Radiographic
examinations: Every portion of the longitudinal and
circumferential butt-welded seams of the shell of the
boiler shall be subjected to radiographic or ultrasonic
examination. Where ultrasonic examination is used, it
shall be demonstrated to the satisfaction of the Inspecting
Authority that the equipment and the technique used are
satisfactory, the manufacturer shall ensure that the operator
employed is competent to use the equipment, apply the
technique and interpret the results of the examination.
The methods employed in obtaining the radiographs shall
be such as to show clearly differences equal to 2% of
the thickness at the welded joints. To determines whether
this result is being attained, an indicator of approved
form which includes a portion equivalent to not more than
2% of the joint thickness shall be placed in the vicinity
of the weld so as to make a record on each radiograph.
Each section of every weld shall be marked so that the
radiographs can be easily corrected to the particular
part of the seam represented.
The examination shall be made from the original films
and the acceptability of the welds shall be decided by
the Inspecting Authority. The welds deemed unsatisfactory
shall be rejected or dealt with under the condition of
regulation 560
and can be radiographed again. The films shall be retained
by the manufacturer for a reasonable period for reference
and be available to the Inspecting Authority, if required.
NOTE:-
(1) Magnetic particle flaw detection:- Magnetic methods
of flaw detection shall be employed wherever possible
for ferritic steel.
(2) Dye-penetrant flaw detection:- Dye penetrant or equivalent
methods of flaw detection shall be employed for Austenetic
or other non-magnetic steel
(3)
All butt welded joints shall be subjected to
non-destructive examination by radiographic, radioscopy
or other approved methods such as ultrasonic testing,
magnetic particle inspection or liquid dye penetrant
inspection.
When radioscopic examination is to be performed
in lieu of radiography on welded components, the
following requirements shall be met, namely:-
(a)
A written procedure shall be submitted for
approval to the Inspecting Authority which shall contain
the following:
(i)
material
and the thickness range;
(ii)
equipment
qualifications;
(iii)
test
object scan plan;
(iv)
radioscopic
parameters;
(v)
image
processing parameters;
(vi)
image
display parameters;
(vii)
image
archiving requirements;
(viii)
accept-reject
criteria (Code reference);
(ix)
performance evaluation;
(x)
Operator
identification.
(b)
The system shall be aided with an image processor
to enhance the quality of the radioscopic images and
system performance quality shall exhibit-
(i)
a
thin section contrast sensitivity of 3%;
(ii)
a
thick section contrast sensitivity of 2%;
(iii)
a
spatial resolution of 3 line pairs per mm;.
(iv)
IQI
sensitivity - 2% of the joint thickness when wire IQI's
are to be used, the wire diameter axis shall be oriented
along the axis of the least sensitivity of the system.
(c)
Radioscopes are to be properly marked to
co-relate with particular part of joint represented.
(d)
The radioscopic examination data shall be
recorded and stored on videotape, magnetic disk or
optical disk at the maker's plant for a sufficient
period after the date of radioscopic examination as
specified by the Inspecting Authority, efficient
radioscopic examination record recall shall be made
available at any time over the record retention period
and shall be traceable to the test objects.
(e)
When repair has been performed as a result of
radioscopic examination, the repaired areas shall be
re-examined using the same radioscopic technique to
evaluate the effectiveness of the repair.
(f)
To aid in proper interpretation of the
radioscopic examination data, the details of the
technique used shall accompany the data.
As a minimum, the information shall include the
approved procedure requirements and system performance
test data.
|
