ASTM A531/A531M-91(2006)

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Designation:A531/A531M–91 (Reapproved 2006)
Standard Practice for
Ultrasonic Examination of Turbine-Generator Steel Retaining
Rings
This standard is issued under the fixed designationA531/A531M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope RecommendedPracticeforNondestructivePersonnelQuali-
fication and Certification SNT-TC-1A, Supplement
1.1 Thispracticecoverstheprocedurestobefollowedwhen
C-Ultrasonic Testing
performing ultrasonic shear and longitudinal wave tests on
turbine-generator retaining rings with an inside diameter to
3. Personnel Requirements
wall thickness ratio equal to or greater than 5:1 and with wall
3.1 The manufacturer shall be responsible for assigning
thicknesses from 1 to 4 in. (25 to 102 mm).
qualified personnel to perform ultrasonic examination in con-
1.2 Although this practice describes methods of ultrasoni-
formance with the requirements of this practice.
cally testing retaining rings by either the contact or immersion
3.2 Personnel performing ultrasonic examinations in accor-
method, it shall not restrict the use of improved inspection
dance with this practice shall be familiar with the following:
methodsastheyaredeveloped.Itisrecognizedthattechniques
3.2.1 Ultrasonic terminology,
for examination and evaluation may be chosen in order to
3.2.2 Instrument calibration,
enhanceorimprovetheresultsortoaccommodatevariationsin
3.2.3 Effect of transducer material, size, frequency, and
procedures,equipment,orcapabilities.Consideringthesechar-
mode on test results,
acteristics,forgingsmaybeinspectedbyacombinationofboth
3.2.4 Effect of material structure (grain size, cleanliness,
the contact and the immersion methods, as mutually agreed
etc.) on test results,
upon between the manufacturer and the purchaser.
3.2.5 Effect of test distance on test results,
1.3 This practice and the applicable material specifications
3.2.6 Effect of nonlinearity on test results,
are expressed in both inch-pound units and SI units. However,
3.2.7 Effect of thickness and orientation of discontinuities
unless the order specifies the applicable “M” specification
on test results, and
designation SI units, the material shall be furnished to inch-
3.2.8 Effect of surface roughness on test results.
pound units.
3.3 Aqualification record (see Note 1) of personnel consid-
1.4 This standard does not purport to address all of the
ered suitable by the manufacturer to perform examination in
safety concerns, if any, associated with its use. It is the
accordance with this practice shall be available upon request.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
NOTE 1—SNT-TC-1 A, Ultrasonic Testing Method, provides a recom-
bility of regulatory limitations prior to use. mended procedure for qualifying personnel. Other personnel qualification
requirement documents may be used when agreed upon between the
2. Referenced Documents
purchaser and supplier.
2.1 ASTM Standards:
4. Ordering Information
E127 Practice for Fabricating and Checking Aluminum
4.1 When this practice is to be applied to an inquiry,
Alloy Ultrasonic Standard Reference Blocks
contract, or order, the purchaser shall so state and shall also
2.2 Other Document:
furnish the following information:
4.1.1 The method or combination of methods to be used for
inspection.
This practice is under the jurisdiction of ASTM Committee A01 on Steel,
Stainless Steel and RelatedAlloys and is the direct responsibility of Subcommittee
4.1.2 The frequency to be used for conducting each inspec-
A01.06 on Steel Forgings and Billets.
tion.
Current edition approved March 1, 2006. Published April 2006. Originally
4.1.3 Report requirements including C-scan plot, if appli-
approved in 1965. Last previous edition approved in 2001 as A531/A531M–91
(2001). DOI: 10.1520/A0531_A0531M-91R06. cable.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from theAmerican Society for Nondestructive Testing, 914 Chicago
the ASTM website. Ave., Evanston, IL 60202.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
A531/A531M–91 (2006)
3 1
5. General Requirements 6.2.1.2 A5, 2.25, or 1-MHz, ⁄4 to 1 ⁄8-in. (19.0 to 28.6-mm)
diameter, longitudinal wave transducer shall be used for
5.1 As far as possible the entire volume of the retaining
performing the longitudinal wave test.
rings shall be subject to ultrasonic inspection. Circumferential
6.2.1.3 Acrylic resin shoes ground to the curvature of the
and axial faces shall be machined flat and parallel to one
retaining ring may be used to maintain the optimum contact
another.
angle between the transducer and outside diameter of the ring.
