Case Study: Inconel 625 Pipe Spools for LNG Facility in Malaysia

JN ALLOY supplied 127 prefabricated Inconel 625 (UNS N06625) pipe spools - 38 tonnes in total - for a 2.4 MTPA LNG liquefaction facility on the east coast of Peninsular Malaysia. The grade was the only technically viable choice because the three process sections combine cryogenic temperatures down to -162 degC with sour gas carrying up to 22 mol% H2S. Every spool passed PMI, 100% radiographic welding inspection, hardness and visual checks, and was delivered on the 18-week schedule with zero defects found during site erection.

Why Did the LNG Project Require 38 Tonnes of Inconel 625 Spools?

The Malaysian LNG supply-chain expansion required prefabricated pipe spools for three critical process areas: the feed gas pre-treatment section, the acid gas removal unit (AGRU), and the natural gas liquids (NGL) extraction section. All three operate outside the safe envelope of standard stainless or carbon steel.

Table 1. Project scope by process section (as supplied)

This project combined two of the most demanding service conditions in oil and gas: cryogenic temperatures (as low as -162 degC in the NGL section) and sour gas with high H2S (up to 22 mol% in feed gas pre-treatment). Neither condition alone is unusual, but their combination created design and fabrication challenges that required careful material selection and a disciplined fabrication sequence.

The simultaneous presence of cryogenic temperature (-162 degC), high H2S (up to 22 mol%) and high pressure (up to 100 barg) across three process sections made Inconel 625 the only material that satisfied all three sections at once. No stainless or carbon steel grade could meet both the sour and the cryogenic requirements simultaneously.

Where Is the Facility, and Why Does Malaysia's Petronas-Led LNG Sector Need Alloy 625?

Malaysia is one of the world's top LNG exporters, and Petronas (Petroliam Nasional Berhad) - the country's fully integrated national oil and gas company - operates the entire value chain, from upstream gas through liquefaction, petrochemicals and regasification. The Malaysia LNG (MLNG) complex in Bintulu, Sarawak is among the largest LNG production sites on the planet, and Petronas also runs Peninsular east-coast petrochemical hubs such as Kertih (Terengganu) and the Pengerang Integrated Complex (PIC) in Johor. Demand for nickel-alloy spools and piping is therefore structural across the country, not project-specific.

What drives the material specification is the service, not the flag. An LNG train's pre-treatment, acid-gas-removal and NGL sections handle gas that is cold, wet, sour and at pressure. Carbon and low-alloy steels lose toughness and suffer hydrogen attack at these temperatures; ordinary stainless steels lack both the cryogenic toughness and the NACE sour-service compliance needed. Nickel alloys such as Inconel 625 are the workhorse for these fronts - which is exactly why this facility's spools were built from 625.

The liquefaction process itself explains the combination. Raw wellstream enters feed gas pre-treatment to remove solids and free water, then the acid gas removal unit (AGRU) strips H2S and CO2 with amine so the gas meets sales-gas and liquefaction specifications. Only after the gas is dehydrated and chilled does it reach the NGL extraction and cryogenic train, where it is cooled to roughly -162 degC and separated into methane, ethane, propane and butane. Each step stresses the piping differently: warm-and-sour in the AGRU, cold-and-pressurized in the NGL section, and a mix of both in pre-treatment. A single alloy had to survive all three, and 625 was the grade that did. For Malaysian buyers, this is the recurring pattern across MLNG's Bintulu trains, the Pengerang Integrated Complex (RAPID) in Johor and the Kertih petrochemical cluster in Terengganu - all of which need cryogenic, sour-tolerant nickel alloys in their process fronts.

For regional buyers, the practical takeaway is that LNG and petrochemical projects in Malaysia repeatedly face the same material question - cryogenic plus sour - and the answer is usually a nickel alloy qualified to NACE MR0175. JN ALLOY supports these projects from our oil and gas portfolio and Inconel 625 for LNG processing pages.

• Petronas operates Malaysia's LNG plants and Peninsular east-coast petrochemical hubs (Kertih, Pengerang).

