ULTRASONIC EXAMINATION PROCEDURE
1. SCOPE OF APPLICATION
1.1 This procedure is in compliance with the requirements of ASME Code Section
? and Section ? Division 1 & Section ?.
1.2 In accordance with this procedure a pulse-echo type of ultrasonic instrument
shall be used for Code product examination. Single probe, angle beam
scanning shall be the principal method, if necessary, straight beam scanning
may also be used.
1.3 This procedure is applicable for ultrasonic examination of weld joint of steel
pressure vessels with plate thickness equal to or greater than 5/16in.(8mm) of
examination, detecting, locating and evaluating the reflectors from the weld
metal, heat affected zone and base metal adjacent the weld.
1.4 Ultrasonic examination of austenitic steel welds are not considered to be within
the scope of this procedure.
1.5 Unless other procedure has been approved and accepted that may specify particular requirements, ultrasonic examination relating to method, evaluation, and detailed technique and requirement shall be in accordance with this procedure.
2. NDE PERSONNEL
2.1 NDE personnel shall be qualified and certified according to WHBC's
Written Practice based on SNT-TC-1A (Current Code Accepted Edition).
3. WRITTEN PROCEDURE REQUIREMENTS
3.1 This procedure shall contain the requirements of essential and nonessential
variables listed as follows. A change of essential variables shall require
re-qualification of this procedure by demonstrating to the satisfaction of the AI. A
change of non-essential variables does not require re-qualification of this procedure.
All changes of essential / non-essential variables shall require revision to and /or
addendum to this procedure.
Essential NonessentiRef. Requirement Variable al variable Para. Weld configurations to be examined, including thickness dimensions and base material product form (pipe, plate, etc.)
The surface from which the examination shall be performed
Technique(s) (straight beam, angle beam, contact and/or immersion)
Angle(s) and mode(s) of wave propagation in the material
Search unit type(s), frequency(ies) and element size(s)/shape(s)
Special search units, wedges, shoes, or saddles, when used
Ultrasonic instrument(s) Calibration (calibration blocks and techniques) Direction and extent of scanning Scanning (manual vs automatic)
Method for discriminating geometric from flaw indications
Method for sizing indications Computer enhanced data acquisition, when used
Scan overlap (decrease only) Personnel performance requirements, when required
Personnel qualification requirement Surface condition (examination surface, calibration block)
Couplant: brand name or type Automatic alarm and/or recording equipment, when applicable
Records, including minimum calibration data to be recorded (e.g. instrument settings)
4. GENERAL EXAMINATION REQUIREMENTS
4.1 Examination coverage
The volume shall be examined by moving the search unit over the examination
surface so as to scan the entire examination volume. Each pass of the search unit
shall overlap a minimum of 10% of the transducer (piezoelectric element) dimension
parallel to the direction of the scan.
4.2 Speed of Search Unit Movements
The speed of search unit movement for examination shall not exceed 6in /s
4.3 Recording Level
A record shall be maintained of all reflections from uncorrected areas having
responses that exceed 50% of the reference level. This record shall locate each
area, the response level, the dimensions, the depths below, the surface and the
5. ULTRASONIC INSTRUMENT, SEARCH UNIT AND PARAMETERS
5.1 Ultrasonic Instrument
A pulse-echo type of ultrasonic instrument shall be used. The following
instruments are recommended in examination.
Instrument Type Manufactured by
Youlian Nantong China
Tanshen Nantong China
5.2 Search Unit
For straight beam, the diameter of transducer shall be 14mm-25mm.For angle
beam, an angle shall be selected as appropriate for the configuration being
examined. The following search units are re-commended to be used in
Search Unit type Beam Angle (β) Frequency Manufactured by
The range of angle is recommended as following:
Wall Thickness(mm) Beam Angle (β) K Value (tgβ)
In generally, the frequency of 2.5MHz shall be used. For the thinner plate, 5MHz
may be used.
5.4 Screen Height linearity
The ultrasonic instrument shall provide linear vertical presentation within ?5% of
the full screen height from 20% to 80% of the calibrated screen height [ base
line to maximum calibrated screen point(s) ]. The procedure for evaluating
screen height linearity is provided in Appendix ? of ASME Sect. ?Sub. A Article
4 and shall be performed at the beginning of each period of extended use ( or
every 3 months, whichever is less).
5.5 Amplitude Control linearity
The ultrasonic instrument shall utilize an amplitude control accurate over its
useful range to +20% of the nominal amplitude ration, to allow measurement of
indications becfon the linear range of the vertical display on the screen. The
procedure for evaluating amplitude control linearity is given in ASME sect. v, Art.
4, appendix II and shall be performed at the beginning of each period of
extended use (or every 3 months, whichever is less).