5.2 The ultrasonic inspection shall be performed after final
6.2.1.4 When agreed upon between the purchaser and sup-
processing and heat treatment for properties, unless otherwise
plier, alternative test frequencies may be used to perform the
specified in the order or contract.
required tests.
5.3 Rings may be tested either stationary (contact) or while
6.2.2 Immersion Method:
rotating (immersion). If not specified by the purchaser, a
6.2.2.1 A5, 2.25, or 1-MHz transducer, ⁄4 to 1 in. (19.0 to
combination of methods may be used at the manufacturer’s
25.4 mm) in diameter, suitable for water immersion, shall be
option. Scanning speed shall not exceed 6 in./s (152 mm/s),
used for performing the required test.
unless automatic recording (C-scan) equipment is employed.
6.2.2.2 The manipulator (holder) for the search tube or
5.4 To ensure complete coverage (during contact testing), transducer, or both, shall provide for angular manipulation of
the search unit shall be indexed approximately 75% of the the transducer for optimum response from the internal discon-
transducer width with each pass of the search unit. During tinuities.The tolerance or play present in the manipulation and
immersion testing establish a transducer index adjustment in the traversing unit should not be excessive so as to prevent
which will ensure complete coverage with sufficient overlap. ultrasonic examination at the required sensitivity level.
6.2.2.3 When agreed upon between the purchaser and sup-
5.5 During the testing, a combination of methods and
plier, alternative test frequencies may be used to perform the
frequencies of 1 MHz, 2 ⁄4 MHz, and 5 MHz may be used for
required tests.
accurately locating, determining orientation, and defining spe-
6.2.2.4 Accessory Equipment—Coaxial cables and search
cific discontinuities detected during overall scanning.
tubesusedinconjunctionwiththeelectronicapparatuscapable
5.6 For reporting purpose, location of indications shall be
of conducting the electrical pulses while immersed in a liquid,
circumferentiallydefinedbyclockposition.Thetestnotchora
and collimators for shaping the sound beam may be used.
similar locator, such as a reference line bisecting the serial
6.3 Recording instruments or alarm systems, or both, may
number, shall be used to define and identify the 12 o’clock
be used, provided sufficient range and sensitivity are available
position.
to properly monitor the test.
6. Apparatus
7. Preparation of the Forging for Ultrasonic Examination
6.1 Ultrasonic, Pulsed, Reflection Type of Instrument, shall
7.1 Surface roughness on the outside and inside diameter
beusedfortheexamination.Thesystemshallhaveaminimum
and radical face surfaces of the ring shall not exceed 125 µin.
capability for examining at frequencies from 1 to 5 MHz.
(3.18 µm) and waviness shall not exceed 0.001 in. (0.02 mm)
6.1.1 The amplifier and the cathode ray tube shall provide
measured in both the axial and circumferential directions. The
linear response (within 5%) for at least 75% of the screen
radical faces of the ring shall be sufficiently perpendicular to
height (sweep line to top of screen).
the axis of the forging to permit axial tests.
6.1.2 The instrument shall contain a calibrated gain control
7.2 All surfaces of the ring to be examined shall be free of
or signal attenuator (in each case, accurate within 65%) that
extraneous material such as surface tears, loose scale, machin-
willallowindicationsbeyondthelinearrangeoftheinstrument
ing or grinding particles, paint, and other foreign matter.
to be measured.
8. Ultrasonic Couplants
6.1.3 When the immersion method of inspection is em-
ployed, suitable equipment must be available so that the
8.1 For contact testing, a suitable couplant, such as clean
retaining rings can be immersed in a liquid coupling agent or
SAE20motoroil,shallbeusedtocouplethetransducertotest
can be subject to inspection by the use of a column or stream
surfaces.
ofthecouplantthroughanappropriatecontainerattachedtothe
8.2 For immersion testing, a liquid such as water, oil,
part or transducer. Equipment must also include fixturing for
glycerin,etc.,capableofconductingultrasonicvibrationsfrom
smoothmechanicalrotationofthepartorthetransducerduring
the transducer to the material being tested shall be used. Rust
scanning.
inhibitors, softeners, and wetting agents may be added to the
6.2 Search Units:
couplant. The couplant liquid with all additives should not be
detrimental to the surface condition of the test specimen or the
6.2.1 Contact Method:
container, and it should wet the surface of the material to
6.2.1.1 A 2.25 or 1.0-MHz, 45° angle beam shear wave
provide an intimate contact. Couplant may be heated to a
search unit shall be employed for shear wave testing (2.25
comfortable working temperature and must be free of air
MHz shall be used unless acoustic attenuation of the material
bubbles.
