Inconel 825 Steam Generator for Air Products NCMP PHG250 Hydrogen Project

ASME U-Stamp | Inconel 825 Shell & Tubes | Duplex 2205 Components | Single-Unit Precision Fabrication

End Customer	Air Products (Global Industrial Gas Leader)
End User / Plant	NCMP — PHG250 Project
Application	Industrial hydrogen / process gas generation
Equipment	Steam Generator PHG250
Quantity	1 unit
Shell Dimensions	DN762 × THK10 × L2285 mm
Unit Weight	1,560 kg
Shell Material	SB424 N08825 (Inconel 825) / Duplex 2205
Tube Material	N08825 (Inconel 825)
Design Standard	ASME Section VIII Division 1 (U Stamp)
Manufacturer	Lmart (Suzhou Lmart Energy Equipment Co., Ltd.)

Customer Background

Air Products is one of the world’s largest industrial gas companies, operating in more than 50 countries and supplying hydrogen, helium, nitrogen, oxygen, and other specialty gases to refineries, petrochemical complexes, steel mills, electronics fabricators, and food processors. Their engineering standards are among the most exacting in the industry — every piece of process equipment they commission must meet strict metallurgical, dimensional, and code-compliance requirements before it is accepted into a production environment.

The NCMP PHG250 project represents a hydrogen generation expansion at an industrial end-user facility. In hydrogen reforming and process heating applications, the steam generator sits at the heart of the thermal cycle: it converts feedwater into high-quality steam that is injected into the reformer or process train, where it reacts with hydrocarbon feedstock to produce hydrogen-rich synthesis gas. The operating environment is punishing — high temperatures, elevated pressures, and a process-side fluid chemistry that is aggressive enough to destroy carbon steel or standard stainless steel in a matter of months. Selecting the wrong alloy is not a maintenance issue; it is a plant-shutdown risk.

NCMP, as the designated plant operator on the PHG250 project, required a single steam generator unit that would deliver consistent thermal performance and survive decades of service in this corrosive environment, with full ASME code documentation to satisfy both their own quality management system and Air Products’ global supplier standards.

Engineering Challenges

Four interlocking challenges defined this project from the moment the inquiry landed on Lmart’s engineering desk.

Corrosive process chemistry. Hydrogen generation environments expose heat exchanger surfaces to steam, synthesis gas, and trace sulfur compounds simultaneously. Carbon steel corrodes rapidly; even standard austenitic stainless grades such as 316L show stress corrosion cracking over extended service. The process-side specification called for a nickel-iron-chromium alloy with demonstrated resistance to chloride stress corrosion cracking, intergranular corrosion, and pitting in acidic sulfate media. Only a small family of high-performance alloys meets that bar. The project team selected N08825 — commercially known as Inconel 825 — as the primary wetted-surface material for both the shell (SB424 plate form) and the tube bundle.

Exotic alloy fabrication complexity. Inconel 825 and Duplex 2205 are significantly harder to fabricate than carbon steel or common stainless grades. Inconel 825 has a narrow safe welding window: interpass temperatures must be controlled tightly, filler metal selection is non-trivial, and post-weld heat treatment protocols must be validated against ASME material specifications. Duplex 2205 — used for structural and secondary wetted components — requires precise heat input management to preserve the balanced austenite-ferrite microstructure that gives it its strength and corrosion properties. Work-hardening during forming and machining is pronounced. Not every fabrication shop has the qualified welding procedures, the trained personnel, or the NDT capability to work in these alloy classes.

Single-unit precision with no margin for rework. At 1,560 kg and a shell diameter of DN762 mm, the PHG250 unit is not a small piece of equipment. Yet it is a one-off: there is no sister unit, no spare to fall back on if the first article fails dimensional or code inspection. Every weld, every tube-to-tubesheet joint, and every dimensional datum must be right the first time. The cost of a non-conformance is not just material and labor — it is schedule, and schedule on a hydrogen generation project is directly tied to plant commissioning milestones.

ASME U-Stamp code compliance. Air Products requires ASME Section VIII Division 1 certification with a U Stamp on all pressure-retaining equipment sourced from China-based manufacturers. This means Lmart’s ASME Certificate of Authorization must be current, the Design Document Package (Manufacturer’s Data Report, Form U-1) must be complete and accurate, and a National Board-registered Authorized Inspector must witness and sign off on critical fabrication hold points. The paperwork is as important as the weld.

Why Air Products Selected Lmart

This was not a first-time relationship. By the time the PHG250 order was placed, Air Products had already qualified and commissioned more than 16 steam generator units fabricated by Lmart across multiple global projects — a track record that spans Brazil, Canada, India, South Korea, and multiple European end-user sites.

