Design and installation of natural gas pipelines – Code of Practice, Part 2: Laying of pipelines in crossings

IS 15663 Part 2: Scope - Key Points & References

Scope Summary:

• This part supplements IS 15663 (Part 1): 2006 which covers design and installation of natural gas pipelines.
• Testing methods default to those in IS 15663 (Part 1) unless otherwise specified.
• Additional references include API RP 1102: 1993 for pipeline crossings of railroads and highways.

Key References & Specifications:

Important Notes:

• Testing & Inspection: Follow Part 1 unless Part 2 specifies otherwise.
• Design & Installation: Part 2 builds on Part 1's foundation.
• Crossings: API RP 1102 provides recommended practices for crossings.

Diagram: Relationship of IS 15663 Parts and API RP 1102

graph LR
  A[IS 15663 Part 1] --> B[IS 15663 Part 2]
  B --> C[Testing per Part 1]
  B --> D[Pipeline Crossings]
  D --> E[API RP 1102]

For detailed formulas, tables, and testing procedures, refer primarily to IS 15663 (Part 1) and API RP 1102 as Part 2 defers to these documents.

IS 15663 Part 2: References Summary

Key Referenced Standards

Testing

• Testing methods shall follow IS 15663 (Part 1) unless otherwise specified (Clause 10.2).

Notes on Standards

• Standards are subject to revision; use the latest edition.
• BIS holds copyright; reproduction requires permission except for implementation use.

Contact for BIS Regional Offices

• Central (New Delhi): 2323 76 17
• Eastern (Kolkata): 2337 84 99
• Northern (Chandigarh): 260 38 43
• Southern (Chennai): 2254 12 16
• Western (Mumbai): 2832 92 95

Summary Diagram of Reference Flow

graph TD
    A[IS 15663 Part 2] --> B[IS 15663 Part 1]
    A --> C[API RP 1102]
    B --> D[Testing Methods]
    C --> E[Pipeline Crossings]

For detailed pipeline design, installation, and testing, refer to IS 15663 Part 1 and API RP 1102.

IS 15663 Part 2: Definitions – Key Points

• Clause 3.1 states that definitions in IS 15663 (Part 1) apply, with additional definitions specific to Part 2.
• Part 2 builds upon Part 1, so refer to IS 15663 (Part 1) for foundational terms related to natural gas pipeline design and installation.
• No explicit formulas or tables for definitions are provided in Part 2; definitions are primarily textual clarifications.
• Testing methods (Clause 10.2) also refer back to Part 1, implying consistency in terminology and procedures.

Recommended Action:

• Use IS 15663 (Part 1) for comprehensive definitions and testing standards.
• Key definitions typically include terms like:
  • Pipeline components (e.g., mainline valve, branch connection)
  • Design parameters (e.g., design pressure, operating pressure)
  • Installation terms (e.g., trenching, welding)

Summary Table: Reference for Definitions and Testing

For detailed definitions and testing procedures, always consult IS 15663 Part 1 alongside Part 2.

IS 15663 Part 2: Approval and Coordination with Authorities

Key Specifications:

• Clause 4.1:
  Prior approval must be obtained from authorities having jurisdiction before starting work on crossings of:

  • Railways
  • Roads/Highways
  • Water courses
  • Buried services

• Adequate arrangements are mandatory for safeguarding these facilities during pipeline installation.

References for Coordination:

• Follow API RP 1102:1993 for recommended practices on steel pipeline crossings of railroads and highways.
• Testing methods as per IS 15663 Part 1 (Clause 10.2).

Summary Table:

Coordination Workflow (Mermaid Diagram):

flowchart TD
    A[Identify Crossing Location] --> B[Contact Relevant Authority]
    B --> C{Approval Granted?}
    C -- Yes --> D[Plan Safeguarding Measures]
    D --> E[Execute Work with Safeguards]
    C -- No --> F[Revise Plan / Resubmit]

Note: Always verify with the latest editions of referenced standards and local regulations before proceeding.

