DHP 7.2 Axial Piston Pump (High Pressure Pump For Industrial Reverse Osmosis)

DHP 7.2 is a key model in the DHP series of Axial Piston Pumps, designed for large and medium-sized seawater desalination and industrial desalination systems. It is developed and produced by WUXI FENIGAL SCIENCE AND TECHNOLOGY CO., LTD. As the first domestic manufacturer of axial high-pressure piston pumps, the company has focused on the R&D of high-pressure piston pumps since 1990. After nearly 15 years of technical efforts, it has realized the localization of products, with its technical level and quality reaching world advanced standards. Its axial piston pumps have become core fluid transportation equipment in industrial reverse osmosis desalination scenarios due to their high corrosion resistance and large flow capacity.

This pump operates based on the principle of axial piston pumps: it achieves high-pressure transportation of low-viscosity corrosive 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. At the same time, it integrates a flushing check valve, which simplifies the pipeline design of reverse osmosis membrane systems, reduces installation space and costs, and is suitable for scenarios requiring continuous large-flow water supply such as factory-level wastewater desalination and medium-sized seawater desalination stations.

Core Advantages for Scenario Adaptation

For seawater desalination and industrial desalination scenarios, DHP 7.2 has two key advantages:

1. Balanced Large Flow and High Stability: With a flow rate of 7.2 m³/h at the rated speed of 1500 rpm, it meets the water supply needs of large and medium-sized systems (e.g., seawater desalination stations with a daily treatment capacity of 100～200 tons); the pulse during operation is much smaller than that of other pump types, with low vibration and noise ≤78 dB(A) (in accordance with EN ISO 3744-2010 standard), making it suitable for industrial sites sensitive to the operating environment;

2. Strong Corrosion Resistance and Long Service Life: 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, with a continuous operation life of over 8000 hours; moreover, it does not require lubrication with oil, reducing daily maintenance links and lowering operation and maintenance costs, making it suitable for desalination projects requiring long-term continuous operation.

Core Technical Parameters of DHP 7.2

 Pump Flow Curve

DHP 7.2 belongs to the DHP4.5～8.2 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 16 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 (0～10.0 m³/h). For example, at a rotational speed of 1000 rpm, the flow rate is approximately 4.8 m³/h; at 1300 rpm, it is approximately 6.2 m³/h; and when reaching the rated rotational speed of 1500 rpm, the flow rate stabilizes at 7.2 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 1500 (r/min)) / Rated Flow Rate 7.2 (m³/h)
For instance, when an industrial desalination system requires a flow rate of 5.5 m³/h, the required rotational speed is (5.5×1500)/7.2 ≈ 1146 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. Both the inlet and outlet sizes are M42×1.5 (depth 22 mm). Pipeline connection must match the thread specifications to avoid interface damage caused by forced connection; it is recommended to use high-pressure resistant gaskets (e.g., PTFE material) to ensure interface tightness and prevent high-pressure medium leakage;

• Motor coupling: A clearance of 3 to 5 mm must be maintained between the pump and motor couplings. The pump shaft must not be subjected to axial or radial loads (such as external forces caused by pipeline gravity or installation deviation) to prevent premature wear of the shaft seal and bearings. The following is a standard connection diagram for the motor and high-pressure pump. You can refer to this diagram to ensure installation accuracy:

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• Foundation and Piping: It is recommended to install the pump unit on a combined structure of concrete base + vibration dampers (the load capacity of vibration dampers must match the total weight of the pump (34.5 kg)) to reduce vibration transmission during medium-speed operation; the diameter of the inlet pipe should not be smaller than the pump's inlet and outlet sizes, and the pipeline length should be shortened as much as possible with fewer bends (the number of bends is recommended to be ≤2, and the bend radius ≥5 times the pipe diameter) to reduce pressure loss (to avoid cavitation caused by insufficient inlet pressure, which affects the flow stability of the pump).

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 plungers and plunger sleeves 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 rapid wear of internal pump components and shortening service life);

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 (idling for more than 5 minutes is likely to cause dry friction and scrapping of plungers); 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 (the maximum pressure resistance of reverse osmosis membranes is usually ≤75 Bar);

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, leading to sudden pressure rise during the next start-up); 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 of pump metal components); 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 7.2 varies with the working pressure. Its power requirement at the rated speed of 1500 rpm is as follows:

The working pressure of seawater desalination systems is usually 70～80 Bar, so a 22.0 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 15.0 kW motor can meet the requirements, effectively reducing the system's initial configuration cost and subsequent energy consumption cost.

Dimensional Parameters

Inlet and Outlet Dimensions

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

The following are examples of dimensions for DHP7.2 motors used in common applications, which can be used for installation space planning (e.g., industrial desalination equipment rooms and medium-sized desalination plants, with a maintenance clearance of ≥500mm):

High-Pressure Piston Pump Maintenance and Warranty Service (for DHP 7.2)

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 and prevent impurities from entering the pump and causing wear of plungers and plunger sleeves);

• 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—if the leakage exceeds 5 drops per minute, the shaft seal needs to be replaced) and the wear of plungers and plunger sleeves (if the wear gap exceeds 0.1 mm, parts need to be replaced). Worn parts should be replaced in time to maintain the flow and pressure stability of the pump;

• 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 (flush with fresh water for 10～15 minutes after each shutdown) to prevent residual salt from crystallizing on the inner wall of the flow channel and causing local pitting corrosion, which affects the pump's sealing performance and service life.

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 and pump body cracking caused by overpressure operation);

• 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 (the delivery cycle of spare parts is ≤7 working days) 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 7.2, 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", and continuously improves the supply chain and sales service system (having established service outlets in more than 30 cities across China). It 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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