The Danfoss APP 11-13 series represents a benchmark in High Pressure Axial Piston Pump technology,specifically engineered for critical water treatment applications.This robust RO High Pressure Pump is designed to handle challenging media such as seawater,brackish water,and wastewater,delivering exceptional performance in reverse osmosis(RO),zero liquid discharge(ZLD),and minimal liquid discharge(MLD)systems.Unlike conventional hydraulic pumps that use oil-based fluids,the APP 11-13 utilizes the pumped water itself for lubrication,completely eliminating the risk of oil contamination in the process stream.With its superior efficiency,durable construction,and minimal maintenance requirements,this pump series offers a reliable and sustainable solution for desalination plants,industrial water treatment,and various containerized or mobile water purification systems worldwide.

　　1 Product Overview and Operational Principle

　　The Danfoss APP 11-13 is an axial piston positive displacement pump,part of Danfoss's broader APP pump family.Its core operational principle involves a rotating cylinder block containing multiple pistons.These pistons are aligned with a stationary swashplate.As the cylinder block rotates,the pistons reciprocate within their bores due to the fixed angle of the swashplate.This reciprocating action creates a repeating cycle of drawing in fluid during the volume-increasing phase and pressurizing it during the volume-decreasing phase.The result is a highly stable and continuous output flow.A key differentiator from centrifugal pumps is that this RO High Pressure Pump provides a fixed displacement per revolution.This means the flow rate is directly proportional to the shaft speed and remains largely unaffected by changes in discharge pressure,ensuring consistent performance across varying system demands.This series includes specific models like the APP 11/1500 and APP 13/1200,which share common platform features but are optimized for different flow and pressure ratings to suit specific application needs.

　　2 Technical Specifications and Performance Data

　　The Danfoss APP 11-13 series is defined by a set of rigorous technical specifications that ensure its capability in high-pressure water applications.The pumps are designed for a maximum continuous outlet pressure of up to 120 bar(1740 psig)for certain models,making them a truly high-intensity High Pressure Axial Piston Pump.The rated displacement varies across the series,with models like the APP 11/1500 having a geometric displacement of 137.4 cm³/rev,while the APP 13/1200 is rated at 197.5 cm³/rev.This directly influences their flow output,which can range from approximately 80 liters per minute up to about 225 liters per minute,depending on the specific model and its operational speed.

　　The operational speed range for these pumps is typically between 700 RPM and 1500 RPM,providing flexibility in drive system design.They require specific inlet pressure conditions to operate correctly and avoid cavitation,with a continuous inlet pressure range of 2 to 5 bar and a maximum peak inlet pressure of 10 bar.The pumps are designed to function with media temperatures between 2°C and 50°C and can operate in ambient temperatures from 0°C to 50°C.With a sound pressure level of 85 dBA and a compact,heavy-duty design,the APP 11-13 series is built for reliable integration into various system layouts.The pump connections are standardized with metric M42 threaded ports for both inlet and outlet,simplifying piping design and installation.

　　3 Core Design Features and Construction

　　3.1 Robust Material Selection for Corrosive Environments

　　The longevity and reliability of the APP 11-13 RO High Pressure Pump are rooted in its extensive use of highly corrosion-resistant materials.Critical wetted components,including the valve body,are constructed from duplex steel(EN1.4462/UNS S31803)and in some cases super duplex steel(EN1.4410/UNS S32750).These advanced stainless steels offer exceptional resistance to pitting and chloride-induced stress corrosion cracking,which is paramount when handling aggressive media like seawater or wastewater.Furthermore,key wearing components are made from carbon fiber-reinforced PEEK(Polyether Ether Ketone),a high-strength polymer known for its excellent wear characteristics and corrosion resistance.The shaft seal utilizes NBR(Nitrile Butadiene Rubber),appropriately selected for compatibility with the pumped media.This strategic material selection ensures a long service life and minimizes the risk of premature failure in some of the most challenging operating environments.

　　3.2 Integrated Flush Valve and Lubrication System

　　A standout feature of the APP 11-13 series is its integrated flush valve.This valve allows fluid to circulate from the pump's inlet to its outlet when the unit is not running.This function prevents stagnation,protects internal components during standby periods,and ensures the pump is immediately ready for operation.More importantly,the pump's design completely eliminates the need for lubricating oil.Instead,it uses the pumped process water for lubricating the piston slippers and other internal bearing surfaces.This oil-free design is a critical advantage in RO and other water treatment processes,as it entirely removes the risk of product water contamination from lubricant leaks.This not only safeguards process integrity but also reduces the need for oil inventory,handling,and disposal.

　　4 Application Areas and Industry Solutions

　　The Danfoss APP 11-13 High Pressure Axial Piston Pump is the cornerstone of numerous critical water treatment systems across the globe.Its primary application is in high-pressure reverse osmosis(RO)systems,particularly in seawater desalination(SWRO)and brackish water reverse osmosis(BWRO)plants.Here,the pump's ability to deliver a stable,high-pressure flow is essential for pushing water through semi-permeable membranes to separate salts and impurities.The pump's corrosion-resistant construction makes it ideally suited for the challenging nature of seawater feed.

