Cryogenic Centrifugal Pumps

Cryogenic centrifugal pumps for marine fuel and cargo handling

Cryogenic centrifugal pumps in marine service are designed for the controlled transfer of low-temperature liquefied gases and fuels between tanks, process lines and supply systems onboard vessels. In practice, they are selected for duties where both the properties of the medium and the vessel environment create demanding operating conditions - for example, LNG fuel supply, LPG cargo discharge, LEG handling, methanol transfer and low-temperature chemical service.

In DESMI’s Marine and New Green Solutions portfolio, the focus is on pump systems that support the safe handling of hazardous or temperature-sensitive media while fitting the realities of shipboard installation. That means attention to suction conditions, available tank space, pressure requirements, boil-off considerations, service access and the need for reliable operation over long trading cycles.

The DESMI cryogenic range relevant to this field includes solutions for both fuel and cargo handling. Some are optimised for alternative marine fuels, while others are intended for liquefied gas and chemical cargo transfer. Together, they address a broad set of low-temperature pumping duties across gas carriers, bunker vessels and other vessels operating with modern fuel systems.

DESMI cryogenic pump range: DesFuel RSL, DesCargo NDW and DesCargo NDB

DESMI’s cryogenic pump range for marine fuel and cargo handling comprises three specific pump types: the DesFuel Deepwell Pump (RSL), the DesCargo Deepwell Pump (NDW) and the DesCargo Booster Pump (NDB). Each has a distinct primary role in the overall system.

DesFuel Deepwell Pump (RSL) is a deepwell pump developed for marine fuel duties involving alternative fuels. It is intended for LNG, methanol/ethanol, ammonia and LPG service. The RSL is used where vessel operators need controlled fuel transfer and dependable supply from low-temperature or hazardous media tanks to the onboard fuel system. A key differentiator is its layout, with the motor, coupling and bearings located outside the tank, supporting accessibility and maintenance planning.

DesCargo Deepwell Pump (NDW) is intended for the cargo transfer of liquefied gases and demanding chemical cargoes. It is used in cargo tanks on vessels such as LPG carriers, LNG carriers, bunker vessels, ammonia carriers, ethylene carriers and CO2 carriers. As a deepwell cargo pump, it is selected where tank-based pumping and stable low-temperature cargo handling are required.

DesCargo Booster Pump (NDB) is used together with the NDW when additional discharge pressure is needed. Rather than replacing the deepwell cargo pump, the booster pump complements it by increasing total system pressure in applications where the deepwell pump alone does not meet downstream pressure demand.

In simple terms, the division is as follows:

• RSL: fuel handling for alternative marine fuels

• NDW: primary cargo transfer for liquefied gas and chemical cargoes

• NDB: pressure boost for cargo systems based on NDW deepwell pumps

Cryogenic centrifugal pumps for LNG, LPG, LEG and methanol applications

The main use of cryogenic centrifugal pumps in this context is the marine transfer of liquefied fuels and cargoes under controlled low-temperature conditions. The exact duty depends on whether the pump is installed in a fuel supply system or in a cargo handling system.

For LNG applications, an LNG pump may be used in marine fuel arrangements where liquefied natural gas must be transferred from storage to the fuel conditioning or supply system. In cargo service, LNG-related pump duties can also include transfer onboard LNG carriers or bunker vessels, depending on system layout and pressure requirements.

For methanol applications, DESMI solutions can support both methanol fuel pump systems and methanol transfer pump duties. The distinction matters. In fuel service, the pump forms part of the vessel’s alternative fuel arrangement and must match the required flow, pressure and operating philosophy of the engine fuel supply system. In transfer service, the methanol pump may be selected for tank-to-system movement, bunkering-related handling or other low-temperature chemical transfer tasks.

For LPG and LEG applications, deepwell cargo pumps are widely used on gas carriers handling liquefied petroleum gas and liquefied ethylene gas. Here, the pump must be selected for the medium, temperature window, required cargo rate and discharge conditions. Similar principles apply to ammonia and CO2 carrier projects, where media compatibility and project-specific verification are central.

Typical applications include:

• LNG fuel transfer on alternative-fuel vessels

• Methanol fuel pump systems for marine propulsion

• Methanol transfer pump duties in bunker or onboard handling systems

• LPG service on gas carriers and related marine installations

• LEG cargo handling on ethylene and gas carrier vessels

• Low-temperature chemical transfer involving ammonia, ethanol or CO2

Because media properties differ significantly, a cryogenic centrifugal pump should always be evaluated against the specific liquid, expected temperature, pressure demand and the overall marine system configuration.

