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- since 1996 -
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langtuteng
Armenia, Joined Nov 2014, 196

langtuteng

Armenia,
Joined Nov 2014
196
16:58 Sep-20-2015
ut for the turbine rotor

hi everyone! has anyone ever inspected the turbine rotor using the UT?
question1: could you tell the procedure of the UT?
question2: in my company, we have to use B2S,B4S,WB45-2,WB70-2,B2S with the plexiglass shoe 7°,14°,21°, sometimes 28° also has to be used. could you tell me why we should have to use so many probes?
quesition3: how long do you spend in UT for the 1000MW turbine rotor?
thanks

1
 
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langtuteng
Armenia, Joined Nov 2014, 196

langtuteng

Armenia,
Joined Nov 2014
196
17:02 Sep-20-2015
Re: ut for the turbine rotor
In Reply to langtuteng at 16:58 Sep-20-2015 (Opening).

why do we only use the B2S 、WB45-2 and WB70-2. can the plexiglass waivd? why?

1
 
 Reply 
 
P V SASTRY
R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D, India, Joined Jan 2003, 195

P V SASTRY

R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D,
India,
Joined Jan 2003
195
21:14 Sep-20-2015
Re: ut for the turbine rotor
In Reply to langtuteng at 17:02 Sep-20-2015 .


Dear Sir,

The answers for the questions that you have asked are quite involved and complex.

In order to answer your questions some essential information is required from you.

At what stage you want to do UT of the rotor. UT on turbine rotor is carried out at different stages. The technique and approach differs with the stage of testing.

UT on turbine rotor is normally carried out at the following stages.

1. After the rough forging and normalizing ( carried out on strips ground along the length of the rotor at 90 degrees angles)

2. After the rough machining and before the quality heat treatment.

3. After the initial quality heat treatment (This is the crucial UT )

4. After the intermediate machining and stress reliving.

5. After final machining ( after gashing and making blade grooves) and stress reliving.

6. After fully blading

7. After putting up some service of a few years/ or more than 20 years.

Please specify the stage of testing.

The short answers for your second question is

You cannot dispense with the plastic shoes making all those angels like 7,14 21 degrees. The testing with those shoes is very much essential particularly for the rotors where discs have been machined and bladed.

These angles are required to see the defects that do not have favorable orientation when tested with straight beam probes. (without shoes)

A rotor manufactured in Europe, has failed catastrophically during service. The detailed failure analysis conducted established that the failure was due to an internal defect that has proliferated during service. (The steam turbine rotors operate under high temperatures where under the influence of the creep and fatigue interaction the internal defects can grow much faster).

This defect was faintly observed during the initial UT but the seriousness could not be established because it is an off center defect and passed the specified limits. The seriousness of this defect could have been easily gauged if only tested with these probes having shoes with these odd angles

This happened in early eighties (not sure of the time) Ever since the testing with probes with these plastic shoes, having these angles, became mandatory.

In service rotors, these shoes are essential to approach areas under the discs which other wise cannot be explored with straight beam probes.

Best wishes

P V SASTRY

1
 
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langtuteng
Armenia, Joined Nov 2014, 196

langtuteng

Armenia,
Joined Nov 2014
196
14:25 Sep-21-2015
Re: ut for the turbine rotor
In Reply to P V SASTRY at 21:14 Sep-20-2015 .

the stage is :After the initial quality heat treatment (This is the crucial UT )

1
 
 Reply 
 
P V SASTRY
R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D, India, Joined Jan 2003, 195

P V SASTRY

R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D,
India,
Joined Jan 2003
195
23:00 Sep-22-2015
Re: ut for the turbine rotor
In Reply to langtuteng at 14:25 Sep-21-2015 .

Dear Sir,

Please specify whether it is HP or IP or LP rotor.

I am assuming that the ingot is made with vacuum degassed or VAD or some vacuum treated steel only.

Please indicate the process and final Hydrogen content.

Sulfur levels normally achieved are less than 0.01%. Please confirm.

Please indicate whether the ingot was given any anti-flaking heat treatment cycle.

Please give the approximate dimensions.

Do you have the UT report made before the heat treatment.

Best wishes

P V SASTRY

1
 
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langtuteng
Armenia, Joined Nov 2014, 196

langtuteng

Armenia,
Joined Nov 2014
196
13:34 Sep-23-2015
Re: ut for the turbine rotor
In Reply to P V SASTRY at 23:00 Sep-22-2015 .

dear sir, thanks for your asking. I am so sorry because I'm just concerned about the ut, other than the chemiscal analysis , disgas and forging. There are so little informations about the rotor. just the ut equipment, probe, attenuation, MDDS and the inspection result on the UT report.

1
 
 Reply 
 
P V SASTRY
R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D, India, Joined Jan 2003, 195

P V SASTRY

R & D, NDT tecniques metallurgy
TAKEN VRS FROM THE POSITION OF SR. DEPUTY GENERAL MANAGER BHEL CORPORATE R&D,
India,
Joined Jan 2003
195
15:38 Sep-23-2015
Re: ut for the turbine rotor
In Reply to langtuteng at 13:34 Sep-23-2015 .


All the questions that I have raised are related to the UT of the rotor. In fact what I have asked is only partial information.

Hydrogen content is related to a UT defect called flaking . In a massive forging having more than 1000 mm diameter, Hydrogen content of more than 2 ppm may cause flaking.

Even if the flake formation is missed somehow the same Hydrogen content coupled with higher Sulfur content will cause fissurization. In the end there may be plain inclusions. Proper interpretation, not only needs keen observation of the Ultrasonic indications along with their dynamics but surmisation with other pertinent information.

Turbine rotor UT is a serious business. One needs to keep lot of background information for making proper testing and interpretation of the defects.

It is very much necessary to know to what specifications you are testing the rotor and what are the acceptance norms.

I am now mainly testing the rotors in active operation. It is long time back since I tested the rotors during the manufacturing. Both are different propositions. I have to dig that information from my old records.

I will come back with available information from my side.

Best wishes

P V SASTRY

4
 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 786

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
786
15:59 Sep-23-2015
Re: ut for the turbine rotor
In Reply to langtuteng at 16:58 Sep-20-2015 (Opening).

As a minimum you will have to develop scan plans to account for the varying curvatures along the length of the rotor. Note that unlike pipes inspection where the beam has two components; the beam in the rotor will have three components (X, Y. Z). This makes the inspection complex as you have to assure the sound from a potential flaw is reflected back to the probe. Finally, you have to build a small buggy with two wheels to rotate the probe at a fixed radial distance over the surface. The radial distance has to be adjustable as needed. Then you will need calibration blocks to establish sensitivity.

This is just the rotor. Then you have to also inspect the blade attachment areas called steeples or dove tails.

Even after all that, the reliability of inspection can be questionable. Because of this reason, it is best that this inspection be left to original equipment manufacturer.

2
 
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