FIELD OF THE INVENTION
This invention generally relates to the field of Non Destructive Testing in particular,
ultrasonic testing of Boiler pressure parts and structural butt welds. In particular, the
invention relates to Ultrasonic Testing on bi-thickness butt welds (figure-1) where
indications due to geometry mislead to a defect. More particularly, the invention relates
to an improved ultrasonic testing method of welded joints for accurately confirming
geometrical indications.
BACKGROUND OF THE INVENTION
In the field of Ultrasonic Testing several types of improved systems for the location and
sizing of defects in materials and welded joints are known in the art. Ultrasonic Testing
systems generate useful data about defect location (i.e. depth, Surface distance), which
are calculated by the systems with trigonometry, using data (i.e. Probe angle, Index of
probe, Thickness) fed by the operator and the beam path travelled by the ultrasound
wave. In case the weld joint geometry (figure-1) is having any sharp edge or steps or
inclined surface on back wall (opposite) side, the beam travels in different
direction(different from expected direction), after hitting Ultrasonic beam there. The
system provide depth and other data based on the beam path travelled by the
ultrasound wave in expected direction resulting in a misleading conclusion on a defect.
For ascertaining that such data is a geometric indication, UT on other surfaces has to
be also done to see whether the other surfaces also provide similar indication on the
same location of the job. If no such indication can be obtained from the other surfaces,
a 1:1 sketch of the weld joint, is drawn based on which sketch and data shown by the
UT equipment, the indications provided by the UT equipment can be accepted as
geometric indications. It is a theoretical confirmation. Sometimes defects may not be
even picked up from the other surfaces if those are oriented in that way. Accordingly,

the actual defects may be erroneously be accepted as mere geometrical indication,
which geometric indications can be misjudged as a real defect.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to propose, an improved ultrasonic
testing method of welded joints for accurately confirming geometrical indications.
Another object of the invention is to propose an improved ultrasonic testing method of
welded joints for accurately confirming geometrical indications, which ensures safety
and fitness of welded structures and installations.
A further object of the invention is to propose an improved ultrasonic testing method of
welded joints for accurately confirming geometrical indications, which eliminates
avoidable repair work of welded joints and improve quality of welded products.
SUMMARY OF THE INVENTION
Accordingly, there is provided an improved ultrasonic testing method of welded joints for
accurately confirming geometrical indications. As an exemplary experiment of the prior
art method, it was noticed while performing UT on one of the important ceiling girder flange
butt weld, an indication as shown in table -1. After careful reading of the drawing, one 1:1 scale
sketch was drawn, and it appeared that the indication was due to irregular shape of the joint,
although no confirmation could be made.
Accordingly, the joint was repaired for the defect shown by UT equipment. After attending the
repair when again UT was performed the same indication was shown by the same UT
equipment. It could then only be confirmed that the indication was indeed due to geometry and
not due to a defect.

Such a disadvantage prompted the inventors to develop an improved method for accurately
ascertaining the nature of the indications exhibited by the ultrasonic Testing system.
After a thorough study of the UT equipment data related to that indication, it was observed
that the Ultrasonic beam was reflecting in random direction after hitting at backwall side edge
‘A’ indicated in figure-2 of the welded joint. After reflection of the beam in random direction
indicated by numeral 4 in figure-2, it was actually hitting the surface on which the UT was
carried out. Accordingly, it was concluded that the indication shown by the equipment is
nothing but a favorable reflection from the surface on which UT was carried out.
Based on this conclusion a theoretical calculation was made to locate the point from which, the
favorable reflection was originating. The calculations are shown in figure-2.
Calculation:
Probe Angle = θ˚
Thickness of thinner part = t mm
Total Beam Path = 1st leg of Beam Path + 2nd leg of Beam Path
1st leg of Beam Path = t x Sec(θ) mm
2nd leg of Beam Path = Total Beam Path - 1st leg of Beam Path
Surface distance between probes (E) = t x Tan(θ) + √{(2nd leg of Beam Path)2 - (t)2 }
Actual Direction of beam after hitting edge (β) = cos-1(t/2nd leg of Beam Path)
After the theoretical calculation, the point of favourable reflection was detected by
using the UT equipment in dual mode with the same angle probe acting as a
transmitter and using another known probe acting as a receiver which was disposed at
a distance ‘E’ indicated in figure-2. If an indication can be received at said position of
the receiver, it can be concluded that earlier indication shown by the UT equipment was
an indication due to geometry not due to defect. As shown in table-1 for a ceiling girder
flange butt weld the probes were disposed from each other at a calculated distance of
144mm, and the indication was received which interalia proved the earlier indication

