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MICROCOPY RESOLUTION TEST CHART
NATIONAL QUREAU OF STANDARDS - 1963
این ع
سه ماه طی
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--TORNIP21700 pm ---
CONF-660811- 2
3-25-66
CFSTI PRICES
H.C. $ loro ;MN.50
MAY 10 1966
CODES AND THE NONDESTRUCTIVE TESTING OF WELDS MASTER
ABSTRACT
The history of the development of pressure vessel and piping codes
is summarized and the problems involved in introducing new tech-
niques, including nondestructive testing requirements, into these
codes are described. These problems include the necessity for
cial
r
establishing procedi: "93 whose results are readily interpretable
with a minimum of dispute, and capable of giving consistently re-
me
producible results when employed by a variety of operators and shops
with a variety of equipment and varying levels of ability. The
generally good record of service performance of code-constructed
...
equipment requires that the introduction of new techniques be justi-
fied on the basis of improved quality of construction consistent with
*
the costs involved. The actual methods of nondestructive testing
presently incorporated in Codes and their acceptance standards, are
reported in some detail.
k
is.

REIRASIDED FOR ANNOUNCEMENT
IN PUCIGAR SCIENCE ABSTRACTS
LEGAL NOTICE
**
: This report mo prepared as an account of Government sponsored work. Nolther the United
Suatos, por the Commission, nor any person acting on beball of the Commission:
racy, completanass, or usefulness of the laformation contained in this report, or that the we
of way Information, apparatus, method, or procesu diooload in this roport may not Infringo
privately owned rights; or
8. Aommes any liabiliuos wil rospoct to the use of, or for damages resulting from the
un of nay information, apparstw, method, or process disclosed in this report,
A. uand la the abova, "per non acting on behalf of the Commission" Includes any on-
ploym or contractor of the Commission, or omployee of such contractor, to the oxtant that
goch employs or contractor of the Commission, or employee of much contractor properos,
dienominator, or provides access to, may information pursuant to belo employment or contract
with the Commission, or bio employment with such contractor.
***ramornstamos
3-25-66
.
Talk Presented to Midwest Welding Conference Symposium on
Nondestructive Testing of Welds at II TRI, Chicago, Illinois 3 Feb. 66
.
.
CODES AND THE NONDESTRUCTIVE TESTING OF WELDS
Edward C. Miller - Oak Ridge National Laboratory*
Gentlemen:
The first speaker in a Symposium such as this should probably present a
broad picture of the entire field of nondestructive testing in relation to
welds; perhaps he should even attempt to paint a glowing picture of its
accomplishments and its prospects in these applications. Unfortunately
my presentation will be largely a recital of the difficulties and frustrations
involved in making Code use of the admitted capabilities of nondestructive
testing of welds. I don't expect to disclose any new techniques or advanced.
developments in the field; rather, the applications I'll describe will probably
..
.
. .
.....
be a disappointment to you. Consequently I'm accepting the assignment as
leadoff speaker with some reluctance and apprehension, but, perhaps, in
.
...on -.
.
.
..
.
discussing the difficulties and even the negative aspects of the subject,
. .
.
I can present a challenge to later speakers to suggest solutions to some of
.
.
the difficulties.
..
.
..
Let me first state a couple of ground rules. I assume I was invited to give
...
this talk because I hold membership in certain Code Committees, but I am
.
.....
also obliged, as a Code Committee member, to make a disclaimer to the
effect that the statements and opinions I express are entirely my own, they
..
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.
do not necessarily represent the official viewpoint of the Codes, and they
.
--.....
are not to be interpreted as official Code interpretations. And in making
*Operated by Union Carbide Corporation for the U. S. Atomic Energy
Commission.
...
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this presentation, I am not doing so as a nondestructive testing specialist,
but, rather, as an engineer who is most anxious to make maximum
use of nondestructive methods as inspection tools in Codes to verify the
adequacy and integrity of welds in press'ıre-containing components.
