Titanium Cargo Heaters for VLGC: Why 91K LPG Carriers Choose Ti Grade 2

Introduction: The VLGC Market and Why Cargo Heating Matters

The Very Large Gas Carrier is the workhorse of global LPG logistics. These vessels — typically ranging from 82,000 to 100,000 cubic meters in cargo capacity — transport liquefied petroleum gas from export terminals in the Arabian Gulf, the US Gulf Coast, West Africa, and Australia to consumption centers across Asia, Europe, and Latin America. The global VLGC fleet has grown substantially over the past decade, driven by expanding US LPG exports following the shale gas revolution and surging Asian demand for propane as both a petrochemical feedstock and a heating fuel.

As of early 2026, the active VLGC fleet numbers approximately 340 vessels, with an orderbook of 80+ newbuildings scheduled for delivery through 2028. The newbuild programs are concentrated at a handful of major shipyards: Hyundai Heavy Industries (HHI) and Daewoo Shipbuilding & Marine Engineering (DSME) in South Korea, Kawasaki Heavy Industries and Mitsubishi Shipbuilding in Japan, and Jiangnan Shipyard, COSCO Shipping Heavy Industry, and Yangzijiang Shipbuilding (YZJ) in China. Each of these yards is building VLGCs to designs licensed from cargo system specialists — primarily a leading Nordic marine systems integrator Gas Solutions (formerly Hamworthy) and TGE Marine (now part of MAN Energy Solutions' marine division).

At the center of every VLGC's cargo handling system sits a piece of equipment that most people outside the marine engineering community never consider: the cargo heater. It is the component responsible for warming liquefied cargo to the temperature required for efficient discharge at the receiving terminal. This task must be performed reliably, repeatedly, and safely for 25 years or more — in one of the most corrosive thermal environments in all of industrial service.

The cargo heater matters for three fundamental reasons. First, without it, the vessel cannot discharge its cargo at terminals that require warmed LPG, effectively limiting trading flexibility. Second, a cargo heater failure during discharge operations can result in delays costing the ship owner tens of thousands of dollars per day. Third, a tube failure that allows seawater to leak into the cargo circuit can contaminate an entire cargo parcel worth $30–50 million, with consequences that cascade through insurance claims, cargo rejection, and commercial disputes.

Understanding why the VLGC fleet has converged on titanium as the material solution for cargo heaters — and what goes into the engineering, manufacturing, and certification of these units — is essential knowledge for anyone involved in gas carrier newbuilding, operation, or maintenance. This article provides that understanding.

What Is a Cargo Heater and Why VLGCs Need One

LPG Cargo Properties

LPG is a mixture of light hydrocarbons, predominantly propane (C3H8) and butane (C4H10), with varying proportions depending on the source and grade. In fully refrigerated VLGCs, propane is carried at its atmospheric boiling point of approximately -42 deg C, while butane boils at approximately -1 deg C. The cargo is maintained in a liquid state at or near atmospheric pressure inside Type A prismatic tanks — large, box-shaped insulated tanks that conform to the hull shape.

The vapor pressure of LPG is a strong function of temperature. At -42 deg C, propane exerts approximately 1 bar of vapor pressure. At -10 deg C, this rises to roughly 3.5 bar. At 0 deg C, it reaches about 4.7 bar. These vapor pressure characteristics are central to understanding why cargo heating is necessary: the discharge temperature and the corresponding vapor pressure determine the rate at which cargo can be transferred to shore tanks and the compatibility with the receiving terminal's infrastructure.

Receiving terminals are designed to accept LPG within a specific temperature window. Many terminals, particularly older installations in Asia, are designed for semi-refrigerated or pressurized storage and require cargo to arrive at temperatures warmer than the fully refrigerated -42 deg C. Even terminals with fully refrigerated storage may require the cargo to be warmed slightly to maintain adequate cargo pump discharge pressure and flow rate during transfer operations.

Cargo Heating vs Reliquefaction: When and Why

A VLGC's cargo handling system includes two distinct thermal management functions: reliquefaction (cooling) and cargo heating (warming). These serve different operational needs.

Reliquefaction operates during the loaded voyage. As heat leaks through the tank insulation, a small fraction of the liquid cargo boils off as vapor. The reliquefaction plant compresses this boil-off gas, condenses it back to liquid using seawater-cooled condensers, and returns it to the cargo tanks. The purpose is cargo preservation — preventing cargo loss during transit.

Cargo heating operates at the discharge port. The cargo heater warms the bulk liquid cargo from its storage temperature (-42 deg C for propane) to the temperature specified by the receiving terminal — typically -20 deg C to 0 deg C, though the exact requirement varies by terminal. The purpose is cargo discharge — enabling efficient transfer from ship to shore.

Some modern cargo handling systems use a combined approach where the reliquefaction compressors are reversed to act as heat pumps, or where dedicated cargo heaters supplement the reliquefaction system's thermal output. In either case, the critical heat transfer equipment that interfaces with seawater requires titanium tubes.

System Architecture: Seawater Circuit to Cargo Tank

The cargo heating circuit of a VLGC follows a straightforward thermodynamic path:

1. Seawater intake: Raw ocean water is drawn through the vessel's sea chest — a screened opening in the hull below the waterline — and pumped by dedicated seawater pumps to the cargo heater.

2. Cargo heater (shell-and-tube heat exchanger): The seawater flows through the shell side (or tube side, depending on design) of a shell-and-tube heat exchanger, giving up thermal energy to the LPG cargo flowing on the opposite side. The seawater enters at ambient ocean temperature — anywhere from 5 deg C in northern winter routes to 32 deg C in the Arabian Gulf — and exits several degrees cooler.

3. Heated LPG return: The warmed LPG flows back to the cargo tanks, gradually raising the bulk cargo temperature toward the target discharge temperature.

4. Seawater discharge: The cooled seawater is discharged overboard through the vessel's sea discharge system.

The temperatures involved are significant. On the seawater side, the heat transfer surfaces see temperatures ranging from 5 deg C to 32 deg C. On the LPG side, the surfaces operate from -42 deg C at startup to the target discharge temperature. The temperature differential across the tube wall drives heat transfer — but it also drives thermal stress and creates condensation conditions that can exacerbate corrosion on the seawater side.

A typical 91K VLGC is equipped with 2 to 4 cargo heaters, depending on the cargo handling system design and the required discharge rate. For a vessel carrying 91,000 cubic meters of LPG that needs to complete discharge within 18–24 hours, the combined heating capacity must be substantial — typically several megawatts of thermal duty distributed across the heater bank.

The Material Challenge: Why Seawater Kills Heat Exchangers

Seawater Corrosion Mechanisms

The seawater side of a cargo heater is one of the most aggressive corrosion environments in marine engineering. Raw, untreated ocean water contains approximately 19,000 ppm chloride ions, 2,700 ppm magnesium, 900 ppm calcium, 900 ppm potassium, dissolved oxygen at 6–8 ppm, various biological organisms (bacteria, algae, barnacle larvae), and — in port and coastal environments — industrial pollutants including sulfides and heavy metals.

This cocktail attacks metallic heat transfer surfaces through multiple simultaneous corrosion mechanisms:

Pitting corrosion is the most dangerous failure mode for stainless steels in seawater. Chloride ions penetrate the passive chromium oxide film at weak points (inclusions, grain boundaries, surface defects), creating small anodic sites where the metal dissolves rapidly while the surrounding cathodic area remains protected. The result is small-diameter, deep pits that can perforate a tube wall without any visible surface degradation. Pitting is insidious because it is localized, difficult to detect during routine inspection, and progresses at rates far higher than uniform corrosion — sometimes exceeding 1 mm/yr at the pit bottom.

