Wärtsilä cargo handling system for semi refrigerated gas carriers

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A leading supplier of complete cargo handling systems for gas tankers

Wärtsilä is the leading supplier of complete cargo handling systems for gas tankers. In the semi-refrigerated segment, Wärtsilä offers a state-of-the-art system which includes the design and delivery of C-type cargo tanks of either cylindrical- or bilobe design.

Our field proven system is designed to ensure safe, dependable, efficient, operator and environmentally friendly operations. Our aim is to reduce your operating costs, contribute to an improved vessel EEDI and reduction of overall GHG emissions to the atmosphere. 

The system is available to the full spectrum of semi-refrigerated carriers, ranging from 4 000 cbm to 30 000 cbm cargo capacities, and is designed to handle LPGs, ammonia, VCM and certain chemicals., Our system is prepared for integration with Wärtsilä’s gas fuel supply system, which further reduces overall GHG emissions from the vessel significantly.
Our delivery includes system engineering, tank design, material supply, supervision, and commissioning aid.

    Technical data

    Primary cargoes on semi-refrigerated gas carriers are LPGs, including C-propane with various ethane content, as well as propylene, ammonia, butane, DME, butadiene, VCM and certain chemicals.

    Our cargo handling system provides shipowners and charterers a safe and flexible solution with the highest degree of efficiency. It is normally designed with two cooled cargo segregations, but tank combinations can be adjusted to support demands for flexibility. The manifold arrangement is designed for different terminal requirements, onshore and offshore, focusing on optimized loading and discharging. This reduces the time spent at terminal and thereby increases the vessels sailing time.

    Depending on owner and charterer’s demand, a deck tank can be part of the system design. The deck tank accommodates coolant for use during gassing up of the cargo tanks, but it can also be used for storage of condensate when gas freeing is needed. Alternatively, the same deck tank can be used for fuel storage – as part of Wärtsiläs fuel supply system (LFSS).

    The deck arrangement is designed for logical and easy access to all equipment, and most weather exposed instruments and major machinery are protected from the environment for improved durability and lifetime performance. The piping layout is designed primarily for gravity drainage of liquid back to cargo tanks, and the safety system includes state-of-the-art vents, gas detection and ESD`s.

    To effectively keep the cargo refrigerated during laden voyage, the system’s reliquefaction plant ensures required pressure control. Connected to vapor domes on the cargo tanks, the reliquefaction system condenses the cargo vapor and returns it to the cargo tank bottom. Our system design ensures that class requirements for cargo cooling redundancy are met.

    Our cargo handling system also comprises a discharging system and a control system. The discharging system features main cargo pumps, booster pumps, cargo heater, level gauging and a high-level alarm system. Our control system is offered in different versions, with the most advanced delivered as part of an IAS system supply. The controls can be delivered with interfaces to subsystems like an inert gas system, load computer or LFSS, and integration of the ballast system is applicable.


    Our cargo handling system is used on semi-refrigerated gas tankers, which are designed to load and carry liquefied gases with a certain pressure. Depending on vessel size the cargo tanks are of cylindrical or bilobe C-type, allowing carriage of cargoes at temperatures as low as -52°C.

    Key benefits

    Wärtsilä’s cargo handling system for semi-refrigerated gas carriers provides ultramodern yet proven technology – fully embracing our accumulated system expertise from decades as a pioneer in gas solutions.

    The system offers flexible solutions for all vessel sizes and a wide range of cargoes and contributes to improved energy efficiency and reduced emissions. One feature leading to reduced GHG emissions and a smaller carbon footprint, is the possibility to integrate the cargo system with Wärtsilä’s gas fuel supply system (LFSS).

    In case the cargo system needs venting, we have integrated an environmentally friendly  and revenue increasing solution for splitting of hydrocarbon and inert gases. The hydrocarbons are retrieved and returned to the cargo tanks, while inert gas is routed to the vent mast.

    Integration with Wärtsilä’s Operim® software. The Operim® enables remote monitoring and diagnostics, contributing to higher system uptime.  

    A well-educated crew is key to safe and correct operation of a cargo handling system, and with our technology we offer training courses developed by Wärtsilä Gas Solutions Academy.

    As part of the Wärtsilä Corporation, Wärtsilä Gas Solutions offers its customers access to the industry’s most extensive global network of services and workshop facilities.

    Contact our 24/7 customer support at +47 815 48 500. For spare parts, please e-mail us with the equipment serial number or the name of the installation at moss-spares@wartsila.com (Inert Gas Systems) spares.wgs@wartsila.com (all other products) 
    For technical support & service, please email us with the equipment serial number or the name of the installation at services.wgs@wartsila.com.
    Equipment serial number is taken from the equipment nameplate and includes all letters and numbers as given on the equipment nameplate.

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