Welding shall be carried out in accordance with 6.5.
5.9.2
Post-weld heat treatment
Post-weld heat treatment shall be required for all butt
welds of pipes made with carbon, carbon-manganese and low alloy steels.
The Administration or recognized organization acting on its behalf
may waive the requirements for thermal stress relieving of pipes with
wall thickness less than 10 mm in relation to the design temperature
and pressure of the piping system concerned.
5.9.3
Non-destructive testing
In addition to normal controls before and during the welding,
and to the visual inspection of the finished welds, as necessary for
proving that the welding has been carried out correctly and according
to the requirements of this paragraph, the following tests shall be
required:
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.1 100% radiographic or ultrasonic inspection of
butt-welded joints for piping systems with design temperatures colder than -10°C,
and with inside diameters of more than 75 mm, or wall thicknesses greater than 10
mm;
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.2 when such butt-welded joints of piping sections
are made by automatic welding procedures approved by the Administration
or recognized organization acting on its behalf, then a progressive
reduction in the extent of radiographic or ultrasonic inspection can
be agreed, but in no case to less than 10% of each joint. If defects
are revealed, the extent of examination shall be increased to 100%
and shall include inspection of previously accepted welds. This approval
can only be granted if well-documented quality assurance procedures
and records are available to assess the ability of the manufacturer
to produce satisfactory welds consistently; and
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.3 for other butt-welded joints of pipes not covered
by 5.9.3.1 and 5.9.3.2, spot radiographic or ultrasonic inspection
or other non-destructive tests shall be carried out depending upon
service, position and materials. In general, at least 10% of butt-welded
joints of pipes shall be subjected to radiographic or ultrasonic inspection.