ASTM A531/A531M-18(2023)
(Practice)Standard Practice for Ultrasonic Examination of Turbine-Generator Steel Retaining Rings
Standard Practice for Ultrasonic Examination of Turbine-Generator Steel Retaining Rings
ABSTRACT
This test method covers the procedures for the standard practice of performing ultrasonic shear and longitudinal wave examinations on turbine-generator steel retaining rings. A pulsed reflection-type ultrasonic instrument shall be used for the tests. Scanning of steel specimens may be performed by either the contact (stationary) or immersion (rotating) methods, both of which may be executed in either the axial or circumferential directions. Tests shall be performed after specimens have gone through final processing and heat treatment for properties, and the circumferential and axial faces machined flat and parallel to one another. Also prior to testing, surface examinations shall be made for surface roughness and tears, loose scales, machining or grinding particles, paint, and other foreign and extraneous matter. Suitable couplant liquids, capable of conducting ultrasonic vibrations, shall be used to couple the transducer to test surfaces.
SCOPE
1.1 This practice covers ultrasonic examination of turbine-generator retaining rings produced in accordance with Specifications A288 and A289/A289M with an inside diameter to wall thickness ratio equal to or greater than 5:1 and with wall thicknesses from 1 in. to 4 in. [25 mm to 102 mm].
1.2 Forgings may be inspected by either the contact or the immersion methods, or combinations thereof, as agreed upon between the manufacturer and the purchaser.
1.3 Supplementary requirements of an optional nature are provided for use at the option of the purchaser. The supplementary requirements shall apply only when specified individually by the purchaser in the purchase order or contract.
1.4 This practice is expressed in inch-pound and SI units; however, unless the purchase order or contract specifies the applicable “M” specification designation (SI units), the inch-pound units shall apply. The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the practice, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.5 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: A531/A531M − 18 (Reapproved 2023)
Standard Practice for
Ultrasonic Examination of Turbine-Generator Steel Retaining
Rings
This standard is issued under the fixed designation A531/A531M; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This practice covers ultrasonic examination of turbine- 2.1 ASTM Standards:
generator retaining rings produced in accordance with Speci- A288 Specification for Carbon and Alloy Steel Forgings for
fications A288 and A289/A289M with an inside diameter to Magnetic Retaining Rings for Turbine Generators
wall thickness ratio equal to or greater than 5:1 and with wall A289/A289M Specification for Alloy Steel Forgings for
thicknesses from 1 in. to 4 in. [25 mm to 102 mm]. Nonmagnetic Retaining Rings for Generators
E127 Practice for Fabrication and Control of Flat Bottomed
1.2 Forgings may be inspected by either the contact or the
Hole Ultrasonic Standard Reference Blocks
immersion methods, or combinations thereof, as agreed upon
E317 Practice for Evaluating Performance Characteristics of
between the manufacturer and the purchaser.
Ultrasonic Pulse-Echo Testing Instruments and Systems
1.3 Supplementary requirements of an optional nature are
without the Use of Electronic Measurement Instruments
provided for use at the option of the purchaser. The supple-
2.2 Other Documents:
mentary requirements shall apply only when specified indi-
ANSI/ASME B46.1 Surface Texture (Surface Roughness,
vidually by the purchaser in the purchase order or contract. 3
Waviness and Lay)
1.4 This practice is expressed in inch-pound and SI units;
Recommended Practice No. SNT-TC-1A Personnel Qualifi-
however, unless the purchase order or contract specifies the cation and Certification in Nondestructive Testing
applicable “M” specification designation (SI units), the inch-
3. Personnel Requirements
pound units shall apply. The values stated in either SI units or
inch-pound units are to be regarded separately as standard.
3.1 Personnel performing ultrasonic examinations to this
Within the practice, the SI units are shown in brackets. The
practice shall be qualified and certified in accordance with a
values stated in each system may not be exact equivalents;
written procedure conforming to Recommended Practice No.
therefore, each system shall be used independently of the other.
SNT-TC-1A or other national standard acceptable to both the
Combining values from the two systems may result in noncon-
purchaser and the supplier.
formance with the standard.
4. Ordering Information
1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4.1 When this practice is to be applied to an inquiry,
responsibility of the user of this standard to establish appro-
contract, or order, the purchaser shall so state and shall also
priate safety, health, and environmental practices and deter-
furnish the following information:
mine the applicability of regulatory limitations prior to use.
4.1.1 The method or combination of methods to be used for
1.6 This international standard was developed in accor-
inspection.
dance with internationally recognized principles on standard-
4.1.2 The frequency to be used for conducting each inspec-
ization established in the Decision on Principles for the
tion.
Development of International Standards, Guides and Recom-
4.1.3 Report requirements including C-scan plot, if appli-
mendations issued by the World Trade Organization Technical
cable.
