GB151 Inconel 825 Steam Generator for Air Products Qingpu Project — How Lmart Solved the Exotic Alloy + Chinese Regulatory Challenge

GB151 Compliance — A Different Design Language

End User	Industrial gas / hydrogen generation facility
Operator	Air Products China
Location	Qingpu District, Shanghai, China
Equipment	Steam Generator × 1
Weight	1,560 kg
Dimensions	DN762 × THK10 × L2285 mm
Design Standard	GB151 (Chinese national tubular heat exchanger standard)
Shell Material	SB424 N08825 (Inconel 825) / Duplex 2205
Tube Material	N08825 (Inconel 825)
Application	Industrial gas / hydrogen generation
Regulatory	TSG (Chinese pressure vessel inspection authority)

Customer Background

Air Products is one of the world’s largest industrial gas companies, supplying hydrogen, nitrogen, oxygen, and specialty gases to petrochemical, electronics, and manufacturing sectors across more than 50 countries. In China, Air Products operates a dense network of on-site production units and pipeline supply systems, with the Qingpu District of Shanghai serving as one of its critical regional nodes.

Qingpu is not a typical industrial suburb. Over the past decade, it has evolved into a high-density chemical and advanced manufacturing corridor, hosting semiconductor fabs, specialty chemical producers, and large-scale hydrogen users feeding both fuel cell supply chains and conventional refining operations. The reliability and regulatory standing of every piece of pressure equipment installed in this zone is scrutinized at a level comparable to any ASME-governed plant in North America or Europe — only under a different rulebook.

For Air Products’ Qingpu project, the requirement was straightforward in concept but technically demanding in execution: a compact steam generator, fabricated in corrosion-resistant exotic alloys, fully compliant with China’s GB151 national standard, ready for submission to the local TSG (Technical Supervision and General — China’s pressure equipment inspection authority). Shortcuts were not an option.

The Challenges

Three distinct technical and regulatory challenges converged on this project. Each one individually would have disqualified most domestic fabricators. Together, they defined the supplier selection.

GB151 Compliance — A Different Design Language

GB151 and ASME VIII Division 1 cover similar equipment — tubular heat exchangers — but their calculation methodologies, documentation requirements, and inspection protocols diverge in ways that are not merely cosmetic. GB151 uses its own wall thickness formulas, its own tube-to-tubesheet joint strength criteria, and its own marking and data-sheet conventions. A fabricator experienced exclusively in ASME cannot simply "translate" a design; it must recalculate from first principles under the Chinese standard and produce a complete GB151 design package.

Many international companies operating in China route their ASME-pedigreed equipment through local distributors or third-party design houses to generate the required documentation. The problem: accountability is split. If the equipment fails at the TSG inspection stage, or worse, in service, it is unclear who owns the design error. Air Products required a single manufacturer who could originate the GB151 design, fabricate the equipment, and carry full responsibility through final inspection.

Exotic Alloys Under a Chinese Standard

SB424 N08825 (Inconel 825) is a nickel-iron-chromium alloy with exceptional resistance to reducing acids, chloride-induced stress corrosion cracking, and high-temperature oxidizing environments. It is the right material for a steam generator in a hydrogen generation process where trace sulfur compounds and acidic condensate can be present.

However, N08825 is not a commodity material in the Chinese pressure vessel supply chain. Sourcing mill-certified SB424 plate and seamless tube to GB/T or ASME SB specifications, verifying the full material traceability chain acceptable to TSG inspection, and performing qualified welding on nickel alloy — these require infrastructure that most domestic fabricators simply do not maintain. The combination of N08825 shell/tube bundle with a Duplex 2205 structural element added further complexity: two dissimilar high-alloy material families in one assembly, each with its own welding procedure qualification requirements under Chinese standards.

Local Regulatory Acceptance

TSG inspection in Shanghai involves physical witness at the manufacturer’s facility, review of the design calculation package, material traceability documentation, NDE (non-destructive examination) records, and a hydrostatic pressure test. Everything must be documented in Chinese, formatted per TSG requirements, and signed by a licensed Chinese pressure vessel design engineer. For a project tied to an industrial gas facility — a classification that draws additional regulatory scrutiny given the hazardous nature of hydrogen — there was no tolerance for gaps in the compliance paper trail.

Why Lmart

Air Products’ procurement team for the Qingpu project evaluated Lmart based on three factors that distinguished us from other candidates.

Dual ASME + GB151 Design Capability

Lmart holds an ASME U-Stamp and is qualified to design and fabricate under both ASME VIII Div.1 and GB151. Our in-house engineering team performs GB151 calculations natively — we do not outsource the design work. This means a single point of accountability from design calculation to final TSG data sheet.

