A miniaturized ultrasonic scanning system for nondestructive in-place, non-immersion testing of brazed joints in stainless-steel tubing is described. The system is capable of scanning brazed tube joints, with limited clearance access, in 1/4 through 5/8 inch union, tee, elbow and cross configurations. The system has the capability to detect defective conditions now associated with material density changes in addition to those which are depended upon density variations. The system includes a miniaturized scanning head assembly that fits around a tube joint and rotates the transducer around and down the joint in a continuous spiral motion. The C-scan recorder is similar in principle to conventional models except that it was specially designed to track the continuous spiral scan of the tube joint. The scanner and recorder can be operated with most commercially available ultrasonic flaw detectors

Haralson, H. S.

Haynes, J. L.

Wages, C. G.

English

NASA Technical Reports Server

REPLY TO
ATTN OF:
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON. D.C. 20546
JAN
 2 8
TOt RSI/Scientific & Technical Information Division
Attention: Miss Winnie-Mi Morgan
FROM: GP/Office of Assistant General Counsel for
Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. Patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. patent No. :
Government or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA Patent Case No.
NOTE - If this patent covers an invention made by a.corporate
employee of a NASA Contractor, the following is applicable:
Yes / X / No / /
Pursuant to Section 305(a) of the National Aeronautics and
Space Act, the name of the Administrator of NASA appears on
the first page of the patent; however, the name of the actual
inventor (author) appears at the heading of column No. 1 of
the Specification, following the words M. . . with respect to
an invention of .
Elisabeth A. Carter
Enclosure
Copy of patent cited above
https://ntrs.nasa.gov/search.jsp?R=19740007017 2020-03-17T14:35:16+00:00Z
United States Patent
-•
Fletcher et al.
[in 3,777,552
[45] Dec. 11, 1973
[54] ULTRASONIC SCANNING SYSTEM FOR
IN-PLACE INSPECTION OF BRAZED TUBE
JOINTS
. [76] Inventors: James C. Fletcher, Administrator of
the National Aeronautics and Space
Administration with respect to an
invention of; Johnny L. Haynes;
Charles G. Wages; Hamilton S.
Haralson, all of Huntsville, Ala.
[22] Filed: Nov. 9, 1971
[21] Appl. No.: 196,898
[52] U.S. Cl 73/67.8 S
[51] Int. Cl GOln 29/04
[58] Field of Search 73/67.8, 67.8 S,
73/67.9
[56] References Cited
UNITED STATES PATENTS
3,548,641 12/1970 Mitchell 73/67.9
3,678,188 7/1972 Okumura 178/6.6 R
3,121,324 2/1964 Cowan 73/67.8 S
3,063,290 11/1962 Kaserman 73/67.8 S
OTHER PUBLICATIONS
Goldman, Ultrasonic Technology (New York, Rein-
hold Pub. Co., 1962) p. 262, 263
Primary Examiner— Richard C. Queisser
Assistant Examiner—Arthur E. Korkosz
Attorney—L. D. Wofford, Jr. et al.
[57] ABSTRACT
A miniaturized ultrasonic scanning system for non-
destructive in-place, non-immersion testing of brazed
joints in stainless-steel tubing. The system is capable
of scanning brazed tube joints, with limited clearance
access, in 1/4 through 5/8 inch union, tee, elbow and
cross configurations. The system has the capability to
detect defective conditions now associated with mate-
rial density changes in addition to those which are de-
pendent upon density variations. The system includes
a miniaturized scanning head assembly that fits around
a tube joint and rotates the transducer around and
down the joint in a continuous spiral motion. The
transducer is 0.300 inch diameter focused beam type
with a liquid filled rubber tip or boot attached, which
provides a simulated immersion test. The scanning
head incorporates suitable mechanical drive features,
limit switches to control scan travel, and a transmitter
to synchronize a facsimile C-scan recorder with the
scanning movement. The C-scan recorder is similar in
principle to conventional models except that it was
specially designed to track the continuous spiral scan
of the tube joint. The scanner and recorder can be op-
erated with most commercially available ultrasonic
flaw detectors.
5 Claims, 3 Drawing Figures
OUSA-Case-MFS-20767-1) ULTBASONIC
SCANNING SYSTEM FOB IN-PLACS INSPECTION
OF BBAZEE TUBE JOINTS Patent (NASA)
6 p " CSCL 14D
00/15
N74-15130
{Judas
26907
PATENTED DEC \\m 3.777.55e
SHCET 1 CF 2
24
F I G . I
32
INPUT
RECORDER
&
CONTROL CHASSIS
|DRUM~[WITH PRINT"]
\ i WIRE s
-1— ^J
DOTTER
OUTPUT INPUT
34 36 J
52 54
/. .-fi»«
LIMIT
SWITCH
ASSEMBLY
&
SERVOTRANSMITTER
28
SCANNING HEAD
38
I OUTPUT
ULTRASONIC
FLAW
DETECTOR
•30
SLIP RING
FIG.2
PATENTED DEC U 1973 3:777.552
SHEET 2 Of 2