IS 15663 Part 2: General Design Considerations - Key Points

1. Design Basis

• Follow allowable stress design principles (Clause 7.2.3).
• External loads per Clause 7.1.1 include soil pressure, traffic, thermal expansion, and seismic effects.
• Refer to API RP 1102:1993 for pipeline crossings at railroads and highways.

2. Allowable Stress Check (Clause 7.2.3)

• Ensure working stress (σ_working) ≤ allowable stress (σ_allowable)
• Typical formula:

[ \sigma_{working} = \frac{P \times D}{2t} + \sigma_{external} ]

Where:

• (P) = internal design pressure
• (D) = outside diameter
• (t) = wall thickness
• (\sigma_{external}) = stress due to external loads

3. External Loads (Clause 7.1.1)

• Consider:
  • Soil weight and pressure
  • Live loads (vehicles, machinery)
  • Thermal stresses due to temperature changes
  • Seismic forces as applicable

4. Referenced Standards

Summary Diagram: Load Interaction on Pipeline

graph LR
A[Internal Pressure] --> B[Pipeline Wall Stress]
C[Soil Load] --> B
D[Traffic Load] --> B
E[Thermal Expansion] --> B
F[Seismic Forces] --> B
B --> G[Allowable Stress Check]

Always verify combined stresses do not exceed allowable limits for safety and durability.

IS 15663 Part 2: Loads on Pipelines — Key Points

1. Types of Loads to Consider (Clause 7.1)

• Internal Loads: From pipe pressurization.
• External Loads: Earth load, live loads (rail/road traffic), hydrostatic loads (water courses), seismic loads.
• Additional Loads: Temperature fluctuations, longitudinal tension, operational fluctuations, ground deformation.
• Impact Factor: Applied to live loads for dynamic effects.

2. Earth and Hydrostatic Loads (Clause 7.1.1.1)

• Earth load = weight of overlying soil on pipe top.
• Hydrostatic load considered in water courses.

3. Stress Calculation (Clause 7.2.1.1)

• Calculate circumferential stress at pipeline invert due to earth and hydrostatic loads.

4. Typical Formula for Earth Load Pressure:

[ p_e = \gamma \times H ] Where:

• (p_e) = earth pressure on pipe (kN/m²)
• (\gamma) = unit weight of soil (kN/m³)
• (H) = depth of soil cover (m)

5. Hydrostatic Pressure:

[ p_h = \rho_w \times g \times h ] Where:

• (p_h) = hydrostatic pressure (kN/m²)
• (\rho_w) = density of water (1000 kg/m³)
• (g) = acceleration due to gravity (9.81 m/s²)
• (h) = water depth (m)

Summary Table of Loads

IS 15663 Part 2: Stress Analysis & Allowable Stresses

1. Stress Due to Internal Pressure (Clause 7.2.2)

• Circumferential (Hoop) Stress, σ_c:

[ \sigma_c = \frac{P \times d}{2t} ]

• Longitudinal Stress, σ_l:

[ \sigma_l = \frac{P \times d}{4t} ]

Where:

• (P) = Internal pressure
• (d) = Outside diameter
• (t) = Wall thickness

2. Combined Stress Evaluation (Clause 7.2.3.2)

• Combine circumferential, longitudinal, and radial stresses.
• Check against yielding using criteria from IS 15663 Part 1 (typically von Mises or maximum principal stress criteria).

3. Allowable Stresses (Clause 7.2.3)

• Allowable stress is based on material yield strength (f_y) and safety factors.
• Typically,

[ \sigma_{allow} = \frac{f_y}{\text{Factor of Safety}} ]

• Factor of Safety usually ranges from 1.5 to 2.0 depending on application.

4. Live Loads (Clause 7.2.1.2)

• Additional stresses from external loads (soil, traffic) must be combined with internal stresses.

Summary Table for Internal Pressure Stresses

flowchart LR
    A[Internal Pressure P] --> B[Circumferential Stress σ_c]
    A --> C[Longitudinal Stress σ_l]
    B & C --> D[Combine Stresses with Radial Stress]
    D --> E[Check Against Allowable Stress σ_allow]
    E --> F[Safe Design if σ_combined ≤ σ_allow]

Note: Always refer to IS 15663 Part 1 for detailed yield criteria

IS 15663 Part 2 – Key Specifications for Casings

1. Wall Thickness of Casing Pipes (Clause 8.2)

• Minimum nominal wall thickness as per API RP 1102 or authority requirements for the crossing (rail/road/water).
• Always adopt the larger thickness requirement between API RP 1102 and local authority.

