ASME Steam Generator for Air Products InoxAP Chennai — Inconel 825 in India’s Industrial Gas Frontier

How Lmart engineered a corrosion-proof, ASME U-stamp steam generator for one of India’s most demanding industrial gas projects.

Customer	Air Products
End User	InoxAP (Inox Air Products × Air Products JV)
Project Name	InoxAP Chennai Sri P Project
Location	Chennai, Tamil Nadu, India
Product	Steam Generator × 1 unit
Weight	1,560 kg
Dimensions	DN762 × THK10 × L2285 mm
Standard	ASME Section VIII Div.1 — U Stamp
Shell Material	SB424 N08825 (Inconel 825) / Duplex 2205
Tube Material	N08825 (Inconel 825)
Application	Industrial gas / hydrogen generation
Sector	Industrial gas, Indian manufacturing

Customer Background

Air Products is one of the world’s leading industrial gas companies, operating across more than 50 countries with deep expertise in hydrogen, oxygen, nitrogen, and specialty gases for petrochemical, refining, and electronics customers. In India, Air Products operates through InoxAP — a joint venture with Inox Air Products, one of India’s largest domestic industrial gas producers. Together, InoxAP has built a significant footprint supplying industrial gases to the fast-growing Indian manufacturing sector.

The Chennai Sri P Project represents part of InoxAP’s strategic expansion into South India’s industrial corridor. Chennai and its surrounding regions host major automotive, electronics, and chemical manufacturing clusters. Demand for high-purity hydrogen and industrial gases in this corridor has surged as Indian manufacturers upgrade their production processes to meet global quality standards. This project required a steam generator capable of reliable, continuous service as a core component of InoxAP’s gas generation and processing infrastructure.

Challenges

Delivering pressure equipment into India’s industrial gas sector presents a layered set of engineering, compliance, and logistics challenges that not every manufacturer can navigate cleanly.

Tropical climate and corrosion environment. Chennai sits near the Bay of Bengal, with year-round high humidity, salt-laden air, and temperatures regularly exceeding 35°C. For equipment handling high-temperature steam in a humid coastal environment, standard carbon steel or even 316L stainless steel offer insufficient corrosion resistance over a long service life. The material specification from Air Products was unambiguous: Inconel 825 (N08825) throughout the tube bundle, with a duplex 2205 shell — a high-pedigree alloy combination capable of resisting both chloride stress corrosion cracking and pitting in humid, chemically aggressive conditions.

Dual compliance requirements. Air Products operates to global procurement standards, which means ASME Section VIII Div.1 U-stamp compliance is non-negotiable — even for equipment installed in India. The InoxAP joint venture further requires that all critical static equipment meets its own internal quality protocols, which mirror those of its global parent. Lmart needed to satisfy both the ASME code authority (a third-party authorized inspection agency) and Air Products’ own inspection and documentation requirements in parallel.

Exotic material procurement and fabrication control. SB424 N08825 plate and N08825 tubing are not commodity materials. Lead times for certified Inconel 825 mill products can be long, traceability documentation requirements are stringent (full PMI, heat certs, CMTR), and welding procedure qualification for nickel alloys demands certified WPS/PQR records that most fabricators simply do not maintain. Managing this supply chain correctly — from mill order through receipt inspection to controlled storage — was essential to keeping the project on schedule.

Export packaging and ocean freight. Equipment destined for India by sea faces a 3-to-6-week transit exposure to salt-spray conditions during ocean freight. Inadequate packaging causes corrosion and mechanical damage that creates costly disputes on arrival. Tropical-grade preservation and export packaging had to be specified and executed as part of the delivery scope, not as an afterthought.

Why Lmart

Air Products has worked with Lmart across multiple projects and geographies. That track record is not accidental.

Lmart holds ASME Section VIII Div.1 U-stamp authorization — a certification that requires rigorous quality system maintenance, regular ASME audits, and demonstrated capability to manufacture to code across a range of pressure vessel types. For a customer like Air Products, this certification is the baseline minimum; what distinguishes Lmart is the consistency of execution behind it.

Lmart’s experience with high-nickel alloys — Inconel 825, Hastelloy, Duplex 2205, Titanium — across dozens of projects for global EPC contractors and equipment OEMs means the material handling, welding qualification, and NDE requirements for this specification are well within standard operating procedure. The company maintains qualified WPS/PQR records for N08825 welding and has a documented history of delivering Inconel 825 equipment to international clients across the oil and gas, petrochemical, and industrial gas sectors.

