ASTM A531/A531M-91(2001)
(Practice)Standard Practice for Ultrasonic Examination of Turbine-Generator Steel Retaining Rings
Standard Practice for Ultrasonic Examination of Turbine-Generator Steel Retaining Rings
SCOPE
1.1 This practice covers the procedures to be followed when performing ultrasonic shear and longitudinal wave tests on turbine-generator retaining rings with an inside diameter to wall thickness ratio equal to or greater than 5:1 and with wall thicknesses from 1 to 4 in. (25 to 102 mm).
1.2 Although this practice describes methods of ultrasonically testing retaining rings by either the contact or immersion method, it shall not restrict the use of improved inspection methods as they are developed. It is recognized that techniques for examination and evaluation may be chosen in order to enhance or improve the results or to accommodate variations in procedures, equipment, or capabilities. Considering these characteristics, forgings may be inspected by a combination of both the contact and the immersion methods, as mutually agreed upon between the manufacturer and the purchaser.
1.3 This practice and the applicable material specifications are expressed in both inch-pound units and SI units. However, unless the order specifies the applicable "M" specification designation SI units, the material shall be furnished to inch-pound units.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:A 531/A531M–91 (Reapproved 2001)
Standard Practice for
Ultrasonic Examination of Turbine-Generator Steel Retaining
Rings
ThisstandardisissuedunderthefixeddesignationA531/A531M;thenumberimmediatelyfollowingthedesignationindicatestheyear
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope fication and Certification SNT-TC-1A, Supplement
C-Ultrasonic Testing
1.1 Thispracticecoverstheprocedurestobefollowedwhen
performing ultrasonic shear and longitudinal wave tests on
3. Personnel Requirements
turbine-generator retaining rings with an inside diameter to
3.1 The manufacturer shall be responsible for assigning
wall thickness ratio equal to or greater than 5:1 and with wall
qualified personnel to perform ultrasonic examination in con-
thicknesses from 1 to 4 in. (25 to 102 mm).
formance with the requirements of this practice.
1.2 Although this practice describes methods of ultrasoni-
3.2 Personnel performing ultrasonic examinations in accor-
cally testing retaining rings by either the contact or immersion
dance with this practice shall be familiar with the following:
method, it shall not restrict the use of improved inspection
3.2.1 Ultrasonic terminology,
methodsastheyaredeveloped.Itisrecognizedthattechniques
3.2.2 Instrument calibration,
for examination and evaluation may be chosen in order to
3.2.3 Effect of transducer material, size, frequency, and
enhanceorimprovetheresultsortoaccommodatevariationsin
mode on test results,
procedures,equipment,orcapabilities.Consideringthesechar-
3.2.4 Effect of material structure (grain size, cleanliness,
acteristics,forgingsmaybeinspectedbyacombinationofboth
etc.) on test results,
the contact and the immersion methods, as mutually agreed
3.2.5 Effect of test distance on test results,
upon between the manufacturer and the purchaser.
3.2.6 Effect of nonlinearity on test results,
1.3 This practice and the applicable material specifications
3.2.7 Effect of thickness and orientation of discontinuities
are expressed in both inch-pound units and SI units. However,
on test results, and
unless the order specifies the applicable “M” specification
3.2.8 Effect of surface roughness on test results.
designation SI units, the material shall be furnished to inch-
3.3 Aqualification record (see Note 1) of personnel consid-
pound units.
ered suitable by the manufacturer to perform examination in
1.4 This standard does not purport to address all of the
accordance with this practice shall be available upon request.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
NOTE 1—SNT-TC-1 A, Ultrasonic Testing Method, provides a recom-
priate safety and health practices and determine the applica- mended procedure for qualifying personnel. Other personnel qualification
requirement documents may be used when agreed upon between the
bility of regulatory limitations prior to use.
purchaser and supplier.
2. Referenced Documents
4. Ordering Information
2.1 ASTM Standards:
4.1 When this practice is to be applied to an inquiry,
E127 Practice for Fabricating and Checking Aluminum
2 contract, or order, the purchaser shall so state and shall also
Alloy Ultrasonic Standard Reference Blocks
furnish the following information:
2.2 Other Document:
4.1.1 The method or combination of methods to be used for
RecommendedPracticeforNondestructivePersonnelQuali-
inspection.
4.1.2 The frequency to be used for conducting each inspec-
This practice is under the jurisdiction of ASTM Committee A01 on Steel, tion.
Stainless Steel and RelatedAlloys and is the direct responsibility of Subcommittee
A01.06 on Steel Forgings and Billets.
Current edition approved Dec. 15, 1991. Published February 1992. Originally
published as A531 – 65. Last previous edition A531/A531M–90. Available from theAmerican Society for Nondestructive Testing, 914 Chicago
Annual Book of ASTM Standards, Vol 03.03. Ave., Evanston, IL 60202.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
A 531/A531M–91 (2001)
3 1
4.1.3 Report requirements including C-scan plot, if appli- 6.2.1.2 A 5, 2.25, or 1-MHz, ⁄4 to 1 ⁄8-in. (19.0 to 28.6-
cable. mm) diameter, longitudinal wave transducer shall be used for
performing the longitudinal wave test.
