The 2006 edition of IS 15663 Part 2 offers detailed procedures for the design, installation, and testing of natural gas pipelines when crossing infrastructures like roads, railways, water bodies, and buried utilities in India. It covers various installation methods including open-cut and trenchless techniques, casing specifications, stress assessments, and safety protocols to maintain pipeline integrity and environmental safety. This code is crucial for professionals involved in pipeline construction where crossings are involved.
Overview
The 2006 edition of IS 15663 Part 2 offers detailed procedures for the design, installation, and testing of natural gas pipelines when crossing infrastructures like roads, railways, water bodies, and buried utilities in India. It covers various installation methods including open-cut and trenchless techniques, casing specifications, stress assessments, and safety protocols to maintain pipeline integrity and environmental safety. This code is crucial for professionals involved in pipeline construction where crossings are involved.
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Frequently Asked
According to IS 15663 Part 2, casing pipes must have a nominal diameter at least two sizes larger than the carrier pipe for railway and road crossings. The minimum wall thickness should comply with the stricter of API RP 1102 or the requirements set by the relevant authority overseeing the crossing, whether it be rail, road, or water. Additional mandates include fatigue assessments for girth and longitudinal welds as per API RP 1102 and adherence to railway or road authority regulations.
IS 15663 Part 2 recommends two primary installation methods for pipeline crossings: open cut and trenchless. Open cut is suitable for conditions with stable soils, manageable depths, and minimal traffic disruption. Trenchless methods, including horizontal directional drilling and microtunneling, are preferred for sensitive environments, high traffic areas, or where excavation is impractical. Safety measures such as barricades, temporary bridges, traffic signals, and diversions are mandatory during open cut installations, whereas trenchless installation minimizes surface disruption.
Stresses on pipelines at crossings must be calculated considering both internal pressure and external loads. Internal pressure induces hoop (circumferential) and longitudinal stresses, computed using standard formulas where hoop stress equals internal pressure times pipe diameter divided by twice the wall thickness, and longitudinal stress equals half the hoop stress. External loads include soil weight, live traffic loads with impact factors, hydrostatic pressures, seismic forces, and thermal effects. For railway and road crossings, allowable stresses are checked against API RP 1102, while other crossings follow IS 15663 Part 1. Combined stresses must not exceed permissible limits to ensure structural safety.
IS 15663 Part 2 specifies that construction at crossings must include proper barricading, temporary bridges or bypasses with railings, and adequate traffic warning signals and diversions to protect workers and the public. Material handling restrictions prevent stacking or loading on main roads, railways, or watercourse banks without prior approval. Flag persons should be deployed for traffic control, and surface protection measures must be observed. Statutory approvals are mandatory before commencement, and railway crossings require trenchless installation methods to avoid traffic interruptions.
Horizontal directional drilling (HDD) as outlined in IS 15663 Part 2 involves drilling a fluid-filled pilot bore using a steerable rig without rotating the drill string. The pilot hole is then enlarged by washover pipes or back reamers to accommodate the product pipe. Pipes are coated with abrasion and corrosion-resistant layers and pulled back using rollers or skates to reduce stress. Entry and exit angles are recommended between 10° to 12° and 5° to 12°, respectively. Continuous monitoring and plotting of the pilot bore trajectory ensure alignment and allow real-time adjustments, ensuring precise and safe installation.
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