rrn
TO
3,777,552
1 2
ULTRASONIC SCANNING SYSTEM FOR IN-PLACE DPSPRIPTJON O^ THF DRAWINGINSPECTION OF BRAZED TUBE JOINTS BRIEF DESCRIPTION O.- THE DRAWINGS
„.„._.-. _ _. - FIG. 1 is a vertical sectional view of the transducerORIGIN OF THE INVENTION
 and rdated dements positioned upon a tube to be
The invention herein was made in the performance 5 tested in the vicinity of a brazed tube joint,
of work under a NASA contract and is subject to the FIG. 2 is a schematic box diagram showing the rela-
provisions of Section 305 of the National Aeronautics tionship of certain important elements of the invention.
Space Act of 1958, Public Law 85-568 (72 Stat. 435; FIG. 3 is a front elevation of the scanning head as-
42 USC 2457). sembly.
BACKGROUND OF THE INVENTION '° DESCRIPTION OF THE PREFERRED
c- ,j , u i EMBODIMENTField of the Invention
_,, . . .. , . . , . . With continued reference to the accompanying fie-This invention relates to u trasonic tube testing and , . ... i j • . • -i 7
. . . . .
 6
 , ures wherein like numerals designate similar parts
more particularly to an ultrasonic scanning system for
 )5 th hout the varjous vjews and *hh injtial attemion
m-place mspect.on of brazed tube joints.
 direct
s
ed to RG thefe js jllustrated a vertica, view of
Nondestructive testing of brazed tube jomts in stain-
 & embodiment of part of the invention compris-
less steel tubing has been prev.ously accomplished with
 ing^ransducer 10 mounted on tube 12. Sleeve 14 en-
radiography. Although X-rays are sensitwe to lack-of- ^
 {ube n and the end of another section of tubi
braze cond.tions, that present a dens.ty difference, they
 20 (not shown) and ides a sea,ed tube jojnt Braze ,jne
are not sensUwe to cold braze or similar conditions ,6 jdes a {j £ sea, befween s,eeve ,4 af]d tube ,2
where the braze alloy has flowed but not bonded, which ^^
 simi|ar6braze line (not shown) provides a sea,
do not present a density change on the X-ray film. Ul-
 between sleeve 14 and the other section of tubing (not
trasomcs has also been applied, but in a limited extent.
 shown) Transducer 10 is enclosed by a cylindrical case
These are small volume apphcations where manual and
 25 18. Flexible boot 20, preferably made of rubber, fits
immersion testing techniques are permitted.
 oyer the end of cylindrical case 18. Sea|ing band 22 fits
Description of the Prior Art over boot 20 so as to hold Jt tightly against case 18,
making a fluid-tight seal. The enclosure 24 created by
The art of ultrasonic testing of larger manufactured transducer 10, case 18, and boot 20 is filled with a
items has developed rapidly in recent years, resulting in
 30 quantity of ultrasonic fluid 26.
a number of usable devices in this field. Several of these jn operatiori) the invention employs an ultrasonic
prior art devices have been related to the testing of technique defined as loss of back reflection. High fre-
tubes or pipes. However, most of these prior art devices
 quency „„„,, energy from the specially designed trans-
fer testing tubes appear to be directed to the testing of
 ducer i0 is focused into the tube 12 under test. The
longitudinal seams in tubes. Only one prior art device 35 transducer 10 utilizes a liquid-filled rubber boot 20 to
known to the inventors is capable of testing a circum- simulate an immersion test. The focused wave 25 is
ferential seam in a pipe. However, that device employs transmitted through the contained (and flexible) vol-
a rather complex method involving stressing the pipe
 ume of flujd 26 into the tube joint and is reflected from
with a magnetizing coil producing an alternating elec-
 the inside diameter 27 of the tube. A loss of back re-
tric field and then testing the stressed member with an 40 fjectjons from inner diameter 27 of the tube 12 because
ultrasonic device. That type of prior art device is lim-
 of a discontinuity in the second path is an indication of
ited to ferromagnetic materials, which are easily mag-
 a defective brazed area.
netized. Looking now at FIG. 2, there is shown a block dia-
SUMMARY OF THE INVENTION gram of the invention. The system incorporates a scan-45
 ning head assembly 28 for providing helical scan move-
Accordingly, it is an object of this invention to pro- ment along the tube 12 in the vicinity of the joint to be
vide an improved ultrasonic scanning system capable of tested. This is accomplished by rotating the transducer
inspection of brazed tube joints. 10 in a circumferential motion around the tube joint
It is a further object of this invention to provide a while traveling down the tube 12 in a longitudinal di-
simple ultrasonic scanning system for in-place inspec- 50 rection, thus generating a continuous helix pattern,