5. General Requirements
6.2.1.3 Acrylic resin shoes ground to the curvature of the
5.1 As far as possible the entire volume of the retaining
retaining ring may be used to maintain the optimum contact
rings shall be subject to ultrasonic inspection. Circumferential
angle between the transducer and outside diameter of the ring.
and axial faces shall be machined flat and parallel to one
6.2.1.4 When agreed upon between the purchaser and sup-
another.
plier, alternative test frequencies may be used to perform the
5.2 The ultrasonic inspection shall be performed after final
required tests.
processing and heat treatment for properties, unless otherwise
6.2.2 Immersion Method:
specified in the order or contract.
6.2.2.1 A5, 2.25, or 1-MHz transducer, ⁄4 to 1 in. (19.0 to
5.3 Rings may be tested either stationary (contact) or while
25.4 mm) in diameter, suitable for water immersion, shall be
rotating (immersion). If not specified by the purchaser, a
used for performing the required test.
combination of methods may be used at the manufacturer’s
6.2.2.2 The manipulator (holder) for the search tube or
option. Scanning speed shall not exceed 6 in./s (152 mm/s),
transducer, or both, shall provide for angular manipulation of
unless automatic recording (C-scan) equipment is employed. the transducer for optimum response from the internal discon-
5.4 To ensure complete coverage, (during contact testing)
tinuities.The tolerance or play present in the manipulation and
the search unit shall be indexed approximately 75% of the in the traversing unit should not be excessive so as to prevent
transducer width with each pass of the search unit. During
ultrasonic examination at the required sensitivity level.
immersion testing establish a transducer index adjustment 6.2.2.3 When agreed upon between the purchaser and sup-
which will ensure complete coverage with sufficient overlap.
plier, alternative test frequencies may be used to perform the
5.5 During the testing, a combination of methods and required tests.
frequencies of 1 MHz, 2 ⁄4 MHz, and 5 MHz may be used for
6.2.2.4 Accessory Equipment—Coaxial cables and search
accurately locating, determining orientation, and defining spe-
tubesusedinconjunctionwiththeelectronicapparatuscapable
cific discontinuities detected during overall scanning.
of conducting the electrical pulses while immersed in a liquid,
5.6 For reporting purpose, location of indications shall be
and collimators for shaping the sound beam may be used.
circumferentially defined by clock position.The test notch or a
6.3 Recording instruments or alarm systems, or both, may
similar locator, such as a reference line bisecting the serial
be used, provided sufficient range and sensitivity are available
number, shall be used to define and identify the 12 o’clock
to properly monitor the test.
position.
7. Preparation of the Forging for Ultrasonic Examination
6. Apparatus
7.1 Surface roughness on the outside and inside diameter
6.1 Ultrasonic, Pulsed, Reflection Type of Instrument, shall
and radical face surfaces of the ring shall not exceed 125 µin.
beusedfortheexamination.Thesystemshallhaveaminimum
(3.18 µm) and waviness shall not exceed 0.001 in. (0.02 mm)
capability for examining at frequencies from 1 to 5 MHz.
measured in both the axial and circumferential directions. The
6.1.1 The amplifier and the cathode ray tube shall provide
radical faces of the ring shall be sufficiently perpendicular to
linear response (within 5%) for at least 75% of the screen
the axis of the forging to permit axial tests.
height (sweep line to top of screen).
7.2 All surfaces of the ring to be examined shall be free of
6.1.2 The instrument shall contain a calibrated gain control
extraneous material such as surface tears, loose scale, machin-
or signal attenuator (in each case, accurate within 6 5%) that
ing or grinding particles, paint, and other foreign matter.
willallowindicationsbeyondthelinearrangeoftheinstrument
to be measured.
8. Ultrasonic Couplants
6.1.3 When the immersion method of inspection is em-
8.1 For contact testing, a suitable couplant, such as clean
ployed, suitable equipment must be available so that the
SAE20motoroil,shallbeusedtocouplethetransducertotest
retaining rings can be immersed in a liquid coupling agent or
surfaces.
can be subject to inspection by the use of a column or stream
8.2 For immersion testing, a liquid such as water, oil,
ofthecouplantthroughanappropriatecontainerattachedtothe
glycerin, etc., capable of conducting ultrasonic vibrations from
part or transducer. Equipment must also include fixturing for
the transducer to the material being tested shall be used. Rust
smoothmechanicalrotationofthepartorthetransducerduring
inhibitors, softeners, and wetting agents may be added to the
scanning.
couplant. The couplant liquid with all additives should not be
6.2 Search Units:
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:
A 531/A531M–91 (2001)
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 successive parallel passes, each
the tip and point midway between the tip and sweep line of the overlapping the previous pass at least 15% of the transducer
second bounce notch indication. Draw a line connecting the (not search unit) width, until t
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