Barriers to Trade (TBT) Committee.
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
This practice is under the jurisdiction of ASTM Committee A01 on Steel, Standards volume information, refer to the standard’s Document Summary page on
Stainless Steel and Related Alloysand is the direct responsibility of Subcommittee the ASTM website.
A01.06 on Steel Forgings and Billets. Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
Current edition approved March 15, 2023. Published April 2023. Originally 4th Floor, New York, NY 10036, http://www.ansi.org.
approved in 1965. Last previous edition approved in 2018 as A531/A531M – 18. Available from American Society for Nondestructive Testing (ASNT), P.O. Box
DOI: 10.1520/A0531_A0531M-18R23. 28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http://www.asnt.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A531/A531M − 18 (2023)
4.1.4 Supplementary requirements, if any. 6.1.4 When the immersion method of inspection is
employed, suitable equipment must be available so that the
5. General Requirements
retaining rings can be immersed in a liquid coupling agent or
5.1 As far as possible the entire volume of the retaining can be subject to inspection by the use of a column or stream
of the couplant through an appropriate container attached to the
rings shall be subject to ultrasonic inspection. Circumferential
and axial faces shall be machined flat and parallel to one part or transducer. Equipment must also include fixturing for
smooth mechanical rotation of the part or the transducer during
another.
scanning.
5.2 The ultrasonic inspection shall be performed after final
processing and heat treatment for properties, unless otherwise 6.2 Amplifier—The amplifier and display shall provide lin-
specified in the order or contract. ear response within 62 %, up to 100 % of full screen height.
6.2.1 Amplifier Calibration—An amplifier vertical linearity
5.3 Rings may be tested either stationary (contact) or while
check shall be made prior to performing the test by observing
rotating (immersion). If not specified by the purchaser, a
a multiple order pattern from a calibration block using a 2 MHz
combination of methods may be used at the manufacturer’s
or 2.25 MHz transducer (see Practice E317). The first back
option. Scanning speed shall not exceed 6 in./s [15 cm/s],
reflection shall be set at 100 % of full screen height. The higher
unless automatic recording (C-scan) equipment is employed.
order back reflections, 10 % and higher in amplitude, shall also
5.4 To ensure complete coverage (during contact testing),
be positioned on the screen and their amplitudes noted. The
the search unit shall be indexed no more than 75 % of the
first back reflection shall be reduced to 50 % and then 25 % of
transducer width with each pass of the search unit. During
full screen height. The amplitudes of the higher order back
immersion testing establish a transducer index adjustment
reflections shall be noted at each step. The vertical linearity
which will ensure complete coverage with sufficient overlap.
will be considered acceptable if the signal heights of the higher
5.5 During the testing, a combination of methods and
order reflections decrease in proportion to the decrease set for
frequencies of 1 MHz, 2 MHz, 2 ⁄4 MHz, and 5 MHz may be the first back reflection. The maximum acceptable error for the
used for accurately locating, determining orientation, and
decrease of the higher order reflections is the greater of 65 %
defining specific discontinuities detected during overall scan- of the expected back reflection height or 62 % of full screen
ning.
height.
5.6 For reporting purpose, location of indications shall be
6.3 Signal Attenuator—The instrument shall contain a cali-
circumferentially defined by clock position. The test notch or a
brated gain control or signal attenuator that meets the require-
similar locator, such as a reference line bisecting the serial
ments of Practice E317 (in each case, accurate within 65 %)
number, shall be used to define and identify the 12 o’clock
that will allow indications beyond the linear range of the
position.
instrument to be measured. It is recommended that these
controls permit signal adjustments up to 25 to 1 (28 dB).
6. Apparatus
6.4 Search Units:
6.1 Electronic Apparatus—A pulse-echo instrument permit-
6.4.1 Contact Method:
ting inspection frequencies of at least 1 MHz to 5 MHz is
6.4.1.1 A 2.25 MHz, 2.0 MHz or 1.0 MHz, 45° angle beam
required. The accuracy of discontinuity amplitude analysis
shear wave search unit shall be employed for shear wave
using this practice involves a knowledge of the true operating
testing (2.0 MHz or 2.25 MHz shall be used unless acoustic
frequency of the complete inspection system. One of the best
attenuation of the material is such that 1 MHz must be
ways to obtain the desired accuracy is by use of a tuned pulser
employed to obtain adequate penetration of the ring section).
and narrow band amplifier of known frequency response, with
Adequate penetration is the ability to clearly resolve the
either a broadband transducer, or a narrow-band tuned trans-
calibration notch above resultant noise level.
ducer of known and matching frequency.