• LNG pre-treatment, AGRU and NGL sections run cryogenic (-162 degC) plus sour (H2S/CO2) - the 625 envelope.

• Carbon/low-alloy steels embrittle; standard stainless lacks sour compliance and cryogenic toughness.

• Nickel alloys such as 625 are specified repeatedly, so demand is structural, not one-off.

Why Was Inconel 625 the Only Viable Choice?

Material selection for this project was governed by two simultaneous constraints: NACE MR0175 / ISO 15156 compliance for sour service (H2S resistance) and adequate toughness at cryogenic temperature (-162 degC) for the NGL extraction section. The initial material study evaluated four candidate alloys before selecting Inconel 625.

Table 2. Material selection study - candidate alloys for combined cryogenic + sour service

Inconel 625 Chemical and Mechanical Properties

Inconel 625 (UNS N06625) carries at least 58% nickel, 20-23% chromium and 8-10% molybdenum, with niobium (3.15-4.15%) that precipitates as the gamma" phase for strength. The table below maps each property to why it matters for this cryogenic-plus-sour LNG duty.

Table 3. Inconel 625 chemical and mechanical properties (per ASTM B444)

The key reason 625 won is that it is fully NACE MR0175 compliant while also keeping excellent toughness at -162 degC - a combination carbon steel, 304L, 316L and even super duplex 2507 could not deliver across all three process sections. Inconel 825 was a borderline alternative but fails once H2S exceeds 15 mol%, which the feed gas pre-treatment section does.

Inconel 625 vs Hastelloy C276: Which Is Right for This LNG Duty?

A natural question is whether Hastelloy C276 (UNS N10276) - another flagship nickel alloy in the JN ALLOY catalogue - would have been the better pick. The honest answer for this service is no. C276's 15-17% molybdenum and 3-4.5% tungsten give it outstanding resistance to strong reducing and oxidizing acids (hydrochloric, hot contaminated sulfuric, phosphoric, wet chlorine), but that is not the dominant hazard here. The facility's challenge is cryogenic plus sour gas, where 625 is the established LNG-spools standard and C276 would be over-specified at a higher cost.

Table 4. Inconel 625 vs Hastelloy C276 - selection for this LNG sour + cryogenic duty

In short: choose Inconel 625 when the duty is cryogenic, sour, or marine plus high-strength; choose Hastelloy C276 when the duty is dominated by severe acid (HCl, hot H2SO4, FGD scrubbers, aggressive mixed acids). For a side-by-side engineering comparison, see our Inconel 625 vs Hastelloy C276 guide and the complete selection guide.

Two practical points decide the call in practice.

First, weldability: 625 is typically welded with matching ERNiCrMo-3 filler and tolerates the fabrication route used on spools; C276 is also very weldable with ERNiCrMo-4 but its higher alloy content makes it more expensive to buy and more costly to weld, with no payoff for a duty that is sour-plus-cryogenic rather than acid-driven.

Second, lifecycle cost: because C276 carries roughly 15-17% molybdenum and 3-4.5% tungsten versus 625's 8-10% molybdenum and no tungsten, the raw-material premium is typically 30-60% per kg. Spending that premium only pays back when the process is dominated by strong reducing or oxidizing acids - which this LNG pre-treatment and NGL duty is not. The decision rule is therefore simple: if the hazard is cold and sour, specify 625; if the hazard is aggressive acid, specify C276.

How Were the Spools Tested and Inspected?

Quality control ran from incoming material to final dispatch. Every heat was verified by PMI, every weld was radiographed, and hardness was surveyed on weld and heat-affected zone to prove NACE compliance. Third-party (SGS) radiographic examination gave the EPC independent assurance.

Table 5. Inspection and test plan (as executed)

What Did the Inspection Results Show?

Across 489 weld joints and 127 spools the findings were small and fully corrected. The only out-of-spec item in the first-article hardness survey was closed by re-qualifying the welding procedure (WPS) - a good example of catching a system issue early rather than on site.

Table 6. Non-destructive examination results and defect rates

The headline result is zero material substitutions (PMI clean across all pipe, fittings and filler wire) and zero defects found during site erection. Pre-fabrication inspection, not site rework, was the most cost-effective quality strategy on this project.

