Design and installation of natural gas pipelines – Code of Practice, Part 1: Laying of pipelines

Scope - IS 15663 (Part 1): 2006

• Applies to land pipelines including up to isolation valves in compressor stations, LNG terminals, sectionalizing valve stations, pigging stations, etc.
• Covers pipeline systems connecting gathering/process plants to dispatch stations.
• Excludes operation and maintenance requirements.
• Refer to Fig. 1 in Annex A for scope illustration.

Key Formula: Internal Design Pressure (Clause 5.4.2)

[ P = \frac{2 \times S \times t \times F \times E \times T}{D} ]

Where:

• P = Internal design pressure (N/mm²)
• S = Specified minimum yield strength (SMYS) (N/mm²)
• t = Nominal wall thickness (mm)
• F = Design factor (from Table 1)
• E = Longitudinal joint factor (usually 1 for IS 1978 pipes)
• T = Temperature derating factor (usually 1)
• D = Outside diameter of pipe (mm)

Table 1: Design Factor (F) for Pipeline Construction

This formula and table ensure safe design pressures considering location and pipeline conditions.

IS 15663 Part 1: Normative References - Key Points

This clause lists essential external standards referenced in IS 15663 Part 1, which form an integral part of the code:

Important Notes:

• These referenced standards are normative, meaning their provisions are mandatory when applying IS 15663.
• Users should check for the latest editions of these standards as they are subject to revision.
• The references cover material specifications, welding quality, inspection techniques, and piping design for gas transmission.

Example: Trench and Cover Dimensions (Clause 7.4.5.3)

• Provides minimum cover depths and trench widths for safe pipeline installation.
• Typical minimum cover: 750 mm (varies by soil and load conditions).
• Typical trench width: depends on pipe diameter plus clearance for installation.

flowchart LR
    A[IS 15663 Part 1] --> B[ASME B31.8 (Gas Piping)]
    A --> C[ASME BPVC Section II C (Materials)]
    A --> D[ASME BPVC Section V (NDE)]
    B --> E[Design & Safety]
    C --> F[Welding & Filler Specs]
    D --> G[Inspection & Testing]

This ensures pipeline design, materials, and inspection meet recognized international standards for safety and reliability.

IS 15663 (Part 1): Terms and Definitions – Key Formulas & Tables

1. Internal Design Pressure (Clause 5.4.2)

The internal design pressure ( P ) must be ≥ Maximum Allowable Operating Pressure (MAOP).

[ P = \frac{2 \times S \times t \times E \times F \times T}{D} ]

Where:

• ( D ) = Outside diameter of pipe (mm)
• ( t ) = Nominal wall thickness (mm)
• ( S ) = Specified Minimum Yield Strength (SMYS) (N/mm²)
• ( E ) = Longitudinal joint factor (typically 1 for ERW, LSAW, HSAW, seamless per IS 1978)
• ( F ) = Design factor (from Table 1)
• ( T ) = Temperature derating factor (usually 1 as per Clause 5.1.3)

2. Design Factor (F) Table for Pipeline Construction (Clause 5.3)

3. Additional Notes

• Longitudinal joint factor (E) = 1 for pipes per IS 1978.
• Temperature derating factor (T) = 1 for standard temperature ranges (see Clause 5.1.3

IS 15663 (Part 1): 2006 — Public Safety, Environmental Protection & Statutory Requirements

Key Specifications:

• Public Safety & Environment

  • Pipeline design, construction, and operation must comply with applicable statutory/regulatory requirements (Annex B), including:
    • Environmental Protection Act, 1986
    • Air & Water Prevention and Control Acts
    • Petroleum and Minerals Pipeline Act, 1962
    • Factories Act, 1948, etc.
  • Environmental impact along the pipeline route must be assessed and mitigated.

• Location Class Determination (Annex C)
  Classify pipeline route sections (1600 m length) based on population density:

  Class	Description	Dwellings (per 1600 m)
  1	Low density	≤ 10
  2	Medium	11 to 45
  3	High	≥ 46 or near schools/hospitals etc.
  4	Urban/High risk	Multi-storey buildings, heavy traffic

• Dewatering (Clause 7.5.10)

  • Use pigs with dry air propellant post hydrostatic test.
  • Pigs must protect internal coating and avoid getting stuck by controlling speed and back pressure.
  • Flushing above-ground piping with water then dry air to remove debris and moisture.

Statutory Compliance Checklist (Annex B):

• Obtain authorizations from landowners and authorities.
• Follow Oil Industry Safety Directorate (OISD) safety guidelines during construction.

