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 5 of 11
2.7.2. Maximum Equivalent Stress During Final Hydrostatic Test
After installation, the pipeline shall be hydrostatically tested to a minimum test
pressure equal to 1.4 times the design pressure or at a pressure stipulated in
the Special Conditions of Contract whichever is higher. However, during
hydrostatic testing, the combined equivalent stress in the pipeline due to
bending and test pressure shall not exceed 90% of the SMYS of pipe material.
2.7.3 Maximum Equivalent Stress During Service
Permissible values of maximum equivalent stress during services shall be
governed by the requirements of ANSI B 31.8/B 31.4 as applicable. The details
of pipeline operating parameters are provided in the Special Conditions of
Contract.
2.7.4 The minimum allowable radius of curvature for the pipeline shall be the
highest value of the minimum pipeline elastic radius as computed from the
considerations outlined in clause 2.7.1 to 2.7.3 above after correction for
drilling inaccuracies or multiplication by the factor 1.85. whichever results in
the highest permissible value of minimum elastic bend radius.
2.7.5 Contractor shall submit all calculations for Company’s approval alongwith
procedure.
2.8 Pipeline Configuration along the Support String Before Entry Point
2.8.3 Contractor shall determine the required pipeline configuration in order to allow
smooth pull in the crossing entry point and admissible stress in the supported
pipeline string. Pipeline combined stress shall not exceed 95% of the specified
minimum yield strength for line pipe material.
2.8.4 Contractor shall furnish all calculation and specify the number of required
supports, description of the supports, their co-ordinates and capacity in metric
tons.
2.8.5 Contractor shall also furnish a drawing of the launching ramp indicating the
pipeline configuration.
2.8.6 The distance between each roller shall also be specified and justified.
\\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