tion of circumferential brazed joints in stainless-steel One circumferential revolution corresponds to one x-
tubing. scan pass, and the travel down the tube is the y- move-
It is yet another object of the invention to provide a ment or travel, as in conventional x-z scanning modes,
system for inspection of brazed tube joints capable of The scanning head assembly 28 was designed for a cen-
locating defects not associated with material density ter-to-center distance between circumferential passes
change. of 0.031 inch.
These and other objects are accomplished in the A commercially available ultrasonic flaw detector 30
present invention which comprises a scanning head as- is connected to scanning head assembly 28. A recorder
sembly for providing helical scan movement along the and control chassis 32, also connected to scanning
tube in the vicinity of the joint to be tested, an ultra- head assembly 28, provides a developed plan view of
sonic flaw detector connected to the scanning head as- the condition of a brazed tube joint to be tested. Re-
sembly, a recorder connected to the scanning head as- corder 32 is similar to other facsimile recorders in that
sembly for providing a developed plan view of the con- it contains a drum 34 and a helically wound print wire
dition of the brazed tube joints to be tested, and an ac-
 6J 36. However, the present invention is not arranged to
cessory for said recorder (called a dotter) for providing operate in a convention manner; in the present inven-
a background of low intensity indicia for the plan view tion, the drum 34 containing the helically wound print
provided by the recorder. wire 36 rotates continuously in one direction rather
3,777,552
than reversing for each jt-scan as in y moreover type
scanning modes.
A special recorder accessory called a "dotter" 38 is
connected to both flaw detector 30 and recorder 32.
Dotter 38 increases the resolution of the recordings 5
produced by the invention. The standard state-of-the-
art C-scan recording uses a dark background (continu-
ous print). The defective areas are shown by an ab-
sence of print (white areas). With this type of record-
ing, small indications are often missed because of a 10
characteristic residue from the dark printing being de-
posited by the print bar over the white defective area
indications. However, with the dotter, the recording
area is a series of low-intensity (brown) dashes; defect
indications print as dark (black) lines. The brown- 15
dotted background prohibits the residue buildup asso-
ciated with standard C-scan recordings and results in
increased resoluion.
Looking now at FIG. 2 and the drawing of the scan-
ning head assembly 28 shown in FIG. 3, transmit- 20
receive signals flow between transducer 10 and ultra-
sonic flaw detector 30 by means of slip ring assembly
40. A contact ring and slip ring comprise the assembly
40 that is electrically insulated from the outer case 42,
inner case 44, and slug 46. The contact ring is station- 25
ary and is electrically connected to the flaw detector
30. The slip ring rotates and is electrically connected
to the transducer 10. As the slug 46 rotates, continuous
contact is maintained between the contact ring and the
slip ring. The transducer 10 is grounded to the slug 46 30
which completes the electrical circuit.
The drive mechanism indues the scanning head
housing comprising outer case 42, inner case 44, motor
' (not shown), slug 46, and drive gear 48 to drive the slug
46 at a predetermined design speed. The slug 46 which 35
houses transducer 10 and boot 20, is rotated around
the tube 12 while it traverses the tube 12 axially by
means of the internal threads 50 of the inner case 44.
Limit switches 52 prevent slug 46 overtravel in either
direction by reversing the mechanism. The total slug 40
travel is 0.500 inch, which will cover one joint end per
scan.
The recorder servotransmitter 54 is an integral part
of the scanning head assembly 28. Servotransmitter 54
is a servo unit which "tracks" rotation of the slug 46
around the tube 12 and synchronizes one slug revolu-
tion to one "X" pass of the recorder C-scan printout.
In the procedure for setting up the invention, front
and rear alignment plates (not shown) are required to
position the joint under test in the center of the scan-
ning head assembly 28. Various configurations of the
tube joints, such as tees, elbows, crosses, etc. can be
successfully tested after the proper alignment plates are
attached. To test a tube joint of a particular size and
configuration, the proper alignment plates are selected
and attached to the scanning head assembly 28. The
scanning head assembly 28 is then placed on a "stan-
