Volume-II of IV - GAIL

5.0 INSPECTION & TESTING
5.1 Visual Inspection
Visual inspection of the as applied coating shall be carried out on every joint, for
the following :
- Mastic extrusion on either ends of the sleeve shall be examined.
- There shall be no sign of punctures or pinholes or bend failure. The external
appearance of the sleeve shall be smooth, free of dimples, air entrapment
or void formation. All sleeves shall be tested for the presence of voids by
knocking on the sleeves. A hollow sound compared to the remainder of the
sleeve may indicate the presence of voids under the sleeve. Such sleeve
shall be tested for adhesion at the discretion of the Company
Representative.
- Weld bead profile shall be visible through the sleeve.
- Visual indicator provided on the backing and the closure patch showing
desired heat is achieved.
5.2 Holiday Inspection
The holiday detector used shall be checked and calibrated daily with an accurate
DC voltmeter. The detector electrode shall be in direct contact with the surface of
coating to be inspected.
The entire surface of the joint section shall be inspected by means of a full circle
holiday detector approved by COMPANY set to a DC voltage applicable as per the
requirements of factory applied mainline coating specification of Company.
Inspection of the sleeves shall be conducted only after the joint has cooled below
50°C. The holiday detector used shall be checked and calibrated daily with an
accurate DC voltmeter. The detector electrode shall be in direct contact with the
surface of coating to be inspected.
No field joint shall be covered or lowered in the trench until it has been approved
by the COMPANY.
5.3 As-applied Coating Thickness
Coating thickness shall be checked by non-destructed methods for each field joint.
Average thickness of the as-applied coating on pipe body shall be established based
on measurement at min. eight locations i.e. four measurement on either sides of
the girth weld at 3, 6, 9, & 12 O’clock positions. To establish the minimum
thickness on the girth weld, four measurement shall be taken on apex on the weld
at 3, 6, 9 & 12 O’clock positions. All such measurements shall be recorded.
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