5.6 Time base linearity
The linearity of the time base shall be within 1% over the whole range, i.e. the
echoes do no not deviate by more than 1% of the time base range from their
5.7 Checking and Calibration of Equipment
The proper functioning of the examination equipment shall be checked and the
equipment shall be calibrated by the use of the calibration standard at the
beginning and end of each examination, when examination personnel are
changed, and at any time that mal-functioning is suspected as a minimum. If
during any check it is determined that the testing equipment is not functioning
properly, all of the product that has been tested since the last valid equipment
calibration shall be reexamined.
6.1 Non-Piping Calibration Block
6.1.1 Basic Calibration Block Configuration
The basic calibration reflectors shall be used to establish a primary reference
response of the equipment. The basic calibration reflectors may be located
either in the component material or in a basic calibration block.
FIG 1 BASIC CALIBRATION BLOCK
Weld Thickness t Block Thickness T Diameter Notch Size
in.(mm) in.(mm) in.(mm) in.(mm)
Width = 1/4 ！6，
Depth = 2%T
(a) Holes shall be drilled and reamed minimum of 3/2 in(38mm). deep, essentially parallel
to the examination surface.
(b) Alternatively, the block may be constructed as shown in ASME V. Article 4,
Appendix J Fig.J-431.
(c) For components equal to or less than 20 in.(500mm) in diameter, calibration block diameter shall
meet the requirements of T-422.214.171.124. Two sets of calibration reflectors(holes,
notches)oriented 90 deg. from each other shall be used. Alternatively, two curved calibration
blocks may be used.
(d) Notches may be provided as required.
(e) The tolerance for hole diameter shall be ?1/32 in(0.8mm). The tolerance on notch depth shall be
+10 and -20%. The tolerance on hole location through the thickness shall be ?1/8 in (3mm).
(1) For each increase in weld thickness of 2 in (50mm). or fraction thereof over 4in. (100mm),the
hole diameter shall increase 1/16 in. (1.5mm).
6.2 The basic calibration block configuration and reflectors shall be as shown in Fig 2. The basic calibration block shall be a section of pipe of the same nominal size and schedule. The block size and reflector locations shall be adequate to perform calibration for the beam angles used.
* Notches shall be located not closer than T or 1 in (25mm),whichever is greater, to any block edge or to other notches.
(a) The minimum calibration block length (L) shall be 8 in. (200mm) or 8T, whichever is
(b) For OD 4in.(100mm)or less, the minimum arc length shall be 270 deg. For OD
greater than 4 in.(100mm), the minimum arc length shall be 8 in.(200mm)or
3T,whichever is greater.
(c) Notch depths shall be from 8% T minimum to 11% T Maximum. Notch widths shall
be 1/4 in.(6mm) maximum. Notch lengths shall be 1 in.(25mm) minimum. (d) Maximum notch width is not critical. Notches may be made with EDM or with end
mills up to 1/4 in.(6mm) in diameter.
(e) Notch lengths shall be sufficient to provide for calibration with a minimum 3 to 1
6.3 Basic Calibration Block Material
Block shall be manufactured from low-or medium-carbon ferritic steel (killed),
normalized to produce a fine-grained structure and homogeneous throught.
6.3.1 In addition to freedom from internal flaws, the material selected shall be free
from undesirable metallurgical structure such as coarse grain pronounced rolling
or casting structure.
6.3.2 Surface Finish
The finish on the surfaces of the block shall be representative of the surface
finishes of the component.
6.4 Calibration Reflectors
6.4.1 Basic Calibration Reflectors
The transverse drilled hole in Fig.1 shall be used.
6.4.2 Welds in Materials With Diameters 20 in. ( 500mm ) and less. The basic
calibration block shall be curved for materials with diameters 20 in. ( 500mm )
and less. Except where otherwise stated in this procedure a single curved basic
calibration block may be used to calibrate the examination on surfaces in
the range of curvature from 0.9 to 1.5 times the basic calibration block diameter.
7. SYSTEM CALIBRATION (GENERAL)
7.1 Angle Beam Calibration (Transversal wave) as applicable the calibration shall
provide the following measurements:
(a) sweep range calibration;
(b) distance-amplitude correction (DAC);
(c) position calibration;
(d) echo amplitude measurement from the transverse drilled hole in the basic
7.2 Straight Beam Calibration
The calibration shall provide the following measurements:
(a) sweep range calibration;
(b) distance-amplitude correction (DAC)
7.3 Calibration Confirmation
Calibration shall be performed prior to use of the system in the thickness range
7.3.1 Sweep Range Correction.
If a point on the DAC curve has moved on the sweep more line than 10% of
the sweep reading or 5% of full sweep, whichever is greater, correct the
sweep range calibration and note the correction in the examination
record. If reflector are noted recorded on the data sheets, those data sheets
shall be voided and a new calibration shall be recorded .All recorded
indication since the last valid calibration or calibration check shall be
reexamined with the corrected calibration and their values shall be changed on
the data sheets.