is such that 1 MHz must be employed to obtain adequate
penetration of the ring section). Adequate penetration is the
9. Method for Shear Wave Testing
ability to clearly resolve the calibration notch above resultant
noise level. 9.1 Calibration Reference:
A531/A531M–91 (2006)
9.1.1 Place a calibration V-shaped notch, with an included indication from the reference notch. Check the notch in the
angle of 60 to 90° and ⁄4 in. (6.35 mm) long, in the outside reverse direction; if a marked difference in amplitude is noted,
diametersurfaceoftheringatasufficientdistancefromtheend make a new notch.
of the ring to eliminate side wall interference. Determine the
9.3.1.2 Adjust the gain until the first bounce indication has
location of the notch by scanning the ring at a sensitivity high
a sweep-to-peak amplitude of 1.5 in. (38 mm). Mark the upper
enough to show the material structure and with the shear wave
tip of this indication and the point midway between the tip and
beam directed circumferentially. Using this procedure, then
the sweep line.
locate the notch in an area representative of the ring material.
9.3.1.3 In a similar manner, locate and mark the position of
9.1.2 Place the notch axially in the ring to a depth of 1% of
the tip and point midway between the tip and sweep line of the
thewallthicknessor0.020in.(0.51mm),whicheverisgreater.
second bounce notch indication. Draw a line connecting the
Make the depth measurement after removal of the upset
two points designating the amplitudes of the first and second
material adjacent to the notch.
notch indications. Likewise, draw a line through the half-
9.1.3 Fortheinspectionoffinishmachinedrings,anoutside amplitude points. Refer to these lines as the amplitude and
referenceblockofthesamealloy,wallthickness,andcurvature half-amplitude reference lines.
astheringbeingtestedmaybeused.Theblockmustbeatleast 9.3.2 Axial:
4 in. (102 mm) wide and long enough to permit three bounces
9.3.2.1 With the transducer located perpendicular to the
from the reference notch.
outside diameter so as to obtain a 3 6 ⁄4-in. (76 6 6.35-mm)
9.1.4 For axial shear wave examination by the immersion
water path as previously described in 9.3.1.1, position the
method, place a circumferentially oriented notch into the
transducer over the circumferential reference notch, and adjust
outsidediametersurfaceoftheringatasufficientdistancefrom
the angle and horizontal position to maximize the indication
the end of the ring so that it can be clearly resolved from the
from the reference notch while directing the ultrasonic beam
outside diameter corner reflection. Dimensions of notch shall toward the nearest end face of the ring.
be the same as described in 9.1.1.
9.3.2.2 Adjust the gain until the first bounce indication has
9.2 Contact Method for Equipment Calibration: a sweep-to-peak amplitude of 1.5 in. (38 mm). Mark the upper
9.2.1 Connect the 2.25-MHz or 1-MHz angle beam search tip of this indication and the point midway between the tip and
the sweep line.
unit to the test instrument and place it directly over the
calibration notch with the crystal directed circumferentially. 9.3.2.3 In a similar manner, locate and mark the position of
Move the search unit circumferentially, directing the sound the tip and point midway between the tip and sweep line of the
beam toward the notch until an indication from the notch second bounce notch indication. Draw a line connecting the
appears.Continuetomovethesearchunitinthesamedirection
two points designating the amplitudes of the first and second
until a maximized second bounce indication appears. notch indications. Likewise, draw a line through the half-
9.2.2 Adjust the sweep length so that the first and second amplitude points. Refer to these lines as the amplitude and
half-amplitude reference lines.
bound indications from the notch are about 1 ⁄2 in. (38 mm)
apart.Markanddesignatethefirstandsecondbouncepositions
9.4 Scanning:
on the sweep line.
9.4.1 Contact Method:
9.2.3 Adjust the gain until the first bounce indication has a
9.4.1.1 Circumferential—With the search unit held by hand
sweep-to-peak amplitude of 1.5 in. (38 mm). Mark the upper
or in a mechanical fixture, place it on the outside diameter
tip of this indication and the point midway between the tip and
surface of the ring with the sound beam directed circumferen-
the sweep line. Check the notch in the reverse direction; if a
tially. Move the search unit in the circumferential direction
marked difference in amplitude is found, make a new notch.
while maintaining the proper contact angle as determined
9.2.4 In a similar manner, locate and mark the position of during calibration. Make s
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