LNG and LPG System Technical Services

LNG and LPG system technical services cover the mechanical, structural, and overhaul scope on marine gas systems - cargo compressor overhaul, deepwell pump rebuild, cryogenic valve service, reliquefaction plant maintenance, tank inspection and leak testing, vacuum insulation repair, PV valve overhaul, and the broader machinery service work that keeps LPG carriers, LNG carriers, and LNG/LPG-fueled vessels operating between dry-dock periods. These services sit within the broader marine technical services scope and handle the mechanical side of equipment delivered by gas system manufacturers.

The procurement decision spans OEM service authorisation (Wartsila Gas Solutions, Cryostar, MAN PrimeServ, Burckhardt Service, Ebara, Nikkiso, Svanehoj/Alfa Laval), riding team capability for at-sea or anchorage service, class society survey witnessing, and the spare parts coordination that pairs service labor with parts availability. Picking the right LNG and LPG technical services partner means matching the provider to the installed OEM equipment, the IGC Code or IGF Code compliance scope, and the regional service presence at major LPG and LNG ports.

What LNG and LPG Technical Services Cover

The mechanical service scope on marine LPG and LNG systems breaks across several recurring work types:

• Cargo compressor overhaul - multi-stage piston compressors (Burckhardt, Sauer, Cryostar) and centrifugal compressors (Wartsila, MAN ES) require periodic top-end and full overhaul. Typical interval: top-end 12,000-20,000 operating hours; full overhaul 30,000-40,000 hours.
• Deepwell pump rebuild - cryogenic cargo pump mechanical seal replacement, bearing renewal, motor inspection, impeller renewal. Ebara, Nikkiso, Svanehoj (Alfa Laval), Frank Mohn (Framo), MAN ES service.
• Reliquefaction plant service - mixed refrigerant or nitrogen-cycle reliquefaction plants on LNG carriers; direct-cycle plants on LPG carriers. Compressor service, heat exchanger cleaning, refrigerant charge maintenance.
• Cryogenic valve overhaul - cargo isolation valves, manifold valves, PV valves. Bestobell, Velan, Cryospec, Herose dominate the cryogenic valve service market.
• Tank inspection and leak testing - UT (ultrasonic) thickness measurement on tank shell, weld inspection, vacuum testing on insulation, helium leak detection on membrane systems and cryogenic piping.
• Vacuum insulation repair - on vacuum-insulated tanks (some Type C LNG fuel tanks), vacuum loss requires re-evacuation; insulation barrier repair where damage detected.
• PV valve overhaul - tank pressure-vacuum protection valves overhaul on 5-year cycle; certified set-pressure testing required.
• Cargo hose inspection and renewal - flexible cargo hoses pressure-tested annually; renewal at end-of-life or visible damage.
• ME-GI, ME-LGIP, and X-DF engine fuel system service - on LNG and LPG-fueled vessels, the engine fuel system (fuel injectors on ME-GI, port admission valves on X-DF, fuel rail on ME-LGIP) requires dedicated overhaul aligned with engine OEM service intervals.

Cargo Compressor Overhaul Scope

Cargo compressors carry the heaviest mechanical service workload across LPG and LNG cargo systems:

• Top-end overhaul - piston rings, valve plates and springs, gaskets, cylinder head inspection. Typically 12,000-20,000 operating hours on piston compressors; the work fits within a routine port call or anchorage service window.
• Full overhaul - complete teardown including main bearings, crankshaft inspection, cylinder liner renewal where required, complete valve set replacement. Typically 30,000-50,000 hours; often coordinated with dry-dock period.
• Centrifugal BOG compressor service - on LNG carriers using centrifugal BOG compressors, dry gas seal replacement at 40,000-60,000 hours; rotor balancing during major overhaul.
• Crankshaft and connecting rod inspection - NDT examination during full overhaul; crankshaft journal machining where wear exceeds OEM tolerance.
• Motor overhaul integration - cargo compressor drive motor rewind or bearing renewal aligned with mechanical overhaul.

Deepwell Pump and Reliquefaction Service

Cryogenic pump and reliquefaction plant service requires specialist capability:

• Cryogenic mechanical seal replacement - the highest-frequency wear item on cargo deepwell pumps. Typically 5,000-12,000 operating hours; some specialist providers offer offshore replacement without dry-dock.
• Pump rotor renewal - impeller and shaft replacement when wear or damage requires; longer downtime than seal replacement.
• Submerged motor service - on submerged-motor designs (some Ebara and Nikkiso pumps), motor rewind requires return to OEM service centre.
• Reliquefaction plant compressor service - the central compressor in mixed-refrigerant or nitrogen-cycle reliquefaction plants follows standard centrifugal compressor service patterns.
• Brazed aluminium heat exchanger cleaning - reliquefaction plant heat exchangers accumulate residue over operating life; cleaning and pressure testing on periodic schedule.
• Refrigerant charge maintenance - mixed refrigerant composition checking, refrigerant top-up, refrigerant analysis on operational schedule.