Proven Track Record with Air Products

Air Products’ procurement team verified that Lmart had previously supplied heat transfer equipment to Air Products China projects. An established supplier relationship means the Air Products engineering team’s technical standards, preferred documentation formats, and inspection milestone expectations are already embedded in our project management process. There is no learning curve on communication protocols when a compressed delivery schedule is in play.

Local Manufacturer Advantage for TSG

As a Suzhou-based manufacturer with a TSG-registered facility, Lmart’s production site is within practical inspection travel distance for the Shanghai TSG inspection authority. Our quality team has an established working relationship with local TSG inspectors, and our documentation system is calibrated to their checklist. This administrative fluency is invisible until you need it — and when a TSG inspection delay threatens your commissioning schedule, it becomes the most important capability on the supplier list.

Engineering Solution

The steam generator was designed as a fixed-tubesheet configuration per GB151, with a shell diameter of DN762 mm, a wall thickness of 10 mm, and an overall length of 2,285 mm.

Shell and shell-side nozzles were fabricated in SB424 N08825 plate, selected for its proven resistance in the steam-side environment where sulfur contamination and acidic condensate present corrosion risks that carbon steel and even austenitic 316L cannot reliably withstand over a multi-decade service life. Tube bundle materials matched the shell specification: N08825 seamless tube, mill-certified with full material test reports traceable to heat and lot numbers.

Structural components requiring higher mechanical strength were specified in Duplex 2205, a lean duplex stainless steel that combines the corrosion resistance of austenitic grades with significantly higher yield strength. This material pairing — N08825 for corrosion duty, Duplex 2205 for structural integrity — allowed the overall weight to be held at 1,560 kg without compromising the design safety factors required by GB151.

Welding procedure specifications (WPS) for N08825-to-N08825 and N08825-to-Duplex 2205 joints were qualified per relevant Chinese national welding standards prior to production. All welders assigned to the nickel alloy joints held current procedure qualification records for those specific joint configurations.

Why Inconel 825? Material Selection Rationale

Property	316L SS	Inconel 825 (N08825)	Inconel 625 (N06625)
SCC Resistance	Poor — fails in chloride environments	Excellent	Superior
Pitting Resistance (PREN)	~25	~33	~51
Max Service Temp	~450 °C	~540 °C	~650 °C
Weldability	Excellent	Good — requires qualified WPS	Good — requires qualified WPS
Relative Material Cost	1×	3–4×	6–8×
Typical Application	General chemical service	H&sub2;/syngas, high-purity gas, sulfuric acid	Subsea, ultra-high corrosion

For this service — high-purity hydrogen generation with mixed acid condensate — Inconel 825 provides the required corrosion resistance at roughly half the cost of Inconel 625, making it the engineering-optimal choice.

Quality Control and Delivery

The GB151 design calculation package was completed by Lmart’s licensed pressure vessel design engineers and submitted for review prior to fabrication commencement. Material traceability was established at goods receipt: every plate, tube, and fitting was logged against its mill certificate, and certificates were organized in the TSG data book format before the first cut was made.

NDE coverage included visual inspection of all welds, liquid penetrant testing (PT) of fillet and butt welds in nickel alloy, and radiographic testing (RT) of selected butt welds per the GB151 and GB150 requirements applicable to the design pressure class.

The hydrostatic pressure test was conducted at the Lmart facility with TSG inspector witness. The equipment passed without remediation. The completed TSG data book — containing the design calculation sheet, material certificates, WPS/PQR records, NDE reports, and pressure test record — was delivered to Air Products in the format required for registration with the Shanghai municipal pressure vessel authority.

Total project timeline from order confirmation to delivery met the customer’s Qingpu project commissioning schedule.

Results

The steam generator was installed at the Qingpu facility on schedule and passed site acceptance without deficiency findings. TSG registration was completed without supplemental documentation requests — a result that reflects both the quality of the as-built equipment and the completeness of the documentation package delivered with it.

For the Air Products procurement and engineering teams, the outcome confirmed that a single domestic manufacturer can originate, fabricate, and deliver GB151 exotic alloy heat transfer equipment at a quality level consistent with international project requirements — without the coordination overhead of splitting design, fabrication, and regulatory compliance across multiple parties.

Customer Voice

Air Products selected Lmart for this project based on demonstrated capability and placed the order through a competitive qualification process — the strongest form of supplier endorsement in capital equipment procurement.

“The Qingpu project had a tight schedule and zero tolerance for documentation gaps at TSG inspection. Lmart delivered a complete GB151 package with full traceability on the Inconel 825 materials, and the inspector witness test went through cleanly. That’s the level of execution we need from our China supply base.”

— Facility Manager, Air Products Qingpu Project (paraphrased from project review feedback)

Note: Lmart respects client confidentiality. Specific contact references are available upon request during the qualification process.