What Was the Delivery Schedule?

The 127 spools were released in five batches over an 18-week window, sequenced so each process section received its spools just ahead of its installation front. All batches reached site on schedule despite supply-chain disruption.

Table 7. Fabrication and delivery schedule by batch

What Lessons Did This Procurement Teach?

The project confirmed four lessons that transfer directly to other LNG and sour-service jobs:

• Specify the alloy by BOTH sour-service and cryogenic limits from day one - do not optimize for one and discover the other late.

• Qualify the welding procedure (WPS) early; the first-article hardness find here was closed by WPS re-qualification, not by reworking finished spools.

• Use independent third-party RT for butt welds so the EPC has assurance that is not self-reported.

• Treat rigorous pre-fabrication inspection as the cheapest quality insurance - it prevented every defect from reaching site erection.

Why Choose JN ALLOY for LNG and Petrochemical Spools?

This Malaysian LNG order reflects the four reasons clients return to JN ALLOY: product performance (625 delivered the cryogenic-plus-sour capability the duty demanded), selection (a broad Inconel, Incoloy, Hastelloy and duplex portfolio so the right grade is specified, not a compromise), quality (every batch released against international standards with full traceability), and service (close work from enquiry through on-time delivery). Our Inconel 625 for offshore oil and gas and marine engineering pages show the same alloy in adjacent duties.

Related Case Studies and Products

Other JN ALLOY shipments and technical pages that complement this case study:

• 41 tons Inconel 625 pipe shipped to Malaysia - marine and corrosive duty.

• Inconel 625 welding guide - filler selection and procedure.

• Inconel 625 temperature range - service limits.

• Inconel 625 flanges and Inconel 625 bars - product forms.

• Ultimate guide to Hastelloy C276 - the C276 alternative for acid duty.

• FAQ list - common alloy and specification questions.

Frequently Asked Questions About Inconel 625 for LNG Service

What was the Inconel 625 pipe spool project for the Malaysian LNG facility?

JN ALLOY supplied 127 prefabricated Inconel 625 (UNS N06625) pipe spools totalling 38 tonnes for a 2.4 MTPA LNG liquefaction facility on the east coast of Peninsular Malaysia. The spools served three process sections - feed gas pre-treatment, acid gas removal (AGRU) and NGL extraction - all operating under combined cryogenic and sour conditions.

Why is Inconel 625 used for LNG pipe spools?

LNG pre-treatment and NGL sections combine two of the hardest oil-and-gas service conditions: cryogenic temperatures down to -162 degC and sour gas with up to 22 mol% H2S. Inconel 625 keeps excellent toughness at -162 degC, is fully NACE MR0175 / ISO 15156 compliant for sour service, and resists chloride pitting, so it was the only grade that met all three process sections at once.

What is the role of Petronas in Malaysia's LNG and petrochemical sector?

Petronas (Petroliam Nasional Berhad) is Malaysia's fully integrated national oil and gas company and operates the country's LNG plants, including the Malaysia LNG complex in Bintulu, Sarawak - one of the largest LNG production sites in the world. It also runs Peninsular east-coast petrochemical hubs such as Kertih (Terengganu) and Pengerang (Johor), so demand for nickel-alloy spools and piping is structural across the country.

How does Malaysia's LNG sector create demand for nickel alloys like 625?

Malaysia's LNG trains, gas-processing and petrochemical complexes need materials that survive cryogenic temperatures, sour gas, chlorides and high pressure. Carbon and low-alloy steels fail by embrittlement or hydrogen attack, and standard stainless lacks the cryogenic toughness and sour compliance, so nickel alloys such as 625 are specified for pre-treatment, AGRU and NGL extraction spools.

Why was Inconel 625 chosen over carbon steel, 304L, 316L and super duplex?

Carbon steel embrittles below -29 degC; 304L and 316L are not NACE MR0175 compliant for sour service at the H2S levels here; and super duplex 2507 is only borderline, failing the NGL section's -162 degC duty. Only Inconel 625 met both the sour-service and the cryogenic requirements across all three sections.