Crevice corrosion is a related mechanism that occurs in geometrically restricted areas where oxygen transport is limited — the tube-to-tubesheet gap, under deposits, and at gasket faces. Within the crevice, oxygen is consumed by corrosion reactions but cannot be replenished by diffusion from the bulk fluid. This creates a differential aeration cell: the oxygen-depleted crevice becomes anodic, while the adjacent freely exposed surface becomes cathodic. In the presence of chloride ions, the crevice solution becomes increasingly acidic (pH can drop below 2), dramatically accelerating metal dissolution. For stainless steels, the critical crevice temperature (CCT) — the temperature above which crevice corrosion initiates — is the most important parameter in material selection. For 316L, the CCT in natural seawater is as low as 15–25 deg C, meaning crevice corrosion can initiate at temperatures well within the operating range of a cargo heater.

Galvanic corrosion occurs when dissimilar metals are in electrical contact in the presence of an electrolyte (seawater). The more active (anodic) metal corrodes preferentially. In marine heat exchangers, galvanic effects can accelerate corrosion at joints between different alloys — for example, between copper-nickel tubes and steel tubesheets, or between stainless steel tubes and carbon steel baffles. Proper material selection for every wetted component is essential to prevent galvanic acceleration.

Microbiologically influenced corrosion (MIC) is caused by bacteria that colonize metal surfaces in stagnant or low-flow areas. Sulfate-reducing bacteria (SRB) are particularly problematic: they thrive in oxygen-depleted environments (such as crevices and under biofilms) and produce hydrogen sulfide as a metabolic byproduct, which attacks most engineering alloys. MIC is responsible for a significant fraction of unexpected tube failures in marine heat exchangers, particularly in units that are laid up or operated intermittently with stagnant seawater.

Erosion-corrosion occurs when high fluid velocity removes the protective corrosion product layer from the metal surface, exposing fresh metal to continued attack. In heat exchanger tubes, erosion-corrosion is worst at tube inlets (where flow velocity is highest and turbulence greatest) and at baffle cut edges (where flow accelerates through restricted passages). Copper-nickel alloys are particularly susceptible — the maximum allowable velocity for 90/10 Cu-Ni in seawater is only 2.5 m/s, which limits heat transfer performance and tube design flexibility.

Historical Failures with Cu-Ni and 316L in Marine Service

The historical record of non-titanium materials in marine seawater heat exchangers is a catalog of premature failures.

90/10 Copper-nickel (Cu-Ni) was for decades the standard tube material in marine heat exchangers. It offers moderate corrosion resistance in clean seawater and has inherent antifouling properties due to copper ion release. However, Cu-Ni has proven unreliable in the real-world conditions that cargo heaters encounter. In polluted harbor water — which contains sulfides from industrial discharge and decaying organic matter — Cu-Ni tubes suffer accelerated attack that can reduce wall thickness by 0.1–0.3 mm/yr. The antifouling benefit is also a liability under evolving environmental regulations: the International Maritime Organization's anti-fouling convention and regional regulations in Europe and Asia increasingly restrict copper release into marine environments.

Field data from the early 2000s VLGC fleet showed Cu-Ni tube bundles requiring replacement after 8–12 years — well short of the vessel's 25-year design life. Each retubing required the vessel to go to drydock, at a cost of $200,000–$500,000 for the bundle replacement alone, plus $30,000–$60,000/day in lost charter hire during the drydock period of 10–20 days.

316L stainless steel was adopted by some operators as an alternative to Cu-Ni, hoping that its higher alloy content would provide better corrosion resistance. In practice, 316L proved worse in seawater service. Its PREN (Pitting Resistance Equivalent Number) of approximately 24 is well below the minimum threshold of 40 considered necessary for reliable performance in natural seawater. Tube failures due to pitting and crevice corrosion were observed within 3–5 years on some vessels, with catastrophic through-wall penetrations occurring at tube-to-tubesheet joints where crevice conditions are most severe.

The economic damage from a tube failure goes far beyond the cost of the tube itself. When seawater enters the cargo circuit through a perforated tube, it contaminates the LPG with water, chlorides, and dissolved salts. This can render an entire cargo parcel off-specification, requiring reprocessing at the receiving terminal or outright rejection. For a fully loaded 91K VLGC carrying approximately 45,000 metric tons of propane at $400–$600/ton, the cargo value at risk is $18–27 million. Even partial contamination of a single tank can result in claims of $500,000–$2,000,000 after quality downgrades, demurrage, and consequential losses.

Cost of Unplanned Drydock for Tube Bundle Replacement

When a tube failure occurs, the operational impact follows a predictable and expensive sequence:

1. Detection: The failure is typically detected by contamination alarms in the cargo system (water content, chloride content) or by abnormal pressure readings in the cargo heater during operation.

2. Operational restriction: The affected cargo heater is isolated. If redundancy allows, the vessel continues operations with reduced capacity. If not, discharge operations may need to be suspended.

3. Root cause investigation: The ship owner and classification society require an investigation to determine whether additional heaters are at risk of similar failure.

4. Drydock scheduling: An unplanned drydock must be arranged — at whatever yard has availability, not necessarily the lowest-cost or most convenient location. Lead time for drydock slots ranges from 2–6 weeks.

5. Tube bundle replacement: The old tube bundle is pulled, the new bundle is fabricated and delivered (lead time 8–16 weeks for titanium, shorter for Cu-Ni but with the same failure mode guaranteed to repeat), and the new bundle is installed and tested.

6. Lost revenue: Throughout this process, the vessel is either operating at reduced capacity or completely off-hire. At VLGC spot charter rates of $30,000–$60,000/day, a 30-day combined drydock and repair period costs $900,000–$1,800,000 in lost revenue alone.

The total cost of a single tube failure event — including the physical repair, cargo claims, lost revenue, survey fees, and classification society expenses — can easily exceed $2,000,000. For a vessel that experiences two such events over a 25-year life (typical for Cu-Ni or 316L), the cumulative cost approaches or exceeds the additional capital cost of specifying titanium tubes at the outset.

This economic reality is what drove the VLGC industry to adopt titanium. The decision was not based on material preference or engineering fashion. It was a lifecycle cost calculation that became inescapable once the failure data from the early non-titanium fleet was compiled and analyzed.

Why Titanium Grade 2 Wins

Corrosion Resistance Data

Titanium Grade 2 (UNS R50400) is a commercially pure titanium containing 99.2%+ Ti, with controlled limits on oxygen, nitrogen, carbon, hydrogen, and iron. Its defining characteristic in marine service is the spontaneous formation of a tenacious, self-healing titanium dioxide (TiO2) passive film upon exposure to any oxygen-containing environment — including seawater.

This passive film has extraordinary stability in chloride environments. While 316L stainless steel begins to pit at chloride concentrations around 200–1,000 ppm (depending on temperature and crevice geometry), and even super duplex 2507 (PREN approximately 42) can experience crevice corrosion above 50–90 deg C in seawater, titanium's passive film remains intact at chloride concentrations exceeding 100,000 ppm — more than five times the chloride content of seawater. The film reforms instantly if mechanically damaged, providing a self-healing capability that no other engineering alloy can match in this environment.

The general corrosion rate of Ti Grade 2 in flowing seawater has been measured in numerous long-term exposure studies at less than 0.003 mm/yr — effectively zero from an engineering standpoint. In many studies, Ti Grade 2 coupons exposed to seawater for 10+ years showed no measurable weight loss. There is no known temperature limit for titanium's corrosion resistance in natural seawater at atmospheric pressure; the material remains fully passive at temperatures far exceeding anything a cargo heater will encounter.

Perhaps most importantly for cargo heater applications, titanium does not suffer from crevice corrosion in natural seawater at any temperature below approximately 70 deg C — and even this limit applies only to chemically concentrated chloride solutions, not natural seawater. Since the seawater-side temperature in a cargo heater never exceeds ambient ocean temperature (maximum approximately 32 deg C), crevice corrosion is simply not a concern. This eliminates the failure mode that is responsible for the majority of tube-to-tubesheet joint failures in non-titanium marine heat exchangers.