Tank Inspection, Leak Testing, and Insulation Repair

LPG and LNG cargo tank integrity is the safety-critical foundation of every voyage. Periodic inspection and repair work:

• UT thickness measurement - ultrasonic thickness testing on tank shell, internal stiffeners, and pipe penetrations. Performed at periodic class survey and special survey.
• Weld inspection - magnetic particle, dye penetrant, and radiographic inspection on critical welds; UT phased array on accessible welds.
• Vacuum testing on insulation - on vacuum-insulated tanks (Type C LNG fuel tanks, some specialty installations), vacuum integrity checking on operational schedule.
• Helium leak detection - the most sensitive test method for membrane systems (GTT Mark III, NO96) and cryogenic piping. Periodic survey under licensor procedures.
• Membrane patch repair - on GTT membrane systems, localised damage repair requires licensor-approved technique and materials. GTT-authorised contractors perform the work.
• Polyurethane insulation repair - on Moss spherical tanks and Type C polyurethane-insulated tanks, foam damage repair to maintain thermal performance.
• Secondary barrier inspection - on Type A (LPG) and Type B (some LNG) containment, the secondary barrier integrity check follows class society survey scope.

Cryogenic Valve and PV Valve Overhaul

Cargo system valves receive significant service attention because of high cycle count and safety-critical function:

• Cryogenic ball valve overhaul - seat replacement (Devlon, PTFE, metal), stem packing renewal, actuator service. Performed on 5-10 year intervals depending on duty.
• Globe valve trim renewal - extended-bonnet globe valves on cargo isolation duty; trim renewal at planned overhaul intervals.
• PV valve overhaul - tank pressure-vacuum protection valves require certified set-pressure testing on 5-year interval; full overhaul typical.
• Manifold butterfly valve service - large-bore butterfly valves on cargo manifold; seat and actuator service.
• Cargo hose inspection - flexible cargo hose hydrostatic testing on annual interval; renewal at end of service life or visible damage.
• Class society witnessed work - PV valve set-pressure testing and certain cargo isolation valve work require class society witnessing for certificate acceptance.

Choosing an LNG and LPG Technical Services Provider

Picking among LNG and LPG technical services providers requires evaluating OEM authorisation, riding team capability, and class society approval:

• OEM service authorisation - Wartsila Gas Solutions Service, MAN PrimeServ (engines and gas systems), Cryostar Service, Burckhardt Compression Service, Ebara Service, Nikkiso (Lewa Nikkiso) Service, Svanehoj Service (Alfa Laval). The right provider holds OEM authorisation matched to installed equipment.
• Class society approval - IGC Code work and IGF Code work require class society approved service providers. DNV, ABS, Lloyd's Register, Bureau Veritas, RINA, ClassNK, KR, CCS approval matched to vessel registry.
• Riding team capability - cargo compressor overhauls and pump rebuilds often require multi-day onboard work; some service events span entire dry-dock periods. Confirm provider capacity for extended riding team.
• Cryogenic certification - cryogenic service requires specific welding qualifications, NDT procedures, and material handling capability. Confirm certification documentation.
• GTT-authorised membrane work - any membrane patch repair or insulation work on GTT Mark III or NO96 systems requires GTT-licensed contractor. This is a small list - verify authorisation.
• Spare parts coordination - service work is only as fast as the parts supply. Provider should coordinate LNG system spare parts delivery against the planned service window.
• Regional service network - LPG and LNG hubs (Houston, Yanbu, Mongstad, Singapore, Qatar, Yokohama, Australia) typically have authorised provider presence; smaller ports may require traveling teams.

Need electrical, instrumentation, or cargo control system work instead (cargo control commissioning, gas detection calibration, ESD testing, custody transfer metrology)? See LPG and LNG automation services for that scope.

Frequently Asked Questions

What is included in LNG and LPG technical services?

LNG and LPG technical services include cargo compressor overhaul (top-end and full), deepwell cargo pump rebuild and cryogenic mechanical seal replacement, reliquefaction plant service, cryogenic valve and PV valve overhaul, cargo tank UT thickness measurement and weld inspection, vacuum insulation repair, helium leak detection on membrane systems, cargo hose inspection and renewal, and ME-GI, ME-LGIP, X-DF engine fuel system service on LNG/LPG-fueled vessels. The work spans routine port-call service to extended dry-dock overhaul.

What service intervals apply to cargo compressors on LPG and LNG carriers?

Cargo compressor service intervals: top-end overhaul (piston rings, valve plates, gaskets) typically every 12,000-20,000 operating hours; full overhaul (bearings, crankshaft inspection, cylinder liners if needed) every 30,000-50,000 hours; dry gas seal replacement on centrifugal BOG compressors every 40,000-60,000 hours. Operating hours accumulate during loading, voyage reliquefaction, and discharge - operators on long voyages with active reliquefaction see faster hour accumulation than vessels using BOG-as-fuel philosophy.

Who is authorised to work on GTT membrane systems?

GTT (Gaztransport & Technigaz) licenses Mark III and NO96 membrane technology; any structural work on these containment systems requires GTT-licensed contractors. The licensed list includes the original ship licensor (typically a major shipyard - DSME, Hyundai Heavy Industries, Samsung Heavy Industries, Hudong-Zhonghua, Jiangnan), GTT-authorised repair contractors, and GTT itself for major intervention. Class societies require licensor authorisation evidence on every membrane work event; non-licensed work is not accepted.

How is cargo tank thickness measurement performed on LPG and LNG vessels?

Cargo tank thickness measurement uses ultrasonic testing (UT) under class society procedure. Service technicians take multiple readings across tank shell, stiffeners, bulkheads, and pipe penetrations using calibrated UT equipment. Phased array UT is increasingly used for higher resolution and weld inspection. Reading patterns and acceptance criteria follow IACS UR Z10 (Hull Inspection and Maintenance) and vessel-specific class society procedures. Periodic survey readings are compared against newbuild baseline to track corrosion and wear rates. Tank entry for UT work requires gas-free atmosphere and confined space entry permit.