A short presentation on: OFFSHORE PIPELINE SYSTEMS: Part 1

A short presentation on: OFFSHORE PIPELINE SYSTEMS: Part 1

Why pipelines?

  • Safer
  • Environment friendly
  • Least energy requirement
  • Lowest maintenance costs
  • Minimal impact on land use pattern
  • Negligible loss of product in transit
  • High reliability

What can be transported?

  • Liquids: Crude Oil, Petroleum Products, Petrochemical Products, Chemicals, Water, LPG
  • Solids(in slurry form): Coal, Ores, Tailings
  • Gas: Natural Gas, Any other Gas

Sequence of Flow (Fig. 1):

Sequence of Flow
Fig. 1: Sequence of Flow

Offshore Pipeline and Riser System (Fig. 2):

Schematic of offshore pipeline and riser system
Fig. 2: Schematic of offshore pipeline and riser system

Stages of an Offshore Pipeline Project

Codes & Standards

  • DnV OS-F101: Det Norske Veritas, Rules for Submarine Pipeline Systems
  • ASME B 31.8: Gas Transmission and Distribution Piping Systems
  • ASME B 31.4: Liquid Transportation Systems for Hydrocarbons, LPG and Anhydrous
  • Ammonia and Alcohols
  • API 1104: Standard for Welding Pipelines and Related Facilities
  • API 1110: Pressure Testing of Liquid Petroleum Pipelines
  • NACE MR 0175: Material Requirements – Sulphide Stress Cracking Resistant Materials for Oil Field Equipment
  • IP 6 : Institute of Petroleum –Pipeline Safety Code

Stages of a Project

  • Conceptual Study
  • Feasibility Study
  • Basic Engineering
  • Detailed Engineering
  • Construction
  • Testing & Commissioning

Conceptual Study:

  • Establish System Requirement
  • Evaluate Constraints on System Design
  • Identify Interface With Other Systems
  • Develop Design Data Requirements
  • Assess Construction Methodology
  • Finalize the Concept

Feasibility Study:

  • Evaluate Technical Options
  • Eliminate Un-viable Options
  • Firming up of Process Facilities
  • Develop Broad System Specifications
  • Establish Project Cost
  • Plan Project Implementation Scheme
  • Finalize Process Scheme & Equipments

Basic Engineering:

  • Environmental & Process Data Review
  • Pipeline Routing & Size Optimization
  • Establish Requirements for
  • Surveys and Investigations
  • Material of Construction
  • Preliminary Analysis
  • Construction, Testing and Commissioning
  • Develop Implementation Schedule

Safety Aspects:

  • Environmental Parameter and Soil Data
  • Pipeline Stability
  • Shore Approaches
  • Trenching and Burial
  • Safety of Existing Facilities

Detailed Design & Engineering

  • Engineering Design Basis
  • Route Engineering & Surveys
  • Engineering analysis and Calculations
  • Specification and Job Standards
  • Engineering for Procurement
  • Drawings for Construction
  • Installation analysis and Procedures

Design Basis:

  • Basic Data
  • Design Codes and Standards
  • Design Philosophy
  • Operation and maintenance philosophy
  • Environmental Criteria
    • Installation
    • Operation
  • Criteria for engineering analysis

Route Selection:

  • Routing Considerations
  • Pipeline length
  • Sensitive areas
  • Obstructions
  • Installation Limitations
  • Crossings
  • Drilling Rig Movement / Access
  • Surveys
  • Geo-physical & Geo-technical Surveys
  • Platform Approach / Riser Face Survey

Pipeline Wall Thickness Selection:

  • Analysis / Calculations
  • Hoop Stress
  • Buckle Initiation
  • Buckle Propagation
  • Collapse Bucking
  • Local Buckling
  • Pipeline Stress Checks
  • Hoop Stress
  • Equivalent Stress
  • Analysis Tools
  • PC Based Software ‘Pipecalc’

Wall Thickness Calculation:

For Offshore Pipelines     t = (PD/2.SMYS.a) + corrosion allowance    where

  • P is the internal design pressure in psig.
  • S is the specified minimum yield strength
  • D is the pipe outside diameter in inches.
  • t is the nominal wall thickness in inches.
  • a is the design factor (0.72 for pipeline and 0.5 for riser)

Allowable Stress Limits (Fig. 3):

Allowable Stress limits
Fig. 3: Allowable Stress limits

Types of Line pipes:

  • Seamless up to 16″
  • LSAW 18” and above

Engineering Analysis:

  • Stability Pipeline (Lateral & Vertical)
  • Pipeline Expansion
  • Pipeline Spans
  • Riser
  • Analysis Tools
  • PC Based Software ‘Pipecalc’

Anti Corrosion Coatings

  • Coating Anti-Types
  • Coal Tar Enamel
  • Fusion Bonded Epoxy

Selection Criteria:

  • Service Conditions
  • Performance Record
  • Ease of Repair
  • Cost Effectiveness
  • Compatibility with Concrete Coating

Pipeline Crossing

  • Exposed Pipelines (Single / Multiple)
  • Buried Pipelines (Single / Multiple)

Analysis

  • Permissible Spans (Static & Dynamic)
  • Stress Analysis
  • Stability of Supports

Design Tools (Fig. 4):

Design tools for pipeline analysis
Fig. 4: Design tools for pipeline analysis

 

 

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3 thoughts on “A short presentation on: OFFSHORE PIPELINE SYSTEMS: Part 1”

  1. Dear Sir,

    Thank you for your great posts in here. I have found many interesting information from this website

    It will be very appreciate if you have a post to describe more detail consideration in stress analysis for offshore project.

    Regards,

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