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 33 OF 53
MEC/S/05/62/01 REVISION A
9.1.6 Wherever the pipeline is laid under tension, as a result of an assembly error (for
example, incorrect positioning of bends, either horizontal or vertical), the trench
shall be rectified or in exceptional cases a new assembly shall be carried out, to
be approved by COMPANY, so that it fits the excavation and the laying bed.
9.1.7 Laying shall be carried out under safe conditions so as to avoid stresses and
temporary deformations of the equipments which may cause damage to the
pipeline itself and to the coating. In localised points where the right-of-way is
restricted to the minimum necessary for the transit of mechanical equipment, the
laying shall be carried out using other suitable means. The pipe shall be placed
on the floor or the excavation, without jerking, falling, impact or other similar
stresses. In particular, care must be taken that the deformation caused during
the raising of the pipe work from the supports, does not exceed the values for
the minimum allowable radius of elastic curvature, so as to keep the stresses on
the steel and on the coating within safe limits. The portion of the pipeline
between trench and bank shall be supported by as many side-booms as
required and approved by COMPANY for holding the line in gentle S-curve
maintaining minimum elastic bend radius as specified in job standard. Lowering
in and back-filling shall preferably be carried out at the highest ambient
temperature.
9.1.8 The pipeline must be laid without interruption for the whole or the length of
section available. Where water is present, no laying shall be permitted until the
ditch has been drained to the extent and for the time necessary to make visual
inspection possible of the bed on which the pipe is to be laid. Following such
inspections, the presence of water will be permitted, provided that it is not so
high as to cause cave-in of the walls of the trench or floating of the pipeline
before backfilling, when weighting is not provided for the pipe.
9.1.9 CONTRACTOR shall take precautions immediately after lowering in to prevent
the movement of the pipe in trench.
9.1.10 In laying parallel pipelines in the same trench, the minimum distances between
the pipeline indicated in the approved drawings shall be observed. Once the first
pipeline has been positioned, it shall in no way be disturbed by laying of the
subsequent pipeline.