That history answers the most important question a procurement engineer asks about a new supplier: can they actually deliver? With Lmart, Air Products already knew the answer. They had seen Lmart’s ASME documentation package, observed fabrication at the Suzhou facility, reviewed mill certificates and welding procedure qualifications for exotic alloy work, and — critically — received and commissioned equipment that performed as designed.

Three factors reinforced the repeat selection for PHG250:

Active ASME U Stamp authorization. Lmart holds a current ASME Certificate of Authorization, renewed through the ASME inspection and audit cycle. The certificate is not a marketing claim — it is a legal authorization that allows Lmart to apply the U Stamp to pressure vessels after Authorized Inspector sign-off. Air Products’ global sourcing policy requires this certification as a non-negotiable prerequisite, and Lmart meets it.

Demonstrated Inconel 825 and duplex alloy capability. Lmart has qualified welding procedures (WPS/PQR) for N08825 and Duplex 2205 fabrication under ASME Section IX. These are not theoretical capabilities; they were demonstrated on prior Air Products units and are documented in Lmart’s quality system.

Responsive project management. Air Products values suppliers who can engage technically during the engineering review phase, not just after the drawing is released for fabrication. Lmart’s engineering team participates in pre-fabrication meetings, reviews client-supplied data sheets, flags potential design-for-fabrication issues early, and provides a realistic schedule with formal hold point notifications. For a one-unit precision project like PHG250, this responsiveness reduces total project risk.

Engineering and Fabrication Solution

The PHG250 steam generator was designed as a fixed tubesheet shell-and-tube heat exchanger optimized for steam generation duty. The shell — DN762 mm inside diameter, 10 mm wall thickness, 2,285 mm overall length — was fabricated from SB424 N08825 plate, cut, rolled, and longitudinally welded using qualified procedures with NiCrMo filler metal to match the base alloy’s corrosion resistance at the weld zone.

The tube bundle consists of N08825 tubes, selected for their resistance to pitting and crevice corrosion in the steam-generating environment. Tube-to-tubesheet joints were expanded and seal-welded, with weld geometry controlled to minimize crevice sites. Duplex 2205 was specified for secondary structural components where high strength combined with corrosion resistance was required without the cost premium of an all-Inconel construction.

Key fabrication controls included:

• Preheat and interpass temperature monitoring at every weld using calibrated contact thermometers, documented in weld maps attached to each weld traveler card
• Positive Material Identification (PMI) on all SB424 and tube material after receipt, before any cutting or forming, to confirm alloy chemistry against mill certificates
• Hydrostatic pressure testing at 1.3× design pressure per ASME Section VIII requirements, witnessed by the Authorized Inspector
• Dimensional inspection against the fabrication drawing at forming, assembly, and final stages — with records attached to the Manufacturer’s Data Report

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 Documentation

Every ASME U-Stamp vessel fabricated at Lmart is manufactured under a documented Quality Control (QC) system that satisfies ASME’s requirements for a Certificate of Authorization holder. For the PHG250 unit, the QC package included:

• Certified Material Test Reports (CMTR) for all pressure-retaining materials (SB424 N08825 shell plate, N08825 tube material, Duplex 2205 components, and all weld consumables)
• Welding Procedure Specifications (WPS) and Procedure Qualification Records (PQR) per ASME Section IX for all weld joints
• Welder performance qualifications for all welders assigned to the job
• Non-Destructive Examination (NDE) reports — radiographic testing (RT) on shell seam welds, liquid penetrant testing (PT) on tube-to-tubesheet welds
• Hydrostatic test report with AI witness signature
• Completed ASME Form U-1 (Manufacturer’s Data Report), signed by the Authorized Inspector and registered with the National Board

The complete documentation package was delivered with the unit, enabling NCMP to satisfy Air Products’ Approved Vendor documentation requirements and their own internal handover process.

Results

The PHG250 steam generator was delivered on schedule, meeting all dimensional, metallurgical, and code requirements specified in the purchase order and Air Products’ engineering data sheet. The unit passed hydrostatic testing at first attempt with no leaks or anomalies. The ASME U Stamp was applied and the Manufacturer’s Data Report was filed with the National Board.

For Air Products and NCMP, the outcome was straightforward: a code-compliant, corrosion-resistant steam generator, delivered with complete documentation, ready for installation without remedial inspection or rework. In a project environment where schedule delays carry real financial consequences, a clean first-article delivery is itself a meaningful result.

For Lmart, the PHG250 unit extends a documented supply relationship with Air Products to more than 16 units — a benchmark that few China-based pressure equipment manufacturers can match with a single technology partner of this scale.

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 PHG250 steam generator arrived complete, on schedule, and with a documentation package that satisfied every item on our ASME checklist. The Inconel 825 fabrication quality was consistent with what we’ve come to expect from Lmart — the welds were clean, PMI confirmed material compliance on every heat, and the hydrostatic test was straightforward. This is why we keep coming back.”

— Quality Engineer, Air Products Procurement Review (paraphrased from project review feedback)

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