Learn - Feb. 19, 2025
When handling large capacity of seawater, selecting a corrosion-resistant vertical axial flow pump is critical. Installing and operating such large-scale pumps is challenging due to: ①High welding standards for chloride-corrosion-resistant materials; ②Large size requiring heavy lifting equipment for transport and installation; ③The need to meet conditions of high flow rates and low head. We aim to provide a detailed guide to assist with the procurement process.
The vertical seawater pump is a single-stage vertical axial flow pump, featuring high flow rate, low head, compact structure, and especially the ability to resist seawater corrosion. These pumps have a wide range of applications, mature technology, large flow rate, high efficiency, good cavitation performance, stable operation, and convenient installation and maintenance. We have rich experience in the application of corrosion-resistant materials. The correct selection of materials ensures that the seawater vertical axial flow pump has excellent corrosion resistance and a long service life.
The vertical axial flow pump operates based on the lift theory from aerodynamics. When fluid flows past an airfoil, it splits into two streams at the leading edge, one passing over the upper surface and the other along the lower surface, before converging again at the trailing edge. Since the path length over the lower surface is longer than that over the upper surface, the flow velocity over the lower surface is higher, resulting in lower pressure on the lower surface compared to the upper surface. According to Bernoulli's principle, this pressure difference creates a lift force on the airfoil. Similarly, the airfoil exerts an equal and opposite force on the fluid, which results in the water being lifted to a certain height.
The main structural components include: suction bell, impeller, guide vane body, elbow, pump shaft, bearings, stuffing sealing, motor, etc.
● Suction Bell : It is the suction chamber of the vertical axial flow pump, and its function is to guide water to the impeller with minimal head loss in a uniform manner.
● Impeller : Its function is to provide axial and rotational kinetic energy to the liquid in the pump casing, pushing the liquid into the guide vane body and the pump outlet pipe.
● Guide vane body : Located above the impeller, its main function is to eliminate the rotational motion of the water flow and convert the kinetic energy of the water flow's rotational motion into pressure energy.
● Pump shaft : Transmits torque to the impeller.
The flow parts of seawater vertical axial flow pumps must possess excellent resistance to seawater corrosion. Suitable materials include stainless steel 316L, duplex stainless steel 2205, super duplex stainless steel 2507, and CD4MCu.
| 316L | 2205 | CD4MCu | 2507 | |
| Element | Cr: 16-18%; Mn: ≤2%; Ni: 10-14%; Mo: 2-3%; | Cr: 22-23%; Mn: ≤2%; Ni: 4.5-6.5%; Mo: 3-3.5%; | Cr: 24.5-26.5%; Mn: ≤1%; Ni: 4.75-6%; Mo: 1.75-2.25%; Cu: 2.75-3.25% | Cr: 24-26%; Mn: ≤1.2%; Ni: 6-8%; Mo: 3-4%; |
| PREN | 26 | 34 | 42 | ≥40 |
| Tensile strength | 170MPa | ≥620MPa | 550MPa | ≥800 MPa |
| Cl- tolerance limit | 3000ppm(20℃) | 20000ppm(60℃) | 50000ppm(80℃) | 15000ppm(80℃) |
Different marine environments, characterized by varying water temperatures and chloride concentrations, impose distinct material requirements. Our experienced sales team will assist in selecting the most appropriate materials based on specific application conditions.
We are experts in corrosion-resistant materials and have a rich references of corrosion-resistant pumps. The superior performance of our seawater vertical axial flow pumps can be attributed to our advanced manufacturing capabilities. Super duplex stainless steel 2507, characterized by its high ferrite and molybdenum content, is susceptible to the formation of brittle phases and casting cracks, particularly in complex castings with significant wall thickness variations. To address these challenges, our casting process involves initial melting in a medium-frequency induction furnace followed by refining in a VOD furnace. This ensures high-quality crude steel liquid. Optimized gating systems, combined with Huazhu CAE/InteCAST technology, facilitate the creation of smooth and unobstructed flow channels for efficient shakeout. For welding, E2594 electrodes are used, with strict control of interpass temperature below 60°C and heat input within the range of 0.5 to 1.2 kJ/mm. Each weld seam undergoes rigorous quality control to meet welding procedure qualification standards.
● Seawater desalination plants
● Seawater salt plants
● Chemical plants
● General industry
● Ships and offshore platforms
Vertical axial flow pumps have a large volume and high flow rate, and thus have high requirements for factory testing center. Before each pump is delivered to the customer, we conduct performance parameter tests to ensure that the flow rate and head meet the customer's needs.
The actual flow-head curve was verified through the GB/T 3216 standard test, with the deviation from the design value being no more than ±3%. This ensures that the efficiency index reaches the Class 1 level (η≥85%) as stipulated in the contract.
Vibration testing is carried out in accordance with ISO 10816-3 standard, and the vibration velocity of the bearing housing is controlled within 4.5 mm/s.
The NPSH cavitation margin test is conducted to verify the anti-cavitation ability of the pump body material, ensuring that the material weight loss rate is less than 0.1g/h under critical cavitation conditions.
Transportation: Comply with the requirements for the export transportation of large equipment
-Packaging and protection
-Shockproof treatment
-Special requirements for sea transportation
We offer 7×24-hour online technical support services for the installation and operation of large pump equipment. When selecting vertical seawater pumps, our sales and engineer team will communicate and confirm installation issues with customers repeatedly. The installation of pumps is determined based on actual working conditions, thus often presenting a wide variety. According to customer requirements, we customize the installation form, size, and inlet and outlet lengths of the pump. Addressing a wide range of customer challenges is integral to our professional and comprehensive pump customization service.
Installation: The vertical axial flow pump needs to be installed on a civil engineering platform, with the pump and motor installed on different structural layers respectively; there is a connection structure between the pump's outlet elbow pipe and the motor base, relying on the mechanical positioning among each structure, the concentric alignment of the motor shaft and the pump shaft can be easily achieved during installation.
vertical axial pumps are self-lubricating bearings and do not require additional lubrication or cooling water.