2. Installation of Casings (Clause 8.3)

• Casing Seals (Clause 8.3.2):
  • End seals at both ends to reduce water/fines intrusion.
  • Water-tight sealing is ideal but some infiltration expected.
  • Ends plugged with compatible anti-corrosion material.
  • Ends should have a minimum slope of 1:2.
  • Cover plugs with neoprene rubber sheet, minimum 2 mm thick.

Summary Table: Casing Requirements

Fatigue Check (Clause 7.2.3.3)

• Check pipelines for fatigue using fatigue endurance limits per API RP 1102.
• Applies to girth welds and longitudinal welds especially at crossings.

flowchart TD
    A[Pipeline Installation] --> B[Check Fatigue (API RP 1102)]
    B --> C{Crossing Type?}
    C -->|Rail/Road/Water| D[Apply Wall Thickness per API RP 1102]
    D --> E[Install Casings]
    E --> F[Fit End Seals]
    F --> G[Plug Ends with Anti-Corrosion Material]
    G --> H[Cover with 2mm Neoprene Rubber]

This ensures structural integrity and protection against environmental ingress.

IS 15663 Part 2: Installation Procedures for Crossings – Key Points

Installation Work (Clause 9.3.1)

• Steps involved:
  • Clearing, grading, trenching to required depth & width
  • Welding casing (if required) and carrier pipes
  • Coating, lowering-in, backfilling
  • Clean-up, restoration
  • Testing, installation of assemblies, insulators, seals
• Approvals: Prior statutory approval mandatory for highway/road crossings.
• Method: Railway crossings must use trenchless methods.

Safety & Traffic Control (Clause 9.3.2)

• Provide barricades, temporary bridges or bypasses with railings.
• Use traffic warning signals/lights and diversions.

Crossing Method Selection (Clause 9.4.2)

• Choose open cut or trenchless based on:
  • Width, depth
  • Bank slopes, soil type
  • Flow conditions

Material Handling (Clause 4.3)

• No stacking/loading on highways, main roads, railways, banks of watercourses.
• Secondary roads require prior approval.
• Traffic and equipment movement must comply with authorities.
• Post flag persons and protect highway surface.

Types of Crossings

Design Considerations

• Follow cover requirements per IS 15663 Part 1.
• Account for pipeline stresses: circumferential, longitudinal, bending.
• For detailed design, refer to API RP 1102.

Typical Installation Workflow (Mermaid Diagram)

flowchart TD
    A[Start: Obtain Approvals] --> B[Site Preparation: Clearing & Grading]
    B --> C[Trenching to Required Depth]
    C --> D{Crossing Type?}
    D -->|Open Cut| E[Pipe Welding & Coating]
    D -->|Trenchless| F[Drilling/Boring]
    E --> G[Lowering-in & Backfilling]
    F --> G
    G --> H[Testing & Assembly Installation]
    H

IS 15663 Part 2: Testing of Pipelines at Crossings – Key Points

1. Allowable Stress Checks

• For railway and road crossings, allowable stresses must comply with API RP 1102.
• For other crossings, follow IS 15663 Part 1 provisions.

2. Hydrostatic Pre-Testing Requirements (Clause 9.1 & 7.2.3.1)

• Pre-test welded pipeline sections ex-situ (before coating) when:
  • Pipes are continuously concrete weight coated (e.g., river/water crossings).
  • Pipeline installed inside casing pipes.
  • Required by jurisdictional authorities.

3. Angle of Intersection & Warning Signs (Clause 9.1)

• Pipeline crossing angle with roads/railways/watercourses per IS 15663 Part 1.
• Warning signs:
  • 1 sign for crossings < 15 m width.
  • 2 signs for crossings > 15 m width.