Mechanical Properties at Operating Temperatures

Ti Grade 2 has a minimum tensile strength of 345 MPa and minimum yield strength of 275 MPa at room temperature, with excellent ductility (minimum 20% elongation). These properties are adequate for the pressure and thermal stress conditions in a VLGC cargo heater, where the seawater-side design pressure is typically 5–10 bar and the temperature range spans from ambient seawater temperature down to cryogenic conditions on the LPG side.

At cryogenic temperatures, titanium maintains its mechanical properties without the brittle-to-ductile transition that affects carbon steels and some ferritic stainless steels. The BCC (body-centered cubic) crystal structure materials like carbon steel undergo a sharp reduction in impact toughness below their ductile-to-brittle transition temperature (DBTT), making them unsuitable for cryogenic contact. Titanium's HCP (hexagonal close-packed) crystal structure does not exhibit this transition, maintaining adequate toughness at temperatures down to -196 deg C. This is relevant because the tube wall in a cargo heater is the boundary between seawater at 5–32 deg C and LPG cargo at temperatures as low as -42 deg C — the tube must withstand this thermal gradient without becoming brittle.

Weight Advantage

Titanium's density of 4,510 kg/m³ is approximately 56% that of steel (7,990 kg/m³) and 51% that of copper-nickel (8,900 kg/m³). For a cargo heater tube bundle containing several hundred tubes, the weight savings from using titanium instead of an equivalent-diameter Cu-Ni bundle is substantial.

Material	Density (kg/m³)	Relative Weight (vs Ti)
Ti Grade 2	4,510	1.00x (baseline)
Super Duplex 2507	7,800	1.73x
316L SS	7,990	1.77x
90/10 Cu-Ni	8,900	1.97x

In a vessel where every ton of structural and equipment weight reduces cargo-carrying capacity, and where cargo capacity directly translates to revenue, the weight advantage of titanium is a meaningful secondary benefit beyond corrosion resistance. A typical VLGC cargo heater weighing 3,660 kg with titanium tubes would weigh approximately 5,000–5,500 kg with Cu-Ni tubes of equivalent thermal performance — a difference of 1,300–1,800 kg per unit, or 5,000–7,000 kg across a four-heater installation.

Lifecycle Cost Analysis: 25-Year TCO

The upfront cost of titanium tubes is approximately 3–4 times that of 316L stainless steel per meter, and roughly 4–5 times that of 90/10 Cu-Ni. This initial cost premium is the most common objection to titanium specification from procurement departments focused on capital expenditure (CAPEX) rather than total cost of ownership (TCO).

However, the lifecycle economics tell a different story. The following table presents a simplified 25-year TCO comparison for a four-heater VLGC installation, based on industry experience and published failure rate data:

Cost Element	Ti Grade 2	90/10 Cu-Ni	316L SS	Super Duplex 2507
Initial tube bundle cost (relative)	3.5x	1.0x	1.2x	2.5x
Number of retubing events (25 yr)	0	2–3	3–5	0–1
Retubing cost per event (bundle + labor + drydock)	—	$300,000–$500,000	$250,000–$400,000	$400,000–$600,000
Lost revenue per retubing (15–30 days)	—	$450,000–$1,800,000	$450,000–$1,800,000	$450,000–$1,800,000
Cargo contamination risk	Near zero	Moderate	High	Low
Cargo contamination cost (per event)	—	$500,000–$2,000,000	$500,000–$2,000,000	$500,000–$2,000,000
25-year lifecycle cost index	1.0x	2.8–4.5x	3.5–6.0x	1.2–2.0x

When evaluated on a net present value basis over the vessel's 25-year design life, titanium is not the most expensive option — it is the least expensive option. The initial premium is recovered within the first avoided retubing event, which for Cu-Ni or 316L typically occurs within 5–10 years of commissioning.

This calculation does not include the commercial value of operational reliability. A VLGC with titanium cargo heaters can be marketed to charterers and cargo owners as a lower-risk vessel, potentially commanding a premium on the charter market. In a competitive freight market, operational reliability is a differentiator.

Environmental Compliance

The environmental regulatory landscape is shifting in ways that further favor titanium over copper-containing alternatives. The IMO's International Convention on the Control of Harmful Anti-fouling Systems prohibits organotin compounds and is increasingly scrutinized for copper-based releases. Regional regulations in European waters (OSPAR Convention), US waters (EPA), and sensitive marine areas (Australian Great Barrier Reef Marine Park) restrict or monitor copper discharge from vessels.

While cargo heater tubes are not anti-fouling coatings, Cu-Ni tubes do release copper ions into seawater during normal operation — this is the mechanism that provides their biofouling resistance, but it is also a source of copper discharge to the marine environment. Titanium tubes release no harmful ions and have no impact on marine water quality.

As environmental, social, and governance (ESG) requirements become increasingly important to ship financiers, insurers, and charterers, the environmental profile of equipment choices will carry more weight in procurement decisions.

Thermal Performance: Thin-Wall Ti Tubes vs Thick-Wall Alternatives

Titanium's corrosion immunity allows the use of thinner tube walls than would be required for materials that need a corrosion allowance. A typical Ti Grade 2 tube for a cargo heater has a wall thickness of 0.7–1.0 mm, compared to 1.2–1.6 mm for Cu-Ni and 1.0–1.2 mm for stainless steels (which need additional thickness to account for pitting corrosion allowance over the service life).

Thinner tube walls mean lower thermal resistance across the tube wall, improving heat transfer efficiency. Titanium's thermal conductivity (approximately 22 W/m-K) is lower than that of copper-nickel (approximately 50 W/m-K) and stainless steel (approximately 16 W/m-K), but the thinner wall compensates for this disadvantage. The overall heat transfer coefficient of a well-designed titanium tube bundle is comparable to Cu-Ni and superior to stainless steel alternatives, while providing indefinite corrosion life.

Engineering Design Deep Dive

Shell Material Selection: SA240 304L vs SA516 Gr.70

The shell side of a VLGC cargo heater contacts the LPG cargo — not seawater. The shell material therefore does not need titanium's seawater corrosion resistance. Instead, it must be compatible with the cargo fluids at their operating temperatures and pressures. Two materials dominate the specification landscape:

SA240 304L (austenitic stainless steel): This is the preferred shell material when the vessel's cargo profile includes ammonia (NH3). Ammonia is corrosive to carbon steel at cargo handling temperatures, and the combination of ammonia with moisture can cause stress corrosion cracking (SCC) in some carbon steel grades. 304L provides adequate corrosion resistance to propane, butane, and ammonia, and has excellent toughness at cryogenic temperatures down to -196 deg C.

The trend toward 304L shells has accelerated in recent years as the ammonia-as-fuel and ammonia-as-cargo markets have grown. Ship owners ordering new VLGCs increasingly specify dual-cargo capability (LPG + NH3) to maximize chartering flexibility. The IMO's 2050 greenhouse gas reduction targets have positioned ammonia as a leading candidate for zero-carbon marine fuel, and VLGCs with ammonia-capable cargo systems are expected to command a premium in the charter market.

In Lmart's delivery track record for the customer, the majority of recent programs — including the HHI H2496/H2515 (82K LPG/NH3), H2708/H2709 (Solvang 60K LPG/NH3), and various BW Gas 84K series — specify SA240 304L shells to maintain ammonia capability.

SA516 Gr.70 (carbon steel): This is selected when the cargo is exclusively LPG (propane/butane) with no ammonia service requirement. Carbon steel is fully adequate for clean, dry LPG at cargo temperatures. It offers superior strength-to-weight ratio for pressure containment compared to 304L and is significantly less expensive. The design temperature limit for SA516 Gr.70 per ASME is -46 deg C (with impact testing), which is adequate for propane service at -42 deg C.

In Lmart's the customer portfolio, the SA516 Gr.70 shell variants are found in dedicated LPG carriers where the owner has no current plans for ammonia trading — for example, certain Kawasaki-built vessels and the Pearl Petrochemical 93K program. These units typically have slightly different dimensions (DN890–900mm shell diameter, 5,901–6,116mm length) reflecting the specific thermal design for LPG-only service.

