.
Trying to check after the part has been made is too late. You need to know that he is verifying all of the properties, not just composition.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[JosexEmir]

Really, the suppliers knows about all "spec" recommended by GE and we already visit few workshops them and we can check that the services are performed according OEM. Anyway, as we purchase pieces of several suppliers (including GE), we need to check the parts when arrive in the company (insurance requirement).

What about other properties, we don't have conditions of to test in site and we need to trust in supplier (tests report, etc.).

 

[arunmrao]

Infiltration of spurious spare parts in the aftermarket is a problem. It is very difficult detecting them, I am not sure, how far PMI can assist.


"Even,if you are a minority of one, truth is the truth."

Mahatma Gandhi.

 

[EdStainless]

Your insurance company should be more concerned with knowing who you buy from than some superficial test.
In fact they should be interested in helping audit the supply chain.
The first thing that dig into at a audit is how thoroughly they audit their suppliers. Good procedures and double checks are all that you can rely on. Checking at the end is loosing game.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[JosexEmir]

Ok I appreciate and respect your opinions.

However, don't believe that to be this way because we are trying minimize any problem of this source. We believe that this tool (PMI) help us to "monitor" our suppliers and supervise us too, and make sure the pieces are being assembled according to the OEM.

The time is being used in this activity is "very small" close to the time required to repair the machine if happen a problem of the material.


One more time, I'd like to thank all and say that this is our opinion about this matter.