8 Self-Designed BOG Compression Units for PIL’s 14,000 TEU LNG Dual-Fuel Container Ships: Turnkey Compressor Package Design, Manufacturing, and After-Sales by Lmart — ABS-Classed, Jiangnan Shipyard

Lmart designed, manufactured, and provides after-sales service for 8 BOG (Boil-Off Gas) compression units installed on PIL’s fleet of four 14,000 TEU LNG dual-fuel container ships — Hull H2785, H2786, H2787, and H2788 — built at Jiangnan Shipyard in Shanghai. Unlike OEM-integrated skids where a third-party compressor is mounted onto a fabricated frame, these units are Lmart’s own product: process design, mechanical design, structural design, procurement, fabrication, assembly, testing, commissioning support, and lifetime after-sales are all within Lmart’s scope.

Ship Owner	PIL (Pacific International Lines) — Singapore-headquartered, one of the largest container shipping lines in Asia-Pacific
Ship Type	14,000 TEU LNG dual-fuel container ships
Equipment	BOG Compression Unit × 8 (2 per ship × 4 ships) — Lmart self-designed compressor package
Hull Numbers	H2785, H2786, H2787, H2788
Shipyard	Jiangnan Shipyard (Group) Co., Ltd. — Shanghai
Classification	ABS (American Bureau of Shipping)
Scope	Turnkey: process design, mechanical design, structural design, procurement, fabrication, assembly, testing, commissioning support, after-sales service
Year	2023

Customer Background and Industry Context

Pacific International Lines (PIL), founded in 1967 and headquartered in Singapore, is one of the largest container shipping companies in the Asia-Pacific region. PIL operates a fleet of container vessels serving more than 500 locations in over 90 countries, with particular strength in intra-Asia, Africa, Middle East, and Oceania trade routes. As global shipping regulations tighten under IMO’s GHG strategy and the CII (Carbon Intensity Indicator) framework, PIL committed to a fleet renewal program centered on LNG dual-fuel propulsion — ordering a series of 14,000 TEU container ships from Jiangnan Shipyard to replace older tonnage and reduce the fleet’s carbon footprint.

The 14,000 TEU LNG dual-fuel container ship represents the mainstream workhorse of modern container fleets. These vessels carry LNG as primary fuel in membrane-type or Type C fuel tanks, with conventional fuel oil as backup. When operating on LNG, the ship’s dual-fuel main engine (typically MAN B&W ME-GI or WinGD X-DF type) requires compressed natural gas supplied at specific pressure and temperature conditions. The BOG compression unit is the system that makes this possible — it captures the boil-off gas that naturally evaporates from the LNG fuel tank due to heat ingress, compresses it from near-atmospheric tank pressure to the injection pressure required by the main engine (typically 12–17 bar for low-pressure dual-fuel engines, or up to 300 bar for high-pressure ME-GI engines), and delivers it as a reliable fuel supply.

Without a functioning BOG compression unit, the ship cannot operate on LNG and must revert entirely to conventional fuel oil — negating the environmental and economic benefits of the dual-fuel investment. This makes the BOG compressor a mission-critical piece of equipment: its reliability directly determines whether the vessel achieves its emissions reduction targets and whether the ship owner realizes the fuel cost savings that justified the significant premium paid for LNG dual-fuel capability. For a four-ship fleet program like PIL’s, the cumulative value at stake is substantial, and the selection of the BOG compression unit supplier is a decision with long-term operational consequences.

Challenges and Engineering Requirements

Process Design for Variable BOG Conditions

Unlike a shore-based compressor operating at steady-state conditions, a marine BOG compression unit must handle widely variable gas flow rates and compositions. The boil-off rate from the LNG fuel tank depends on ambient temperature, sea state (sloshing increases heat transfer), tank fill level, and the LNG composition loaded at different bunkering ports. During bunkering operations, flash gas generation can cause sudden spikes in BOG volume. During low-speed maneuvering in port, engine fuel demand drops while BOG generation continues. The compressor package must manage all of these transient conditions without tripping — requiring anti-surge protection, capacity modulation (typically stepless or multi-step unloading), and coordination with the ship’s gas management system (GMS) via automated control logic.