The choice between these shell materials should be explicitly specified in the purchase order and cargo system license agreement. Changing shell material after fabrication has begun is costly and schedule-disruptive — the welding procedures, NDE requirements, and material procurement lead times are significantly different.

Tube Specification: SB 388 Gr.2 vs SB 338 Gr.2

The titanium tubes in VLGC cargo heaters are specified to ASME Boiler and Pressure Vessel Code (BPVC) material standards. Two specifications are commonly referenced, and understanding the difference is important for procurement:

SB 338 Gr.2: This is the ASME adoption of ASTM B338, covering seamless and welded titanium alloy tubes for condensers and heat exchangers. It specifies chemical composition, mechanical properties, dimensional tolerances, and testing requirements for tubing intended for heat exchanger service.

SB 388 Gr.2: This is the ASME adoption of ASTM B388, covering seamless and welded titanium alloy tube specifically for condensers. While the material grade (Grade 2) is identical in both specifications, SB 388 includes additional requirements for surface finish, ovality, and straightness that are specific to condenser and heat exchanger applications with tight tube-to-tubesheet fit requirements.

In the customer's cargo heater specifications for VLGC programs, SB 388 Gr.2 is the standard tube material callout. This reflects the customer's preference for the tighter dimensional tolerances of SB 388, which facilitate consistent tube-to-tubesheet expansion and reduce the risk of crevice geometry variations that could affect long-term performance — even though titanium itself is immune to crevice corrosion in seawater, consistent joint quality improves hydrostatic test reliability and long-term leak tightness.

Typical Dimensions and Why They Converge

One of the notable features of the VLGC titanium cargo heater market is the convergence of physical dimensions across different programs and vessel classes. The typical specifications cluster around:

Parameter	Standard Range	Most Common Value
Shell OD	DN 890–900 mm	DN 890 mm
Shell wall thickness	8–10 mm	8 mm
Overall length	5,901–7,060 mm	7,060 mm
Unit weight	3,635–4,000 kg	3,660 kg

This convergence is not coincidental. It reflects the optimization of cargo heater geometry for the standardized cargo tank arrangements found in modern VLGCs:

1. Shell diameter (DN 890): The cargo heater must fit within the available space in the vessel's cargo machinery room, which is constrained by the cargo tank geometry. The DN 890 mm shell diameter represents the optimal balance between heat transfer area (larger diameter = more tubes = more area) and physical installation constraints.

2. Length (7,060 mm): The tube length determines the heat transfer area per tube and the overall thermal performance. The 7,060 mm length provides sufficient area for the design heat duty while remaining within the handling constraints for installation through the vessel's access openings. The shorter variants (5,901–5,911 mm) are used in programs with lower heat duty requirements or different installation geometry.

3. Weight (3,660 kg): The unit weight reflects the combined mass of the shell, tube bundle, tubesheets, baffles, nozzles, and internals. The consistency of this weight across programs confirms the standardized nature of the design — the customer specifies a standard design envelope that is adapted for each vessel program through changes to tube count, baffle spacing, and nozzle configuration rather than wholesale redesign.

Baffle Design, Tube Pitch, and Expansion Joints

Inside the cargo heater shell, segmental baffles direct the shell-side fluid (LPG or seawater, depending on which side is shell-side) in a cross-flow pattern over the tube bundle. The baffle design affects several critical performance parameters:

Baffle cut: Typically 25–35% of shell diameter for cargo heater applications, balancing shell-side pressure drop against heat transfer coefficient. A larger baffle cut reduces pressure drop but may create stagnant zones where fouling or corrosion can initiate.

Baffle spacing: Determines the number of cross-flow passes and the shell-side velocity between baffles. Closer spacing increases velocity and heat transfer but also increases pressure drop. For seawater service, the velocity must be maintained above approximately 0.5 m/s to prevent fouling and below approximately 3 m/s to prevent erosion (though titanium's erosion resistance allows higher velocities than Cu-Ni or stainless steel).

Tube pitch: The center-to-center distance between adjacent tubes in the tube bundle. Typical tube pitch for marine cargo heaters is 1.25 times the tube outer diameter (standard triangular pitch per TEMA), providing good shell-side fluid distribution and adequate clearance for tube-to-tubesheet welding access.

Expansion joints: The temperature differential between the shell side and tube side in a cargo heater can be extreme — from ambient seawater temperature on one side to -42 deg C on the other. This differential creates differential thermal expansion between the shell and the tube bundle. Fixed-tubesheet designs (TEMA type BEM or NEN) handle this with an expansion joint (bellows) in the shell, which absorbs the differential movement without imposing excessive stress on the tube-to-tubesheet joints.

TEMA Type Selection for Marine Cargo Heaters

TEMA (Tubular Exchanger Manufacturers Association) classification defines the geometry of shell-and-tube heat exchangers using a three-letter code. For VLGC cargo heaters, the most common configurations are:

BEM (Bonnet covers, one-pass shell, fixed tubesheets): This is the simplest and most common configuration. Both tubesheets are welded to the shell, and the tube bundle is not removable. An expansion joint in the shell accommodates differential thermal expansion. This type is preferred when the shell-side fluid (LPG) is clean and non-fouling, eliminating the need for mechanical cleaning access to the shell side.

NEN (Channel with removable cover, one-pass shell, fixed tubesheets): Similar to BEM but with a removable channel cover that provides access to the tube-side for inspection and cleaning without removing the tube bundle. This is specified when the tube-side fluid (seawater) may require periodic inspection or mechanical cleaning.

The choice between fixed tubesheet and floating head designs is a fundamental engineering decision that affects cost, weight, maintainability, and thermal performance. For VLGC cargo heaters, fixed-tubesheet designs dominate because the cargo-side (LPG) is non-fouling and does not require shell-side bundle removal for cleaning.

Classification Society Requirements

Overview: What Classification Means for Cargo Heaters

Every heat exchanger installed on a classified vessel must be approved by the vessel's classification society. The society reviews the design calculations, approves the materials and fabrication procedures, witnesses key manufacturing steps, conducts final inspection and testing, and issues the certificate that authorizes the equipment to be installed aboard the vessel. Without this certificate, the equipment cannot be used — period.

For titanium cargo heaters in the VLGC fleet, six classification societies account for virtually all newbuilding activity:

DNV (Det Norske Veritas)

DNV classification is common for European-owned tonnage and vessels registered under Norwegian, Singaporean, and Bahamian flags. DNV's rules for pressure vessels and heat exchangers (DNV-RU-SHIP Pt.4 Ch.7) include specific requirements for titanium materials, including:

• Material certification to DNV material grade designations (cross-referenced to ASME/ASTM)
• Welding procedure qualification per DNV standards (additional to ASME Section IX requirements)
• Mandatory survey at key hold points: material inspection, fit-up inspection, welding inspection, NDE review, hydrostatic test witness, final survey
• Documentation in English with DNV-specific forms and certificates

In Lmart's delivery track record, DNV-class the customer cargo heaters include the Pearl Petrochemical 93K VLGC program (DN900mm, 4,000 kg units with SA516 Gr.70 shells) — a 9+3 unit program totaling 12 heaters.

ABS (American Bureau of Shipping)

ABS is one of the most commonly specified societies for VLGCs, reflecting the large US-traded fleet and the preference of many Korean shipyards (particularly HHI) for ABS classification. ABS requirements are defined in the Rules for Building and Classing Marine Vessels and include:

• Material approval per ABS Rules (Section 2-1-2 for nonferrous metals including titanium)
• Welding procedure approval with ABS-witnessed qualification tests
• Survey schedule aligned with ABS Surveyor presence at the manufacturing facility
• Pressure test to ABS requirements (typically 1.5x design pressure for hydrostatic test)

ABS-class units dominate Lmart's the customer cargo heater portfolio, covering HHI hulls H2496, H2515, H2581, H2632, H2694, H2705–H2724, and H2765, as well as dual-class ABS+KR and ABS+NK units.

