Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF : RANCHI (BIHAR)
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
STANDARD SPECIFICATION
TITLE WELDING OF ONSHORE GAS
SPECIFICATION NO. PAGE 29 OF 48
PIPELINES
MEC/S/05/62/02 REVISION
15.9 Regulation of Amplification During Production Testing
The amplification during production testing shall be obtained by adding 2-6 dB
(according to the surface condition of the pipe and its cleaness) to the reference
amplification.
15.10 Qualification of Ultrasonic Testing Operators
Before the inspection begins or during the same inspection, the COMPANY may
require a qualification test for the ultrasonic equipment operators.
15.11 Evaluation of Indications Given by Ultrasonic Tests
Each time that echoes from the weld bead appear during production testing, the
instrument amplification shall be altered to coincide with the reference
amplification and the probe shall be oved until maximum response is obtained,
paying attention all the time of the probe-tube coupling.
If, under these conditions, the heights of the defect echo is equal to or greater
than that of the reference echo, the defect shall be evaluated according to other
clauses of this Specification. If the defect has also been detected by the
radiographic and or visual examination, the dimensions shall be judged
according to the type of examination which detects the greater defect. Returns
which are less that 50% of the reference echo, will not be considered. If returns
are above 50% but lower than 100% of the reference echo, and if the operator
has good reasons to suspect that the returns are caused by unfavourably
oriented cracks, the same shall be informed to the COMPANY. Moreover, when
there is a defect to be repaired, such defect shall be removed for a length
corresponding to the one where no more return echo is given.
15.12 Other Equipment
The use of rules calibrated in centimeters, attached if possible to the probe, for
the precise location of the position of welding defects, is recommended. Defect
location is effected by measuring the projection distance between the probe
output and the reflecting surface.
\\Akjha\work contrac\standard TS for Pipe Line WC (Vol-II) MASTER FOLDER\02A welding onshore gas pipeline\Welding of Onshore Gas Pipelines with addendum - I 02A.doc