ABS Classification for Marine Gas Fuel Systems

BOG compression units on LNG fuel gas supply systems fall under ABS Rules for Building and Classing Marine Vessels, specifically the requirements for gas fueled ships referencing the IMO IGF Code (International Code of Safety for Ships Using Gases or Other Low-Flashpoint Fuels). This imposes stringent requirements on gas-tight integrity, material selection for cryogenic and methane service, safety instrumented functions (emergency shutdown, gas detection, ventilation interlocks), hazardous area classification (Zone 1 / Zone 2 per IEC 60079), and explosion-proof equipment ratings. Every aspect of the compression unit — from pressure-containing components to electrical enclosures to the control system architecture — must comply with these rules and pass ABS plan approval and survey.

Turnkey Design Responsibility vs. OEM Integration

When a compressor OEM like Burckhardt or Sauer supplies a BOG compressor, the OEM retains design authority over the compressor itself, and the skid fabricator builds around it. In this PIL project, Lmart holds design authority over the entire compression unit — the compressor selection and specification, process design (P&ID, heat and mass balance, safety analysis), mechanical design of all pressure-containing components, structural design of the skid, piping design, instrumentation and control system design, and the complete documentation package submitted to ABS for plan approval. This is a fundamentally different scope: Lmart is not executing someone else’s design, but originating the design and taking full engineering responsibility for the unit’s performance, safety, and reliability over its service life.

Series Production for a Four-Ship Fleet Program

Eight compression units across four ships demand production repeatability: identical process performance, interchangeable spare parts, consistent documentation, and delivery schedules aligned with the shipyard’s hull construction milestones. Manufacturing variability between the first and eighth unit would create problems for the ship owner’s crew training and spare parts inventory, and for the shipyard’s installation and commissioning planning. Lmart’s production system must ensure that Unit 8 is functionally identical to Unit 1 — while incorporating any design improvements identified during the production campaign without creating configuration divergence across the fleet.

Commissioning Support and After-Sales Service Planning

Designing the compression unit is only the beginning — Lmart’s scope extends through commissioning at the shipyard and into the operational life of the equipment. During sea trials, Lmart’s commissioning engineers must be on board to supervise initial start-up, verify operating parameters against design specifications, tune control system settings to actual operating conditions, and train the ship’s crew on normal operation, alarm response, and basic maintenance procedures. The after-sales commitment requires Lmart to maintain a spare parts inventory, provide technical consultation on operational issues, and be available for on-site service at the ship’s location — a commitment that requires dedicated service engineering resources and a parts logistics system capable of shipping to ports worldwide.

Why PIL Selected Lmart

Turnkey compressor package design capability. Lmart’s ability to provide a fully self-designed BOG compression unit — from P&ID to commissioned equipment — was the primary differentiator. Rather than coordinating between a compressor OEM, a skid fabricator, a controls integrator, and a piping designer, PIL and Jiangnan Shipyard deal with a single entity that owns the entire design and takes undivided responsibility for performance. This eliminates the interface risks and finger-pointing that can arise when multiple suppliers share responsibility for a complex system, and it simplifies the warranty and after-sales support structure.

After-sales service commitment. A BOG compression unit on a container ship operates for 20–25 years, and its maintenance needs evolve over time — wearing parts replacement, performance optimization, troubleshooting, and eventual overhaul. Lmart’s commitment to lifetime after-sales support, backed by complete design documentation and in-house knowledge of every component, means that PIL has a direct line to the original designer when operational issues arise. This is particularly valuable for a Singapore-based ship owner operating on routes that regularly call at Chinese ports, where Lmart’s service engineers are locally available.

Series production economics for fleet programs. Ordering all 8 units from a single supplier who controls the entire design-to-delivery chain yields significant cost advantages compared to multi-vendor procurement. Material purchasing in batch quantities, tooling amortization across 8 units, standardized engineering documentation, and streamlined ABS approval (approved design for Unit 1 applies to Units 2–8 with minor revision) all contribute to a lower per-unit cost and shorter delivery lead time for the later ships in the series.