dard" tube joint containing pre-placed defects of
known size, and a final adjustment of the alignment ,_
plates is accomplished to locate the joint in the center
of the scanning head assembly 28. The limit switches
52 are adjusted to provide the required scan coverage,
the position of transducer 10 is adjusted for proper fo-
cusing, and the ultrasonic instrument is peaked to indi-
 65
cate a defective condition. The scanning head assembly
28 can now accept and test tube joints of the same size
as the "standard" joints.
45
From the foregoing, it may be seen that applicant has
invented a novel type of miniaturized ultrasonic scan-
ning system for in-place inspection of brazed tube
joints. The system has the capability to detect defective
conditions not associated with material density changes
in addition to those which are dependent upon density
variations. The developed scan system is capable of
scanning brazed tube joints, with limited clearance ac-
cess, in % through 5/8-inch union, tee, elbow, and cross
configurations. The average test time for a particular
tube size and configuration, after a 30 minute set-up
sequence is 3 or 4 minutes. The system is capable of de-
tecting brazing defects as small as 0.008 inch by 0.010
inch. Although the system was designed for nonde-
structive, in-place, non-immersion testing of brazed
joints in stainless-steel tubing, it will be understood by
those skilled in the art that the system could also be
modified so as to be capable of testing welded joints.
What is claimed is:
1. An ultrasonic scanning system for in-place inspec-
tion of brazed tube joints comprising:
a scanning head assembly having both stationary and
moveable portions, for providing helical scan
movement along the tube in the vicinity of the joint
to be tested;
an ultrasonic flaw detector connected to said scan-
ning head assembly;
a recorder connected to said scanning head assembly
for providing a developed plan view of the condi-
tion of a brazed joint to be tested, said recorder
comprising a helically-wound print wire which ro-
tates continuously in one direction;
an accessory for said recorder connected to both said
recorder and said flaw detector for providing a
background of low intensity indicia for the plan
view provided by said recorder;
said scanning head assembly comprising:
a. a transmit-receiver assembly comprising:
(1) a transducer;
(2) an enclosure containing said transducer, said
enclosure comprising:
(a) a cylindrical case surrounding said trans-
ducer;
(b) a flexible boot fitting over one end of said
case;
(c) a sealing band fitting over said boot for
holding said boot tightly against said case;
and
(d) a quantity of ultrasonic fluid sufficient to
fill the portion of said enclosure not filled by
said transducer;
(3) a slip-ring assembly for carrying transmit-
receive signals between said transducer and
said ultrasonic flaw detector;
b. a drive mechanism for revolving and translating
said transducer along a tube to be inspected in
order to generate a continuous helix around the
tube; and
c. a servotransmitter in circuit between said trans-
mit-receiver assembly and said recorder for
tracking the revolution of said transducer around
the tube and synchronizing one revolution to one
"X" pass of the recorder.
2. The ultrasonic scanning system of claim 1 wherein
said drive mechanism comprises:
a cylindrical scanning head housing case, said case
containing internal threads, said case having an
3,777,552
opening on one side of its circumference said open-
ing running the full length of said case and large
enough in width to accept a tube joint, whereby
said case may be positioned over and surrounding
a tube joint to be tested. 5
3. The ultrasonic scanning system of claim 2 wherein
said drive mechanism comprises:
a slug mounted inside said scanning head housing
case, said slug housing said transducer and said
boot, said slug having an opening on one side of its 10
circumference large enough to accept a tube joint,
said slug being mounted on said internal threads of
said scanning head housing case so that said slug
may rotate around a tube joint to be tested while
it is traversing the tube joint axially.
4. The ultrasonic scanning system of claim 3 wherein
said drive mechanism comprises:
means to drive said slug at a predetermined design
speed.
5. The ultrasonic scanning system of claim 4 compris-
ing:
at least one limit switch to prevent overtravel of said
slug in either direction by reversing said drive
mechanism.
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Ultrasonic scanning system for in-place inspection of brazed tube joints

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