7.3.2 Instrument Linearity Checks (calibration)
The calibration interval for the simulate type of equipment shall be no more than
3 months and for digital type shall be no more than 1 year.
7.3.3 DAC Correction
If a point on the distance-amplitude correction (DAC) curve has decreased 20%
or 2 dB of its amplitude, all data sheets since the last calibration or calibration
check shall be marked void. A new calibration shall be made and recorded and
area covered by the voided data shall be reexamined. If any point of the
distance amplitude correction (DAC) curve has increased more than 20% or 2
dB of its amplitude, all recorded indications since the last valid calibration or
calibration check shall be examined with the corrected calibration and their
values shall be changed on the data sheets.
DAC 8. Distance Amplitude Correction ！，
8.1 Angle Beam
(a) Position the search unit for maximum response from the SDH that
gives the highest amplitude.
(b) Adjust the sensitivity(gain) control to provide an indication of 80；？?
of full screen height. This is the primary reference level. Mark the 5；？
peak of this indication on the screen.
(c) Position the search unit for maximum response from another SDH and
mark the peak of the indication on the screen.
(d) Position the search unit for maximum response from the third SDH
and mark the peak on the screen.
(e) Connect the screen marks of the SDHs to provide the DAC curve.
8.2 Straight Beam
(a) Position the search unit for the maximum indication from the SDH,
which gives the highest indication.
(b) Adjust the sensitivity (gain) control to provide an 80；？?5；？ of FSH
indication. This is the primary reference level. Mark the peak of this
indication on the screen.
(c) Position the search unit for maximum indication from another SDH.
(d) Mark the peak of the indication on the screen.
(e) Position the search unit for maximum indication from the third SDH
and mark the peak on the screen.
(f) Connect the screen marks for the SDHs and extend through the
thickness to provide the distance-amplitude curve.
9.1 Surface preparation
9.1.1 Base Metal
The base metal on each side of the weld shall be free of weld spatter,
surface irregularities, or foreign matter that might interfere with the
9.1.2 Weld Metal
Where the weld surface interferes with the examination, the weld shall be
prepared as needed to permit examination.
9.2.1 The couplant used in UT examination should be as same as that used in
calibration. The No. 20 motor oil or glycerin or paste (C.M.C) shall be
recommended to use.
9.2.2 The shape of the sole must be adapted to the tube diameter and the set from
sole edge doesn’t exceed 0.1mm.
9.3 Scanning Requirements
9.3.1 Angle Beam Scanning
126.96.36.199 Scanning for Reflectors Oriented Parallel to the Weld
The angle beam shall be directed at approximate right angles to the weld axis
from two directions where possible. The search unit shall be manipulated
so that the ultrasonic energy passes through the required volumes of weld and
adjacent base metal. The scanning shall be performed at a gain setting at
least two time the primary reference level. Evaluation shall be performed with
respect to the primary reference level.
188.8.131.52 Scanning for Reflectors Oriented Transverse to the Weld
The angle beam shall be directed essentially parallel to the weld axis. The
search unit shall be manipulated so that the angle beam passes through the
required volumes of weld and adjacent base metal specified by the referencing
Code Section,. The scanning shall be performed at a gain setting at least two
times the primary reference level. Evaluation shall be performed with respect to
the primary reference level. The search unit shall be rotated 180 deg. and the
9.4 Straight Beam
The scanning of the adjacent base metal shall be performed to detect
reflectors that might affect interpretation of angle beam results, and is not to be
used as acceptance-rejection examination. Locations and areas of such
reflectors shall be recorded.
9.5 The weld and base metal shall be scanned, where required by the referencing
Code Section to the extent possible with the straight beam search unit. The
scanning shall be performed at a gain setting of at least two times the primary
reference level. Evaluation shall be performed with respect to the primary
9.6 Scanning Sketch
9.6.1 Scanning for butt welded joint
9.6.2 Scanning for welded joint,joint with nozzles to shell,drum and header.
10.1 Examination Using DAC
For examination using a distance amplitude correction curve (DAC),any
reflector which causes an indication in excess of 20% of DAC shall be
investigated to the extent that it can be evaluated in terms of the acceptance
standards given in 11.of this procedure.
10.2 Examination Using Other Than DAC
For examination using other than DAC, evaluate according to the requirements
of ASME sect ?, Div,1. or Sect. I.
10.3 Discrimination of Geometric from Flaw Indications
10.3.1 Category and cause of Geometric Indications
Not all ultrasonic reflectors indicates flaw, since certain metallurgical
discontinuities and geometric condition may produce indications that are not
relevant. Included in this category are plate segregates in heat-affected zone that
become reflective after fabrication. Under straight beam examination, these may