The Rohre HPS 39 is a heavy-duty axial piston high-pressure pump featuring a geometric displacement of 441.4 cc/rev, engineered as a near-perfect volumetric match to the Danfoss APP 43/1700 (444 cc/rev). Operating at a continuous 70 barg, the HPS 39 delivers exactly 39.10 m³/h at 1500 rpm. For Seawater Reverse Osmosis (SWRO) system integrators, this close volumetric alignment allows the HPS 39 to act as a highly compatible, budget-disruptive alternative—slashing legacy European procurement CAPEX by 1/5 to 1/8 while utilizing the identical motor torque profile.
For reverse osmosis system integrators (SIs) and water treatment EPC contractors, sourcing high-pressure pumps that can replace legacy infrastructure without altering the existing electric motor configuration is the ultimate goal for cost optimization.
Recently, our engineering team evaluated a direct field comparison between the Danfoss APP 43/1700 and the Rohre HPS 39. By analyzing the official manufacturer specification sheets, we can provide a definitive compatibility guide for engineering teams looking to retrofit their systems.
Danfoss APP 43 Specifications
Rohre HPS 39 Specifications
Volumetric Mapping: A Near-Perfect Match
When swapping axial piston pumps, matching the geometric displacement (cc/rev or cm^3/rpm) is critical because it dictates the torque requirement of your existing electric motor. The data reveals an incredibly close alignment:
- Danfoss APP 43 @1700RPM: Features a geometric displacement of 444 cc/rev. At its maximum speed of 1700 rpm, it delivers a rated flow of 44.6 m³/h at a continuous maximum pressure of 70 bar.
- Rohre HPS 39 @1500RPM: Features a geometric displacement of 441.4 cc/rev. Running at a standard motor speed of 1500 rpm, it delivers a rated flow of exactly 39.10 m³/h at a continuous maximum pressure of 70 barg.
*Note on Flow Rates: While the Danfoss APP 43/1700 states 44.6 m³/h at its maximum 1700 RPM, both pumps share an identical volumetric efficiency of over 98% when running at a synchronized standard speed of 1500 RPM (yielding ~39 m³/h). The difference in the datasheet is purely due to the rated testing speeds, not hydraulic loss.
Proven Field Deployment: The Caspian Sea Technical Verification
Material and hydraulic verification under challenging environmental conditions is the ultimate test for any high-pressure axial piston pump. To validate the real-world durability of our large-flow series, the Rohre HPS 39 has been successfully integrated into a modular SWRO (Seawater Reverse Osmosis) installation in the Caspian Sea region, specifically handling coastal industrial process water infrastructure.
In this heavy-duty application, the HPS 39 operates consistently under highly fluctuating salinity profiles. The fluid-end parts—precision-machined from Super Duplex stainless steel—have demonstrated exceptional resistance to localized crevice corrosion and pitting, with zero pressure ripples or pulsations in the high-pressure manifold. This real-world deployment proves that top-tier material integrity and operational stability can be achieved alongside a highly optimized capital expenditure (CAPEX) structure.
The Retrofit Evaluation: Integrating with the Existing Drive
Since the hydraulic and torque profiles match so precisely, integrating the Rohre HPS 39 into an existing Danfoss APP 43/1700 installation becomes highly straightforward, with only two engineering considerations:
1. Flow Rate and Operational Speed Adjustment
If your system’s existing electric motor is paired with a Variable Frequency Drive (VFD) and was originally running the Danfoss APP 43 at 1700 rpm to achieve ~44.6 m³/h, the Rohre HPS 39 can be regulated via the VFD up to a safe operational envelope, or run at 1500 rpm to deliver a stable 39.10 m³/h. If the system is already fixed at a 1500 rpm synchronous motor speed, both pumps will produce virtually the same output (~39 m³/h), making the performance swap seamless.
2. Mechanical Coupling and Housing Connections
While the internal hydraulics match perfectly, legacy European manufacturers often utilize proprietary or specific SAE mounting flange and shaft spline configurations. To retain your existing motor without any modification, Rohre provides tailored matching bell housings and flexible coupling adaptors. This ensures the HPS 39 bolts natively onto your current drive frame.
Data Verification: Rohre HPS 39 vs. Danfoss APP 43/1700
The metrics below are pulled directly from authorized technical data boundaries:
- Geometric Displacement:
- Rohre HPS 39: 441.4 cc/rev
- Danfoss APP 43/1700: 444 cc/rev
- Rated Flow Rate:
- Rohre HPS 39: 39.10 m³/h (at 1500 rpm / 70 barg)
- Danfoss APP 43/1700: 44.6 m³/h (at 1700 rpm / 70 bar)
- Continuous Maximum Outlet Pressure:
- Rohre HPS 39: 70 barg (at 1500 rpm) / 85 barg (at 1200 rpm)
- Danfoss APP 43/1700: 70 bar (1015 psi)
- Housing & Wetted Materials:
- Rohre HPS 39: Duplex 2205 / Super Duplex 2507 Stainless Steel
- Danfoss APP 43/1700: Super Duplex / PEEK
- Procurement Advantage:
- Slashes legacy European CAPEX by 1/5 to 1/8. For large-scale multi-skid installations, this reallocation of budget allows engineering teams to optimize high-grade energy recovery devices (ERD) or significantly lower their bidding price in international tenders.
Conclusion and Next Steps for System Integrators
The technical data confirms that the Rohre HPS 39 is a highly viable, volumetrically equivalent alternative to the Danfoss APP 43/1700. It offers the exact same heavy-duty pressure thresholds (70 bar continuous) and material integrity (Super Duplex steel) required for harsh saltwater environments, but at a fraction of the cost.
If you are planning an upgrade or a direct pump replacement for your current maintenance cycle, simply provide our engineering team with your existing motor’s frame size (IEC/NEMA) and your VFD frequency setpoints. We will supply the exact pump block and connection interface drawings needed for a smooth, high-ROI integration.
We will supply the exact pump block and connection interface drawings needed for a smooth, high-ROI integration. You can also utilize our online selection and TDH calculation tools to draft your preliminary pipeline designs.