KR (Korean Register)

KR classification is required for many vessels built at Korean shipyards, particularly those ordered by Korean ship owners or those registered under the Korean flag. KR's requirements for pressure equipment are closely aligned with ABS but include additional Korean-language documentation requirements and specific surveyor scheduling protocols.

Dual classification (ABS+KR) is common for VLGCs built in Korea, requiring the manufacturer to satisfy both societies' requirements simultaneously. This means dual surveyor attendance at hold points, dual documentation packages, and dual material certification review. In practice, most experienced manufacturers maintain a unified quality plan that satisfies both societies, with marginal additional effort for the second certification.

NK (ClassNK / Nippon Kaiji Kyokai)

NK is the predominant society for Japanese-built vessels and is common for Japanese-owned tonnage built overseas. NK's Rules and Guidance for the Survey and Construction of Steel Ships include specific provisions for titanium and titanium alloy materials.

NK-class the customer cargo heaters in Lmart's portfolio include units for Kawasaki hull numbers 22N1709, 22N1421, 22N1730, and 22N1725/32, as well as the SA516 Gr.70 shell variants (DN890, 5,901–5,911mm) produced in batches of 3, 4, 2, 4, and 1 units. Dual-class ABS+NK units are also supplied.

BV (Bureau Veritas)

BV classification is common for French-owned tonnage, certain Chinese-built vessels, and vessels trading in regions where BV has strong market presence (West Africa, Mediterranean). BV's Rules for the Classification of Steel Ships include NR216 (Rules for Materials and Welding) with provisions for titanium.

BV-class units in Lmart's portfolio include the GASWOLIA VLGC and the TGE Marine ethylene vaporizer programs for various European-owned gas carriers.

CCS (China Classification Society)

CCS is required for Chinese-flagged vessels and is increasingly accepted as the primary or secondary classification for vessels built at Chinese shipyards (COSCO, Jiangnan, YZJ, CMHI, Hengli). CCS's Rules for Materials and Welding include provisions for titanium alloy pressure equipment.

CCS-class units are prominent in the TGE Marine portfolio, particularly for the ethylene vaporizer and forcing vaporizer programs supplied to Jiangnan Shipyard (H2546, H2567–H2570) and COSCO (N588).

Type Approval vs Project-Specific Approval

Some classification societies offer type approval — a pre-certification of a standard design that allows subsequent units to be manufactured under a simplified approval process. For cargo heaters, however, the variation in heat duty, nozzle configuration, and material selection between programs typically requires project-specific approval for each order. The manufacturer submits design drawings and calculations for each specific unit, the society reviews and approves (with or without comments), and fabrication proceeds under the approved drawings.

Documentation Package: What the Shipyard Expects

The documentation package for a VLGC titanium cargo heater delivered to a shipyard typically includes:

1. Design documentation: General arrangement drawings, pressure part drawings, strength calculations per ASME VIII Div 1, thermal design calculations
2. Material certificates: Mill test reports (MTRs) for all pressure-containing materials, including complete chemical analysis and mechanical test results per ASME and classification society requirements
3. Welding records: Welding procedure specifications (WPS), procedure qualification records (PQR), welder performance qualifications (WPQ), and weld maps identifying each production weld and the applicable WPS
4. NDE reports: Radiographic, ultrasonic, liquid penetrant, and helium leak test reports for all welds per the approved NDE plan
5. Dimensional inspection: As-built dimensional report confirming conformance to approved drawings
6. Pressure test: Hydrostatic test certificate with test pressure, hold time, and witness signature
7. Classification certificate: The society's final survey report and certificate of conformity
8. Data book: Compiled quality documentation in hard copy and electronic format, typically running to several hundred pages per unit

This documentation package is the quality passport that allows the cargo heater to be installed on the vessel and accepted by the ship owner's technical superintendent during the commissioning process.

Manufacturing: What Makes Titanium Cargo Heaters Hard to Build

Titanium Welding: Argon Shielding, Color Inspection, Atmosphere Control

Titanium is highly reactive with oxygen, nitrogen, and hydrogen at temperatures above approximately 500 deg C. During welding, the molten weld pool and the heat-affected zone (HAZ) must be completely shielded from atmospheric contamination by inert gas — typically high-purity argon (99.995%+). Failure to maintain adequate shielding results in oxygen and nitrogen pickup that causes embrittlement, reduced ductility, and loss of corrosion resistance.

The practical implications for cargo heater manufacturing are significant:

Primary shielding: The GTAW (Gas Tungsten Arc Welding / TIG) torch provides argon shielding to the molten weld pool through the standard torch cup. For titanium, the cup diameter and gas flow rate must be larger than for steel welding to ensure complete coverage of the weld pool.

Trailing shield: As the torch moves forward, the just-solidified weld and HAZ remain above 500 deg C for a distance behind the arc. A trailing shield — an argon-filled device attached behind the torch — continues to protect these areas until they cool below the oxidation threshold. The trailing shield must be properly sized and positioned for the specific joint geometry.

Backing gas: On the root side of the weld (inside the tube for butt welds, inside the tube-to-tubesheet crevice for seal welds), argon backing gas must be maintained to prevent oxidation of the weld root. This typically requires purging the tube interior with argon before welding and maintaining flow throughout the welding operation.

Weld color inspection: The most immediate indicator of titanium weld quality is the weld color. A properly shielded titanium weld is bright silver to light straw (gold). These colors indicate minimal oxygen pickup and acceptable weld quality. As contamination increases, the weld color progresses through dark straw, blue, purple, and finally gray or white — each step indicating increasing oxygen/nitrogen contamination and degraded mechanical properties.

The color acceptance criteria (per AWS D1.9 and classification society requirements) are:

Weld Color	Oxygen Content (approx.)	Acceptability
Bright silver	< 100 ppm	Acceptable
Light straw (gold)	100–200 ppm	Acceptable
Dark straw	200–400 ppm	Marginal (society-dependent)
Blue	400–800 ppm	Not acceptable — remove and reweld
Purple/gray	> 800 ppm	Not acceptable — remove and reweld

Every weld pass on every titanium joint in a cargo heater is subject to visual color inspection. Any weld showing blue, purple, or gray discoloration must be ground out and re-welded — there is no option to accept or repair contaminated titanium welds.

Tube-to-Tubesheet Joint: Expansion + Seal Weld

The tube-to-tubesheet joint is the most critical fabrication detail in a titanium cargo heater. Each cargo heater contains hundreds of tube-to-tubesheet joints (two per tube — one at each tubesheet), and every joint must be leak-tight and structurally sound for the 25-year design life.

The joint is made in two steps:

Step 1 — Hydraulic expansion: The tube is inserted through the tubesheet bore and hydraulically expanded to achieve a metal-to-metal interference fit. The expansion pressure and resulting wall reduction are carefully controlled — typically 5–8% wall reduction — to achieve a tight joint without over-expanding the tube (which can cause tube thinning and reduced fatigue life).

Step 2 — Seal weld: A GTAW seal weld is applied at the tube-to-tubesheet face, fusing the tube end to the tubesheet bore. This weld provides the primary leak seal and must be performed with full argon shielding on both sides (torch side and tube interior). The weld must have full fusion to the tube wall and tubesheet bore without undercut, porosity, or lack of penetration.

For titanium tube-to-tubesheet joints, the tubesheet material on the seawater side is typically solid titanium (SB 265 Gr.2) or steel/stainless steel with titanium cladding (SB 265 overlay). The seal weld is Ti-to-Ti, ensuring corrosion resistance at the most vulnerable location in the heat exchanger.

NDE Requirements for Ti Welds

The non-destructive examination (NDE) program for a VLGC titanium cargo heater is extensive:

Liquid penetrant testing (PT): Applied to all accessible titanium welds (butt welds, nozzle welds, tubesheet welds) to detect surface-breaking defects. PT on titanium requires non-chlorinated penetrant to prevent chloride contamination.

