5.2-Ton Inconel 825 Steam Generator for Air Products’ Exploratory Ventures Project — ASME U Stamp

How Lmart engineered and delivered a large-format PHG830 steam generator in N08825 and Duplex 2205 for a demanding mining and mineral processing application — at a scale where zero defects are the only acceptable standard.

Customer	Air Products and Chemicals, Inc. (NYSE: APD)
End User	Exploratory Ventures — Mining & Mineral Processing
Industry	Industrial Gas / Mining & Mineral Processing
Project	Exploratory Ventures Project
Product	Steam Generator (PHG830 large-format)
Quantity	1 unit
Unit Dimensions	DN1772 × THK10 × L4482 mm
Unit Weight	5,200 kg
Design Standard	ASME Section VIII Division 1, U Stamp
Shell Material	SB424 N08825 (Inconel 825) / Duplex 2205
Tube Material	N08825 (Inconel 825)
Application	Process steam generation for hydrogen/gas supply in mining operations
Key Outcome	Single-unit, zero-defect delivery of the largest Inconel 825 steam generator Lmart has supplied to Air Products

Customer Background and Industry Context

Air Products is one of the world’s foremost industrial gas companies, operating across more than 50 countries with revenues exceeding $12 billion. Their business is built on supplying the gas streams — hydrogen, nitrogen, oxygen, syngas — that make large-scale chemical, refining, and materials processing operations possible. When a mining or mineral processing company needs a reliable hydrogen supply for ore reduction or hydrocracking, or inert nitrogen blanketing for hazardous atmospheres, it is typically an industrial gas major like Air Products that designs, owns, and operates the supply infrastructure on-site.

Exploratory Ventures represents exactly this type of arrangement. Mining and mineral processing operations generate some of the most demanding environments for industrial equipment: remote locations far from major fabrication or service centers, continuous high-availability requirements, aggressive process chemistry, and significant mechanical loading from thermal cycling. A plant shutdown at a remote mine site is not a maintenance inconvenience — it is an operational catastrophe, with ripple effects measured in lost production, logistics costs, and contract penalties.

For the steam generator at the heart of Air Products’ gas supply unit at this site, the combination of process severity, remote deployment, and single-unit configuration left no room for performance shortfall. The equipment had to work correctly from commissioning onward, with no second chances.

Challenges

This project presented four interrelated engineering and manufacturing challenges, each compounded by the large physical scale of the vessel.

1. Large-diameter shell fabrication in exotic alloy plate. At DN1772 — a shell inner diameter of 1,772 mm — this vessel sits well into large-format pressure vessel territory. Fabricating a shell of this diameter from SB424 N08825 plate requires a plate rolling capability that few shops possess for nickel alloy material. N08825 work-hardens more aggressively than carbon steel, and large-diameter rolling of heavy-gauge nickel alloy plate demands both the right equipment and experienced operators who understand how the material responds under forming loads. A deviation in shell roundness or a weld misalignment at this scale propagates directly into tube bundle fit-up difficulties and potential stress concentration points.

2. Corrosion performance under mining process chemistry. Mining and mineral processing streams are chemically hostile. Hydrogen sulfide, chlorides, acidic condensates, and oxidizing compounds are common in the gas and liquid streams associated with hydrometallurgical and pyrometallurgical operations. Inconel 825 (N08825) was specified precisely for its resistance to this combination: the alloy’s molybdenum and copper additions provide resistance to reducing acids and sulfur-containing environments, while its chromium content provides oxidation resistance. However, the protective performance of N08825 is only as reliable as the integrity of the weld heat-affected zones. Improper welding procedures can sensitize the alloy’s microstructure, creating corrosion-susceptible zones at exactly the locations where mechanical stress is also highest.