Without attempting to define or describe the Codes in detail, let me try
kaltinacion entre otra
to tell you some of the things Codes are expected to accomplish and some
of the limitations and restrictions within which Codes must operate; non-
desiructive testing, when used in Codes, is also expected to contribute to these
same objectives and to function within these same limitations. I shall
as
limit myself to the Codes with which I have some connection, particularly
:
.
the ASME Boller and Pressure Vessel Code and its Section III, Nuclear Vessels,
and the ASA B31 Code for Pressure Piping. These Codes are expected to provide
indistin
uniform, economical, and consistently reliable safety standards for the con-
struction of pressure-containing equipment which can then be operated with
oini
confidence in normally anticipated service, with the usual provisions for
periodic reinspection for service deterioration. This may be an over simpli-
S
fication, but it is probably a sufficient basis for discussion of the subject
at hand.
The first ASME Boiler Code appeared a little over 50 years ago, as a result
of two sets of circumstances. First, for a considerable period of time -
roughly 10 years or more on either side of the turn of the century, explosions
tie. ............
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ind ishontirici .........
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of boilers and resultant fatalities were occurring with increasing frequency
and severity as new boilers were being bư!lt and old boilers were being
pushed to operate at higher and still higher temperatures and pressures.
Second, in recognition of this situation, many states and municipalities
developed boiler construction safety rules of their own so that boiler
manufacturers, users, and insurors were soon confronted with a confusion
necessariamente
of dozens of different rules and requirements; some were difficult to meet
and some contained provisions which were. neither practical nor necessary.
will
To remedy this situation, the ASME -- as a professional society with no
particular axe to grind other than the professional responsibility of contributing
r ocolorations
to the establishment of high standards of safety and good engineering practice --
was asked to develop a set of rules for the construction of power boilers in
.
the hope chat these rules could be adopted as a single uniform standard by
id
all interested parties. The first ASME Code appeared in 1914; it received a
isturinn.
Disini
general and reasonably prompt acceptance throughout the industry;and as it be-
came generally adopted, the incidence of boller failures was significantly
reduced. The Code was later expanded to cover unfired pressure vessels,
milieuthibitishwastewardesac mix Mo
and, still more recently, nuclear vessels. Today it is accepted in almost
all the states of the U.S. and provinces of Canada; and it has achieved recognition
in many foreign countries to the extent, in fact, that one enterprising foreign
fabricating concern has actually name itself "ASME Code Vessels, Ltd."
In spite of the establishment and acceptance of the Code, failures of pressure-
containing equipment do occur from time to time; but objective studies show
.
O
LOUS
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that the incidence of fallures in relation to the total number of boilers and
pressure vessels in service is remarkably small; further, investigations of
the causes of these failures show that most of them have resulted from causes
which the Code was not intended to cover: such as human error including negligence
and inadequate maintenance, and operation under conditions exceeding those
for which the component was designed or expected to function safely. Most
of these failures would have happened regardless of the quality of construction,
only a few have been due to inadequacies in the Code. Failures are generally
subjected to investigation after they happen. Often these investigations show
deficiencies in design or workmanship below Code standards; even then, these
deficiencies are seldom directly involved in the failures. This is not always
the case and sometimes, particularly if litigation is involved, the available
1'
information resulting from investigations of failures may not be as thorough
or objective as one might wish.
However
with a generally excellent record of service performance as evidence of con-
struction adequacy, the Code is perhaps slow to make major changes, in fact, it is
sometimes charged with complacency in responding to new ideas. Nevertheless,
the Code does attempt to keep reasonably abreast of advances in technology,
but it generally does so by accepting developments as they become confidently
established in practice, and not by attempting to anticipate them. This is
particularly true in cases where newer techniques of design, fabrication or
inspection are difficult to standardize over the whole spectrum of Code-applicable
construction; where there are difficulties, inconsistencies, or anomalies in the
----
g
onna
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.,
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interpretations of results; where there is doult of the necessity for using the
new techniques to accomplish Code objectives; and also, for a very practical
concern over adding requirements which will increase costs without producing
a corresponding increase in the essential safety of the construction. This
situation is not intended to prohibit the use of new developments, but it ..
does tend to make their use.permissive rather than mandatory.