Radiographic testing (RT): Applied to all butt welds on pressure-containing titanium components. RT reveals internal defects (porosity, inclusions, lack of fusion) that are not detectable by surface methods.

Helium leak testing: Every tube-to-tubesheet seal weld is tested using helium as a tracer gas. The tube side is pressurized with helium, and a mass spectrometer detector on the shell side detects any helium that passes through a weld defect. The sensitivity of helium leak testing (typically 1 x 10⁻⁶ mbar-l/s) is orders of magnitude better than hydrostatic testing, which can only detect relatively large leaks. This test is the definitive quality verification for tube-to-tubesheet joints.

Ultrasonic testing (UT): Applied to shell welds and nozzle welds where radiography is impractical due to geometry. UT on titanium requires calibration blocks of the same material and thickness as the production component.

Positive Material Identification (PMI): All titanium components are verified for grade and composition using portable X-ray fluorescence (XRF) or optical emission spectroscopy (OES). This prevents material mix-ups — a particularly important control for titanium, where Grade 2 and Grade 5 appear identical visually but have very different mechanical properties and weldability.

QC Hold Points Specific to Marine Ti HEX

The quality control program for a VLGC titanium cargo heater includes mandatory hold points — stages in fabrication where work must stop until the classification society surveyor has inspected and released the operation. Typical hold points include:

1. Material inspection: Verification of MTRs against purchase order and design specification; visual inspection and dimensional check of titanium tubes, tubesheets, and shell plates
2. Tube bundle fit-up: Verification of tube insertion, tubesheet bore dimensions, and tube projection before expansion
3. Tube-to-tubesheet expansion: Verification of expansion parameters (pressure, wall reduction) on test specimens
4. Tube-to-tubesheet welding: Visual (color) inspection of seal welds; helium leak test
5. Shell welding: RT/UT of shell longitudinal and circumferential welds
6. Final assembly: Dimensional check of completed unit against approved drawings
7. Hydrostatic test: Pressurization to test pressure (typically 1.5x design pressure) with surveyor witness
8. Final survey: Verification of nameplate data, documentation completeness, and physical condition

These hold points are defined in the Inspection and Test Plan (ITP), which is approved by the classification society and the cargo system licensor (the customer or TGE Marine) before fabrication begins. Each hold point requires advance notification to the surveyor, and work cannot proceed until the surveyor has signed the hold point release.

600+ PQR Qualification Base

Welding procedure qualification is the foundation of quality in titanium fabrication. A Procedure Qualification Record (PQR) documents the results of a welding test that demonstrates the ability to produce sound welds under specific conditions (material, thickness, joint type, welding position, filler metal, shielding gas, heat input). Each PQR supports one or more Welding Procedure Specifications (WPS) that are used in production.

For a manufacturer serving the VLGC market across multiple classification societies, the PQR library must cover:

• Ti-to-Ti welds in multiple thicknesses and joint configurations
• Ti-to-dissimilar-metal welds (where required)
• Multiple welding positions (flat, horizontal, vertical, overhead)
• Multiple tube diameters and wall thicknesses
• Qualification per each classification society's supplementary requirements

Building a comprehensive PQR library requires years of investment. A manufacturer with 600+ PQRs — covering the full range of materials, joint types, and classification society requirements encountered in marine heat exchanger production — has a significant competitive advantage. Each PQR represents not only the direct cost of the qualification test but also the accumulated knowledge and process refinement that allows production welds to be executed consistently and efficiently.

Delivery Track Record

the customer Partnership: 59+ Cargo Heaters Across 20+ Vessel Hulls

Suzhou Lmart Energy Equipment Co., Ltd. has delivered 59+ the customer-specified titanium cargo heaters for VLGC and LPG/NH3 carrier programs in the 60K–93K class. This production volume, accumulated over multiple consecutive order batches, represents one of the most sustained manufacturing relationships in the marine titanium heat exchanger sector.

The the customer cargo heater program spans two material configurations:

Configuration A: SA240 304L Shell / SB 388 Gr.2 Tube

Standard specification: 3,660 kg, DN890mm, THK 8mm, Length 7,060mm

Vessel/Hull	Vessel Class	Shipyard	Classification	Ship Owner/Operator
HHI H2496/H2515	82K LPG/NH3	Hyundai Heavy Industries	ABS	—
HHI H2581	84K LPG	Hyundai Heavy Industries	ABS	—
HHI H2632 (KSS 84K)	84K LPG	Hyundai Heavy Industries	ABS+KR	KSS Line
HHI H2694 (KSS II 84K)	84K LPG	Hyundai Heavy Industries	ABS+KR	KSS Line
HHI H2705–H2724	84K LPG	Hyundai Heavy Industries	ABS	BW Gas (BW LPG)
HHI H2765	84K LPG	Hyundai Heavy Industries	ABS	Transpetrol
HHI H2708/H2709	60K LPG/NH3	Hyundai Heavy Industries	DNV	Solvang
Kawasaki 22N1709	VLGC	Kawasaki Heavy Industries	NK	—
Kawasaki 22N1421	VLGC	Kawasaki Heavy Industries	NK	—
Kawasaki 22N1730	VLGC	Kawasaki Heavy Industries	NK	—
Kawasaki 22N1725/22N1732	VLGC	Kawasaki Heavy Industries	NK	—
K-Line H1469	VLGC	—	ABS	K-Line
Anglo Eastern (Lavender Passage)	VLGC	—	ABS+NK	Anglo Eastern
GASWOLIA	VLGC	—	BV	—

Configuration B: SA516 Gr.70 Shell / SB 388 Gr.2 Tube

Specification	Classification	Units	Vessel Program
3,635 kg / DN890 / 5,901mm	NK	3+4+2+4+1 = 14 units	Various Kawasaki VLGC
4,000 kg / DN900 / 6,116mm	DNV	9+3 = 12 units	Pearl Petrochemical 93K
3,710 kg / DN890 / 5,911mm	NK	2 units	Kawasaki VLGC
3,950 kg / DN900 / 6,116mm	NK	2 units	Kawasaki VLGC

TGE Marine: 118+ Marine Ti Heat Exchangers

In parallel with the the customer cargo heater program, Lmart has manufactured 118+ TGE Marine-specified titanium heat exchangers covering a broader range of equipment types for gas carrier cargo handling systems:

LPG Condensers (30 units)

Specification	Classification	Units	Shipyard/Hull
3,780 kg / DN600mm	GL	8 units	STX B5044/B5046
3,780 kg / DN600mm	BV	6 units	STX B5048/B5060
3,780 kg / DN600mm	BV	2 units	Dingheng DH0006/DH0007
3,780 kg / DN600mm	DNV	2 units	Dingheng DH0008/DH0010
3,811 kg / DN660mm	DNV	12 units	Meyer Werft S665 series

LPG Heaters/Vaporizers (21 units)

Specification	Classification	Units	Shipyard/Hull
3,680 kg / DN570mm	GL	4 units	STX B5044/B5046
3,680 kg / DN570mm	BV	3 units	STX B5048
3,680 kg / DN570mm	BV	1 unit	Dingheng DH0006
3,680 kg / DN650mm	DNV	5 units	—
3,680 kg / DN650mm	LRS	7 units	—
3,680 kg / DN650mm	BV	1 unit	—

Ethylene Vaporizers (23 units)

Specification	Classification	Units	Shipyard/Hull
1,640 kg / DN400mm	BV	3 units	—
1,640 kg / DN400mm	GL	1 unit	—
1,640 kg / DN400mm	DNV	6 units	—
1,640 kg / DN400mm	LRS	5 units	—
1,640 kg / DN400mm	CCS	7 units	Jiangnan H2546
1,640 kg / DN400mm	DNV	1 unit	COSCO N588

Forcing Vaporizers (4 units)

Specification	Classification	Units	Shipyard/Hull
1,815 kg	BV	1 unit	Xinle XL-157
2,270 kg	ABS+CCS	1 unit	Jiangnan H2546
2,270 kg	CCS	1 unit	—
1,815 kg	BV	1 unit	—

