Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF : RANCHI (BIHAR)
Document6
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
TITLE MAINLINE CONSTRUCTION
(ONSHORE)
STANDARD SPECIFICATION
SPECIFICATION NO. PAGE 29 OF 53
MEC/S/05/62/01 REVISION A
7.2.5 The pads, dies and rolls of the bending equipment shall have relatively soft
surfaces to avoid damage to the pipe coating. Where applicable, fully retaining
bending shoes shall be used. Roller type bending machines are preferred.
7.2.6 The ends of each bent length shall be straight and not involved anyway in the
bending. The length of the straight section shall permit easy joining. In no event
shall the end of the bend be closer than 1.5m from the end of a pipe or within
one meter of a girth weld.
7.2.7 The ovalisation caused on each pipe by bending shall be less than 2.5% of the
nominal diameter at any point. Ovalisation is defined as the reduction or
increase in the internal diameter of the pipe compared with the nominal internal
diameter. A check shall be performed on all bends in the presence of
COMPANY by passing a gauge consisting of two discs with a diameter equal to
95% of the nominal internal diameter of the pipe connected rigidly together at a
distance equal to 300mm.
7.2.8 Cold bent pipes on site shall have the corrosion coating carefully checked with
the aid of a holiday detector for cracks in the coating down to the pipe wall. It
must also be checked whether the coating has disbonded from the pipe wall
during bending by beating with a wooden mallet along the outer radius. Any
defects or disbonding of the coating caused during bending (also forced ridges
in the coating) shall be repaired at the CONTRACTOR's expense in accordance
with COMPANY approved procedures.
7.2.9 When pipelines are laid in parallel, the horizontal bends shall be concentric.
7.3 Miter and Unsatisfactory Bends
All bends showing buckling, wrinkles, cracks or other visible defects or which are
in any way in disagreement, in whole or in part, with this specification shall be
rejected.
No miter bends shall be permitted in the construction of the pipe line.
CONTRACTOR shall cut out and remove any bend or bends which do not meet
the specifications and shall replace the same with satisfactory bends at no
additional cost to the COMPANY. In the event the CONTRACT provides for
supply of line pipe by COMPANY, the pipes required for replacement will be
furnished by COMPANY, but the cost of replacement of such pipes shall be
borne by CONTRACTOR.