Proximity to Jiangnan Shipyard and established relationship. Lmart has delivered multiple equipment packages to Jiangnan Shipyard across different product categories — heat exchangers, process vessels, and compressor packages. This established working relationship means that interface dimensions, documentation formats, delivery logistics, and on-site coordination procedures are already aligned. Lmart’s Zhangjiagang facility is approximately 150 km from Jiangnan’s Changxing Island yard in Shanghai, enabling same-day delivery by flatbed truck and rapid response for on-site support during installation and commissioning.

Commissioning and after-sales as part of the package. Most compressor skid fabricators deliver the equipment and their responsibility ends at the shipyard gate. Lmart’s scope extends through on-board commissioning during sea trials and into the operational life of the equipment. For PIL — a ship owner operating on routes that regularly call at Chinese and Southeast Asian ports — having the original designer and manufacturer available for rapid-response technical support is a significant operational advantage. Lmart’s after-sales capability includes spare parts supply from stock, remote diagnostic support via data link, and on-site service engineering at the vessel’s location when required.

Engineering and Manufacturing Solution

Each BOG compression unit is a self-contained compressor package designed to receive low-pressure boil-off gas from the LNG fuel tank and deliver compressed natural gas at the pressure and quality required by the dual-fuel main engine’s fuel gas supply system. The unit is engineered as a complete modular assembly — ready for installation on the ship’s foundation and connection to the ship’s piping interfaces with minimal on-board work.

Process Design

Lmart’s process engineering team developed the compression cycle, including stage count, pressure ratios per stage, intercooling requirements, and capacity control strategy. The P&ID defines every process connection, instrument, valve, and safety device on the unit. A HAZOP study was conducted on the P&ID in collaboration with the shipyard’s and ship owner’s technical teams, with results documented and incorporated into the design before ABS plan submission. Key process parameters include:

• Suction conditions: near-atmospheric pressure (slightly above tank relief valve set point), temperature approximately −130 to −110 °C depending on tank conditions
• Discharge conditions: pressure matched to engine fuel gas supply requirements, with aftercooling to meet engine inlet temperature specification
• Capacity modulation: stepless or multi-step unloading to match variable BOG generation rate to engine fuel demand
• Anti-surge protection: automated recycle system to prevent compressor surge during rapid load changes
• Safety functions: ESD (Emergency Shutdown) with gas-freeing and inert gas purge capability, integrated with ship’s safety system

Mechanical and Structural Design

All pressure-containing components — compressor cylinders, interstage vessels, pulsation dampeners, aftercoolers, piping, and safety valves — are designed in accordance with applicable pressure equipment codes (ASME Section VIII, ASME B31.3, and ABS Rules). The skid base frame is designed per marine structural requirements, with FEA analysis covering combined static loads, compressor dynamic forces, and ship motion accelerations (roll, pitch, heave per ABS criteria). Material selection for gas-wetted components follows IGF Code requirements for methane service, with Charpy impact testing at the minimum design temperature to verify toughness.

The structural skid frame serves as the foundation for the entire compression unit. Unlike static onshore installations, marine compressor packages must withstand the continuous dynamic loading of a ship at sea — including combined roll, pitch, and heave accelerations that impose lateral and vertical forces on every component and pipe connection. Lmart’s structural engineers model these load cases using classification-society-specified acceleration values for the ship’s engine room location, combined with the reciprocating inertia forces generated by the compressor itself. Foundation rails are precision-machined to ≤ 0.1 mm/m flatness to ensure accurate compressor-to-driver alignment. Chock pad locations and hold-down bolt patterns are coordinated with Jiangnan Shipyard’s foundation drawings to ensure proper interface upon installation.

Pulsation analysis per API 618 methodology is performed during the engineering phase to size pulsation dampeners and define piping geometry that minimizes acoustic resonance. For reciprocating compressors handling methane, pressure pulsations in the suction and discharge piping can cause fatigue failure of pipe connections, instrument fittings, and small-bore branches if not properly managed. The pulsation study output directly informs the pipe spool dimensions, dampener bottle sizing, and pipe support locations — making it one of the most critical engineering activities in the design phase.