shown by the UT equipment at a surface distance of 177mm, depth 23mm was nothing
but an indication due to geometry. In the same way as shown in table-1 for a pipe +
flat end cover joint, the UT equipment in a pulse echo mode showed a defect at a
depth of 17mm with a Beam Path of 188mm and a Surface Distance of 133mm. The
innovative method confirmed that the indication was a geometric indication as shown
by a conventional UT method, was nothing but a favorable surface reflection at 144mm
away from the probe. By this present invention we can save money, time, and useful
resources and reduces unnecessary rework. Present invention gives confidence in
quality of the product.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure-1 shows a bi-thickness butt weld which gives geometric indications in UT;
Figure-2 is a schematic diagram illustrating the principle of the present invention;
Figure-3 shows a process flow chart of the method according to the invention;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
DRAWINGS
Referring to Figure-1,
In figure-1, a bi-thickness butt weld shown. To weld such joint usually a step is
provided on thicker side to meet the edge at the same level. In figure-1 indicated by
letters ‘A’ and ‘B’ are two sharp edges. When ultrasound beam hits at any sharp edge,
after hitting beam travels in random directions. While performing UT on this kind of
joints mostly upper edge indicated with letter ‘A’ interferes in UT. That leads to beam
travelling in random direction and which give indications. Those indications are nothing
but geometric indications.

Referring to Figure-2,
In trial-1 we used an angle probe shown in figure-2 by numeral 1 as transmitter as well
as receiver. Which shown a defect in direction indicated by numeral 4 at depth ‘D’ and
surface distance ‘C’.
In trial-2 we used an angle probe shown in figure-2 by numeral 1 as transmitter and
normal probe shown in figure-2 by numeral 5 as receiver with dual mode in UT
equipment indicated by numeral 6 in figure-2. Both probes are separated by a
calculated distance indicated by ‘E’ in figure-2. And we got the indication which was
shown as a defect in trial-1, which is nothing but a geometric indication due to beam
hitting at sharp edge. In figure-2‘t’ indicates thickness of thinner side and ‘T’ indicates
thickness of thicker side. In figure-2 ‘β’ indicates angle of actual ultrasound beam.
Referring to Figure-3,
Figure-3 shows process flow chart of the present invention.
Referring to Table-1
In Table-1 for ceiling girder flange bi-thickness butt weld UT. UT equipment in pulse
echo mode with 45° angle probe as transmitter as well as receiver shown a defect at
the depth of 23mm with Beam Path 250mm, Surface Distance 177mm. New invented
method in which UT equipment in dual mode with 45° angle probe as transmitter and
normal probe (0°) as receiver confirmed it was a geometric indication and indication
shown by conventional UT method was nothing but favorable surface reflection at
144mm away from probe.
In Table-1 for Pipe + Flat end cover bi-thickness butt weld UT. UT equipment in pulse
echo mode with 45° angle probe as transmitter as well as receiver shown a defect at
the depth of 17mm with Beam Path 188mm, Surface Distance 133mm. New invented
method in which UT equipment in dual mode with 45° angle probe as transmitter and
normal probe (0°) as receiver confirmed it was a geometric indication and indication
shown by conventional UT method was nothing but favorable surface reflection at
108mm away from probe.

WE CLAIM :
1. An improved ultrasonic testing method of welded joints for accurately confirming
geometrical indications, comprising the steps of :-
generating an indication from the ultrasonic testing equipment during performing
Ultrasonic testing on a bi-thickness butt weld with pulse echo mode using one of
an angle probe of 35° ,45° ,60° 70° angle;
developing a sketch at 1:1 scale of the weld joint to check whether the beam
hitting at any shape edge, the indication being assigned as one exhibiting a
defect, if not hitting;
assigning the indication based on said 1:1 sketch of the weld joint as an
indication due to geometry, if the beam is heating the sharp edge;
assigning the indication as a geometric indication when after the hitting sharp
edge when the ultrasound beam travels in random direction and hitting the
surface on which UT was carried out;
calculating the direction of the ultrasound beam after hitting the sharp edge to
detect the point from which the indication was originated and calculating the
surface distance between the probe and the point where the ultrasound is
hitting;
setting the UT equipment in dual mode and by using same angle probe acting as
a transmitter and another probe acting as a receiver;
disposing the transmitter and the receiver at a calculated distance to obtain an
indication, if obtained the indication is due to geometry, and not due to a defect;
and
concluding that said indication is not due to geometry but due to a defect if no
indication can be obtained with the transmitter and receiver being disposed at
said calculated distance.