Multipurpose Cargo Heater-Condensers (2 units)

Specification	Classification	Units	Shipyard/Hull
4,450 kg	BV	2 units	Othello H992 LPG/NH3/VCM carrier

Ethylene Condensers (20 units)

Specification	Classification	Units	Shipyard/Hull
6,085 kg	ABS	8 units	Hyundai MIPO 8163–8169
6,200 kg	LRS	12 units	Jiangnan H2567–H2570, S4031–S4036

Shipyard Coverage

The combined the customer and TGE Marine programs demonstrate delivery capability to virtually every major gas carrier shipyard in the world:

• Hyundai Heavy Industries (Ulsan, South Korea) — 30+ units
• Kawasaki Heavy Industries (Kobe/Sakaide, Japan) — 20+ units
• COSCO Shipping Heavy Industry (Dalian/Nantong, China)
• Jiangnan Shipyard (Shanghai, China)
• STX Offshore & Shipbuilding (Jinhae, South Korea)
• Meyer Werft (Papenburg, Germany)
• Dingheng Shipbuilding (Jiangsu, China)
• Hyundai MIPO Dockyard (Ulsan, South Korea)
• Xinle Shipbuilding (Jiangsu, China)

Ship Owner Fleet

The end-users of these cargo heaters include internationally recognized gas carrier operators:

• BW LPG (formerly BW Gas) — World's largest VLGC owner, Oslo-listed
• K-Line (Kawasaki Kisen Kaisha) — Major Japanese shipping group
• Solvang ASA — Norwegian gas carrier specialist
• Transpetrol — Independent gas carrier operator
• Anglo Eastern — Hong Kong-based ship management company
• Pearl Petrochemical — Middle East petrochemical logistics
• KSS Line — Korean Shipping Services

Vessel Classes Served

The delivery track record covers the full range of modern gas carrier sizes:

• 60K class: LPG/NH3 carriers (Solvang HHI H2708/H2709)
• 82K class: LPG/NH3 carriers (HHI H2496/H2515)
• 84K class: LPG carriers (HHI H2632, H2694, H2705–H2724, H2765)
• 88K class: VLGC (COSCO programs)
• 91K class: VLGC standard
• 93K class: VLGC/VLAC (Pearl Petrochemical, Hengli programs)
• 99K class: VLEC (Jiangnan programs)
• 100K class: VLEC (YZJ ACS programs)

Procurement Guide for Shipyards and Owners

Key Specs to Lock in the Purchase Order

For procurement engineers drafting purchase specifications for titanium cargo heaters, the following parameters must be explicitly defined to avoid ambiguity and change orders:

1. Shell material: SA240 304L (for ammonia capability) or SA516 Gr.70 (LPG only). This decision must be aligned with the cargo system license and the ship owner's intended cargo profile.

2. Tube material specification: SB 388 Gr.2 or SB 338 Gr.2 per the cargo system licensor's standard. Include the ASME specification and grade explicitly.

3. Classification society: Specify primary and secondary societies (e.g., ABS+KR) and provide the vessel's classification ID and hull number.

4. Design code: ASME Section VIII Division 1 is standard, with TEMA class for the heat exchanger type. Confirm whether the design is to be registered with the National Board.

5. Design conditions: Design pressure and temperature for both shell side and tube side, including coincident conditions (e.g., vacuum on shell side during hydrostatic test of tube side).

6. Nozzle schedule: Size, rating, facing, and orientation of all nozzles — any deviation from the licensor's standard drawing must be flagged early.

7. Paint and preservation: Marine paint system specification (typically shop primer + epoxy + topcoat for external surfaces, bare for titanium internals), and preservation requirements for shipment and storage.

8. Documentation format: Hard copy quantity, electronic format (PDF, native CAD), and language requirements.

Lead Time Expectations

Lead times for titanium cargo heaters are driven by three sequential activities:

• Titanium material procurement: 8–12 weeks for tubes, 10–14 weeks for tubesheets and plate. Titanium supply chains have limited surge capacity, and lead times can extend during periods of high demand.
• Fabrication: 10–14 weeks from material receipt to hydrostatic test completion, depending on the manufacturer's production load and the complexity of the classification survey schedule.
• Documentation and shipping: 2–4 weeks for final documentation compilation, packing, and transportation to the shipyard.

Total lead time from purchase order to delivery: 20–30 weeks is typical for standard configurations. First-article units (new design, new classification society, or new manufacturer qualification) may require 4–8 additional weeks for design review and approval.

FAT Witness Points

Factory Acceptance Testing (FAT) for titanium cargo heaters typically includes the following witness points for the ship owner's representative and/or the cargo system licensor's quality engineer:

1. Material verification: Review of MTRs and PMI results for all titanium and pressure-containing materials
2. Tube-to-tubesheet joint inspection: Visual (color) inspection of seal welds, review of helium leak test results
3. Hydrostatic test witness: Present during pressurization to test pressure, hold time, and depressurization
4. Dimensional verification: Confirmation of nozzle positions, overall dimensions, and nameplate data
5. Documentation review: Verification of the complete quality documentation package

Ship owners are encouraged to attend at least the hydrostatic test and final inspection, as these represent the last opportunity to identify any issues before the equipment leaves the manufacturer's facility.

Packaging and Shipping for Marine Equipment

Titanium cargo heaters are classified as oversized, heavy-lift cargo for transportation purposes. Proper packing and preservation is critical to prevent damage during transit:

• Nozzle protection: All nozzle openings sealed with blind flanges or welded caps, with desiccant inside to prevent internal condensation
• Surface protection: External surfaces wrapped in VCI (Vapor Corrosion Inhibitor) film or shrink-wrap; titanium surfaces require no additional corrosion protection but must be protected from mechanical damage
• Cradle mounting: Units secured in purpose-built steel cradles with vibration damping, designed for sea freight loading (roll-on/roll-off or lift-on/lift-off)
• Documentation: Packing list, weight certificate, dimensional certificate, and handling/lifting instructions enclosed in a weatherproof document pouch

For Korean and Japanese shipyard deliveries, sea freight from Chinese manufacturing facilities typically takes 3–7 days. For European yards (Meyer Werft, etc.), transit time is 30–40 days.

Beyond Cargo Heaters: Complete Marine Heat Exchanger Portfolio

A VLGC's cargo handling system requires a family of titanium heat exchangers beyond the cargo heaters themselves. Sourcing these as an integrated package from a single qualified manufacturer offers significant advantages in quality consistency, delivery coordination, and commercial efficiency.

LPG Condensers

The reliquefaction system on a VLGC uses compressors to compress boil-off gas and condensers to liquefy it using seawater cooling. The LPG condenser operates with the same seawater corrosion challenge as the cargo heater and requires titanium tubes for the same reasons. Typical LPG condensers in the TGE Marine program are DN600–660mm units weighing 3,780–3,811 kg — smaller than cargo heaters but manufactured to the same quality standards.

Ethylene Vaporizers

Very Large Ethylene Carriers (VLECs) require vaporizers to convert liquid ethylene to gas for discharge. These units are typically smaller (1,640 kg, DN400mm) but operate at even lower temperatures than LPG cargo heaters — liquid ethylene boils at -104 deg C. The cryogenic-to-seawater temperature gradient is extreme, making titanium tubes essential and thermal stress management critical.

Forcing Vaporizers

Forcing vaporizers generate gas pressure to push cargo from the tanks to the discharge manifold. They operate by evaporating a small quantity of liquid cargo using seawater heat. Typical units are 1,815–2,270 kg. While smaller than cargo heaters, they are equally critical to the cargo discharge operation.

CIP Cleaning Units for VLGC/VLEC

Clean-In-Place (CIP) units are an increasingly important component of modern VLGC/VLEC cargo handling systems. When a vessel switches between cargo grades (e.g., from propane to ammonia, or from ethylene to VCM), the entire cargo system must be cleaned to prevent cross-contamination. the customer VLGC/VLEC CIP units handle this cleaning operation.

