Fabrication
References
1. American Petroleum Institute.( 2008). API 934-A: Materials and Fabrication of 2-1 / 4Cr-1Mo Steel Heavy Wall Pressure Vessels for High- Pressure Hydrogen Service Operating at Temperatures Above 825 ° F( 440 ° C). Washington, DC: American Petroleum Institute.
2. American Petroleum Institute.( 2020). API 941: Steels for Hydrogen Service at Elevated Temperatures and Pressures in Petroleum Refineries and Petrochemical Plants( Nelson Curve)( 8th ed.). Washington, DC: American Petroleum Institute.
3. American Society of Mechanical Engineers.( 2021). ASME Boiler and Pressure Vessel Code, Section VIII, Division 2: Alternative Rules – Pressure Vessels. New York, NY: ASME.
4. Tubular Exchanger Manufacturers Association.( 2019). TEMA Standards: Standards of the Tubular Exchanger Manufacturers Association( 10th ed.). Tarrytown, NY: TEMA.
5. Firth, D. M., Keen, D., Jones, C., & Karstensen, A.( 2005). Cracking and repair of closing welds in 2.25 Cr-1 Mo steel vessels operating in high temperature synthesis gas. In Ammonia Technical Manual( Vol. 2005). MPT Solutions, PO Box 31-310, Lower Hutt, New Zealand.
This method ensures that even small defects are identified during fabrication, improving the defectfree delivery of the equipment and reliability of the equipment. In addition to PAUT, hardness testing was emphasised pre- and post-heat treatment, to validate material strength and toughness, ensure compliance with specifications, and detect any defects or anomalies that might have resulted from improper heat treatment as shown in Figure 7. Replica testing was also introduced to detect any microscopic and metallurgical issues that visual inspection might have missed, ensuring comprehensive weld quality evaluation. These improvements— ranging from enhanced material and consumable requirements, and advanced welding techniques to state-of-the-art inspection methods— are all aimed at improving the long-term reliability and operational safety of the equipment. By doing rigorous root cause analysis and adhering to its findings, API 934 guidelines, integrating industry best practices, these changes ensured that the equipment can reliably perform under demanding operating conditions, minimising risks of failure and maximising operational efficiency.
Moving forward While several fabrication and inspection improvements have been made to the new units, the possibility of cracks still developing at the weldments in the near or far future of service persists. Therefore, a suitable replacement strategy and permanent resolution must be further developed. This will include proposing a fail-proof design improvement, along with properly engineered heat treatment protocols that can reduce material susceptibility to cracking while enduring the severe high-temperature, high-pressure hydrogen service conditions. Looking ahead, the next step would involve leveraging on advanced Finite Element Analysis( FEA) and Computational Fluid Dynamics( CFD) simulations to further investigate any potential design shortcomings and refine it based on findings from a detailed thermo-mechanical stress analysis. These advanced simulations will enable a deeper understanding of how the equipment responds under actual operating conditions, transient or steady state, highlighting any areas that could benefit from incremental improvements. Moreover, continuous improvement remains a key focus, aiming not only to address current issues but also to eliminate their root causes permanently. Through ongoing optimisation of design, materials and consumables selection, fabrication processes, and inspection protocols, it will be possible to achieve a higher standard of equipment integrity and reliability.
Conclusion In conclusion, the comprehensive approach taken in addressing the issues related to the
Boiler Feed Water Preheater Heat Exchanger has successfully incorporated some fabrication improvements, focusing on enhancing material testing, welding practices, heat treatment processes, and inspection methodologies. These actions were driven by a commitment to resolving the root causes of previous failures and improving the long-term reliability of the equipment in hightemperature, high-pressure hydrogen service. The implementation of post weld heat treatment( PWHT) of the whole equipment inside a furnace, making obligatory the Intermediate Stress Relief( ISR) instead of Dehydrogenation Heat Treatment( DHT), and the adoption of advanced inspection techniques such as Phased Array Ultrasonic Testing( PAUT), etc. all served to significantly improve the structural integrity and operational safety of the equipment. The commitment to continuous improvement ensures that the equipment will perform at its highest potential, minimising risks, and enhancing plant operational performance for years to come.
About the authors
Ir. Ts. Nur Athirah Bt Ishar is a Staff Engineer with 13 years of experience in mechanical static equipment within the ammoniaurea fertiliser industry. Starting her career in Maintenance, she managed reliability programmes and major repairs of pressure vessels, tanks, and heat exchangers. Now a Technical Authority at PETRONAS plant, she leads solutions for static equipment integrity and compliance. She holds a mechanical engineering degree and Graduate Certificate from Stevens Institute of Technology, NJ. A passionate advocate for continuous improvement, she actively contributes to training, seminars, and technical publications. Outside of work, she enjoys reading, gardening, and traveling.
Ir. Mohd. Norhisyam Awang is a Principal Mechanical Engineer with 28 years of experience in the petrochemical industry holding engineering roles at PETRONAS plants including Manager, Reliability, Project and Maintenance Engineer. He specialises in static unfired equipment but also has exposure to rotating, fired, and bulk handling systems. He holds a Bachelor of Science in Mechanical Engineering & Applied Mechanics from University of Pennsylvania, Philadelphia, USA, Master of Business Administration( Muamalah) from Selangor Islamic University and a Grade 1 Steam Engineer certification. Currently serving as Principal Static Unfired in PETRONAS, he provides vital consultations and solutions for mechanical static issues, leading improvements and establishing best practices for plant equipment, work processes, and technical standards. Off-duty, he enjoys offroading, scuba diving, and camping.
24 Heat Exchanger World October 2025 www. heat-exchanger-world. com