Sealless Pumps

Sealless Pumps for Reliable, Leak-Free Fluid Handling

A sealless pump is designed without a conventional mechanical shaft seal. In a sealless magnetic drive pump, motor torque is transmitted through a magnetic coupling across a containment shell, so the pumped liquid remains enclosed within the hydraulic boundary. This principle is especially relevant where even minor leakage can create safety, environmental or operational consequences.

Typical drivers for selecting sealless pumps include hazardous liquid handling, stricter emission control, reduced product loss, and the need to avoid the maintenance burden often associated with seal wear and seal support systems. In practical B2B operations, that means fewer unplanned interventions around sealing arrangements and a more contained transfer solution for difficult media.

DESMI works with sealless technologies for applications where reliability and containment must go together. This is particularly relevant in alternative fuel systems, cargo duties, chemical handling, process services and utility installations that operate continuously or in safety-critical environments.

DESMI Sealless Pumps Across Centrifugal, Deepwell, Gear and Screw Pump Designs

DESMI’s portfolio shows that a sealless pump is a technology principle, not just one pump type. Different pump designs suit different liquids, viscosities, pressures, temperatures and installation conditions. DESMI’s sealless range includes:

This breadth matters in specification work. Low-viscosity liquids and higher-flow transfer duties often point towards a sealless centrifugal pump. More viscous media may be better suited to internal gear or triple screw solutions. Deep-tank or submerged installations may require a deepwell arrangement. Higher differential pressure can favour a multistage configuration. By covering these different principles, DESMI can support a more accurate fit between pump technology and process conditions.

Applications for Sealless Pumps in Marine, Industry, Energy and Utility Systems

Sealless pumps are relevant wherever liquid escape must be minimised and operational continuity is commercially important. In marine environments, this includes fuel transfer, cargo handling, service duties and specialised systems for low-flashpoint or aggressive media. Containment is often a direct operational requirement, not just a design preference.

In industry, a sealless mag drive pump is commonly selected for chemicals, solvents, additives, process liquids and other media that are toxic, flammable, volatile or difficult to seal with conventional arrangements. Utility and energy systems may use sealless technology for continuous-duty circulation, transfer or booster duties where leakage can affect compliance, workplace safety and maintenance planning.

Typical application areas include:

• Fuel transfer pumps and alternative fuel handling

• Cargo liquid transfer in marine systems

• Chemical and process services

• Utility duties requiring contained operation

• Continuous-duty pumping where uptime is critical

• Installations with strict environmental or emission requirements

For engineering teams and buyers, the key question is not only whether the fluid can be pumped, but whether it can be pumped with the required level of containment, reliability and maintainability over time.

Sealless Centrifugal Pump Solutions with Magnetic Drive Technology

DESMI offers several sealless centrifugal pump options based on magnetic drive technology, including the NSL, ESL, TSL and MV ranges. In these designs, torque is transmitted magnetically rather than through a shaft passing through a conventional mechanical seal. This reduces one of the most common leakage paths found in standard sealed centrifugal pump arrangements.

For many low-viscosity or moderately demanding process media, a sealless centrifugal pump provides an effective combination of hydraulic efficiency, contained operation and operational reliability. The pump concept is well suited to applications where process continuity, reduced emissions and a lower risk of leakage are key design criteria.

The different DESMI centrifugal families cover a range of installation and performance needs. NSL, ESL and TSL support sealless centrifugal transfer in various process layouts, while the MV multistage design addresses duties where a higher head is needed. This means a sealless magnetic drive pump can be selected not only for containment, but also for the actual hydraulic requirements of the system. For further background on this technology in marine fuel applications, see DESMI’s article on magnetic drive centrifugal pumps for the marine green fuel transition.

Typical selection advantages of magnetic drive centrifugal designs:

• Contained transfer without a conventional dynamic shaft seal

• Strong suitability for low-viscosity and demanding process liquids

• Reduced leakage risk in safety-sensitive installations

• Lower seal-related maintenance exposure

• Flexible configuration across standard and higher-head duties

Sealless Pump for Cryogenic Liquid and Alternative Fuels

A sealless pump for cryogenic liquid is particularly relevant when handling LNG and other low-temperature or difficult alternative fuels, where leakage, evaporation and safety risks must be tightly controlled. In these applications, a deepwell arrangement can be advantageous because the pump operates submerged in the tank and is designed around the installation conditions of the fuel system.