For Air Products, the decision also reflected confidence in Lmart’s documentation capability. Global procurement customers require data books that meet a high standard: material traceability to heat number, full NDE reports, ASME Code Data Report (Form U-1), and hydro test records. Lmart has refined its documentation process across years of project delivery to meet exactly this expectation.

Engineering Solution

The steam generator was designed under ASME Section VIII Div.1, configured as a PHG250-class unit with a shell inner diameter of DN762 mm, a shell wall thickness of 10 mm, and an overall tube length of 2,285 mm. At 1,560 kg, this is a compact but high-integrity unit engineered for continuous duty in an industrial gas plant environment.

Material selection rationale. The combination of SB424 N08825 (Inconel 825) for the shell and N08825 for the tube bundle was driven by the dual demands of the Chennai environment and the process medium. Inconel 825 is a nickel-iron-chromium alloy stabilized with titanium and copper additions, providing exceptional resistance to sulfuric and phosphoric acid environments, seawater, and reducing and oxidizing acids. In a coastal industrial setting where steam-side and shell-side fluids both carry aggressive contaminants, N08825 delivers a service life that carbon steel or standard austenitic stainless steels cannot match.

The duplex 2205 shell provides the structural backbone: higher tensile strength than 316L, superior resistance to chloride stress corrosion cracking, and a cost-effective complement to the Inconel tube bundle. This material pairing is a proven configuration in industrial gas and petrochemical applications where long-term reliability matters more than first-cost minimization.

Design verification. All pressure parts were designed and checked against ASME Section VIII Div.1 code calculations. Wall thickness, nozzle reinforcement, flange ratings, and hydro test pressure were determined and documented per the applicable code paragraphs, reviewed by the Authorized Inspector prior to fabrication commencement.

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.

Execution and Quality Control

Fabrication began with incoming material inspection: all N08825 plates, tubes, and fittings were checked against certified material test reports (CMTRs), positive material identification (PMI) tested using XRF, and dimensionally verified before any cutting or forming work commenced.

Welding was performed by qualified welders using procedures qualified specifically for N08825 welding (GTAW root pass with matching filler metal, with full documentation of preheat, interpass temperature, and heat input controls). All weld joints on pressure-containing parts were inspected by visual examination and liquid penetrant testing (PT) per ASME Section V. Radiographic testing (RT) was applied to longitudinal and circumferential seam welds per the required UW-51 full radiography classification.

Hydrostatic testing was conducted at 1.3 times the maximum allowable working pressure (MAWP), held for the required duration with the Authorized Inspector (AI) present for witness. Test results were recorded on the ASME Code Data Report (Form U-1), which was subsequently submitted to the National Board of Boiler and Pressure Vessel Inspectors for registration — a requirement that gives InoxAP and Air Products a permanent, externally verified record of the equipment’s compliance history.

Following acceptance testing, the steam generator was surface-treated and preserved for ocean freight. Nozzle openings were fitted with bolted blank flanges and desiccant packs. The unit was wrapped in VCI (Vapor Corrosion Inhibitor) film, crated in a timber export crate with fumigation certification, and secured with moisture-absorbing silica gel packs within the crate to maintain a low-humidity micro-environment during the approximately 4-to-6-week ocean transit to Chennai port.

Results

The steam generator was delivered on schedule to InoxAP’s Chennai facility and installed as part of the Sri P Project’s process equipment package. Post-installation commissioning confirmed the unit met all process parameters without modification. The equipment entered continuous service supporting InoxAP’s industrial gas generation operations in South India.

For Air Products and InoxAP, the project validated Lmart as a qualified supplier for ASME pressure equipment in the Indian market — a designation that carries weight in a procurement environment where unqualified suppliers create compliance risk and delay. The successful delivery adds Chennai to Lmart’s growing map of reference installations across Asia, the Middle East, and Europe.

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 documentation package Lmart provided was exactly what we needed — complete ASME Form U-1, full material traceability, RT films, and hydro test records. The unit arrived in excellent condition despite the long ocean transit, and commissioning went smoothly. We look forward to working with Lmart again as we continue to expand our India operations.”

— Operations Manager, InoxAP / Air Products India (paraphrased from project review feedback)

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