DHP 3.5 Axial Piston Pump (High Pressure Pump For Industrial Reverse Osmosis)

DHP 3.5 is a key model in the DHP series of Axial Piston Pumps, designed for scenarios requiring low-to-medium speed and high stability. It is developed and produced by WUXI FENIGAL SCIENCE AND TECHNOLOGY CO., LTD. Since 1990, the company has focused on the R&D of high-pressure piston pumps and is the first domestic manufacturer of axial high-pressure piston pumps. After nearly 15 years of technical efforts, it has realized the localization of products, with its technical level and quality reaching world advanced standards. The axial piston pumps produced by the company have become core fluid equipment in the fields of seawater desalination and industrial desalination.

As a pump type specifically designed for high-pressure, low-viscosity corrosive fluids, DHP 3.5 is based on the principle of axial piston pumps. It achieves efficient transportation of media such as seawater and industrial saline wastewater by the reciprocating movement of plungers parallel to the drive shaft in plunger bores, which changes the volume of the pump cavity. Compared with traditional piston pumps, it uses the transported fluid itself as the lubricating medium, eliminating the need for a lubricating oil tank and fundamentally avoiding oil leakage pollution—perfectly meeting the strict cleanliness requirements of seawater desalination and industrial desalination.

Scenario Adaptation Advantages

For seawater desalination and industrial desalination scenarios, DHP 3.5 has two core advantages:

1. Low Speed and High Stability: With a rated speed of only 1650 rpm, it has smaller pulses, lower vibration during operation, and noise ≤77 dB(A) (in accordance with EN ISO 3744-2010 standard), making it suitable for small and medium-sized desalination systems that require long-term continuous operation (such as island seawater desalination stations and factory wastewater treatment lines);

2. Strong Corrosion Resistance and Integration: Key components of the pump body are made of 2205 duplex stainless steel (SAF 2205/EN 1.4462/UNS 31803), which has excellent corrosion resistance to high-salinity media. It also integrates a flushing check valve, simplifying the pipeline design of reverse osmosis membrane systems, reducing installation space and costs, and lowering system complexity.

Core Technical Parameters of DHP 3.5

Pump Flow Curve

DHP 3.5 belongs to the DHP3.5～4.0 series and is a fixed-displacement pump. Under a working pressure of 80 Bar, the flow rate has a strictly proportional relationship with the rotational speed. The flow curve on Page 15 of the manual allows for intuitive query of the flow rate corresponding to different rotational speeds: the horizontal axis represents rotational speed (700～1800 rpm), and the vertical axis represents flow rate (0～4.0 m³/h). For example, at a rotational speed of 1000 rpm, the flow rate is approximately 2.1 m³/h; at 1400 rpm, it is approximately 2.94 m³/h; and when reaching the rated rotational speed of 1650 rpm, the flow rate stabilizes at 3.5 m³/h.

If it is necessary to calculate the target rotational speed based on actual needs, the formula provided in the manual can be used:
Selected Motor Speed (r/min) = (Required Flow Rate (m³/h) × Rated Speed 1650 (r/min)) / Rated Flow Rate 3.5 (m³/h)
For instance, when an industrial desalination system requires a flow rate of 2.5 m³/h, the required rotational speed is (2.5×1650)/3.5 ≈ 1179 rpm, which is accurate and easy to calculate.

Installation and Operation Instructions 

Key Installation Requirements

• Interface Identification: The port marked "I" on the pump body is the inlet, and "O" is the outlet. The installation direction must be strictly distinguished to avoid damage to the check valve and plungers inside the pump due to reverse connection; the inlet size is G1-1/4〞 (depth 20 mm), and the outlet size is G3/4〞 (depth 20 mm), so pipeline connection must match the interface specifications;

• Motor Coupling: A clearance of 3～5 mm must be maintained between the couplings of the pump and the motor, and the pump shaft must not bear axial or radial loads (such as external forces generated by forced pipeline connection) to prevent premature wear of the shaft seal and bearings. Page 20 of the manual provides a standard connection diagram for the motor and the high-pressure pump, which can be referred to ensure installation accuracy:

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• Foundation and Piping: It is recommended to install the pump unit on a base with vibration dampers to reduce vibration transmission during low-speed operation; the diameter of the inlet pipe should not be smaller than the pump inlet size, and the pipeline length should be shortened as much as possible with fewer bends to reduce pressure loss (to avoid cavitation caused by insufficient inlet pressure).

