Executive Summary

Client:​ A Major LNG Receiving Terminal (Asia-Pacific Region)

Challenge:​ Ensuring absolute reliability and leak-tight sealing in the Boil-Off Gas (BOG) recondensation system, where valve failure could lead to safety hazards, operational shutdowns, and significant financial loss.

Solution:​ Implementation of Dofun’s custom-engineered cryogenic ball valves and globe valves specifically designed for ultra-low temperature and high-pressure differentials.

Results:​ Achieved zero fugitive emissions from the valve package, guaranteed stable system pressure, and enabled continuous, safe operation of the terminal’s critical BOG management system.

Introduction: The Critical Role of BOG Management

In Liquefied Natural Gas (LNG) terminals, maintaining cryogenic temperatures (-162°C / -260°F) is a constant battle. Heat ingress causes a portion of the LNG to continuously vaporize, creating Boil-Off Gas (BOG). Efficiently managing this BOG is paramount for safety, product conservation, and operational efficiency. The BOG recondensation system​ is the heart of this process, re-liquefying the gas and returning it to the storage tanks. The valves controlling this process operate in one of the most demanding environments on earth: extreme cryogenic temperatures, high pressure cycles, and with a media that must be contained with zero leakage.

The Challenge: Precision and Reliability Under Extreme Conditions

The terminal’s engineering team faced persistent concerns with the existing valves in their BOG compression and recondensation loop:

1. Leakage at Stem Seals:​ Standard valve packing could not maintain a seal under the extreme thermal contraction and expansion cycles, leading to fugitive emissions of methane, a potent greenhouse gas.
2. Internal Leakage (Seat Failure):​ Valve seats degrading under high-pressure drops across the control valves resulted in an inability to shut off tightly, disrupting precise pressure control essential for the recondensation process.
3. Operational Failure Risk:​ The consequences of valve failure in this system are severe, including safety shutdowns (ESD activations), flaring of BOG (environmental and economic loss), and costly unplanned maintenance.

The client needed a valve supplier that understood the nuances of cryogenic service and could provide a robust, engineered solution, not just an off-the-shelf product.

The Dofun Solution: Engineered for Cryogenic Excellence

Dofun’s engineering team conducted a detailed analysis of the application parameters and proposed a customized valve package with the following critical features:

• Extended Bonnet Design:​ All valves supplied for the cryogenic service were equipped with extended bonnets. This design creates a “cold box” effect, ensuring the stem seals and actuation components operate at ambient temperatures, far away from the ultra-low temperature fluid in the body. This prevents packing freeze and ensures reliable, long-term sealing.
• Cryogenic Grade Materials:​ Key components, including stems, balls, and seats, were manufactured from specially selected stainless steels and alloys that retain their toughness and mechanical properties at -196°C.
• Low-Temperature Carbon (LTC) Stainless Steel:​ The valve bodies themselves were crafted from LTC grade stainless steel, which is impact-tested to guarantee resistance to brittle fracture under cryogenic conditions.
• Specialized Seat Seals:​ We utilized advanced polymer seals (such as PCTFE) known for their excellent resilience and sealing performance at cryogenic temperatures, ensuring bubble-tight shut-off.
• Fire-Safe Design:​ In compliance with industry safety standards like API 607/API 6FA, the valves were designed with fire-safe features to maintain containment in the event of a fire.

Implementation and Results: A Partnership for Success

Dofun worked closely with the terminal’s EPC (Engineering, Procurement, and Construction) contractor to ensure seamless integration. Our technical support team provided detailed installation guidance and documentation.

The results after one year of continuous operation have been outstanding:

• Zero Fugitive Emissions:​ The Dofun valve package has successfully eliminated fugitive emissions from the designated BOG recondensation system, as verified by LDAR (Leak Detection and Repair) monitoring.
• Enhanced System Stability:​ The precise control and reliable shut-off provided by the valves have contributed to stable pressure control within the recondensation loop, optimizing the terminal’s energy efficiency.
• Zero Unplanned Downtime:​ The client has reported no valve-related shutdowns or interventions since installation, validating the robustness and reliability of the solution.
• Client Endorsement:​ “The BOG system is too critical for compromise. Dofun not only met the stringent technical specifications but their proactive engineering support gave us full confidence. The performance of their cryogenic valves has been flawless.”— Lead Project Engineer, LNG Terminal.

Conclusion

This case study demonstrates that in high-stakes industrial applications like LNG processing, valve selection is a strategic decision. Dofun’s ability to deliver custom-engineered, highly reliable cryogenic solutions proved essential for the safe, efficient, and uninterrupted operation of a major terminal’s BOG management system.

Facing a critical fluid control challenge in your energy or process facility?

[Download Our Cryogenic Valve Technical Specification Sheet] to learn more about our engineered solutions.

[Contact Our Engineering Team] for a confidential consultation on your specific project requirements.