Summary Table: Location Class Criteria

Dewatering Process Flow (Mermaid.js):

flowchart TD
    A[Hydrostatic Test Complete] --> B[Insert Dewatering P

IS 15663 Part 1: Pipeline Design - Key Formulas, Tables & Specs

1. Internal Design Pressure (Clause 5.4.2)

[ P = \frac{2 \times t \times S \times E \times F \times T}{D} ]

Where:

2. Design Factor (F) (Table 1: Clause 5.3)

3. Design Considerations (Clause 5.1.1 & 5.1.3)

• Safety: Ensure structural

IS 15663 Part 1: Materials and Components - Key Points

1. Material Requirements (Clause 6.1)

• Must meet mechanical properties for design (Clause 5).
• Must satisfy corrosion control requirements (Clause 6.8.1.2).
• Suitable for fabrication/construction methods.

2. Internal Design Pressure (Clause 5.4.2)

• Internal design pressure ( P ) ≥ Maximum Allowable Operating Pressure (MAOP).
• Formula to calculate ( P ):

[ P = \frac{2 \times S \times t \times E \times F \times T}{D} ]

Where:

• ( D ) = Outside diameter (mm)
• ( t ) = Nominal wall thickness (mm)
• ( S ) = Specified Minimum Yield Strength (SMYS) (N/mm²)
• ( E ) = Longitudinal joint factor (usually 1 for IS 1978 pipes)
• ( F ) = Design factor (from Table 1)
• ( T ) = Temperature derating factor (usually 1)

3. Design Factor ( F ) (Table 1)

Summary:

• Use SMYS, wall thickness, and diameter with factors ( E, F, T ) to compute design pressure.
• Materials must be

IS 15663 Part 1: Pipeline Installation Key Points

Burial Depth & Cover (Clause 1.0)

• Normal burial depth: 1.0 m
• At crossings (watercourse/rail/road): Minimum cover as per Table 2 (not provided here)
• Critical locations: Increase wall thickness and cover

Design & Structural Integrity (Clause 5.1.1)

Pipelines must withstand:

• Internal pressure and temperature
• Bending moments and soil-pipe interaction
• External loads (traffic, soil, environmental)
• Dynamic loads (earthquake, flooding)

Important Calculations Include:

• Buoyancy control:
  [ \text{Buoyant force} = \rho_{\text{water}} \times g \times V_{\text{pipe}} ] Ensure weight + ballast > buoyant force to prevent uplift.

• Crossing analysis:
  Trenchless methods require soil data for stability and stress checks.

• Thermal expansion:
  [ \Delta L = L \times \alpha \times \Delta T ] Where (\alpha) = coefficient of thermal expansion.

• Seismic analysis:
  Evaluate seismic forces using relevant ground acceleration and pipeline flexibility.

Typical Table 2 (Example for minimum cover at crossings)

graph LR
A[Pipeline Design] --> B[Pressure & Temperature]
A --> C[Bending & Soil Interaction]
A --> D[External Loads]
A --> E[Buoyancy Control]
A --> F[Thermal Expansion]
A --> G[Seismic Analysis]

Summary: Ensure burial depth per Table 2, verify structural integrity via combined load calculations, control buoyancy, accommodate thermal effects, and perform seismic safety checks.

IS 15663 Part 1: Testing and Inspection - Key Points

Testing Equipment (Clause 7.5.4)

Essential instruments for pipeline testing include:

• Cleaning pigs, gauging pigs, caliper pigs (detect deformities smaller than allowable limits)
• Fill pumps with adequate capacity
• Portable tanks for continuous water supply during pressurization
• Pressure gauges:
  • Bourdon gauge with 0.01 kg/cm² accuracy, 0.05 kg/cm² increments
  • Two 48-hour recording pressure gauges with charts & ink
• Temperature measurement:
  • Two temperature recorders for water temperature
  • Thermocouples for pipe wall temperature
  • Two laboratory thermometers in thermo-wells
• Volume measurement to determine water volume causing 0.5 kg/cm² pressure drop
• Communication equipment for test section coordination
• Temporary scrapper traps for independent pig launching/receiving
• Injection facilities for additives/inhibitors

Inspection & Tests (Clause 6.8.1.1.7)

• Non-destructive testing (NDT): Ringing test for coated pipes to detect damage.
• Electrical test: Megger test to verify insulation integrity between reinforcement and pipe.

Summary Table: Pressure Gauge Accuracy

Additional Notes

• Follow ASME B31.8 for gas transmission piping system standards.
• Use API RP 5L1 for pipeline coating inspection guidelines.
• Ensure all equipment calibration and maintenance before tests.

flowchart LR
    A[Start Testing] --> B[Cleaning & Gauging Pigs]
    B --> C[Fill Pipeline with Water]
    C --> D[Monitor Pressure & Temperature]
    D --> E[Record Data (Pressure & Temp)]
    E --> F[Non-Destructive Testing (Ringing, Megger)]
    F --> G[Analyze & Repair Defects]
    G --> H[Complete Inspection]

This ensures a comprehensive, standardized approach to pipeline testing and inspection as per IS 156

IS 15663 Part 1: Marking and Identification Key Points

Identification (Clause 7.4.4)

• Applicability: Pipes & bends > 50 mm nominal bore.
• Marking:
  • Serial number indelibly marked on pipe.
  • Mark length before bending.
• Before Cutting:
  • Transfer painted serial & stamped pipe numbers to both sides of the joint.
  • Record new length after cutting.

