ASTM A531/A531M-91(1996)

NOTICE: This standard has either been superseded and replaced by a new version or
withdrawn. Contact ASTM International (www.astm.org) for the latest information.
Designation: A 531/A 531M – 91 (Reapproved 1996) An American National Standard
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
Ultrasonic Examination of Turbine-Generator Steel Retaining
Rings
This standard is issued under the fixed designation A 531/A 531M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.
A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Personnel Requirements
1.1 This practice covers the procedures to be followed when 3.1 The manufacturer shall be responsible for assigning
performing ultrasonic shear and longitudinal wave tests on qualified personnel to perform ultrasonic examination in con-
turbine-generator retaining rings with an inside diameter to formance with the requirements of this practice.
wall thickness ratio equal to or greater than 5:1 and with wall 3.2 Personnel performing ultrasonic examinations in accor-
thicknesses from 1 to 4 in. (25 to 102 mm). dance with this practice shall be familiar with the following:
1.2 Although this practice describes methods of ultrasoni- 3.2.1 Ultrasonic terminology,
cally testing retaining rings by either the contact or immersion 3.2.2 Instrument calibration,
method, it shall not restrict the use of improved inspection 3.2.3 Effect of transducer material, size, frequency, and
methods as they are developed. It is recognized that techniques mode on test results,
for examination and evaluation may be chosen in order to 3.2.4 Effect of material structure (grain size, cleanliness,
enhance or improve the results or to accommodate variations in etc.) on test results,
procedures, equipment, or capabilities. Considering these char- 3.2.5 Effect of test distance on test results,
acteristics, forgings may be inspected by a combination of both 3.2.6 Effect of nonlinearity on test results,
the contact and the immersion methods, as mutually agreed 3.2.7 Effect of thickness and orientation of discontinuities
upon between the manufacturer and the purchaser. on test results, and
1.3 This practice and the applicable material specifications 3.2.8 Effect of surface roughness on test results.
are expressed in both inch-pound units and SI units. However, 3.3 A qualification record (see Note 1) of personnel consid-
unless the order specifies the applicable “M” specification ered suitable by the manufacturer to perform examination in
designation SI units, the material shall be furnished to inch- accordance with this practice shall be available upon request.
pound units.
NOTE 1—SNT-TC-1 A, Ultrasonic Testing Method, provides a recom-
1.4 This standard does not purport to address all of the
mended procedure for qualifying personnel. Other personnel qualification
safety concerns, if any, associated with its use. It is the
requirement documents may be used when agreed upon between the
responsibility of the user of this standard to establish appro-
purchaser and supplier.
priate safety and health practices and determine the applica-
4. Ordering Information
bility of regulatory limitations prior to use.
4.1 When this practice is to be applied to an inquiry,
contract, or order, the purchaser shall so state and shall also
2. Referenced Documents
furnish the following information:
2.1 ASTM Standards:
4.1.1 The method or combination of methods to be used for
E 127 Practice for Fabricating and Checking Aluminum
inspection.
Alloy Ultrasonic Standard Reference Blocks
4.1.2 The frequency to be used for conducting each inspec-
2.2 Other Document:
tion.
Recommended Practice for Nondestructive Personnel Quali-
4.1.3 Report requirements including C-scan plot, if appli-
fication and Certification SNT-TC-1A, Supplement
cable.
C-Ultrasonic Testing
5. General Requirements
5.1 As far as possible the entire volume of the retaining
rings shall be subject to ultrasonic inspection. Circumferential
This practice is under the jurisdiction of ASTM Committee A-1 on Steel,
and axial faces shall be machined flat and parallel to one
Stainless Steel and Related Alloysand is the direct responsibility of Subcommittee
A01.06on Steel Forgings and Billets. another.
Current edition approved Dec. 15, 1991. Published February 1992. Originally
5.2 The ultrasonic inspection shall be performed after final
published as A 531 – 65. Last previous edition A 531/A 531M – 90.
processing and heat treatment for properties, unless otherwise
Annual Book of ASTM Standards, Vol 03.03.
specified in the order or contract.
Available from the American Society for Nondestructive Testing, 914 Chicago
Ave., Evanston, IL 60202. 5.3 Rings may be tested either stationary (contact) or while
A 531/A 531M
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- tubes used in conjunction with the electronic apparatus capable
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.
be used for the examination. The system shall have a minimum
(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.
will allow indications beyond the linear range of the instrument
8. Ultrasonic Couplants
to be measured.
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 SAE 20 motor oil, shall be used to couple the transducer to test
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,
of the couplant through an appropriate container attached to the
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
smooth mechanical rotation of the part or the transducer during
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
9. Method for Shear Wave Testing
penetration of the ring section.) Adequate penetration is the
ability to clearly resolve the calibration notch above resultant 9.1 Calibration Reference:
noise level. 9.1.1 Place a calibration V-shaped notch, with an included
3 1
6.2.1.2 A 5, 2.25, or 1-MHz, ⁄4 to 1 ⁄8-in. (19.0 to 28.6- angle of 60 to 90° and ⁄4in. (6.35 mm) long, in the outside
mm) diameter, longitudinal wave transducer shall be used for diameter surface of the ring at a sufficient distance from the end
performing the longitudinal wave test. of the ring to eliminate side wall interference. Determine the
6.2.1.3 Acrylic resin shoes ground to the curvature of the location of the notch by scanning the ring at a sensitivity high
retaining ring may be used to maintain the optimum contact enough to show the material structure and with the shear wave
angle between the transducer and outside diameter of the ring.
beam directed circumferentially. Using this procedure, then
6.2.1.4 When agreed upon between the purchaser and sup- locate the notch in an area representative of the ring material.
plier, alternative test frequencies may be used to perform the
9.1.2 Place the notch axially in the ring to a depth of 1 % of
required tests. the wall thickness or 0.020 in. (0.51 mm), whichever is greater.
6.2.2 Immersion Method: Make the depth measurement after removal of the upset
6.2.2.1 A 5, 2.25, or 1-MHz transducer, ⁄4 to 1 in. (19.0 to material adjacent to the notch.
25.4 mm) in diameter, suitable for water immersion, shall be 9.1.3 For the inspection of finish machined rings, an outside
A 531/A 531M
reference block of the same alloy, wall thickness, and curvature half-amplitude reference lines.
as the ring being tested may be used. The block must be at least
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
outside diameter surface of the ring at a sufficient distance from
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
unit to the test instrument and place it directly over the
the sweep line.
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. Continue to move the search unit in the same direction
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
bound indications from the notch are about 1 ⁄2 in. (38 mm)
half-amplitude reference lines.
apart. Mark and designate the first and second bounce positions
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 the entire surface of the ring has
two points designating the amplitudes of the first and second
been scanned. Rotate the search unit 180° and repeat the
notch indications. Likewise, draw a line through the half-
procedure.
amplitude points. Refer to these lines as the amplitude and
9.4.1.2 Axial—The sensitivity established for the circumfer-
half-amplitude reference lines.
ential test shall also be used for the axial test. Place
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