AA 085 01 06

CORPORATE STANDARD

Rev. No. 00
PAGE 1 OF 14

Non Destructive Examination of Turbine & Generator Shafts

COPYRIGHT AND CONFIDENTIAL

The Information on this document is the property of BHARAT HEAVY ELECTRICALS LIMITED
It must not be used directly or Indirectly in any way detrimental to the Interest of the company.

List of Contents
1
1.1
1.2
1.3
2
3
4
4.1
4.2
4.3
4.4
4.5
5
6
6.1
6.2
7
7.1
8
8.1
8.2
8.3
8.4
8.5
8.6
9
10
11
12

Page

General
Scope of Application
Purpose of Examination
Certificate of Examiners
Applicable Standards
Preparation of Forging
Testing of UT -Equipment
UT-Instrument
Probes
Check of Testing Equipment
Calibration of Testing Instrument
Couplant
Test Planning
Execution of Examination
Scope of Examination
Speed of Testing
Special Features due to the Applied Examination Technique
Plexiglas-adapter- wedges
Description of Indications
Flaw Echo Height
Flaw Echo Shape
Dynamic Characteristic, Extent of Indications
Dependence of frequency
Back Wall Echo drop 3 dB
Limit of the Flaw Detection sensitivity
Recording- and Decision Criterias
Surface Crack Examination of the cross-section transitions
Surface Crack Examination of the axial hole bore
Reporting
Figure 1 and Figure 2
Table 1 and Table 2
Table 3
2 Enclosures

2
2
2
2
2
2
2
2
3
3
3
3
3
4
4/5
5
5
5
5
5
5/6
6
6
6
6
6/7
7
7
7/8/9
10
11
12

Revisions :

APPROVED :

Cl. 33.1.0. of MOM of FC&F+HTM

INTERPLANT MATERIAL RATIONALISATION

COMMITTEE-MRC (FCF+HTM)

Rev. No. 00

Amd.No.

Reaffirmed:

Dt:

Dt :

Year :

Prepared

Issued

HARIDWAR

Corp. R&D

Dt. of 1st. Issue

FEB. 2008

AA 085 01 06

CORPORATE STANDARD

Rev. No. 00
PAGE 2 OF
1
1.1

14

General
Scope of Application
This test procedure is applicable for the manual ultrasonic examination and surface crack
examination (MT) of free forgings for turbine and generator shafts by the supplier. It may also
be used up to the preparation of a specific test instruction for automated UT-Examination for
such examinations.
It determines the conditions for UT-examination of forging items after machining in as simple
as possible contour condition with body surfaces parallel to the axis. The last heat treatment,
which determines the mechanical properties, must already have been done.

1.2

Purpose of Examination
The purpose of examination is to check as much as possible of the volume of the shaft under
consideration of geometry and labour consumption for flaws resulting from the manufacturing
process. It is aimed at finding flaws through to the core area of the shaft with highest
detection sensitivity (see Cl:9 recording- and decision criteria). Furthermore cross-section
transitions and the axial boring of the shafts are to be checked for surface crack examination
(MT).

1.3

Certificate of Examiners
The forgings have to be tested by experienced and level II certified NDT-personnel (UT/MT)
according to EN 473 or ASNT SNT-TC-1A.
An current list of certified NDT-personnel according to the required certification shall be sent
to Siemens.

Applicable Standards
SEP 1923, DIN 54120, EN 27963, EN 10204, EN pr 10 228, DIN 54 126

Preparation of Forging
The examination surface of the forging shall be according to order drawing (Ra < 20 m), in
order to get a coupling of probes on the shaft which is as perfect as possible.

Testing of UT Equipment

4.1

UT-Instrument
UT instrument deployed for this examination shall be in accordance with the relevant
standards and rules (DIN 54 126). They shall be of impulse-echo type and with the aid of a
gain controller, adjustable in decibel (dB), measurements of echo relationship shall be
rendered possible with 1 dB accuracy. In the working range of the applied equipment
sensitivity the amplifier shall have no threshold and shall show no saturation. The testing
ranges shall overlap, whereby the time base shall be linear adjustable with an accuracy of
< 2% of testing range.

