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.
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
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
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)