NSL Centrifugal Pump
What is an NSL centrifugal pump?
The NSL centrifugal pump is a vertical in-line, single-stage pump designed for the transfer and circulation of water, seawater, diesel, lubricating oils, and other low-viscosity liquids.
Its compact in-line design enables straightforward installation while reducing space requirements in both new and existing systems. Combining high hydraulic efficiency, low NPSHr characteristics, and a wide range of material options, the NSL series is suited for demanding applications such as cooling, ballast, bilge, firefighting, water circulation, district energy, and diesel transfer.
Why choose the NSL Centrifugal Pump?
The NSL centrifugal pump is designed for applications requiring high flow rates, reliable operation, and long service life. With capacities up to 2,400 m³/h, heads up to 195 m, and operating pressures up to 25 bar, the NSL series is well suited for cooling, ballast, firefighting, water circulation, district energy, and liquid transfer applications.
A key advantage of the NSL design is its low NPSHr performance. Advanced impeller geometry helps reduce the risk of cavitation, making the pump suitable for installations with demanding suction conditions while contributing to reduced vibration and longer component life.
The vertical in-line configuration enables installation directly within the pipeline, reducing the required footprint and simplifying integration compared to traditional end-suction pumps. For seawater and other corrosive media, the NSL can be supplied in materials such as NiAlBronze and Super Duplex stainless steel, providing excellent resistance to corrosion and erosion.
High hydraulic efficiency helps reduce energy consumption and operating costs, while robust construction and spacer coupling options simplify maintenance and minimize downtime.
The NSL is particularly suitable when the application requires:
- High flow rates and continuous operation
- Low cavitation risk and reliable suction performance
- Compact installation within existing pipe systems
- Energy-efficient liquid handling
- Corrosion-resistant materials for seawater service
- Easy maintenance and long-term reliability
How is the NSL Centrifugal Pump designed?
The NSL centrifugal pump features a single-stage, vertical in-line design with a modular construction that supports multiple material configurations, hydraulic arrangements, and maintenance-friendly design options. This enables the pump to be adapted to different media, operating conditions, and application requirements across marine, industrial, utility, and aquaculture applications.
Material options
The NSL series is available in several material configurations to suit different operating environments.
For freshwater applications, pump casings can be supplied in:
- Grey cast iron (GG20)
- Ductile cast iron (GGG40 EN1561-GJS-400)
For seawater and corrosive media, available materials include:
- NiAlBronze (EN1982 CC333G)
- Super Duplex stainless steel (1.4410 / SAF 2507)
The casing is fitted with a replaceable sealing ring in either NiAlBronze or Super Duplex, while the shaft is manufactured from high-quality duplex stainless steel or Super Duplex materials.
Service-friendly design
The NSL series is available as monobloc, spacer-coupled, and bearing-supported configurations to suit different installation requirements. For high-capacity and heavy-duty applications, spacer-coupled versions allow the complete bearing housing, shaft, bearings, mechanical seal, and impeller assembly to be removed without dismantling the motor or pipework. This simplifies inspection and maintenance procedures while helping reduce service time and downtime.
In addition to its standard vertical in-line configuration, selected NSL variants can be supplied for horizontal mounting where installation requirements make this preferable.
Cavitation resistance
The NSL centrifugal pump is designed with low NPSHr characteristics to support reliable operation under demanding suction conditions. Advanced impeller geometry helps reduce the risk of cavitation, contributing to lower vibration levels, improved hydraulic performance, and extended component life. For applications with particularly low available NPSH or increased cavitation risk, DESMI also offers the NSLV-R and NSLH-R centrifugal pumps with inducer, specifically developed to enhance suction performance in challenging operating conditions.
Hydraulic performance
To maximize hydraulic efficiency and operational reliability, the NSL is equipped with dynamically balanced impellers according to ISO 21940-1 G6.3, with tighter balancing grades available on request. The advanced double-curved impeller design supports efficient liquid handling and reduced energy consumption across a wide operating range. Standard impeller materials include NiAlBronze and Super Duplex, making the pump suitable for demanding freshwater and seawater applications.
Sealing and temperature range
The pump is fitted with a single-acting mechanical shaft seal as standard. The design supports liquid temperatures up to 140°C (284°F). For higher operating temperatures, a balanced mechanical shaft seal arrangement is available to ensure reliable performance under more demanding conditions.
Applications for the NSL Centrifugal Pump
The NSL centrifugal pump is designed for the transfer and circulation of low-viscosity liquids across marine, industrial, utility, energy, and aquaculture applications. Its high-flow hydraulic design and wide range of material configurations make it suitable for both freshwater and seawater duties. Selected configurations can be supplied as self-priming pumps with a separate built-on priming pump, making the NSL suitable for applications where reliable suction performance is required.
Marine cooling and utility systems
The NSL is widely used on commercial vessels and offshore installations where reliable liquid circulation, transfer, and self-priming capability are essential.
- Freshwater and seawater cooling circuits for main engines, generators, and auxiliary equipment
- Ballast water transfer and tank management
- Bilge water pumping
- Firefighting, emergency fire pumps, and fire jockey pumps
- General service duties including washdown water and utility water circulation
- Transfer of diesel fuel and lubricating oils
- Main engine preheating systems
- Exhaust gas cleaning support applications
Industrial water circulation
The NSL supports continuous-duty water circulation and liquid transfer in industrial and utility environments.