Deepwell and booster pump configurations for low-temperature service

Deepwell pump and booster pump layouts are used in cryogenic marine systems because they solve different hydraulic and installation challenges. A deepwell pump is installed to draw liquid directly from the tank, which is often the most practical arrangement where suction conditions are difficult, tank geometry is restrictive or submerged access to the medium is needed. A booster pump, by contrast, is added downstream when the system requires higher total discharge pressure than the primary deepwell pump delivers on its own.

In low-temperature marine service, the choice between a stand-alone deepwell pump and a combined deepwell-plus-booster solution depends on several project factors:

• Tank arrangement: deep and narrow cargo or fuel tanks often favour a deepwell solution

• Suction conditions: low available suction head and cold media handling often benefit from tank-mounted pump arrangements

• Required head: longer transfer distances or higher downstream pressure demand may require a booster stage

• System pressure: cargo discharge and process integration can make additional pressure necessary

• Vessel operating profile: bunkering, cargo transfer rate and fuel consumption patterns influence pump sizing and layout
  

For cargo applications, the NDW serves as the primary deepwell cargo pump, while the NDB can be added where the duty point requires more pressure. This combined configuration is relevant when cargo has to be delivered against higher line resistance, elevated terminal backpressure or a more demanding discharge profile.

For fuel duties, the RSL deepwell pump arrangement is used where controlled transfer from the vessel’s fuel tank is required, with the design supporting accessibility outside the tank for key drive and bearing components.

In all cases, the configuration should be based on the full operating envelope rather than nominal flow alone. Engineers typically assess normal duty, start-up conditions, low tank levels, temperature variation, pipe losses and contingency operation before selecting the final layout.

Why cryogenic centrifugal pumps matter for performance, safety and uptime

For shipowners, yards and operators, the value of cryogenic centrifugal pumps is directly linked to safe operation, stable performance and reduced interruption risk. A pump handling LNG or other cryogenic liquids works in conditions where vapour formation, poor NPSH margin, unstable flow or unsuitable materials can quickly affect both performance and availability.

Well-matched cryogenic pump systems help to address several operational priorities:

• Safe low-temperature operation - the pump design must suit the thermal and mechanical demands of cryogenic liquids.

• Dependable flow - transfer performance must remain stable across normal operating conditions.

• Reduced cavitation risk - low NPSH conditions and vapour sensitivity make hydraulic design especially important.

• Pressure support - booster stages can help to meet terminal or deck line requirements when the primary pump should not carry the full pressure burden.

• Lower lifecycle cost - correct pump selection can reduce wear, unplanned stops and unnecessary energy loss.

• Operational continuity - reliable transfer equipment supports schedule adherence, bunkering efficiency and predictable cargo operations.
  
  

In marine environments, performance must also be viewed in relation to compliance and system safety. A cryogenic centrifugal pump that fits the duty correctly is easier to document, easier to integrate and more likely to support long-term uptime. This is particularly important where alternative-fuel systems are becoming more central to vessel design and operational planning.

Deepwell pump technology for cryogenic liquids

A deepwell pump is a vertical pump arrangement in which the motor is positioned outside the tank while the pumping element is located deep in the tank or in a dedicated pump well. Power is transmitted through a vertical shaft, allowing the pump hydraulic section to operate where the liquid is available while keeping the motor in a more accessible position.

This configuration is well suited to cryogenic duties for several reasons. First, it supports controlled transfer directly from the tank, reducing the need for more complex suction arrangements. Second, it makes efficient use of vertical space, which is valuable in marine installations where footprint and access are often constrained. Third, it enables a pump concept that aligns well with tank discharge and cargo-transfer requirements for liquefied gases.

For cryogenic liquids such as LNG, LPG, ammonia and ethylene, the deepwell concept supports stable liquid pick-up and practical system layout. It also allows the pumping unit to be placed where suction conditions are more favourable than they would be for a remotely installed deck-mounted pump. That can be important when managing NPSH conditions and reducing the risk of vapour-related instability.

In many projects, the deepwell pump is the primary transfer machine. Where line losses or terminal conditions demand higher discharge pressure, a booster pump is then added downstream rather than overloading the deepwell pump with duties better handled elsewhere in the system.

Engineering features of DESMI cryogenic centrifugal pumps

The engineering of cryogenic centrifugal pumps must account for more than simple hydraulic duty. It also needs to address temperature-driven material behaviour, shaft arrangement, sealing philosophy, accessibility, integration with ship systems and the operating characteristics of the liquid itself.

Relevant technical considerations typically include:

• Hydraulic design - selected to deliver stable flow, appropriate head and acceptable NPSH performance for low-temperature liquids.

• Material selection - matched to the medium, temperature range and marine operating environment.

• Shaft arrangement - especially important in deepwell pumps, where the vertical transmission path must support reliable operation over time.

• Sealing approach - defined according to the pump type, medium and installation concept.

• Thermal behaviour - cryogenic temperatures affect clearances, contraction and overall mechanical response.