Control and Instrumentation System

Each unit includes a local control panel (LCP) with a PLC-based control system managing compressor start/stop sequencing, capacity modulation, anti-surge control, lubricating oil system monitoring, cooling system control, and all safety instrumented functions. The LCP interfaces with the ship’s gas management system (GMS) and integrated automation system (IAS) via hardwired signals and serial communication. All field instruments in the gas-containing zone are certified for Zone 1 hazardous area classification per IEC 60079, and the control system architecture follows SIL (Safety Integrity Level) requirements per IEC 61508/61511 for the ESD functions.

The control logic is developed in-house by Lmart’s automation engineering team — another critical element of the self-design scope. This includes the compressor capacity control algorithm (matching compression output to variable BOG generation and engine fuel demand), the anti-surge protection logic (detecting approach to the surge line and activating the recycle valve before the compressor enters surge), and the ESD sequence logic (gas isolation, depressurization, and inert gas purge in the correct sequence with the correct timing). Factory acceptance testing (FAT) of the control system is performed with simulated process signals to verify all control loops, alarm thresholds, ESD sequences, and communication interfaces before the panel is shipped to the assembly floor for integration with the mechanical package.

Piping and Gas-Tight Integrity

Gas-service piping is fabricated from materials certified for low-temperature methane service, with 100% radiographic examination of all butt welds per ABS Rules. Pipe stress analysis per ASME B31.3 verifies that thermal expansion, pressure loads, weight, and dynamic forces from compressor operation and ship motion do not exceed allowable pipe stresses or nozzle loads on the compressor and vessel connections. After hydrostatic testing at 1.5× design pressure, each gas circuit undergoes pneumatic leak testing with nitrogen at 1.1× design pressure, verified by soap-bubble inspection and pressure-decay monitoring. Internal cleanliness is maintained per the compressor manufacturer’s specification — all piping is flushed, dried, and sealed with inert gas purge prior to delivery.

Auxiliary Systems Integration

Each compression unit integrates multiple auxiliary systems into a single skid-mounted package:

• Lubricating oil system: oil tank, pumps (main + standby), filters, cooler, instruments, and piping — pre-filled, tested, and ready for operation
• Cooling system: intercooler and aftercooler heat exchangers with cooling water circuit, temperature control valves, and associated piping
• Inert gas purge system: nitrogen supply connections and automated purge valves for gas-freeing the compressor and piping before maintenance or after ESD
• Vent and drain system: gas vent connections routed to the ship’s vent mast, liquid drain connections to the appropriate collection system
• Structural accessories: walkways, access platforms, maintenance access points, and lifting provisions for major component removal

Quality Control and Project Execution

The 8-unit production campaign was managed under a project-specific quality plan approved by ABS, with an Inspection and Test Plan (ITP) defining hold points, witness points, and review points for every critical manufacturing and testing milestone. ABS surveyors were present at the Lmart facility for all hold-point activities. As the design authority, Lmart bears responsibility not only for fabrication quality but also for design verification — confirming through testing and inspection that the as-built equipment matches the approved design intent and will perform safely and reliably in service.

Key QC Milestones (per unit)

• Design review gate: ABS plan approval of P&ID, general arrangement, structural drawings, pipe stress analysis, HAZOP close-out, and ESD cause-and-effect matrix
• Material receiving inspection: verification of mill certificates, material identification (PMI by XRF), dimensional checks, and Charpy impact test reports for low-temperature materials
• Skid frame fit-up and welding: NDT of structural welds per approved WPS, dimensional survey of foundation machined surfaces (≤ 0.1 mm/m flatness)
• Piping NDE: 100% RT of all gas-service butt welds, PT/MT of socket welds and structural welds per ITP requirements
• Compressor alignment: laser alignment verification of compressor-to-driver alignment on machined skid foundation, with documented shimming records
• Hydrostatic test: each pressure circuit tested at 1.5× design pressure with ABS surveyor witness — hold point
• Pneumatic leak test: nitrogen leak test at 1.1× design pressure with soap-bubble inspection of all joints
• Functional test: control system I/O check, ESD sequence verification, instrument calibration, motor solo run (where applicable)
• Final inspection: dimensional survey, weight measurement, surface treatment verification, preservation for transport, and ABS final endorsement

Series Production Management

To maximize production efficiency while meeting the staggered delivery schedule for Hull H2785 through H2788, Lmart organized the 8 units in two production waves of 4 units each. The first wave covered the two units for H2785 and two for H2786; the second wave covered H2787 and H2788. This batch approach enabled:

• Consolidated material procurement with volume pricing for pipe, fittings, valves, and instruments
• Standardized fabrication jigs and assembly fixtures reused across all 8 units
• Lessons-learned from the first wave incorporated into the second wave (e.g., piping routing optimizations, cable tray bracket improvements) without creating configuration divergence — all changes formally tracked via engineering change notices approved by ABS
• Staggered ABS survey scheduling to distribute surveyor workload and avoid bottlenecks at hold points

Documentation Package

As the design authority for the compression unit, Lmart is responsible for the complete documentation package — a substantially larger scope than a fabrication-only assignment. The documentation submitted to ABS and delivered to the shipyard and ship owner includes:

• Process documentation: P&ID, heat and mass balance, utility consumption summary, process description, HAZOP report and close-out
• Mechanical documentation: design calculations, general arrangement drawings, assembly drawings, piping isometrics, structural drawings, pipe stress analysis reports
• Safety documentation: ESD cause-and-effect matrix, hazardous area classification drawings, SIL assessment report, safety valve sizing calculations
• Quality documentation: ITP, material certificates with traceability matrix, WPS/PQR/WPQ records, NDE reports, dimensional reports, hydrostatic and pneumatic test records
• Operation and maintenance documentation: O&M manual, spare parts list with recommended quantities, lubrication schedule, alignment procedure, troubleshooting guide

Each documentation package runs to several hundred pages per unit. For the 8-unit fleet program, Lmart maintains a master document set with unit-specific deviations tracked via a configuration management system — ensuring that PIL receives accurate as-built documentation for each individual unit while maintaining fleet-wide consistency.

Results and Business Impact

All 8 BOG compression units were delivered to Jiangnan Shipyard on schedule, meeting the construction milestones for PIL’s four-ship fleet program. ABS plan approval and survey endorsement were achieved for all units without major non-conformances, confirming that Lmart’s self-designed compressor package meets the safety and performance standards required under the IGF Code and ABS Rules for gas-fueled ships.

This project establishes Lmart as a compressor package designer and manufacturer — not merely a skid fabricator assembling third-party OEM equipment. The distinction is commercially significant: as the design authority, Lmart controls the intellectual property, defines the spare parts bill of materials, and provides after-sales technical support directly to the ship owner without dependency on an external OEM. For PIL, this means a single point of contact for any operational issue over the 20–25 year service life of the equipment — from routine spare parts supply to performance optimization to major overhaul planning.

From a manufacturing perspective, the 8-unit campaign validated Lmart’s production planning and quality management systems for series production of complex compressor packages. Workshop scheduling, material batch procurement, jig and fixture reuse, and coordinated ABS survey scheduling all contributed to a per-unit cost and lead time that improved progressively from Unit 1 through Unit 8 — the natural learning curve benefit of series production, captured and documented for application to future fleet programs.

The successful delivery of 8 identical units for a fleet program demonstrates Lmart’s capacity for series production of complex compressor packages under classification society oversight. In a market where LNG dual-fuel newbuilding orders continue to grow — driven by IMO decarbonization targets and the expanding LNG bunkering infrastructure — this reference positions Lmart to compete for similar fleet-scale BOG compressor contracts from other container lines, bulk carriers, and tanker operators investing in LNG dual-fuel tonnage. The after-sales dimension adds recurring revenue potential: each delivered unit represents a long-term service relationship with the ship owner, including scheduled maintenance support, spare parts supply, and performance monitoring advisory services throughout the vessel’s operational life.

Customer Voice

PIL’s decision to entrust a critical fuel gas system component to Lmart’s own design — rather than specifying an established European or Japanese compressor OEM — reflects the confidence built through prior equipment deliveries to Jiangnan Shipyard and the technical depth demonstrated during the design review and HAZOP process. The repeat order structure (2 units per ship × 4 ships) further underscores the ship owner’s satisfaction with the design, manufacturing quality, and commercial terms.

“Having the compressor package designer and manufacturer as a single entity simplified our technical review process and gives us confidence in long-term after-sales support. The consistency across all eight units was exactly what we needed for a fleet program.”

— PIL fleet engineering (paraphrased from project review meetings)

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