Overview of Centrifugal Pumps Used in Mariculture Industry

Centrifugal pumps are the most critical fluid transfer equipment for mariculture (ponds, land-based factory RAS recirculating aquaculture systems, hatcheries, and supporting facilities for ocean ranches). Featuring large flow rate and low head for 24-hour continuous operation, they perform tasks including raw water intake, water recirculation, filtration, sewage discharge, and aeration support. Self-priming centrifugal pumps, horizontal end-suction centrifugal pumps and vertical centrifugal pumps are the most widely adopted types, while a small number of multi-stage centrifugal pumps are applied for pressurization.

1. Main Application Scenarios

1).Seawater Intake (Raw Water Lifting) For coastal ponds, high-pond shrimp farming and hatcheries: horizontal / self-priming centrifugal pumps extract seawater from offshore areas and deliver it to sedimentation tanks and storage reservoirs. Affected by tidal fluctuations, pre-filters are commonly equipped to stop seaweed, shells, fish and shrimp from entering and clogging the pump cavity.

2).RAS Recirculating Water System (Highest application proportion in factory farming) Vertical centrifugal pumps are mostly selected as the main circulation pumps for the loop: culture tank → microfilter → protein skimmer → biofilter → UV sterilizer → culture tank. They keep water flowing continuously, transport residual feed and faeces to water treatment units and maintain dissolved oxygen. RAS imposes the strictest reliability requirements on pumps; pump shutdown will easily lead to oxygen depletion and mass mortality of shrimp/fish.

3).Water Exchange & Sewage Discharge Horizontal centrifugal pumps are generally used for regular pond water exchange, bottom sewage removal and backwashing (backflush of microfilters and sand filter tanks).

4).Pressurization for Aeration / Ozone System Centrifugal pumps provide pressurization for Venturi jet aerators and ozone mixing units to increase dissolved oxygen content.

5).Temperature Control System Circulating transfer for seawater heat exchange, heating / cooling loops.

2. Common Pump Types & Material Selection

2.1 Pump Types

1).Horizontal end-suction centrifugal pump: for water intake and large-flow water exchange, easy maintenance.

2).Self-priming centrifugal pump: for coastal water intake with fluctuating water levels; no pump priming required.

3).Vertical inline centrifugal pump: for indoor RAS circulation, small footprint.

4).Multi-stage centrifugal pump: high-pressure backwashing and ozone pressurization (small flow, high head).

2.2 Wetted Part Materials (Core Selection Criteria)

1).316L: Commonly used in small and medium farms for ordinary offshore and low-salinity seawater.

2).2205 Duplex Stainless Steel: Main recommended grade, resistant to pitting and crevice corrosion, suitable for long-term continuous operation.

3).2507 Super Duplex Stainless Steel: For high salinity and heavily polluted offshore working conditions.

4).Nickel Aluminum Bronze: Traditional seawater pump material, resistant to seawater erosion and marine biofouling.

5).Regular 304: Not recommended for long-term seawater service; prone to rapid pitting and perforation.

Seals: EPDM rubber is the primary option. Ordinary nitrile rubber cannot be used.