3. Single-unit delivery tolerance for a remote site. The Exploratory Ventures project specified one steam generator — not two units in parallel, not a fleet of smaller vessels with built-in redundancy. A single large unit supplying the entire process means that if the vessel fails, the plant stops. Air Products’ procurement standards for single-unit critical equipment therefore require a level of QC rigor that goes beyond what might be acceptable for one vessel in a multi-unit battery. Every weld, every tube-to-tubesheet joint, every dimensional check carries full production weight. There is no allowance for "we will catch it on the next unit."

4. Weight and handling complexity in fabrication and logistics. At 5,200 kg, this vessel is not moved with standard shop rigging. Large-format vessels require heavy-lift planning from the early stages of fabrication — not just at the point of final shipment. The orientation of the vessel during welding, the positioning for NDE, the sequencing of assembly steps, and the design of the shipping supports all need to account for the mass and the fragility of the alloy tube bundle relative to the structural shell. An unsupported tube bundle in a large shell, if handled incorrectly during assembly, can cause permanent tube deformation that no amount of rework will fully correct.

Why Air Products Chose Lmart

The Exploratory Ventures award was built on an established supply relationship. By the time this project was in procurement, Air Products had engaged Lmart across more than a dozen projects spanning steam generators, heat exchangers, and specialty pressure vessels — a working history that covered the full range of documentation requirements, NDE protocols, and material handling procedures that define ASME-compliant nickel alloy fabrication.

Lmart holds a current ASME Certificate of Authorization with U Stamp, administered under a Quality Control System subject to regular audits by the National Board of Boiler and Pressure Vessel Inspectors. More specifically, Lmart’s Welding Procedure Specifications and Procedure Qualification Records cover P-45 (nickel alloy) base metals, which is the precondition for any N08825 fabrication under ASME Section IX. This qualification does not exist on paper alone — it is backed by documented weld test records, mechanical test data, and Charpy impact results that establish the procedure’s validity for the shell and tube joint configurations used in this vessel.

For a single-unit critical application destined for a remote mining site, the procurement decision rested on one core question: which fabricator has demonstrably built vessels like this before, to this standard, without defects requiring rework or reinspection? The answer, based on the project history between the two companies, was Lmart.

Engineering and Manufacturing Solution

The PHG830 large-format steam generator was designed as a fixed-tubesheet shell-and-tube heat exchanger, with the shell serving as the steam-generating pressure boundary and the tube bundle carrying the process gas stream.

Shell fabrication at DN1772. The shell was formed from SB424 N08825 heavy plate, rolled in multiple passes to achieve the required 1,772 mm internal diameter within the dimensional tolerances specified by ASME UG-80 (shell roundness) and the customer’s data sheet. Longitudinal seam welds were executed under a qualified WPS for N08825-to-N08825 joining using matching filler metal, with preheat and interpass temperature limits strictly controlled and recorded on the weld traveler. Duplex 2205 was incorporated in structural shell attachments and support elements where the higher yield strength of the duplex grade provides the necessary mechanical performance at reduced wall thickness.

Tube bundle in N08825. Tubes were sourced as seamless drawn N08825 tubing with full mill certification traceable to ASME SB-163, the material specification governing nickel alloy tubing for heat exchanger and condenser service. The tube bundle assembly, including tube layout, baffle spacing, and pass partition arrangement, followed the design conditions in Air Products’ thermal datasheet. At 4,482 mm shell length, the tube bundle requires careful handling during insertion to avoid tube-to-baffle contact damage. A purpose-built insertion guide was used to protect the tube bundle during assembly into the shell.

Tube-to-tubesheet welding. Given the critical service and single-unit configuration, all tube-to-tubesheet joints were specified as full-strength fusion welds rather than the expanded-and-seal-welded joints permissible in lower-risk applications. Welders performing this work were qualified specifically to P-45 base metal procedures. All completed tube-to-tubesheet welds were examined by liquid penetrant testing (PT) after the initial weld pass and again on the final weld surface, with radiographic testing (RT) performed on a representative sample defined in the Inspection and Test Plan agreed with Air Products and the Authorized Inspector.