Operation Precautions Specific to Seawater Desalination/Industrial Desalination Scenarios

1. Filtration Configuration: Impurity particles (such as sediment and suspended solids) in seawater and industrial wastewater can wear the precision components inside the pump. A filter with an absolute accuracy of 10 μm (filtration efficiency ≥99.98%, β10>5000) must be installed before the pump inlet. Bag filters or spiral wound filters with only 90% efficiency are strictly prohibited (prone to particle leakage, causing wear of plunger sleeves);

2. Pressure Protection: A low-pressure control switch (set to 2 Bar, matching the minimum inlet pressure requirement of the pump) should be installed at the inlet end, which will automatically shut down the pump when the inlet pressure is lower than this value to prevent pump idling; a high-pressure control switch (set to 70 Bar) and a safety valve (pressure adjustment range 5～9 MPa, customizable) should be installed between the pump outlet and the reverse osmosis membrane to prevent damage to the membrane module or pipeline due to system overpressure;

3. Start-Up, Shutdown and Flushing: In high-salinity scenarios (such as seawater desalination), the pump cavity must be flushed with fresh water after each shutdown to discharge residual concentrated brine (long-term residual concentrated brine is likely to crystallize and block the flow channel); if the shutdown lasts more than 3 days, flushing with fresh water is required; if it lasts more than 15 days, flushing with fresh water containing a bactericide is necessary (to prevent microbial growth and corrosion); starting the pump with the rear valve closed is strictly prohibited, as this may trigger the safety valve or cause pipeline burst.

Power Parameters

The power of DHP 3.5 varies with the working pressure. Chapter 7.1 of the manual specifies its power requirements at the rated rotational speed of 1650 rpm, as follows:

The working pressure of seawater desalination systems is usually 70～80 Bar, so an 11.0 kW motor is recommended to ensure stable pump operation without energy waste; for industrial desalination scenarios with lower pressure (e.g., below 60 Bar), a 7.5 kW motor can meet the requirements, effectively reducing the energy consumption cost of the system.

Dimensional Parameters

Inlet and Outlet Dimensions

Overall Dimensions (with Independent Fan Motor/Inverter Motor, Unit: mm)

The following are examples of the dimensions of DHP3.5 with commonly used motors, which can be used as a reference when planning installation space (such as industrial desalination equipment rooms, island desalination station layout, etc.):

High-Pressure Piston Pump Maintenance and Warranty Service (for DHP 3.5)

Daily Maintenance Key Points

• Lubrication Management: The transported fluid is used as the lubricating medium, so no additional lubricating oil is needed. Daily maintenance only requires judging whether to replace the filter element based on the filter pressure difference (a pressure difference exceeding 0.5 Bar indicates filter element blockage, which needs to be replaced in time to ensure clean inlet fluid);

• Regular Inspection: Under standard operating conditions (10 μm filtration, normal pressure/speed), a comprehensive inspection is recommended every 8000 hours. Focus on checking the sealing performance of the shaft seal (for leakage) and the wear of plungers and plunger sleeves (excessive wear will lead to a flow rate reduction of more than 10%), and replace worn parts (such as seals and plunger sleeves) in a timely manner;

• Corrosion Protection: The pump body is made of 2205 duplex stainless steel (with excellent corrosion resistance), but in high-salinity scenarios such as seawater desalination, the shutdown flushing process must be strictly implemented to avoid local corrosion (such as pitting corrosion caused by salt accumulation on the inner wall of the flow channel, which affects the pump's sealing performance and flow stability) due to residual salt.

Warranty Service

• Basic Warranty: A 1-year free maintenance service is provided from the date of delivery (excluding faults caused by man-made damage or non-compliant operation, such as component wear caused by not installing a filter);

• Extended Protection: If the pump operates under specified conditions at all times (meeting filtration, pressure and speed requirements), it can enjoy an 8000-hour maintenance-free warranty, with a maximum period not exceeding 18 months from the date of delivery;

• After-Sales Support: The manufacturer provides fault detection, on-site maintenance, factory repair and spare parts supply services to ensure the continuous and stable operation of seawater desalination and industrial desalination systems. Support can be obtained through the contact information below.

Manufacturer's Contact Information

• Company: WUXI FENIGAL SCIENCE AND TECHNOLOGY CO., LTD. (FG Water Technologies)

• Address: Chuangyi Industrial Park, No. 100 Dicui Road, Binhu District, Wuxi City, Jiangsu Province, P. R. China

• Tel: +86-510-85163211

• Mobile: +86-13646187144

• Email: [email protected]

• Official Website: https://www.fgwater.com

Company Introduction

WUXI FENIGAL SCIENCE AND TECHNOLOGY CO., LTD. (FG Water Technologies), the manufacturer of DHP 3.5, has focused on the research and development of high-pressure piston pumps since 1990 and is the first domestic enterprise to produce axial high-pressure piston pumps. After nearly 15 years of in-depth cultivation and innovation, the enterprise has realized the localization of axial high-pressure piston pumps. Its technical level and product quality have reached world advanced standards, and its production scale ranks among the top in the domestic industry, effectively solving the bottleneck problem of relying on imported products in related fields.

In collaboration with its OEM partner Shenzhen CW Environment Technology, the enterprise widely applies axial high-pressure piston pumps in fields such as seawater desalination, industrial desalination and membrane concentration. It always adheres to the tenet of "quality first, integrity-based, customer satisfaction", continuously improves the supply chain and sales service system, and is committed to providing customers with efficient core fluid equipment and technical solutions to support the implementation of the "Made in China 2025" strategy and industrial foundation strengthening strategy.

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