Incidentally, this attitude toward new developments is not limited to nondestructive
agai itu
testing of welds - It is equally significant when applied to the more sophisti-
b
:.
-
.
internation order that the hottest and has been modern station
cated methods of mathematical and experimental stress analysis,
newer and more elaborate methods of welding and to forming, heat treating
e
and other fabrication techniques.
on this kind the train
s
This may be the time to introduce another thought which may provoke some con-
troversy, particularly in this audience. The integrity and competence of the
antenimiento
state that interess
fabricators —- including both supervision and workers —and their jxide of
workmanship are perhaps the best single assurance of adequate fabrication. This
involves the development of good manufacturing, fabrication, and-particularly,
imeminimumiskitetit duisterende til dibimidades de tratam wiele inimesed on the content
welding procedures, and close supervision and surveillance of their application
while they are being performed to provide a guarantee of quality of welded con-
struction. NDT Inspection
of the type we are talking about using in Codes-
may locate defects after the fact but it does not prevent them
you simply can't
inspect quality into a completed piece of equipment; and, even if defects located
n
nur
by inspection are subsequently repaired, it's really better to have the fabricating
and welding done right in the first place. There is admittedly some psychological
pr
twistiny
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contribution to quality of workmanship if the welder knows or suspects
that a weld will be subjected to critical inspection such as radiographic
examination. In any event, fabricators are obliged to strike a realistic
balance between in-process monitoring and post-fabrication inspection, and
the Codes try to make suitable provisions to permit this. The continuous
monitoring of production welding to the extent necessary to provide quality
equivalent to that established by post-weld nondestructive examination me
while desirable from a quality standpoint
produces complications and even
interference, and it is generally more expensive than after-tine-fact NDT.
.
Now, returning to my primary subject, the introduction of nondestructive
...-.
.
examination of welds into Codes requires that one have extensive
.
. .
information regarding the capabilities and limitations of a given technique
. . .
-
in a broad variety of applications as applied to a broad variety or materials,
.
.
.
It requires that all the parties involved have confidence in the tests and in
.
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the results of the tests; that the tests be capable of sufficiently precise
definition; and that the results be reproducible by a variety of operators with
....-...
differing levels of skill —
some, unfortunately, considerably below the level of
.
.
NDT "experts". Perhaps I should repeat this last phrase, for this represents
the major differences between NDT in Codes and NDT designed to provide
ever-more searching techniques for detecting smaller and smaller flaws.
The time-honored methods of nondestructive inspection used in Codes have
been largely limited to visual examination, hydrostatic testing, and, when
more searching examination was required -- radiography. In recent years,
other nondestructive testing techniques
and these will be discussed in
.
darbinimai....
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rio
...in.
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greater detall by other speakers in this Symposium-have been introduced
for materials and manufacturing in-process control as well as for acceptance
te
tests. However, they have not been adopted as widely in Codes for relatively
conventicnal pressure-containing components, largely because potential
users are unfamiliar with the methods and do not have confidence in their
inferi'ndominimera
medio de animale
capabilities or their results, and also because some of the nondestructive
tests involve sophisticated techniques requiring a high level of professional
understanding and technical skill for their application and interpretation.