Survey and Marking (Clause 7.2.2)

• Pipes must be surveyed and marked for traceability before installation.

Coating (Clause 6.8.1.1.2)

• Coating requirements must be adhered to for corrosion protection; marking should not damage coating integrity.

Summary Table for Identification Marking:

Practical Tips:

• Use durable paint or stamping tools.
• Ensure markings are readable after coating.
• Maintain a logbook for serial numbers and length changes.

flowchart LR
    A[Pipe > 50 mm] --> B[Mark Serial Number & Length]
    B --> C{Pipe to be Bent?}
    C -- Yes --> D[Measure Length Before Bending]
    D --> E[Mark & Record]
    C -- No --> E
    E --> F{Pipe to be Cut?}
    F -- Yes --> G[Transfer Markings to Both Joint Sides]
    G --> H[Record New Length]
    F -- No --> I[Proceed to Installation]

This ensures traceability and compliance with IS 15663 Part 1.

IS 15663 Part 1: Repair and Maintenance Considerations

1. Repairs in Concrete Coating (Clause 6.8.1.1.9)

• Permitted for:
  • Damage during handling/storage.
  • Spalling > 25% thickness.
• For spalling area between 0.1 m² and 0.3 m², remove damaged concrete and repair per approved procedure.

2. Pipe Defects and Repairs (Clause 7.4.7)

• Follow approved welding and repair methods.
• Use specified welding rods/electrodes per ASME BPVC Section II Part C.
• Employ non-destructive examination per ASME BPVC Section V.

3. Internal Design Pressure (Clause 5.4.2)

• Formula for internal design pressure ( P ):

[ P = \frac{2 \times t \times S \times F \times T}{D \times E - t \times F} ]

Where:

4. Design Factor Table (Table 1)

IS 15663 Part 1: Scope & Pipeline System Overview

Scope Illustration

• Applies to on-land pipelines, including up to isolation valves at compressor stations, LNG terminals, sectionalizing valve stations, pigging stations.
• Covers pipelines connecting gathering/process plants to dispatch stations.
• Excludes operation and maintenance requirements.
• Illustrated in Fig. 1, Annex A (not provided here).

Pipeline System Design Overview

• Designed for public safety and to withstand all installation, testing, and operating loads.
• Must consider combined effects of:
  • Pressure, temperature, bending
  • Soil-pipe interaction
  • External loads, environmental factors
  • Buoyancy control in flood-prone areas
  • River crossings (prefer trenchless if possible)
  • Thermal expansion/contraction
  • Seismic analysis for earthquake-prone zones

Key Formula: Internal Design Pressure (Clause 5.4.2)

[ P = \frac{2 \times t \times S \times F \times E \times T}{D} ]

Where:

• (P) = Internal design pressure (N/mm²)
• (t) = Nominal wall thickness (mm)
• (S) = Specified minimum yield strength (SMYS) (N/mm²)
• (F) = Design factor (from Table 1)
• (E) = Longitudinal joint factor (usually 1)
• (T) = Temperature derating factor (usually 1)
• (D) = Outside diameter of pipe (mm)

Table 1: Design Factor (F) for Pipeline Construction

IS 15663 (Part 1) : 2006 - Key Statutory & Regulatory Requirements

Applicable Statutory Acts (Annex B, Clause 4)

• Environmental Protection Act, 1986
• Environmental Protection Rules, 1986
• Coastal Area Classification and Development Regulation
• Manufacture Storage and Importation of Hazardous Chemicals Rules, 1989
• Factories Act, 1948
• Air (Prevention and Control) Act, 1981
• Water (Prevention and Control) Act, 1974
• Forest (Conservation) Act, 1980
• Petroleum and Minerals Pipeline Act, 1962
• Indian Electricity Rules, 1956

Additional Standards Referenced (Clause 31.8)

Location Class Determination (Annex C)

Classify pipeline route sections (1600 m) based on dwellings:

• Class 1: ≤10 dwellings
• Class 2: 11-45 dwellings
• Class 3: ≥46 dwellings or presence of schools, hospitals, etc.
• Class 4: Areas with multi-storey buildings (≥4 floors), heavy traffic, dense utilities

Dewatering (Clause 7.5.10)

• Use pigs and dry air post hydrostatic test
• Maintain pig speed and back pressure to avoid damage or sticking
• Flush above-ground piping with water then dry air
• Dispose water per statutory requirements

Summary Table: Location Class Criteria

This ensures compliance with environmental, safety, and operational statutory requirements for gas pipelines per IS 15663