LEG pumps

LEG pumps for Liquid Ethylene Gas handling

In this context, LEG stands for liquid ethylene gas. It is handled as a cryogenic liquid cargo or process medium, and this places specific demands on pump design. Temperatures can be extremely low, vapour formation must be controlled, and the consequences of leakage are more serious than in conventional water or general industrial liquid service. That is why LEG pumps are not simply selected on flow and head alone. Engineers also need to consider tightness, low-temperature capability, NPSH behaviour, material compatibility and the practical arrangement of the complete pump system.

For DESMI, the most relevant LEG pump solutions are those developed for demanding marine cargo and hazardous-liquid handling duties. Deepwell cargo pumps are particularly relevant where liquid ethylene gas is carried onboard dedicated gas carriers, while magnetic drive pump and sealless pump concepts for cryogenic liquids become highly relevant where minimising leakage is a primary concern. The result is a solution space that balances cryogenic performance with safe day-to-day operation and maintainability.

Typical engineering priorities for LEG handling include:

• Very low temperature capability

• Stable transfer of volatile liquid media

• Reduced leakage risk in hazardous areas

• Reliable hydraulic performance under marine operating conditions

• Maintainable design with documented materials and performance data

Where LEG pumps are used onboard ships and in land-based systems

LEG pumps are most commonly associated with marine cargo operations. Onboard LPG and LEG carriers, pump systems are used for cargo discharge, internal transfer and related tank duties where cryogenic liquid must be moved reliably from cargo tanks to downstream piping and terminal connections. In these installations, pump design must account for vessel motion, restricted space, hazardous-atmosphere considerations and the need for dependable operation over long service intervals.

There is also a distinction between cargo transfer and fuel-related systems. A cargo pump onboard a gas carrier is selected primarily for transfer of the transported medium, often at comparatively high flow rates and with tank installation as a core part of the design. A fuel transfer pump, by contrast, is linked to the vessel's fuel supply arrangement and must support safe, controlled delivery to downstream fuel conditioning or consumption systems. Both can involve low-temperature liquids, but the duty profile, pressure requirement and service layout are different.

For land-based systems, the DESMI source base is more limited for direct LEG references, so the application picture should be framed more carefully. Relevant onshore duties can include transfer between storage and process systems, terminal handling, or selected low-temperature liquid duties where cryogenic pumping and leakage prevention are important. In these cases, the same selection logic still applies: the pump must suit the medium, the temperature, the available suction conditions and the required level of containment.

• Onboard ship use: cargo discharge, tank transfer, marine gas cargo duties, selected fuel-related low-temperature systems

• Land-based use: terminal transfer, storage-to-process duties and other controlled low-temperature liquid handling applications

• Key difference: cargo pumps are generally transfer-focused, while deepwell fuel pumps are designed around controlled supply within a fuel system

DESMI cargo pumps and DesFuel pump solutions for LEG applications

For LEG applications, the two most relevant DESMI solution families are DesCargo deepwell cargo pumps and DesFuel deepwell pumps. Each serves a different purpose in practice, and understanding that distinction is central to correct specification.

For marine transport of liquid ethylene gas, DESMI cargo pumps are the primary fit. The DesCargo deepwell range is developed for liquefied gas and related marine cargo duties, including LPG, LEG, chemicals and CO2. This makes it the natural solution when the requirement is cargo handling onboard a ship, particularly where the pump is installed in the cargo tank and must combine cryogenic capability with robust marine service design. You can review the range on the cargo pumps product page and the DesCargo Booster Pump - NDB page.

DesFuel deepwell pumps are relevant where the application is closer to fuel-system handling and where safe containment is a key design criterion. The DesFuel Deepwell Pump - RSL uses a sealed magnetic coupling, and the motor, coupling and bearings are placed outside the tank. This layout supports safer maintenance access and can reduce the need for intrusive tank-related service work. Although presented by DESMI mainly for alternative fuel duties such as LNG, ammonia, methanol, ethanol and LPG, the design logic is highly relevant in LEG-related environments where controlled, low-leakage handling is required.

In short, the practical fit is as follows:

• DesCargo deepwell cargo pumps: primarily for onboard marine cargo transfer of LEG and comparable liquefied gases
  
  

• DesFuel deepwell pumps: primarily for onboard fuel-related low-temperature or hazardous-liquid duties where sealed magnetic coupling is advantageous
  
  

• Magnetically driven centrifugal pumps: relevant for selected hazardous-liquid and contained onshore duties where sealless operation is preferred

Deepwell cargo pump design for cryogenic LEG service

The deepwell cargo pump concept is well suited to cryogenic LEG service because it is designed around installation in the cargo tank and direct handling of liquefied gases under marine operating conditions. In DESMI's cargo pump configuration, the pump arrangement is built around the base arrangement, pipe and pump cylinder. This design supports efficient transfer from the tank while keeping the system aligned with the operational realities of gas carriers.

