Customer Story

LNG Loading Emergency Shutdown: Surge Analysis Research

Beyond Pressure: How Lamar University Used Datacor Impulse to Reveal Pipe Stress Risks in an LNG Emergency Shutdown

Challenge Overview

LNG is loaded onto tankers through specialized loading arms constructed from expensive low-temperature alloys for cryogenic service. In an emergency shutdown, flow through these arms must be halted rapidly by closing a sequence of valves, opening vent valves, and tripping transfer pumps. The sudden deceleration of flow creates pressure surge that can exceed pipe design pressures and cause extreme pipe stress, potentially worsening an already critical emergency.

A research team at Lamar University used Datacor Impulse to model this emergency shutdown system and evaluate surge behavior across six scenarios, including five failure modes where components of the shutdown system malfunction.

What You Will Learn

  • How Datacor Impulse was used to model an LNG loading terminal emergency shutdown system and evaluate surge pressure under normal and failure-mode conditions

  • How six transient scenarios were analyzed, including pump trip failure, vent valve failure to open, and combinations of both failure modes

  • How surge pressure results were compared against the pipe design pressure of 220 psia (15 bar) to identify which scenarios exceeded design limits

  • How unbalanced pipe forces were calculated in Impulse and exported to ANSYS for time history structural analysis, revealing pipe stress and vibration risks that pressure alone did not capture

  • How valve characteristic sensitivity analysis affected surge response, and why this matters for emergency system design

  • Why evaluating pipe forces, not just pressures, is essential for fully characterizing emergency shutdown risk in LNG systems

Key Results

  • Under normal emergency shutdown conditions, maximum surge pressure was 145.3 psia, well within the 220 psia design limit

  • The worst-case scenario (pumps fail to trip and vent valves fail to open) produced 332 psia, exceeding the design pressure of 220 psia

  • Unbalanced pipe forces in the worst-case scenario exceeded 12,000 lbf near the transfer valves, revealing structural stress risks not apparent from pressure analysis alone

  • Force results exported from Impulse to ANSYS confirmed displacement, vibration, and pipe stress concerns requiring structural attention

  • The study demonstrated that unaddressed surge and pipe stress during an emergency shutdown could trigger a secondary emergency condition

Case Study Snapshot

  • Product: Datacor Impulse

  • Industry: Liquefied Natural Gas

  • Region: Beaumont, TX, USA

  • Application: Emergency shutdown surge analysis, transient force calculation, ANSYS integration

  • Key Methodology: Multi-scenario transient analysis, pipe force imbalance calculation, structural analysis integration

  • Pipe Design Pressure: 220 psia (15 bar)