• Motor configuration - in deepwell designs, the motor remains outside the tank for practical installation and service access.

• System integration - the pump must work with piping, controls, hazardous-area requirements and vessel-specific interfaces.

For true liquefied-gas duties, these factors are shaped by cryogenic operating conditions. LNG, LPG, ammonia, ethylene and CO₂ all require careful evaluation as cryogenic or low-temperature media. By contrast, a methanol pump, methanol fuel pump or methanol transfer pump is usually selected on the basis of hazardous liquid handling, compatibility and fuel-system integration rather than cryogenic temperature capability in the same sense as LNG service.

It is also useful to distinguish between cryogenic deepwell pumps and a magnetic-drive pump. A magnetic-drive pump is a sealless concept often selected where leakage control is a primary concern for hazardous liquids. That can be highly relevant in some chemical or fuel applications, but it is a different pump architecture from the cryogenic deepwell and booster arrangements used for liquefied-gas transfer. DESMI supports both technology areas, depending on the duty and containment requirements.

Cryogenic centrifugal pumps and system design considerations

Selecting the right cryogenic centrifugal pump arrangement starts with the system duty, not just the product name. The same vessel may require different pump concepts depending on whether the task is cargo transfer, tank-stripping support, bunker discharge or fuel supply.

Key selection criteria include:

• Liquid type - LNG, LPG, ammonia, ethylene, CO₂ and methanol differ in temperature profile, vapour behaviour and compatibility requirements.

• Required flow - transfer capacity must match operational targets without oversizing the system.

• Discharge pressure - required head at deck line, process interface or terminal connection is central to pump selection.

• NPSH conditions - cryogenic liquids can be sensitive to pressure margin and vapour formation.

• Tank and piping layout - available installation geometry influences whether a deepwell arrangement is the most effective solution.

• Deck line or terminal interface demands - line losses and receiving-system pressure can determine whether boosting is required.

• Hazardous area and vessel integration - the pump arrangement must align with the wider ship design and control philosophy.

In practice, the decision often comes down to whether a deepwell-only solution is sufficient or whether a combined deepwell and booster pump system will provide a better operating margin. If the deepwell pump can achieve the required flow and discharge conditions efficiently, the simpler arrangement may be preferable. If downstream pressure demand is higher, or if the terminal interface creates additional resistance, a booster pump can be introduced to support the pressure requirement without compromising the transfer role of the deepwell unit.

This system view is important for both technical performance and total cost of ownership. Correctly dividing duties between pump stages can reduce stress on the primary transfer pump, improve controllability and support more reliable long-term operation.

Standards, documentation and compliance for cryogenic pump projects

Cryogenic pump projects in marine service rely on more than pump performance data. They also require robust documentation, clear technical interfaces and support for project-specific compliance. This is especially important for shipowners, yards, classification stakeholders and engineering teams working with hazardous media and alternative-fuel installations.

Depending on the project, relevant documentation may include:

• general arrangement drawings

• datasheets and performance curves

• material specifications

• operation and maintenance manuals

• test data and inspection records

• installation guidance

• spare-parts documentation

• project-specific compliance and interface information
  
  

For cryogenic centrifugal pump design and testing, standards such as ISO 24490 are commonly relevant to centrifugal pumps for cryogenic service. Depending on the application and project scope, pumps can also be supplied in designs aligned with broader centrifugal pump requirements such as ISO 13709 / API 610, where applicable. Hazardous-area considerations may also apply, and pump or motor configurations can be supplied in accordance with project-specific requirements where documented.

For vessel installations, class-related and owner-specific requirements are often part of the approval process. DESMI supports this by helping customers structure the technical package needed for review, installation and commissioning. Where specific standards, approvals or hazardous-area configurations are required, these should always be confirmed against the selected design and project documentation rather than assumed to be standard across all configurations.

Service, spare parts and lifecycle support

Pump selection is only the start of a successful cryogenic project. Long-term performance depends on technical support, commissioning quality, planned maintenance and timely access to spare parts. This is particularly true for marine cryogenic systems, where downtime can affect vessel schedules, cargo-handling windows and fuel availability.

DESMI supports customers throughout the equipment lifecycle, including:

• technical advice during specification and system design

• support with documentation and project clarification

• commissioning and start-up support

• maintenance planning for operational reliability

• spare-parts identification and supply

• ongoing dialogue on optimisation and service needs

For operators, the value of this support is practical. It helps to maintain uptime, reduce troubleshooting time and protect the long-term performance of the installed system. For yards and integrators, it helps to keep interfaces clear and documentation aligned. For procurement teams, it reduces risk by linking equipment supply to a long-term partner with global reach and experience in marine pumping technology.

DESMI’s wider service and engineering capabilities are designed to support reliable operation and lower total cost of ownership across marine, offshore and industrial projects.