For liquid ethylene gas, low-temperature capability is essential. DESMI's NDW deepwell cargo pumps are presented as suitable for duties involving LPG, LEG, chemicals and CO2, with documented temperature capability down to -165°C. This makes the range relevant for cryogenic liquid transfer where both hydraulic efficiency and material suitability are required. The deepwell arrangement also supports practical cargo tank integration, which is a major advantage in dedicated marine transport applications.

Where higher discharge pressure is needed, booster pump integration becomes important. DESMI offers the NDB booster pump as a complementary solution to increase total system pressure together with the NDW deepwell cargo pump. This can be relevant where terminal interface conditions, line losses or downstream process requirements exceed the pressure capability of the primary cargo pump alone.

From an engineering standpoint, the deepwell cargo pump approach offers several practical advantages:

• Designed for onboard cargo tank installation

• Suitable for cryogenic liquids, including liquid ethylene gas

• Can be configured with booster pump support where higher discharge pressure is required

• Adapted to marine operating conditions and cargo-handling duty cycles

Magnetic drive pump and sealless pump principles in LEG-related duties

A magnetic drive pump is often selected when leakage must be minimised or where conventional shaft-seal arrangements are less attractive from a safety or maintenance perspective. In a magnetically coupled pump, torque is transferred without a direct shaft penetration in the traditional sense, allowing the pumped liquid to remain within a sealed containment boundary. For hazardous or environmentally sensitive liquids, this can be a strong operational advantage.

The same logic applies to a sealless pump for cryogenic liquid duties. Where liquid ethylene gas or another volatile low-temperature medium must be handled with a high level of containment, a sealed construction can reduce the risk associated with external leakage points. This does not remove the need for careful engineering, but it can improve safety and simplify maintenance planning in the right duty.

DESMI's DesFuel deepwell pump uses a sealed magnetic coupling, with the motor, coupling and bearings located outside the tank. This is relevant because it combines containment with practical service access. DESMI also offers magnetically driven centrifugal pumps for hazardous-liquid duties, including the ESL range, where low maintenance, compact layout and reliable operation are key benefits. In land-based systems or auxiliary duties, this kind of magnetic drive pump can be particularly attractive where sealed operation is prioritised.

Why sealed and sealless principles are relevant in LEG-related applications:

• Reduced risk of leakage from dynamic sealing points

• Safer operation in hazardous or sensitive environments

• Lower maintenance demand in selected duties

• Improved suitability for volatile and difficult liquids

• Practical benefits where access for service is restricted

Documentation, compliance and technical clarification for Liquid Ethylene Gas systems

For Liquid Ethylene Gas systems, pump selection should always be supported by documented technical data. Engineers, shipyards, owners and procurement teams typically need more than a nominal product match. They need evidence that the selected pump can be configured to meet the required duty point, temperature conditions, material requirements and installation constraints.

Relevant review points usually include:

• published performance curves and duty-point verification

• material specifications for cryogenic service

• temperature and pressure limits

• available certificates and test documentation

• integration with vessel or system design

• maintenance and spare parts planning
  
  

The supplied DESMI source material clearly documents ATEX approval for the magnetic-drive NSL pump. For LEG cargo-pump applications, it is important not to assume broader certifications or class approvals unless they are confirmed for the specific design and scope. Where standards, certificates or authority requirements apply, DESMI can supply the relevant technical clarification and advise whether a pump can be supplied in accordance with the requirements of the project.

For technical teams, access to documentation is often decisive during design review and procurement. DESMI supports this process with product information, technical dialogue and application-specific clarification so that the final selection is based on verified operating conditions rather than general assumptions.

How to evaluate the right LEG pump for your duty

The right LEG pump depends on duty type first, and product family second. Before comparing models, it is worth establishing whether the project concerns on-board cargo handling, alternative-fuel supply at sea or a selected land-based cryogenic transfer scenario. That decision shapes the pump concept, installation arrangement and documentation you will need.

A structured evaluation often includes the following questions:

1. Is the duty cargo handling or fuel supply?
   A deepwell cargo pump is typically the relevant route for cargo transfer, while the DesFuel Deepwell Pump is aimed at marine fuel duties.
   
   

2. What temperature range must the pump handle?
   Cryogenic temperature capability is fundamental, especially if the duty approaches the lowest documented limits.
   
   

3. Is the fluid strictly LEG, or part of a broader liquefied-gas portfolio?
   Some operators value pump standardisation across LPG Pumps, LEG Pumps, LNG Pumps, Ammonia Pumps and Methanol Pumps, as well as chemicals or CO₂ applications where technically relevant.

   
   
   

4. What are the required capacity and pressure?
   The hydraulic duty point should be defined clearly, including expected operating variations.
   
   

5. What is the installation context?
   On-board tank arrangement, fuel system layout, terminal interface or retrofit constraints can all influence pump selection.
   
   

6. How important are maintenance access and lifecycle support?
   Ease of service, spare parts availability and fleet commonality can affect total cost of ownership significantly.
   
   

7. Is this a newbuild, retrofit or fleet standardisation project?
   The answer often determines how much flexibility is needed in configuration, documentation and implementation planning.
   
   

Where the duty is not fully standard, an application review with DESMI engineers is the fastest way to narrow the choice and avoid over- or under-specification.

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