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PAGE 3 OF 14

A regular inspection and maintenance of the instruments at least once a year must to be able
be proved.
4.2

Probes
The testing probes will generally be used with straight-longitudinal waves (e.g. B2S, B4S,
B5S, SEB4H0) and angle-transversal waves (e.g. WB45-2N, and WB70-2N), therefore the
selection of probes conforms to the geometrical conditions of the shaft.
In the application of the probes it must be taken into consideration that probes shall be adapted
to the contour of the surface of the shaft in sound direction or small probes shall be used. This
is always the case, when the curvature of the surface of the shaft is R A. Therefore A is the
length of the coupling area of the probe in bend direction.

4.3

Check of Testing Equipment

For equipment calibration and for control of equipment function and probes calibration blocks 1
and 2 according to DIN 54 120 and EN 27963 or other calibration blocks shall be available.

4.4

Calibration of Testing Instrument

The calibration of the time base range shall be done with the aid of calibration blocks according
to DIN 54 120 or EN 27963 respectively or on the test piece, where at least two reference
echos with known sound paths shall be used.

4.5

Couplant
The couplant shall wet the surface of the shaft enough to ensure a perfect coupling on the test
surface. The applied couplant must not cause any corrosive damage.

Test Planning
Before beginning the inspection the identification number according to the order drawing shall
be stamped as a reference point in circumferential direction as the 12 oclock position on the
face of the shaft end as seen in the drawing. After any subsequent machining of the shaft, the
12 oclock marking must be transferred to the identical position. In the delivery condition of the
shaft the marking shall be framed with oil paint. The correctness of the identification shall be
certified by the responsible factory quality representative by hard stamping of his sign in the
identification area.
Before the start of the inspection by means of the relevant drawing of the shaft, the inspector
has to inform himself about the later position of the bore hole, the geometrical contour,
dimensions etc. The volume in the area of the later bore hole shall be completely checked
before. Indications from detection limit in the bore hole volume must be recorded.
It should be possible to turn the shaft during the examination. In case of recordable indications,
the shaft must be rotatable.

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PAGE 4 OF

14

Execution of Examination

6.1

Scope of Examination
Sound directions (according to SEP 1923) have to be applied as follows:
A3 Examination of the total surface of the shaft in radial direction with the probe B2S.
Exceptionally the probe B4S with the 4 MHz - frequency may be used, when spurious echos
(phantom echos) or insufficient detection sensitivity limit (> 1mm FBH) occurs by using the
probe B2S.
A4 Examination in axial direction from all face areas and sections with the probes B2S
and B4S. The maximum beam path for the detection sensitivity limit of 3.0 mm FBH (flat bottom
hole) in the direction A4 is to be reported.
A5

Sound attenuation measurement according to SEP 1923 in radial direction over the whole length
of the shaft, therefore the axial distance between two measurement points should not be more
than 1000 mm. In the case of the attenuation measurement, irregularities which require further
investigations can occur. For example, can probe- and/or material dependent attenuation values
be identical and/or lower with the higher frequency (e.g. 5 MHz) as with the lower frequency
(e.g. 4 MHz). In such cases possibly further investigations of the frequency spectrums of the
probes must be carried out. Narrow-band probes whose center frequency fits as close to the
nominal frequency should be used. This should if possible be engaged by a probe particular
frequency analysis. The Specimen number of the used probes is to be recorded in the UT record.

A7

Examination of the total circumferential surface of the shaft in both circumference direction (cw
and ccw) with angles of incidence of 7, 14 and 21 for the probe B2S.
In case of spurious echos (phantom echos), the probe B4S with corresponding
angles of incidence of 3.5, 7, 10.5, 14, 17.5, 21 and 24.5 is to be taken into consideration
for this circumferential direction (A7).
From experience it is known that with the application of B2S-probe spurious echos occur only
by the angles of incidence of 014.
In case of examining shafts for the E-Series (6.9 m2 12.5 m2) the whole body surface (LPBody) in both circumference directions (A7) additionally with an angle of 28 (B2S).

A7

Examination of the total circumferential surface of the shaft in both circumference direction with
an angle of incidence of 45 (WB45-2N).

A8

Examination of the body in near-surface range up to a depth of about 150 mm in axial direction
with an angle of incidence of 70 (WB70-2N).

