Volume-II of IV - GAIL

MECON LIMITED
Delhi
PROCESS & PIPING
DESIGN SECTION
TECHNICAL SPECIFICATION
FOR
PIPELINE CROSSINGS USING
HORIZONTAL DIRECTIONAL
DRILLING METHOD
TECHNICAL SPECIFICATION NO. : MEC/S/05/62/75 REV-0 Page 4 of 11
2.5 Pipeline Axis
The plane containing the pipeline route axis shall be perpendicular to the
horizontal plane. There shall be no bending of the pipeline route axis at
depths shall lower than 2 meters below ground level.
2.6 Back-reamed hole and Pipeline Interface
2.6.1 Contractor shall derive combination of:
- Back-reamed hole diameter
- Bentonite density
- Pipeline submerged weight in bentonite (and means to achieve that
weight)
to optimise the crossing design in terms of pipeline stresses and power
requirement
2.6.2 Contractor shall indicated what maximum shear stress in the pipeline coating
will result from his choice of above parameters and other characteristics
described in this section.
2.6.3 Contractor shall furnish all calculations for Onner’s approval. If shear stress in
pipe coating is, in the opinion of Owner, beyond the permissible limits,
Contractor shall revise his choice of parameters to reduce shear stress on pipe
coating to permissible value.
2.7 Contractor shall determine in the minimum allowable elastic bend radius for
pipe from the following consideration:
2.7.1 Maximum Longitudinal Stress During Installation
Total maximum longitudinal stress in the pipeline due to tension and bending
at any location shall not exceed 90% of the SMYS of the pipe material.
Contractor shall, in order to check this requirement, evaluate the maximum
tensile forces to which the pipeline is subjected to at any phase of its
installation during the pulling operation.
\\Akjha\work contrac\standard TS for Pipe Line WC (Vol-II) MASTER FOLDER\75 pipe line crossing using HDD method\Specification for PL CUHDDM 75.doc