- Cooling tower circulation systems
- Process water distribution
- Industrial cooling and heating loops
- HVAC circulation systems
- Utility water transfer applications
- Water supply and distribution networks
- Irrigation systems
- General industrial service duties
Energy and district infrastructure
The NSL is well suited for energy-efficient circulation and transfer duties within modern heating, cooling, and power generation systems.
- District heating networks
- District cooling networks
- Combined heat and power (CHP) installations
- Data center cooling systems
- Immersion cooling applications
- Industrial energy recovery systems
Aquaculture and RAS Applications
The NSL helps maintain stable water flow and circulation within modern aquaculture facilities and recirculating aquaculture systems (RAS).
- Intake water pumping from rivers, lakes, and seawater sources
- Water circulation in fish farming facilities
- Oxygenation and treatment systems in RAS facilities
- Cooling and heating loops
- Water containing additives used in aquaculture processes
- Oil transfer applications up to 500 cSt
Environmental and water treatment applications
The NSL can be configured for applications involving seawater handling, water treatment, and emerging environmental technologies.
- Seawater desalination systems
- Water treatment and process water circulation
- Carbon capture systems
- Cooling water systems for environmental process applications
Frequently Asked Questions about the NSL Centrifugal Pump
What liquids can the NSL centrifugal pump handle?
The NSL is designed for the transfer and circulation of water, seawater, diesel, lubricating oils, and other low-viscosity liquids. Depending on the operating medium, the pump can be supplied in materials such as cast iron, NiAlBronze, or Super Duplex stainless steel to ensure reliable performance in both freshwater and corrosive seawater applications.
How does the NSL centrifugal pump work?
The NSL centrifugal pump uses a rotating impeller to increase the velocity and pressure of a liquid. Liquid enters through the suction inlet, where the impeller accelerates the flow and directs it through the pump casing. The casing converts velocity into pressure before the liquid is discharged into the system, enabling efficient transfer and circulation across a wide range of applications.
Is the NSL suitable for seawater applications?
Yes. The NSL can be supplied in corrosion-resistant materials such as NiAlBronze (EN1982 CC333G) and Super Duplex stainless steel (1.4410 / SAF 2507), making it suitable for seawater cooling, ballast systems, offshore installations, aquaculture facilities, and other demanding marine applications.
How does the NSL help reduce the risk of cavitation?
The NSL is designed with low NPSHr characteristics and a hydraulically optimized impeller geometry that helps reduce the risk of cavitation under demanding suction conditions. Lower cavitation risk contributes to reduced vibration, improved hydraulic performance, and longer component life. For installations with particularly challenging suction conditions, DESMI also offers NSLV-R and NSLH-R pumps with inducer.
How do I select the right NSL centrifugal pump?
Selecting the right NSL pump depends on factors such as required flow rate, differential head, liquid properties, temperature, pressure, and installation conditions. The NSL range covers capacities up to 2,400 m³/h, heads up to 195 m, and operating pressures up to 25 bar. DESMI's Pump Selection Program can help identify the most suitable pump configuration for your specific application.
When is the NSL centrifugal pump the right choice?
The NSL is the right choice when high flow rates, reliable continuous operation, and compact installation are required. Its vertical in-line design allows installation directly within the pipeline, reducing footprint requirements compared with traditional end-suction pumps. With capacities up to 2,400 m³/h, low NPSHr performance, and material options for both freshwater and seawater service, the NSL is widely used in cooling systems, ballast operations, firefighting systems, district energy networks, water circulation systems, and aquaculture applications.
NSL Centrifugal Pump Technical Data
The technical data below provides an overview of the operating range and material options available within the NSL centrifugal pump series.
Technical data
| Nominal diameter (DN) | 80 to 350 |
| Flow rate - 50 Hz | Up to 2000m³/h (8800 US gpm) |
| Flow rate - 60 Hz | Up to 2400m³/h (10600 US gpm) |
| Head | Up to 195 m (640 ft) |
| Pressure | Up to 25 bar (360 psi) |
| Temperature | Up to 140°C (284°F) |
| Motor | Standard and EX motors |
| VFD | Direct or Bulkhead/Wall-mounted |
| ATEX approved | Yes |
Material specification
| Pump casing | Cast Iron |
| Impeller | NiAl-Bronze |
| Sealing ring | NiAl-Bronze |
| Rear cover | Cast Iron |
| Shaft | Stainless Steel |
| Shaft seal | Mechanical |
Alternative material combinations are available and includes: Cast Iron, Ductile Iron, Bronze, NiAl-Bronze, Stainless Steel and Super Duplex Stainless Steel
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NSL centrifugal pump brochures
Download brochures and product overviews for the NSL centrifugal pump series. These documents provide information about pump design, performance characteristics, material options, and typical application areas.
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NSL Centrifugal Pump manuals
Access installation, operation, and maintenance manuals for the NSL centrifugal pump series. These documents provide guidance on commissioning, operation, inspection, troubleshooting, servicing, and recommended maintenance procedures to help ensure safe operation, reliable performance, and long service life.
NSL Centrifugal Pump curves
DESMI performance curves and hydraulic testing are performed according to EN/ISO 9906 Grade 2B as standard, ensuring reliable performance data for pump selection and system design.
NSL Centrifugal Pump drawings
Download dimensional sketches, assembly drawings, and 3D CAD files for the NSL centrifugal pump series. These drawings support system design, installation planning, engineering documentation, and integration into new or existing piping systems. Available file formats include DWG, IGS, and STP for use in CAD and engineering software.
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