A9

Examination of body in near- surface range up to a depth of about 150 mm in radial direction
with the probe SEB4H0 in case the detection sensitivity limit in the volume range near the back
wall echo will not be 1 mm FBH when tested in radial direction (A3).
The prescribed directions of incidence are presented in picture 1.
The above mentioned sound directions are valid for shafts with parallel surfaces in axial
direction only.

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PAGE 5 OF 14

Examination of cross-section transitions:

The cross-section transitions in the meaning of this procedure are areas where the diameters
differ at quality heat treatment 200mm.
All cross-section transitions are to be tested to 100% from the accessible surface in radial-axial
direction (A8) with angles of incidence of 70 (WB70-2N) according to picture 2. It is sufficient
to test the volume up to the middle of the shaft from one side only. There is no need of
examination, if the detection limit is verified 3 mm FBH from the axial direction (A4) for the
corresponding crossing.
6.2

Speed of Testing
For visual screen monitoring the testing speed shall not exceed 100 mm/s.

7
7.1

Special Features due to the Applied Examination Technique

Plexiglas-Adapter- Wedges
For acoustic incidence of longitudinal waves in radial-tangential sound direction according to
the above mentioned angles plexiglas adapter-wedges may be used. The resulting occurrence
of loss of sound energy may reduce the detection sensitivity limit. To minimize losses and
disturbing spurious echos it is taken care that the thickness of plexiglas-adapter- wedges
between transducer and testing surface shall be as small as possible.
According to experience loss of sound energy of 4 dB arises by plexiglas-adapter- wedges with
5 mm thickness and 0-angle of incidence. It is important that all other used plexiglas-adapter
wedges shall have the same thickness.

Description of Indications
Indications from defects inside the material must be characterized by their echo height and
shape, by their dynamic characteristics and if necessary by their frequency dependence.
Furthermore, indications in connection with back wall echo drop 3 dB are to be recorded as
well as the detection sensitivity limit for the largest sound path.

8.1

Flaw Echo Height

The evaluation of indications on the basis of their echo amplitude will be done according to the
AVG (DGS)-method, whereby the equivalent reflector size should be recorded as equivalent
flat bottom hole (FBH) in mm.

8.2

Flaw Echo Shape

The indications are characterized according to the following echo shapes:
single echo (in German Einzelecho)
many single echos (in German viele Einzelechos)
group echo resolvable (in German Gruppenecho auflsbar)
group echo not resolvable (in German Gruppenecho nicht auflsbar)
ring zone
grass (structural indications)

EE
VE
GA
GN
RZ
GR

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PAGE 6 OF 14
The max. FBH-size in an area of group indications (GA`s and GNs) must be always
determined by using the max. echo peak.
The screen patterns of the relevant echo shapes are shown in Table 3.
8.3

Dynamic Characteristic, Extension of Indications

The determination of the extent of single indications has to be done according to the half
amplitude method. The sound field characteristics of the probes are to be taken into
consideration. In the event that during the determination of the half amplitude extension of the
flaw a change in the beam path is detected, the existence of a flaw with a plane angular
orientation has to be assumed and recorded.
If the existence of angular or eccentric oriented flaws is suspected, the echo amplitude is to
be recorded after optimising the angles of incidence. The following shall be taken into
account:
a) When in case of radial/ tangential direction from 0, 21 (A3, A7) the reflectivity of a indication
according to table 1 will go through a maximum, no additional examinations are
necessary.
b) When in case of radial/ tangential direction from 0, 21 (A3, A7) an increase of the reflectivity
of the indication according to table 1 will be remarked, then additional examinations with
sound angles 28 and 35 shall be performed independent of the recordability of the
indication.

8.4

Dependence of Frequency
By means of changing the test frequency within the range of 2 - 4 MHz reflection positions
can provide portions with differing sound reflection amplitudes. This dependence of frequency
is to be recorded, if the FBH-values of the same individual flaw which have been determined
with different frequencies deviate for 50% and more from each other. The recording should
happen only in case the decision limit has been passed over by the indication.

8.5

Back Wall Echo drop 3 dB

The back wall echo drop is to be measured in the area of recordable indications of the shaft.