However, as efforts were made to codify the design, fabrication and inspection
:
of nuclear reactor vessels and other critical components, it became in-
referansen
creasingly necessary that consideration be given to the introduction of non-
destructive testing techniques, largely for two reasons:
sinistration is
1. Concern for the possible consequences of failure of a nuclear power
reactor, operating at relatively high pressures and elevated tempera-
tures, made it necessary to consider methods which could increase
confidence in the reliability of pressure-containing components;
etin e
2. Certain features of design, thermal stresses, and problems of fabri-
cation, made it desirable to permit thinner walls in nuclear power
reactors than in conventional vessels operating under comparable
temperature and pressure conditions; this was accomplished by more
sophisticated stress analyses, limitations on design features to
reduce stress concentrations at geometric discontinuities, and more
thorough inspection and the use of a greater variety of faspection
techniques.
t
One of the first applications of special NDT techniques beyond the more-or
less conventional radiography was the somewhat hesitant reference to it in
the first Nuclear Code Case Interpretation (around 1956), Case 1234. Let me
read from the Case:
"5 (d) - It is the intent of the foregoing that full penetration
welds be used wherever possible, for the purpose of achieving con-
tinuity of metal and facilitating the required radiographic examination.
Non-full penetration welds are intended to be allowed only when the
spacing of the openings is such as to make the achievement of full
penetration welds through the vessel or nozzle walls physically
impossible."
"(6) All welds which are subject to stress caused by pressure shall be
radiographically inspected, except win.e this is impractical for non-
full-penetration welds at close-spaced openings as permitted in item
(5). Wherever possible all weld joints shall be designed to permit
radiographic examination to Code standards. When the weld joints
cannot be designed to permit radiogiaphy to Code standards, radio-
graphic examination shall nevertheless be made in accordance with
best obtainable practice. In addition, when radiography to Code
standards is not feasible or when any radiography is impractical,
welds shall be examined by other nondestructive methods such as
liquid penetrant, magnetic particle, or ultrasonic, to prove their
soundness. None of these items applies to seal welis,"
..
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..who.
... .-*• ..
-9-
"18) In view of these severe service requirements, particular con-
sideration shall also be given to materials, construction, and in-
spection, including supplementary methods of nondestructive testing,
so that soundness and good practice will result. Due regard shall
be given to such items as smoothness of welds and to location and
detail of structural attachments."
Note that no attempt was made to detail the techniques or to spell out accept-
ance and rejection standards, other than that "soundness and good practice
should result."
· A later case, No. 1275N detailed procedures for the ultrasonic examination
of welds; but actually, this was largely permissive, for the only UT exam-
ination of welds actually required was limited to certain nozzle geometries
and was intended. to locate laminations, underbead cracking, incomplete
penetration, or lack of fusion. Actually, this is largely, the rase even today,
for UT examination (as well as other NDT methods, but not including radiography)
is limited largely to verification of the soundness of materials-and, to a very
·limited extent, to welds. And we're having trouble enough doing even that
the present UT requirements in the Code for plates and forgings are still not
very good, even though they have been modified two or three times in supple-
mentary "Case Interpretations."
An area where actual ultrasonic testing of welds is mandatory, is in Case 1355,
electroslag welding. It reads, in part: :
"Reply: (2) All butt-welded joints produced by electroslag welding
shall be examined throughout their entire length by radiography in
- 10 -
accordance with the requirements of Par. PW-ll of Section I, Par.
N-624 of Section III or Par. UW-51 of Section VIII. In addition to
the radiographic examination, the weld shall be inspected by the
ultrasonic method throughout its entire length in accordance with
the requirements of Par. N-625 of Section III."
Details of procedures and acceptance standards for NDT are to be found
in Section III, Nuclear Vessels, but these are still limited in their actual
required use.
There is little that is really novel or informative in the way of disclosing
new and improved NDT techniques in the existing. Codes, and I shall
limit my discussion of them to stating the techniques used and some of the
problems involved
but I shall not attempt any detailed presentation of
these Code provisions. And I'll stick with Section III of the Code, since
NDT is used in the Nuclear Code more than in other sections.
One place NDT is used is in the examination of cut edges of plates and
forgings and openings, largely in weld joint preparation
let me read from
N-513.1 and 513.2:
..