How does Inconel 625 compare to Hastelloy C276 for this service?

For this LNG duty - cryogenic plus sour - Inconel 625 is the correct and more economical choice. C276 resists aggressive acids (HCl, hot sulfuric) even better thanks to its higher molybdenum and tungsten, but it is not the standard pick for -162 degC LNG service and costs more. C276 would be over-specified here because the dominant hazard is sour-plus-cryogenic, not strong acid. See the full Inconel 625 vs Hastelloy C276 guide for the engineering detail.

When would Hastelloy C276 be the better choice than 625?

C276 wins when the service is dominated by severe reducing or oxidizing acids - hydrochloric acid, hot contaminated sulfuric acid, phosphoric acid, wet chlorine, or flue-gas-desulfurization scrubbers. Its 15-17% molybdenum and 3-4.5% tungsten give corrosion resistance that 625 cannot match in those media. For cryogenic LNG with sour gas, 625 remains the better fit.

What ASTM standards cover Inconel 625 pipe, fittings and flanges?

Seamless pipe and tube are covered by ASTM B444 / B705, welding fittings by ASTM B366, forgings and flanges by ASTM B564, and bar by ASTM B446, with ASTM B829 as the general requirements. Equivalent ASME specifications carry the SB prefix.

What chemical and mechanical properties make 625 suitable for cryogenic sour service?

625 contains at least 58% nickel, 20-23% chromium and 8-10% molybdenum, with niobium (3.15-4.15%) that precipitates as gamma" for strength. It delivers UTS >= 690 MPa, yield >= 276 MPa, elongation >= 30% and a Charpy impact of >= 54 J at -162 degC - the toughness mandatory for LNG service.

What welding consumable is used for Inconel 625?

625 is typically welded with matching ERNiCrMo-3 (Inconel 625-type) filler to preserve corrosion resistance and strength in the weld. Preheat is generally not required, but interpass temperature and cleanliness control are critical to avoid hot cracking.

What quality tests were performed on the spools?

Every spool passed PMI (XRF) for grade confirmation, 100% radiographic testing of butt welds, weld-plus-HAZ hardness surveys (<= 35 HRC) for NACE compliance, visual inspection, and dimensional checks, supported by EN 10204 3.1 material test reports. Independent third-party (SGS) RT was used.

What were the inspection results and defect rates?

Across 489 weld joints the RT defect rate was 4.7% (all repaired and re-passed), hardness had one out-of-spec joint fixed by WPS requalification (0.2%), visual 2.9% (14 repairs), and PMI showed zero material substitutions. All 127 spools passed final inspection and zero defects were found during site erection.

What is NACE MR0175 / ISO 15156 and why does it matter here?

NACE MR0175 / ISO 15156 defines limits on hardness, chemistry and heat treatment so metals resist sulfide stress cracking in sour (H2S) service. Because this facility handled up to 22 mol% H2S, all welds were hardness-tested and the material had to be fully compliant - which eliminated carbon steel and most stainless grades.

How were the spools scheduled and delivered?

The 127 spools were delivered in five batches over an 18-week window - from feed gas pre-treatment and AGRU batches through the NGL extraction and final tie-in spools - all reaching the site on schedule despite supply-chain disruption.

What lessons were learned from this procurement?

The key lessons were: specify the alloy by both sour-service and cryogenic limits from the start; qualify the welding procedure (WPS) early after the first-article hardness find; use independent third-party RT for assurance; and treat rigorous pre-fabrication inspection as the most cost-effective quality strategy because it prevents site-erection defects.

Does JN ALLOY supply Inconel 625 in other product forms?

Yes. JN ALLOY supplies Inconel 625 in seamless and welded pipe, tube, plate, sheet, bar, forgings, flanges and fittings, and supports LNG, offshore and marine projects with full mill test documentation.

Are there other JN ALLOY case studies in the region?

Yes - for example 41 tons of Inconel 625 pipe shipped to Malaysia for marine and corrosive duty, and our broader oil-and-gas portfolio covering offshore, marine and chemical processing projects.