6.4.1.2 A 5 MHz, 2.25 MHz, 2.0 MHz or 1 MHz, ⁄4 in. to
6.1.1 Apparatus Qualification and Calibration—Basic
1 ⁄8 in. [20 mm to 30 mm] diameter, longitudinal wave trans-
qualification of the ultrasonic test instrument shall be per-
ducer shall be used for performing the longitudinal wave test.
formed at intervals not to exceed twelve months or whenever
6.4.1.3 Acrylic resin shoes ground to the curvature of the
maintenance is performed that affects the equipment function.
retaining ring may be used to maintain the optimum contact
The date of the last calibration and the date of the next required
angle between the transducer and outside diameter of the ring.
calibration shall be displayed on the test equipment.
6.4.1.4 When agreed upon between the purchaser and
6.1.2 The horizontal linearity shall be checked on a distance
supplier, alternative test frequencies may be used to perform
calibration bar using the multiple order technique (see Practice
the required tests.
E317). The horizontal linearity shall be 62 % of the metal
6.4.2 Immersion Method:
path.
6.4.2.1 A 5 MHz, 2.25 MHz, 2.0 MHz, or 1 MHz
6.1.3 The accuracy of the linearity shall be checked by
transducer, ⁄4 in. to 1 in. [20 mm to 30 mm] in diameter,
ultrasonically verifying the thickness of the component in at
suitable for water immersion, shall be used for performing the
least one location beyond the near field of the transducer. If
required test.
necessary, minor adjustments for differences in the ultrasonic
velocities between the calibration bar and the forging shall then 6.4.2.2 The manipulator (holder) for the search tube or
be made. transducer, or both, shall provide for angular manipulation of
A531/A531M − 18 (2023)
the transducer for optimum response from the internal discon- as the ring being tested may be used. The block must be at least
tinuities. The tolerance or play present in the manipulation and 4 in. [10 cm] wide and long enough to permit three bounces
in the traversing unit should not be excessive so as to prevent from the reference notch.
ultrasonic examination at the required sensitivity level. 9.1.4 For axial shear wave examination by the immersion
6.4.2.3 When agreed upon between the purchaser and method, place a circumferentially oriented notch into the
supplier, alternative test frequencies may be used to perform outside diameter surface of the ring at a sufficient distance from
the required tests. the end of the ring so that it can be clearly resolved from the
6.4.2.4 Accessory Equipment—Coaxial cables and search outside diameter corner reflection. Dimensions of notch shall
tubes used in conjunction with the electronic apparatus capable be the same as described in 9.1.1.
of conducting the electrical pulses while immersed in a liquid,
9.2 Contact Method for Equipment Calibration:
and collimators for shaping the sound beam may be used.
9.2.1 Connect the 2.25 MHz, 2.0 MHz or 1 MHz angle
6.5 Recording instruments or alarm systems, or both, may beam search unit to the test instrument and place it directly
be used, provided sufficient range and sensitivity are available over the calibration notch with the crystal directed circumfer-
to properly monitor the test. entially. Move the search unit circumferentially, directing the
sound beam toward the notch until an indication from the notch
7. Preparation of the Forging for Ultrasonic Examination
appears. Continue to move the search unit in the same direction
7.1 Surface roughness on the outside and inside diameter
until a maximized second bounce indication appears.
and radical face surfaces of the ring shall not exceed an Ra of
9.2.2 Adjust the sweep length so that the first and second
125 μin. [3.18 μm] (Ra is defined in ANSI/ASME B46.1), and
bound indications from the notch are about 1 ⁄2 in. [38 mm]
waviness shall not exceed 0.001 in. [0.02 mm] measured in
apart. Mark and designate the first and second bounce positions
both the axial and circumferential directions. The radical faces
on the sweep line.
of the ring shall be sufficiently perpendicular to the axis of the
9.2.3 Adjust the gain until the first bounce indication has a
forging to permit axial tests.
sweep-to-peak amplitude of 1.5 in. [38 mm]. Mark the upper
tip of this indication and the point midway between the tip and
7.2 All surfaces of the ring to be examined shall be free of
the sweep line. Check the notch in the reverse direction; if a
extraneous material such as surface tears, loose scale, machin-
marked difference in amplitude is found, make a new notch.
ing or grinding particles, paint, and other foreign matter.
9.2.4 In a similar manner, locate and mark the position of
8. Ultrasonic Couplants
the tip and point midway between the tip and sweep line of the
second bounce notch indication. Draw a line connecting the
8.1 For contact testing, a suitable couplant, such as clean
two points designating the amplitudes of the first and second
SAE 20 motor oil, shall be used to couple the transducer to test
notch indications. Likewise, draw a line through the half-
surfaces.
amplitude points. Refer to these lines as the amplitude and
8.2 For immersion testing, a liquid such as water, oil,
half-amplitude reference lines.
glycerin, etc., capable of conducting ultrasonic vibrations from
9.3 Immersion Method for Equipment Calibration:
the transducer to the material being tested shall be used. Rust
9.3.1 Circumferential:
inhib
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