Hydrostatic Test Pressure Formula (General Practice)

[ P = 1.5 \times \text{Design Pressure} ]

• Test pressure usually 1.5 times the maximum operating pressure, adjusted per pipe class and code.

References Table Summary

flowchart TD
    A[Pipeline Crossing] --> B{Type of Crossing}
    B -->|Railway/Road| C[Check stresses per API RP 1102]
    B -->|Other| D[Check stresses per IS 15663 Part 1]
    C & D --> E[Hydrostatic Pre-Test if required]
    E --> F{Conditions for Pre-Test}
    F -->|Concrete Coated Pipes| G[Pre-test before coating]
    F -->|Casing Pipe Installed| G
    F -->|Authority Mandated| G

For detailed stress limits and test pressures, refer to API RP 1102 and IS 15663 Part 1.

IS 15663 Part 2: Safety and Traffic Management at Road & Railway Crossings

Key Specifications (Clause 9.3 & 7.2.1.2.1)

• Safety Measures Before Installation:

  • Provide barricades and railing on temporary bridges or bypasses, especially for open-cut road crossings.
  • Install adequate traffic warning signals, traffic lights, and diversions to ensure safe traffic flow during construction.

• Live Load Considerations:

  • Consider railway and highway live loads as per Clause 7.1.1.2 and API RP 1102.
  • Account for additional consequential loads depending on construction methods.

Reference Standards for Traffic Loads & Crossings

Typical Live Load Values (from API RP 1102 & IS 15663)

Summary Diagram: Safety Setup at Crossings

flowchart LR
    A[Start Installation Work] --> B[Set up Barricades & Railings]
    B --> C[Provide Traffic Warning Signals]
    C --> D[Establish Temporary Bypass/Bridge]
    D --> E[Implement Traffic Diversions]
    E --> F[Consider Live Loads (Rail & Road)]
    F --> G[Proceed with Pipeline Installation]

Note: Always consult latest editions of IS 15663 and API RP 1102 for detailed load tables and safety norms.

Protection Measures for Water Course Crossings (IS 15663 Part 2 - Clause 9.4)

• Preliminary Surveys:

  • Conduct geotechnical & hydrological surveys for moderate/torrential flows.
  • Obtain permissions & follow conditions from concerned authorities.

• Crossing Types:

  • Open cut or trenchless.
  • Uncased or cased (carrier pipe inside casing).
  • Design stresses: circumferential, longitudinal, bending (refer API RP 1102 for railway/road crossings).

• Backfilling & Protection (Clause 9.4.5):

  • Initial padding: 300 mm thick earth/sand/approved material around pipe.
  • Avoid direct contact with boulders/rocks.
  • Backfill with compacted soil.
  • Over backfill: 0.25 m thick boulder mattress (75–150 mm boulders) encased in galvanized wire mesh (3 mm diameter, max 50 mm spacing).
  • Top protection: 100 mm thick plain cement concrete layer.
  • Mattress length = bank excavation length + 2 m on either side.
  • Mattress width = 2 m + highest water level distance.

• Bank Erosion Protection:

  • Slope < 45°: use gabion mattresses.
  • Slope > 45°: provide gabion walls.

Summary Table: Backfill & Protection Layers

flowchart TD
    A[Pipe in Trench] --> B[300 mm Protective Padding]
    B --> C[Compacted Soil Backfill]
    C --> D[0.25 m Boulder Mattress]
    D --> E[100 mm Concrete Layer]
    E --> F[Natural Ground Level]

Note: No drilling on embankments; maintain clean water course and traffic safety as per Clause 4.3.

IS 15663 Part 2: Handling of Buried Services and Interference

Key Specifications (Clause 9.5)

• Minimum clearance between new pipeline and existing buried services (pipelines, cables):
  • 500 mm minimum clearance.
• Minimum clearance between pipelines (new and existing):
  • 300 mm minimum clearance unless otherwise specified by pipeline owner/operator.
• Safeguarding buried services:
  • Precautions must be approved by the owner of existing services.
• Interference survey:
  • Conduct to detect electrical potential interference due to dissimilar potentials.
  • Adopt mitigation measures (e.g., cathodic protection, insulation).