Lmart's 2025 CIP order book reflects the growing demand for this equipment:

Program	Vessel Class	Units
COSCO 88K VLGC	88K	4 units
Hengli 93K VLAC	93K	3 units
Jiangnan PG/SJ VLEC 99K	99K	5 units
YZJ ACS VLEC 100K	100K	5 units
Iino Kaiun 93K VLGC	93K	1 unit

LNG Fuel Vaporizers and NG Fuel Heaters

As the marine industry transitions to LNG-fueled propulsion, vessels require fuel gas supply systems that include vaporizers and heaters to convert liquid LNG to gaseous natural gas at the temperature and pressure required by the engines. These units operate with seawater heating and require titanium tubes.

Reliquefaction System Heat Exchangers

Modern VLGC reliquefaction systems include multiple heat exchangers beyond the main condenser — intercoolers, aftercoolers, and subcoolers — many of which use seawater cooling. The complete reliquefaction heat exchanger package is often sourced alongside the cargo heaters.

LGE Propylene Compressor Packages

For VLEC programs, Lmart has also supplied LGE propylene compressor package components:

• 2024: 6 units (ABS) for VLEC H2747/H2748/H2777/H2778/H2779/H2780
• 2025: 7 units (ABS) for VLEC 99K H2823/H2825/H2827–H2831

These packages demonstrate the breadth of cargo system equipment capability beyond heat exchangers alone.

Industry Trends

VLGC/VLEC Newbuild Orderbook 2025–2028

The VLGC/VLEC newbuild market is in one of its strongest cycles. The orderbook as of early 2026 includes:

• VLGC (82K–93K): Approximately 60 vessels scheduled for delivery through 2028, with orders placed at HHI, DSME, Kawasaki, Jiangnan, COSCO, YZJ, and CMHI
• VLEC (85K–100K): Approximately 25 vessels on order, reflecting growing ethylene trade volumes and the opening of new ethylene export terminals in the US Gulf Coast
• VLAC (Very Large Ammonia Carriers): A new vessel class emerging from the ammonia-as-fuel and green ammonia trade, with early orders placed at multiple yards

Each of these vessels requires titanium heat exchangers for its cargo handling system. At an average of 3–4 titanium heat exchangers per vessel (cargo heaters alone), the market requires approximately 250–350 titanium heat exchanger units for delivery over the 2025–2028 period — not including condensers, vaporizers, and CIP units.

Ammonia as Fuel: New Cargo Heating Requirements

The IMO's greenhouse gas reduction strategy has positioned ammonia as a leading candidate for zero-carbon marine fuel. Several engine manufacturers (MAN Energy Solutions, WinGD) have announced ammonia-fueled engine development programs, and shipyards are offering ammonia-ready vessel designs.

For cargo heater manufacturers, ammonia-as-fuel has two implications:

1. Shell material shift to 304L: All new-generation VLGCs/VLACs with ammonia capability require stainless steel shells to resist ammonia corrosion. The proportion of 304L-shell cargo heaters in the orderbook has increased from approximately 40% to over 70% in recent years.

2. New equipment types: Ammonia fuel supply systems require dedicated heat exchangers for fuel vaporization and heating, adding to the total titanium heat exchanger content per vessel.

FuelEU Maritime and Emissions Impact on Equipment Choices

The European Union's FuelEU Maritime regulation, effective from January 2025, imposes greenhouse gas intensity targets on vessels calling at EU ports. This regulation accelerates the adoption of alternative fuels (LNG, ammonia, methanol) and increases the value of operational efficiency in all shipboard systems.

For cargo heating systems, the emissions impact is indirect but real. More efficient cargo heaters reduce the energy required for cargo discharge, which reduces the vessel's fuel consumption during port operations. Titanium's superior thermal performance (enabled by thinner tube walls and resistance to fouling) contributes to this efficiency advantage.

Additionally, the restriction on copper discharge to marine environments — while currently focused on anti-fouling coatings — may eventually extend to all shipboard copper-containing equipment in contact with seawater, further favoring titanium over Cu-Ni alternatives.

Lmart Capability

Suzhou Lmart Energy Equipment Co., Ltd. operates a dedicated pressure vessel and heat exchanger manufacturing facility in Suzhou, Jiangsu Province, China. The facility holds:

• ASME U stamps — Pressure vessels, power boilers, and repairs per ASME BPVC
• PED 2014/68/EU — European Pressure Equipment Directive compliance
• ISO 9001 — Quality management system
• Classification society approvals — DNV, ABS, BV, CCS, LR, NK, KR

The titanium fabrication capability includes GTAW welding with full argon shielding systems, hydraulic tube expansion equipment, helium leak testing stations, and a controlled-environment assembly area for titanium tube bundle fabrication. The PQR library exceeds 600 qualified procedures covering the full range of materials, joint types, and classification society requirements encountered in marine heat exchanger production.

With 59+ the customer titanium cargo heaters, 118+ TGE Marine titanium heat exchangers, and a broader portfolio spanning 150+ project references across marine, petrochemical, and industrial applications, Lmart has demonstrated sustained delivery capability in one of the most demanding segments of the pressure equipment industry.

The facility's location in the Yangtze River Delta — within logistics reach of Jiangnan Shipyard, COSCO Nantong, YZJ, and other major Chinese shipbuilding clusters — provides transportation advantages for the Chinese-built portion of the global VLGC orderbook. For international shipyards (HHI, Kawasaki, Meyer Werft), Lmart manages export logistics including multi-society classification coordination, international heavy-lift shipping, and multi-language documentation packages.

Conclusion

The VLGC fleet's adoption of titanium cargo heaters is not a trend or a material preference — it is an engineering conclusion driven by decades of operational experience with the consequences of using inferior materials in continuous seawater service. Ti Grade 2 is the only commercially available tube material that delivers genuine immunity to chloride pitting, crevice corrosion, erosion-corrosion, and MIC across the full range of temperatures and flow conditions that a VLGC cargo heater encounters over its 25-year service life.

The economic case for titanium is equally decisive. While the initial tube cost is 3–4 times that of stainless steel alternatives, the total lifecycle cost — accounting for zero retubing, zero corrosion-related downtime, zero cargo contamination risk, and reduced structural weight — makes titanium the lowest-cost option when evaluated over the vessel's operating life.

For shipyards and ship owners specifying titanium cargo heaters, the critical procurement considerations are manufacturer qualification (classification society approvals, licensor audit history), titanium fabrication capability (welding, NDE, clean assembly), delivery track record (units delivered, shipyards served, owner fleet), and full package capability (cargo heaters, condensers, vaporizers, CIP units from a single source).

These are the parameters that define supplier capability in this market. They are also the parameters that a track record of 59+ the customer cargo heaters and 118+ TGE Marine heat exchangers is designed to demonstrate.

For detailed technical specifications or to discuss requirements for your VLGC/VLEC program, contact Lmart's marine heat exchanger team.

Further Reading

• Tube Material Selection: When Titanium or Duplex Makes Sense — Engineering guidance on choosing between Ti Grade 2, duplex, and super duplex for heat exchanger tubes in corrosive service.
• Titanium Heat Exchangers — Lmart's titanium heat exchanger product page with specifications and application overview.
• the customer 91K Reliquefaction & Booster Pump Skids — Related VLGC cargo system equipment manufactured by Lmart.
• the customer VLGC/VLEC CIP Units — Clean-In-Place units for VLGC cargo system cleaning between cargo grades.
• How Modular Skid Packages Help EPC Projects Control Delivery Risk — Procurement strategy for managing schedule risk in multi-equipment marine packages.
• Fixed Tubesheet vs Floating Head vs U-Tube — Comparative guide to shell-and-tube heat exchanger configurations.
• Packing & Preservation for Overseas Shipment — Logistics guidance for marine equipment export.
• Projects & References (150+ Cases) — Lmart's full project portfolio across marine, petrochemical, and industrial applications.