.
...
"N-513.1 As fabrication progresses, the vessel manufacturer shall
-
· carefully examine the edges of plates, forgings, openings, and fittings
to detect defects that have been uncovered during fabrication."
"N-513.2 Cut edges of plates and forgings and of openings exceeding
the lesser of 3 in. or the material thickness therein in material 1-1/2 in.
thick and over, and cut edges of fittings, shall be examined for cracks,
- ll -
laminations, and similar discontinuities by a magnetic particle method
in accordance with N-626 or by a liquid penetrant method in accord-
ance with N-627. All cracks and nonlaminar defects shall be removed.
The extent of any laminations shall be determined by the use of ultra-
sonic examination of the adjacent area in accordance with Specification
N-321. Discontinuities parallel to the surface, such as inclusions,
which are aisclosed by either method may be accepted without repair
if they do not exceed 1 in. in length."
It also provides for examination of repaired areas —
"N-514,2 The repaired areas, including those reported by the materials ?
manufacturer, shall be examined by a magnetic particle method in ac-
cordance with N-626 or by a liquid penetrant method in accordance
with N-627 to determine that the repairs are satisfactory as required
in N-618.2."
"N-528.2 The areas to be repaired shall be rewelded using qualified
welding procedures and welders and the rewelded area shall be re-
examined by the methods specified for the examination of the original
weld to ensure that it has been satisfactorily repaired, except that if
the depth of the deposit removed does not exceed the lesser of 3/8in. ?
or 10 per cent of the weld thickness, the examination may be made by
a magnetic particle method in accordance with N-626 or a liquid
penetrant method in accordance with N-627. The post-weld heat-
treating rules in N-532 shall apply to all weld repairs."
There are limited provisions for the certification of NDT operators -
"N-623.1 Examination Techniques - It is the duty of the Inspector
- 12 -
to assure himself that the riondestructive examination methods of
N-624, N-625, N-626, and N-627 which are used follow the
techniques specified therein, and that the examinations are performed
by operators who are certified by the manufacturer as being qualified
in the techniques of the methods that are used and in the interpretation
and evaluation of the results."
"N-623.2 Operator Requirements - The manufacturer shall certify that
each operator meets the following requirements:
(a) He has vision, with correction if necessary, equivalent to 20/30
for distance and is able to read a Jaeger Type No. 2 Standard Chart
at a distance of 12 in. This requirement shall be checked annually.
(b) He is competent in the techniques of the particular nondestructive
examination method for which he is certified, including making the ex-
amination and interpreting and evaluating the results, except that where
the examination method consists of more than one operation, he may be
certified as being qualified only for one or more of these operations."
The business of penetrameters has undergone some changes in recent years.
This has resulted in equivalent sensitivities ranging from about 2% at 3/4 in.
thickness to 1% at 4 in. and thicker. At 1/2in. and below, a slit has been
added to the penetrameter, but frankly, I confess I am unaware of the reason's
for or the advantages of the slit. Certainly the equivalent sensitivity at 1/4 in.
and less may run up to 10% or more.
The ASTM E-142, MIL-STD 271, and
DIN wire penetrameters provide much better sensitivity below 3/4 in. The
Code does not tell much about radiographic techniques, it only requires that
.................... ..cdota inice
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brands in women on the site inimene on toimib bo'
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- 13 -
they be capable of showing the penetrameters and producing film with an age-D
density of 1.3 for single film viewing and 1.8 for composite double film. The
acceptance standards are contained in:
"N-624.8 - Acceptability Standards - Sections of weld that are shown
by radiography to have any of the following types of defects are un-
acceptable unless the defects are removed and the weld is repaired
.
as provided in N-528.
(a) Any type of crack or zone of incomplete fusion or penetration.