Handling Crossings (Clause 3.1.10)

• Trenchless Crossings methods:
  • Jacking, boring, micro-tunnelling, drilling, horizontal directional drilling.
  • No traffic disruption during installation.

Summary Table: Minimum Clearances

Interference Mitigation (General Engineering Practice)

• Use insulating joints or coatings.
• Apply cathodic protection systems.
• Ensure electrical continuity and grounding.

flowchart LR
    A[Existing Buried Service] -->|Min 500 mm clearance| B[New Pipeline]
    A -->|Interference Survey| C[Electrical Potential Check]
    C --> D[Mitigation Measures]
    D --> E[Insulation / Cathodic Protection]

For detailed design, refer to API RP 1102 for pipeline crossing practices and IS 15663 Part 1 for laying guidelines.

Horizontal Directional Drilling (HDD) - IS 15663 Part 2 Key Points

Definition & Process (Clause 9.2.2.1):

• HDD is a steerable, surface-launched method to install pipes in a shallow arc without rotating the drill string.
• A fluid-filled pilot bore is drilled, then enlarged by washover pipe/back reamer to product pipe size. Multiple enlargements may be needed.
• Excavation is by fluid-assisted cutting head.

Design & Installation:

• Entry angle: 10°–12°, Exit angle: 5°–12° (desirable).
• Pipe coating must resist abrasion and corrosion; smooth, hard, well-bonded surface.
• Pipe rollers/skates reduce pulling force and stress.
• Drilling fluid remains in annulus post-installation for soil support.

Monitoring:

• Continuous pilot bore tracking and plotting for alignment and course correction.

Important Specifications & Recommendations

Design Considerations

• Geotechnical & Hydrological Data: Must be available before HDD to select rig/accessories.
• Pipeline Cover: As per IS 15663 Part 1.
• Pullback Force: Minimized by protective devices and lubrication.

Simplified HDD Workflow Diagram

flowchart LR
    A[Geotechnical Survey] --> B[Select Rig & Accessories]
    B --> C[Drill Fluid-Filled Pilot Bore (No Rotation)]
    C --> D[Enlarge Bore with Washover Pipe/Back Reamer]
    D --> E[Pullback Product Pipe with Protective Coating]
    E --> F[Retain Drilling Fluid in Annulus]
    F --> G[Continuous Monitoring & Alignment Correction]

For detailed load calculations, pipe stress analysis, and fluid parameters, refer to IS 15663 Part 1 and

Backfilling and Restoration (IS 15663 Part 2, Clause 9.4.5)

• Initial Backfill:

  • Use earth, sand, or approved material as cushion around pipe.
  • Minimum cushion thickness: 300 mm all around the pipe.
  • Avoid placing boulders, rocks, gravel directly on pipe.

• Main Backfill:

  • Use excavated or other suitable material, thoroughly compacted to prevent erosion.

• Surface Protection at Watercourse Crossings:

  • After backfilling, place a 0.25 m thick boulder mattress (boulders 75–150 mm diameter).
  • Boulders encased in 3 mm dia galvanized iron wire mesh, max 50 mm spacing.
  • Mattress length = bank excavation length + 2 m extension each side.
  • Width = 2 m + highest water level on slope.
  • Cover mattress with 100 mm thick plain cement concrete for protection.

• Bank Erosion Protection:

  • For slopes < 45°, use gabion mattresses.
  • For slopes > 45°, provide gabion walls.

Summary Table for Backfill Cushion

Key Notes:

• Compaction is critical to prevent soil/bank erosion.
• No drilling on embankments allowed.
• Installation loads must be considered for trenchless methods (Clause 7.1.1.3).

flowchart TD
    A[Excavation] --> B[Initial Cushion Backfill (300 mm)]
    B --> C[Main Backfill & Compaction]
    C --> D[Boulder Mattress (0.25 m thick)]
    D --> E[Wire Mesh Encasing Boulders]
    E --> F[Concrete Cover (100 mm)]
    F --> G[Bank Protection (Gabion Mattresses/Walls)]

This ensures pipe protection, bank