Thermal design for process cycling. Mining and mineral processing operations are not perfectly steady-state. Planned and unplanned interruptions to the ore feed, process upsets, and shift changes all introduce thermal transients into the steam generator. The tube bundle design incorporated sufficient flexibility in the tube-side flow arrangement to accommodate differential thermal expansion between the N08825 shell and the N08825 tubes during these transients, minimizing stress accumulation at the tubesheet joints over the vessel’s intended service life.

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.

Project Execution, Quality Control, and Delivery

Fabrication was executed under Lmart’s ASME Quality Control System with defined hold points and witness points coordinated with the ASME Authorized Inspector (AI). The following QC milestones were managed throughout the project:

Material receiving and PMI. Every piece of nickel alloy material entering the pressure boundary — plate, tubes, flanges, nozzle forgings — was received with mill MTRs, verified against the ASME material specification requirements, and subjected to positive material identification (PMI) using an XRF analyzer. No material entered fabrication without documented traceability. This step is non-negotiable for exotic alloy work: misidentified or substituted alloy material can pass a visual inspection and still perform catastrophically in service.

Shell rolling and dimensional inspection. Shell plate rolling was inspected for roundness at each shell course before seam welding. Dimensional records were captured and reviewed against the UG-80 tolerance before proceeding to fit-up. Any deviation in shell roundness at this stage — before the seam is welded — is correctable. After welding, it is not.

Weld inspection hold points. Fit-up of every pressure weld joint was inspected before welding. Root pass inspection was conducted before deposition of fill and cap passes. All completed pressure welds on the shell, heads, and nozzles were examined by radiographic testing (RT) in accordance with ASME UW-51 for full radiography. The NDE reports, including RT film and interpretation records, formed part of the final ASME documentation package.

Hydrostatic test. The completed vessel was hydrostatically tested at 1.3 times the design pressure in accordance with ASME UG-99, with the AI present as a witness point. Test pressure, duration, temperature, and inspector sign-off were recorded on the official test record included in the Manufacturer’s Data Report.

Heavy-lift packaging and shipping. Given the 5,200 kg vessel weight and the remote destination, the shipping cradles and packaging were engineered for the actual transport conditions — not simply for domestic trucking. The vessel was braced against vibration and dynamic loads, nozzle openings were blanked and sealed, and the tube bundle was protected against moisture ingress during the transit period. Shipping marks, handling instructions, and tipping indicators were applied in compliance with the customer’s logistics requirements.

Results

The PHG830 steam generator was delivered to Air Products’ schedule and accepted without punch list items. The Authorized Inspector’s final sign-off and the completed ASME U Stamp Data Report (Form U-1) were provided to the customer in advance of the physical delivery, allowing Air Products’ engineering team to complete the pre-commissioning documentation review without delay.

At 5,200 kg and DN1772 × L4482 mm, this vessel represents the largest single Inconel 825 steam generator Lmart has supplied under the Air Products relationship. The project confirmed Lmart’s manufacturing capability for large-format exotic alloy pressure vessels — an increasingly relevant qualification as industrial gas supply units for mining, hydrogen, and energy transition applications trend toward larger single-train configurations.

The vessel entered service at the Exploratory Ventures site and, consistent with the reliability expectations that drove the N08825 material specification in the first place, has continued to operate without reported maintenance issues since commissioning.

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 Exploratory Ventures project gave us a hard test on large-format Inconel fabrication — a vessel this size in N08825 demands both the rolling capability and the welding discipline to back it up. Lmart delivered the complete ASME documentation package ahead of the vessel, which is exactly what we need to keep our commissioning schedule on track. The quality of the workmanship on the tube-to-tubesheet joints was evident from the NDE records. It is the standard we expect from a qualified vendor on a single-unit critical application.”

— Project Director, Air Products (paraphrased from project review feedback)

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