-
(b) Any elongated inclusion such as slag or tungsten, which has
a length greater than:
1/4 in. for t up to 3/4 in.,
, E.,,.,
o
1/3 t fort from 3/4 in. to 2-1/4 in.,
Kr
3/4 in. for t over 2-1/4 in.,
where t is the thickness of the thinner part being welded.
technice
(c) Any group of inclusions in line that have an aggregate length
ticis modi
greater than t in a length of 12t, except when the distance between
Serrattuna stambenom
the successive imperfections exceeds 6L, where L is the length of
the longest imperfection in the group.
(d) Porosity in excess of thai shown as acceptable by the porosity
standards given in Appendix IV."
I shall not detail techniques for UT, penetrant, or magnetic particle. They
are undergoing substantial revision, but they are generally patterned after
the corresponding ASTM procedures. Perhaps I have time to read some of
their acceptance standards:
- 14 -
"N-625.4 Standards for Ultrasonic Examination - Any crack, lack of
fusion, incomplete penetration, inclusion, or cavity which is India.
cated by a reflection equal to or greater than 80 per cent of the appli-
cable reference hole reflection and which has a linear dimension as
indicated by transducer movement exceeding:
1/4 in. for thicknesses up to 3/4 in.,
1/3 of the thickness for thicknesses from 3/4 in. to 2-1/4 in.,
3/4 in. for thicknesses over 2-1/4 in., is unacceptable.
If there is doubt regarding the proper interpretation of ultrasonic re-
sults, such doubt shall be resolved to the satisfaction of the Inspector
by examination using other nondestructive methods."
"N-626.5 Acceptance Standards - All cracks and linear defects except
linear inclusions not exceeding 6 inclusions in any 1-1/2 in. by 6 in.
rectangle or 3-1/2 in. diameter circle with these taken in the most
unfavorable location relative to the inclusions being evaluated, and
not exceeding 1/4 in. in length for thicknesses up to 3/4 in., 1/3 of
the thickness in length for thicknesses from 3/4 in. to 2-1/4 in., and
3/4 in. in length for thicknesses over 2-1/4 in. are unacceptable and
shall be eliminated. Aligned acceptable inclusions shall be separated
•
from one another by a distance equal to the length of the shorter in-
clusion. All nonlinear defects which are indicated to have any di-
mension which exceeds 3/32 in. are unacceptable and shall be eli-
.
-.
minated. Where permitted by the rules of this Subsection, defects may
be repaired in accordance with N-513 or N-528. Whenever a defect is
removed and subsequent repair by welding is not required, the affected
..... ..votede .....vowed. ...
i
- 15 -
arer shall be blended into the surrounding surface so as to avoid sharp
notches, crevices, or corners."
N-627.7 Acceptance Standards - All cracks and linear defects except
linear inclusions not exceeding 6 inclusions in any 1-1/2 in. by 6 in.
rectangle or 3-1/2 in. diameter circle with these taken in the most un-
favorable location relative to the inclusions being evaluated, and not
exceeding 1/4 in. in length for thicknesses up to 3/4 in., 1/3 of the
thickness in length for thicknesses from 3/4 in. to 2-1/4 in., and
metamine
3/4 in. in length for thicknesses over 2-1/4 in. are unacceptable
i
and shall be eliminated. Aligned acceptable inclusions shall be
twitter och
rom
separated from one another by a distance equal to the length of
n
the shorter inclusion. All nonlinear defects which are indicated to
have any dimension which exceeds 3/32 in, are unacceptable and
t is
shall be eliminated. Where permitted by the rules of this Subsection,
tatistikat e com
defects may be repaired in accordance with N-513 or N-528."
me**, Littoistaiser bor
The foregoing is a general survey of the extent to which NDT techniques are
presently used in Codes. Obviously there is amply room for improvement and
it will come, inevitably, as NDT techniques become more standardized and
.
s
oramento antither with interior
as confidence in them increases.
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END
DATE FILMED
6 / 16 /66







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