Introduction
Surge analysis is a critical component of ensuring the safety and reliability of LPG pipeline systems. Rapid operational changes such as valve closures, emergency shutdowns, or pump trips can generate high transient pressures, exceeding design limits and risking pipeline integrity.
At iFluids Engineering, we use advanced hydraulic modeling tools such as PIPENET Vision to simulate steady-state and transient conditions, ensuring pipelines are protected against surge-induced failures. Our approach focuses on accurately predicting surge behavior and recommending practical, site-specific mitigation strategies to maintain uninterrupted and safe LPG transportation.
Key Observations Across Projects
Through detailed steady-state and transient simulations across multiple LPG pipeline projects, we observed:
- System Resilience: Most LPG pipelines analyzed demonstrated robust operational resilience, with transient surge pressures remaining within the Maximum Allowable Operating Pressure (MAOP) under various scenarios.
- Critical Surge Scenarios: Significant pressure transients were associated with sudden valve closures at bottling plants, pump trips at dispatch terminals, and abrupt throughput changes.
- Pipeline Pressure Profiles: Pressure profiles across different sections highlighted localized peaks, particularly near control valves and pump discharge points.
- Mitigation Strategies: Where surge pressures approached critical thresholds, operational measures like controlled valve closure timings and coordinated pump shutdowns were recommended. In a few cases, additional surge protection devices, such as surge relief valves, were advised.
- Seasonal Considerations: Surge pressures varied slightly between summer and winter conditions, underlining the importance of modeling environmental factors.
- Stress Validation: Select projects included stress analysis (via CAESAR II) to ensure mechanical integrity under transient surge loads, fully complying with standards like ASME B31.4.
Codes and Standards Followed
The Surge Analysis was conducted in full compliance with internationally recognized codes and standards, including:
- OISD-214: Cross Country LPG Pipelines
- ASME B31.4: Pipeline Transportation Systems for Liquid Hydrocarbons
- API 5L: Specification for Line Pipe
These standards ensured that the pipeline design and surge control measures aligned with industry best practices for safety, reliability, and performance.
Conclusion
Effective surge analysis plays a vital role in safeguarding LPG pipeline infrastructure, preventing operational disruptions, and extending asset life.
By adopting a structured methodology combining steady-state validation and transient scenario simulations, iFluids Engineering ensures that pipeline operations remain safe, compliant, and optimized against hydraulic transients.
Our experience across diverse LPG networks reinforces the need for proactive surge risk assessments as part of any pipeline integrity management program.
1. HPCL – Uran Chakan Shikrapur LPG Pipeline UCSPL Surge Analysis Study
Project Overview
iFluids Engineering carried out an extensive Surge Analysis study for a major LPG transportation pipeline network, ensuring safe and reliable pipeline operations under transient conditions. The integrated network spanned across dispatch and receiving stations, including multiple spur lines and complex valve and pump arrangements. The objective of the surge study was to evaluate potential pressure surges caused by events like sudden valve closures, pump trips, and emergency shutdowns, ensuring that the system’s design remains within safe operational limits.
Equipments Covered in Surge Analysis
The Surge Analysis comprehensively covered critical pipeline equipment across the network, including:
- Booster Pumps: Operated at dispatch stations to initiate and maintain flow at required pressures.
- Mainline Pumps: Ensured sustained high-pressure transportation across long distances.
- Remote Operated Valves (ROVs): Critical control elements at terminal and bottling plant inlets and outlets.
- Sectionalizing Valves (SVs): Deployed strategically along the pipeline to isolate sections during operational upsets.
- Block Valves (BVs): Installed for additional shutdown control to protect system integrity.
- Pressure Control Valves (PCVs): Maintained safe downstream pressure at receiving stations.
- Pipeline Sections and Spur Lines: Including connections to bottling plants and storage facilities.
Each equipment’s operation under transient conditions was simulated to evaluate pressure surges and validate pipeline integrity under various emergency and normal operating scenarios.
Key Highlights
- Steady-state and transient conditions were modeled using a reputable simulation software.
- Multiple surge scenarios, such as sudden valve closures, pump trips, and simultaneous events, were simulated.
- Surge pressures observed were within allowable limits, confirming mechanical and operational safety.
- Operational improvements and surge mitigation strategies were recommended to enhance pipeline safety and longevity.
2. GAIL – Study On Surge Analysis For VSPL.
The project involved a detailed evaluation of transient hydraulic conditions to ensure pipeline safety, mechanical integrity, and operational reliability under various upset scenarios.
- Steady State Simulation – A steady-state hydraulic model was developed reflecting the real-world pipeline network, incorporating parameters such as pipe diameters, lengths, elevations, valve arrangements, pump configurations, and flow rates. The model validation involved comparing simulation results against operational DCS data, confirming that the pressure and flow profiles aligned with design expectations.
- Transient Surge Simulation – Using a reputed modeling software, multiple surge scenarios were modeled, including:
- Sudden valve closures at key locations
- Mainline and booster pump trips
- Flow ramp-up operations
- Emergency shutdowns and withdrawal stoppages
Each case was evaluated against the Maximum Allowable Operating Pressure (MAOP) of the pipeline. The objective was to predict the maximum surge pressures generated and ensure they remained within safe limits.
Key Equipment and Components Studied
The analysis considered the behavior and performance of critical pipeline equipment, such as:
- Mainline Pumps (booster and discharge configurations)
- Battery Limit Valves and Motor Operated Valves (MOVs)
- Pressure Control Valves (PCVs)
- Surge Protection Devices (review recommendations)
Equipment behavior during transients like pump trips and valve closures was carefully analyzed to assess potential overpressure risks and design improvements.
Observations
- In all simulated transient cases, maximum surge pressures remained within the design pressure rating of the pipeline system.
- Critical valves and pumps exhibited predictable pressure fluctuations with no mechanical integrity violations.
- Surge effects were effectively mitigated by operational control measures such as optimized valve closure times and controlled pump trips.
3. HPCL – Surge Analysis For LPG Cross-Country Pipeline Systems Using Pipenet Vision
The pipelines covered extensive lengths and varied elevations, necessitating advanced simulation methodologies to predict system behavior during sudden flow changes such as valve closures, pump trips, and emergency shutdowns.
Project Insights
The analysis focused on two major pipeline corridors involving LPG transfer operations.
Key activities included:
- Steady-State Simulation: Validated normal operational conditions, pressure profiles, and flow behavior.
- Transient Surge Simulation: Modeled critical scenarios including sudden closure of Motor Operated Valves (MOVs), Remote Operated Valves (ROVs), Pressure Control Valves (PCVs), and tripping of dispatch and mainline pumps.
- Equipment Studied: Mainline pumps, booster pumps, sectionalizing MOVs, ROVs, battery limit valves, and surge protection devices.
- Stress Validation: Select pipeline sections were analyzed using ASME B31.4 code compliance checks for sustained, displacement, and occasional loads.
Simulation results were benchmarked against the Maximum Allowable Operating Pressure (MAOP) and design specifications to ensure pipeline mechanical integrity.
Key Observations
- Surge pressures observed during all analyzed transient events were within the safe design envelope of 48 kg/cm² (gauge).
- No mitigation measures, such as surge tanks or additional relief valves, were deemed necessary based on the observed pressure profiles.
- Slack line conditions were identified during specific shutdown sequences, prompting operational control recommendations.
- Mechanical Integrity: All stress analysis results were found satisfactory and within ASME allowable stress limits.
- Safety Compliance: System behavior under transient events confirmed the reliability and resilience of the pipeline infrastructure.