8.6

Limit of the Flaw Detection Sensitivity

The detection limit is the value of the smallest detectable circular disk reflector (FBH) under
consideration of a signal/noise ratio of 6 dB. The detection limit is to be determined for all
applied probes and sound directions and to be recorded in FBH together with the
corresponding details, e.g. probe, sound direction, sound path, etc.
For areas with quality level 1a a detection limit of 0.5 mm FBH is to be aimed for and for the
remaining areas a detection limit of 1.0 mm FBH.

Recording- and Decision Criterias

Recordable are:
- Indications according to table 2

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PAGE 7 OF 14

Decision limits are:

- Indications according to table 2
- Transgression of the attenuation values
2 MHz : 2 dB/m
4 MHz : 6 dB/m
5 MHz : 10 dB/m
- Indications from flaw areas, which will be exposed after final machining of the shaft
- In case of recodable indications in the area of the later bore hole, a special permission for
drilling is required
- detection limit exceeds 1,5 mm FBH in direction A3 and A7 with the probes B2S or B4S and
WB45-N2
- detection limit exceeds 1,0 mm FBH in direction A9 and A7 with the probe SEB4H0 and in
direction A8 with the probe WB70-N2
With transgression of the above-mentioned features, a deviation report is to be
prepared.
10

Surface Crack Examination of the cross-section transitions

The areas of the cross-section transitions (areas with diameter differences 200 mm at the
heat treatment) are subjected additionally to a surface crack examination (MT) in dependence
prEN 10228 in the delivery condition. A yoke magnet with alternating current is to be used
for magnetization. The surface roughness must correspond to Ra < 20 mm. For the recording
limit and admissibility criteria, quality class 3 is to be used (see pr EN 10 228, table 2).

11

Surface-Crack-Examination of the Axial Hole Bore

The axial boring is subjected to a surface crack examination (MT) to preferably in length
direction in the delivery condition. The surface roughness must correspond to Ra < 6,3 mm.
For the recording limits and admissibility criteria, quality class 4 is to be used (see prEN
10228, table 2). An Eddy current examination (ET) can also be carried out alternatively. For
this the manufacturer must make out a test instruction and submit it to the orderer for
confirmation.

12

Reporting
Following the examinations an inspection and testing certificate 3.1 B according to EN 10204
is to be drawn up. The MT must be documented in accordance with EN 10 228. The UT report
must contain the following information for the purpose of repeatability of the examination:
a) Details about the examined object
- identification data (ident-No., material, heat-No., etc.)
- surface condition
- step of the production flow when the examination happened
b) Details about the examination technique
- examination instruction
- scope of examination
- instrument

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PAGE 8 OF 14
- probes
- frequency
- couplant
- kind of calibration
- values of correction
c) Results of the examination
- limit of the flaw detection sensitivity
- sound attenuation values in dB/m
- recorded indications
The indications to be recorded are to be described by sufficient information concerning their
position, location, size and/or depth extension etc. and are to be described in a dimensioned
sketch of the shaft, the sectional view or a handling of the surface true to size to register.
Here, minimum entries must be made in accordance with the indication list (enclosure 1).
While filling out the table, the following is to be considered:
The position specifications of the table are probe positions.
Volume positions are always entered in degrees.
Indication types EE+VE of extension and/or GA, GN and RZ are always indication areas.
Here, it is necessary for the axial and volume positions and also for the beam path to register
the from-, to - and to maximum values as soon as required. In the case of EE+VE without
extension (punctual), the maximum values information is sufficient.
In the column "FBH", the replacement reflector size of indication is indicated. Here, the
information is sufficient up to the first place after the comma.
Back wall attenuation 3 dB is entered in the column "BEA".
In the columns one Angle of incidence both, the angle as well as the direction referring to the
reference point, is to be specified. The following information e.g. must be made like this:
Probe-No. Acc. to
SEP 1923
A3
A7
A7
A7
A7
A8
A8
A7/A8

Angle of incidence (degree)

axial

tangential

0
0
0
0
0
70T
70G
7T

0
7cw
7ccw
14cw
14ccw
0
0
7cw

Remarks

T = direction TS
G = direction GS
Possible combination

GS = generator side and therefore always output end. The information of the output
end is always given in the order drawing (BZ).
In the column "probe", the trade name of the used probe registered e.g. becomes
B2S, WB45-N2, SEB4H0 and so on.
The column "file name" can be used if the dates to indications are saved electronically.