　　Beyond standard desalination,this pump series is also deployed in advanced Zero Liquid Discharge(ZLD)and Minimal Liquid Discharge(MLD)systems.These systems are designed to recover nearly all water from industrial wastewater,leaving behind only solid waste.The reliability and high-pressure capability of the APP 11-13 are crucial for concentrating waste streams to their final state.Application examples extend to containerized solutions for hotels,resorts,and residential complexes in coastal areas;mobile systems for humanitarian and military organizations;marine systems for ships and yachts;and offshore platforms in the oil and gas industry.This versatility demonstrates the pump's adaptability to diverse and often remote operational settings.

　　5 Operational Advantages and Economic Benefits

　　5.1 Superior Energy Efficiency and Low Operating Costs

　　The axial piston design of the Danfoss APP 11-13 is inherently more efficient than centrifugal pump technologies,especially in high-pressure applications.This RO High Pressure Pump can achieve operational efficiencies exceeding 90%,which translates directly to lower energy consumption.For continuous operations like large-scale desalination plants,this efficiency advantage results in substantial savings in electricity costs,which constitute a significant portion of the total lifecycle expense.The pump's positive displacement characteristic ensures that flow is delivered consistently regardless of pressure,avoiding the energy losses associated with throttling valves or bypass lines that are common in centrifugal pump systems.This high efficiency also contributes to a reduced carbon footprint,supporting sustainability goals.

　　5.2 Reduced Maintenance and High Reliability

　　The APP 11-13 is engineered for minimal maintenance and maximum uptime.Its simple design,with fewer components compared to alternative solutions,enhances overall reliability.When operated within Danfoss's specified technical parameters,the pump can achieve maintenance intervals of up to 8,000 hours.Furthermore,the design allows for straightforward field servicing without the need for specialized tools,which reduces both maintenance time and costs.The combination of robust,corrosion-resistant materials and an oil-free lubrication system eliminates failures commonly associated with material degradation and oil contamination.This leads to a longer overall service life and a lower total cost of ownership,as unplanned downtime and frequent part replacements are significantly reduced.

　　6 System Integration and Implementation Notes

　　Successfully implementing the APP 11-13 pump requires careful attention to system design and ancillary components.Proper filtration is critical to protect the pump's precision components from abrasive particles.A main filter rated to remove particles larger than 10µm with an efficiency of 99.98%is strongly recommended upstream of the pump.To prevent cavitation,which can cause severe damage,the inlet pressure must be maintained within the specified range of 2 to 5 bar continuous pressure.Installing a low-pressure protection switch on the suction side is a common practice to safeguard the pump.

　　The pump offers flexible installation options,supporting both horizontal and vertical mounting,which helps system designers optimize the layout for space-constrained applications.Its compact and lightweight design,relative to its performance,further eases integration.Due to its minimal pressure pulsation,the APP 11-13 typically does not require a pulse damper,simplifying the system and reducing installation costs.If the pump is to be driven by a variable frequency drive(VFD)for speed control,it is essential to select a heavy-duty constant torque VFD.Standard pump-and-fan type VFDs may not be capable of providing the required starting torque and can lead to operational issues.

　　Frequently Asked Questions(FAQs)

　　1.Is the Danfoss APP 11-13 accurately described as a hydraulic pump?

　　While it operates on an axial piston principle common to hydraulic pumps,the APP 11-13 is specifically engineered as a High Pressure Axial Piston Pump for water applications.The critical distinction is that it uses the pumped water for lubrication,unlike traditional hydraulic pumps that use oil.This makes it a"high-pressure water pump"rather than a conventional hydraulic pump,and it is uniquely suited for processes where oil contamination is unacceptable,such as in the production of potable water.

　　2.What makes the materials used in this RO High Pressure Pump so durable?

　　The pump utilizes duplex and super duplex stainless steels for critical wetted components.These alloys provide exceptional resistance to chloride-induced pitting and stress corrosion cracking,which are common failure modes in seawater environments.Components like pistons and slippers are made from carbon fiber-reinforced PEEK,a high-strength,low-friction polymer that offers excellent wear resistance and is impervious to corrosion.This material selection is the foundation for the pump's long service life and ability to handle aggressive media.

　　3.How does the efficiency of this positive displacement pump compare to a centrifugal pump in RO service?

　　In high-pressure RO applications,positive displacement pumps like the APP 11-13 are significantly more efficient than centrifugal pumps.Centrifugal pumps experience a drop in efficiency at higher pressures,whereas axial piston pumps maintain high efficiency,often over 90%,across their operating range.This is because they deliver a fixed amount of fluid per revolution,minimizing energy losses.For an RO plant,this efficiency directly translates to lower energy consumption for the same output of purified water,making it a more cost-effective and sustainable solution.

　　4.What are the key considerations for pairing this pump with a variable frequency drive(VFD)?

　　It is crucial to use a heavy-duty constant torque VFD.The APP 11-13,as a positive displacement pump,presents a constant torque load to the motor,meaning the torque requirement is independent of speed.Standard"pump and fan"VFDs are designed for variable torque loads(where torque is proportional to the square of the speed)and lack the current capability to start and run this type of pump reliably,which could lead to VFD trips or motor stall.Always consult with the VFD manufacturer to ensure compatibility.

　　5.Can the APP 11-13 series handle parallel operation for system expansion?

　　Yes,these pumps are well-suited for parallel operation.This allows multiple pump units to work together on a common high-pressure manifold to meet increased system flow requirements.This scalability provides significant flexibility for system designers,enabling capacity expansion without a complete system redesign.Parallel operation also offers potential redundancy benefits for critical applications where continuous operation is essential,as one pump can be taken offline for maintenance without halting the entire process.