DESMI’s DesFuel Deepwell Pump (RSL) is developed for alternative fuel flexibility and can be supplied for duties involving LNG, ammonia, methanol, ethanol and LPG. The design supports safe transfer without modification between these fuel types according to DESMI product information, making it relevant for operators planning fuel flexibility across evolving marine and energy requirements.

The RSL concept is built for deepwell service with stage-based hydraulic performance. Depending on pump size and configuration, the range covers capacities from 0.5 to 80 m3/h, with multiple stage options to match the required outlet pressure and head. DESMI documentation also describes nominal speed at 3500 rpm, maximum tank pressure up to 20 bar, and outlet pressure levels reaching up to 55 bar on larger configurations.

For buyers and specifiers, this matters because cryogenic and alternative fuel systems are defined by more than flow alone. Tank arrangement, available NPSH, vapour behaviour, pressure envelope, installation geometry and fuel compatibility all influence the final pump selection. A sealless pump for cryogenic liquid must therefore be evaluated as part of the full fuel-handling system, not as a stand-alone component. A relevant example is DESMI’s customer reference on "ammonia fuel system supported by magnetic drive pumps"

Selecting the Right Sealless Pump for Duty, Liquid and Installation

Selecting the correct sealless pump starts with the duty point, but it should not end there. Flow and head remain fundamental, yet they must be assessed together with viscosity, pressure, temperature, NPSH, installation layout, material compatibility and the operational consequences of maintenance access. A sealless centrifugal pump, a deepwell pump and a positive displacement pump can all be valid solutions, but they solve different hydraulic and installation challenges.

For low-viscosity liquids and general transfer duties, a sealless centrifugal pump is often the most direct choice. Where the required head is higher, a multistage design such as MV may be more appropriate. If the liquid is more viscous or if a positive displacement characteristic is preferred, internal gear or screw pump principles may offer better hydraulic behaviour. For alternative-fuel tanks and submerged installations, a deepwell concept such as the RSL can deliver advantages in tank integration, NPSH performance and service access.

Material selection is equally important. Hazardous liquids, chemicals, cryogenic media and seawater-related duties may all require different material combinations in the wetted parts and containment system. The same applies to temperature and pressure limits, hazardous-area requirements and installation interfaces. For this reason, pump selection should be made against the actual process data rather than by pump category alone.

Main specification criteria for sealless pumps:

• Required flow and differential head

• Liquid viscosity and whether centrifugal or positive displacement behaviour is more suitable

• Operating pressure and temperature range

• Available NPSH and suction conditions

• Material compatibility with the pumped liquid

• Installation layout, including in-line, base-mounted or deepwell arrangement

• Maintenance access and service strategy

• Hazardous-area requirements such as ATEX where relevant

• Lifecycle priorities, including uptime, spare parts planning and total cost of ownership

If your project involves alternative fuels, chemicals or other hazardous liquids, DESMI can help you compare duty requirements across pump principles and identify the most suitable contained solution for the application.

Compliance, Documentation and Lifecycle Support

In demanding B2B installations, the pump itself is only part of the specification process. Technical documentation, interface data, manuals and long-term service support are equally important when operational risk must be reduced. DESMI supports sealless pump projects with product data sheets, drawings, manuals and technical guidance that help engineers, purchasers and operators validate fit, plan installation and manage lifecycle performance.

Documentation requirements often include hydraulic data, dimensional drawings, material information, operating limits and maintenance instructions. In some applications, hazardous-area considerations such as ATEX also need to be addressed. Where that applies, DESMI can supply relevant pump variants in designs intended to meet the applicable installation requirements, subject to the specific product version and duty. In marine applications, project-specific class, flag or fuel-system requirements may also need to be reviewed as part of the overall package.

Lifecycle support matters particularly in systems where sealless pumps are selected to reduce maintenance disruption. Access to spare parts, service planning and technical troubleshooting helps preserve the value of the original specification. With more than 185 years of pump experience and a global presence in over 100 countries, DESMI supports customers with engineering dialogue, service agreements and long-term operational follow-up across marine, industry, energy and utility applications. You can also review technical documentation and product resources and discuss project requirements directly with DESMI’s engineering teams.

If you are evaluating sealless pumps for a new installation or retrofit, contact DESMI for support with duty review, pump selection, documentation and lifecycle planning.