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PAGE 9 OF 14

At the column "inspection areas", the following insertions e.g. are reasonable:
coupling TS or GS
journal TS or GS
Body
In the column "remark" e.g., references of additional indication representations in other
enclosures are reasonable.
d) General
- date of examination, location of examination
- name of examiner (during the application by several examiners, it must be follow able
which test section was tested by which examiner)

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Rev. No. 00
PAGE 10 OF 14

Figure 1 :

Direction of incidence

Figure 2 : Examination of the transitions of the cross section

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PAGE 11 OF 14

Table-1 : Scope of inspection

Test No.
A3
A4
A5
A7

testing area

sound direction

100% surface area of journal and body

100% front face of body and front face of clutch
sound attenuation measurement per 1000 mm
100% surface area of body and journal

radial with the probe B2S (B4S)

axial with the probe B2S and B4S
radial with the probe B2S, B4S and B5S
2 circumferrential directions
in case of probe B2S with = 7/14/21
in case of probe B4S with
= 3,5/7/10,5/14/17,5/21/24,5
in case of probe WB45-N2 with = 45
in case of E-Shaft (6 m2 12,5 m2 ) additionally
the LP-Body with the probe B2S, = 28

A8

100% surface area of body

2 axial directions with the probe WB70-2N,

= 70 up to a depth of about 150 mm
additionally cross section transitions with probe
WB70-2N, = 70 when acc. to point 6 required

A9

100% surface area of body up to a depth of

about 150 mm

radial with the probe SEB4 when acc. to point 6

required

Table 2: Recording / decision limit

testing
area

EE/VE
without extension

EE/VE with extension

GA, GN, RZ

backwall
echo drop
[dB]

maximum
actual
reflector
length
EE/VE

Maximum
areas
length
(axial or
radial)
GA, GN

recording
limit
mm FBH

decision
limit
mm FBH

recording
limit
mm FBH

decision
limit
mm FBH

body area
0-150 mm

all
indications

all
indications

10 mm

10 mm

rest of the
areas

10 mm

decision limit

1) The sound field properties of probe are to be taken in to consideration

2) Total radial extension: 15% of diameter at the indication area
Axial extension : 20% length of body or length of shaft journal at the indication area
In case of indications in the transition of body to shaft journal the axial extension of indications shall
always be related to the length of the shaft journal. An axial extension of several GA/GN- areas is
evaluated as an axial GA/GN- area, if the distance between that GA/GN- areas is less than the twofold
length of the biggest one GA/GN- area.
3) In the case of the determination of the axial extension of GA/GN- areas, it is to be considered, whether
indications occur with extensions > beam. The decision limit of the real reflector length on the other
hand applies to such indications.

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Rev. No. 00
PAGE 12 OF 14

Table 3: Echo shapes in the application of ultrasonic testing of shafts

Screen picture

Echo shape

Symbol

single echo

EE

many single echos

1)

VE

group echos
resolvable2)

GA

group echos
not resolvable2)

GN

ringzone

RZ

1) An echo shape is to be classified as VE, if the depth distance between the single echos is more than
5% of shaft-diameter on the test location.
2) Group echos are considered resolvable, if the distance between the peak of the largest echo and
the base of the adjoining echo is > 18 dB. This classification is applicable for 500 mm the time-base
range only.

Insp.
Area

File
Name

Type

Angle of
Incidence

Location, Date

UTProbe

Axial
position

Drg.No

List

Sign.

Circumferential
position

Sonic
distance

KSR
EFH

Page

Report

Release

RES
BEA

of

Remarks

CORPORATE STANDARD

Dept. Name

No.

Job Name

Annexure 1

Indication

AA 085 01 06

Rev. No. 00

PAGE 13 OF 14

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Rev. No. 00
PAGE 14 OF 14

Annexure 2
Company

Certificate acc. To EN 10 204- 3.1B

Page

of

Ultrasonic - Report
Ident-No.

Specifications

Item

Material

Order-No.

Heat-No.

Type
of
probe

mm

mm

Scanning
direction

Calibr.
probe

distance

Calibr.
Sensitivity
(dB)

Drawing No:

Detectable
Limit
(mm
FBH)

Sound
Path
(mm)

Correction
Values
(dB)

Test
Sensitivity
(dB)

Rema rks