What is a seawater centrifugal pump?

What is a seawater pump?

Seawater centrifugal pumps are the type of pump that mainly used for conveying seawater or salty water. Due to the high corrosion of seawater, the most ideal material for seawater pumps are duplex stainless steels including CD4MCu and S31803, Titanium alloy is also a good choice for seawater pumps if the user has a higher budget. Seawater pumps play an important role in various industrial and municipal operations situated near the ocean or other salty water applications. Centrifugal pumps, known for their reliability, efficiency, and cost-low, are commonly used for seawater applications. This article provides an overview of centrifugal seawater pumps, including their structures and working principle, general applications, model selection, maintenance and advantages compared to other type of pumps.

The working principle of Centrifugal Seawater Pump 

The working principle of a seawater centrifugal pump is to use a rapidly rotating impeller to accelerate the water in the pump body, thus imparting speed and kinetic energy to the water. The water is ejected from pump discharge under the action of pressure. The big centrifugal force generated by the impeller allows these pumps to efficiently move large volumes of water. A centrifugal seawater pump has three main components: impeller, pump body and driving part. The impeller is installed at the end of the pump shaft in the pump body. When the impeller rotates at high speed, it sucks water through the center of the impeller and throws it out from the tip of the blade at high speed.  The function of the pump body is to convert high-speed water flow into pressure, it is also the place the bearings and mechanical seal are installed. The driving part provides the power required to rotate the impeller, which is usually an electric motor, but a diesel engine would also be preferred by some users if the electricity it not available at site.

Main advantages of the centrifugal sea water pumps

l  Big flow and suitable head.

Centrifugal seawater pumps are able to convey big volume of sea water at the suitable discharge pressure, and the flow rate and head of pump can be adjusted by the changing the diameter of the pump impeller or by changing the pump speed.

l  Few maintenances design.

Compared with positive displacement or reciprocating pumps, the centrifugal seawater pumps have a simple but mature design of only one rotating part, which makes them more reliable and thus require few maintenances.

l  Wear resistance

By adopting the duplex stainless steels as the wetted parts of the pumps, the centrifugal seawater pumps can work with the fluids with a few solids or particles. Due to the higher hardness grade of the duplex stainless steels, the pump impeller and casing can withstand the abrasion from the solids or particles like sands in the sea water.

l  Lower investment

Thanks to the reliable performance and relatively low cost, centrifugal type of pumps are widely used in various industries, and therefore such centrifugal seawater pumps can be always obtained easily from various suppliers.

General applications of seawater centrifugal pumps

Centrifugal seawater pumps can be manufactured with fully customized design to meet the different flow rates and discharge pressures from various sea water applications:

l  Seawater desalination

In order to producing the freshwater, desalination plants need the seawater centrifugal pumps to provide high pressure to enable the saline water to move through the membranes.

l  Ship ballast water transfer

For stability and trimming purpose, centrifugal seawater pumps are needed on ships to move the seawater in and out of ballast tanks.

l  Offshore platforms

Seawater centrifugal pumps are widely used for injection of sea water into the oil wells and hydrocarbon processing operations on offshore drilling platforms.

l  Cooling of power plants

The coastal power plants needs big seawater pumps to intake and circulate the sea water for the purpose of cooling the condensers.

l  Aquaculture

The Marine aquaculture farms rely on centrifugal seawater pumps to continuously replenish seawater into the farming tanks.

l  Bilge and firefighting on ships

Ships need centrifugal seawater pumps to intake the seawater that remains in the bottom of ships, while fire pumps provide seawater to the ship’s fire-extinguishing system.

l  Flood control at coastal regions

The coastal regions are always faced with flood problems, which need centrifugal pumps to remove the seawater and rain water.

Model selection guidance of seawater centrifugal pumps

The proper model selection of centrifugal seawater pumps requires a comprehensive consideration of the below specifications:

l  Pump capacity and discharge pressure.

The pump model and size are determined by the required capacity and discharge pressure, the user is supposed to provide such information to pump suppliers for selection of the correct pump model.

l  Pumping fluid characteristics

The specific gravity of seawater is generally various from 1030 kg/m³ to 1050 kg/ m³, the calculation of driving part power should fully consider the density of seawater.

l  Wetted parts MOC of seawater pumps

Due to the corrosive characteristics of seawater, duplex stainless steels must be adopted as the wetted parts material for centrifugal seawater pumps, other lower grade materials would be corroded in a short period of time.

l  Suction depth

Suction depth of the centrifugal seawater pumps must be taken into consideration during the pump model selection, different suction depth requires different pump speed and different configurations to meet the requirement of suction depth, otherwise, the cavitation would happen and therefore damage the pump.

l  Cost consideration

During the model selection of seawater centrifugal pumps, users should not only focus on the initial investment, but also have to consider the power consumption of pump unit as well as the maintenance of the pumps.

Maintenance notices

Due to the corrosion and abrasion of the seawater, proper and in time maintenance is necessary to prevent the damage of centrifugal seawater pumps, here are some notices of maintenance as follow:

l  Pay attention to the pump flow rate, discharge pressure, vibration and power consumption, the changes of those values may suggest potential problems.

l  On time inspection (e.g. 3 months interval) of pump casing, impeller, mechanical seal, flush plan pipelines, bearings and shaft, replace the worn parts in time before the failure to avoid more loss.

l  Checking the consumption of lubricant oil and refill it if it is necessary.

l  Flushing the pump by freshwater after the operation of pump to eliminate the potential crystallizations in the pump casing.

l  Repainting the non wetted parts of the centrifugal seawater pump if the original painting is gone.

l  Checking the engine status in time to avoid any failure on the power end.

By following the above notices of maintenance may increase the service life of the sea water centrifugal pumps.

The technical advancements of seawater centrifugal pumps

Nowadays, new technologies have been adopted to improve the performance of seawater centrifugal pumps, which widely increased the application range where the centrifugal sea water pumps can be used.

l  Titanium alloy has been introduced as the wetted parts material of centrifugal sea water pumps, which maximumly increases the life of the pump parts.

l  Seawater centrifugal pumps with Silicon carbide lining becomes a new direction of the technology in this industry.

l  Optimized hydraulic model of the centrifugal seawater pumps increased the pump efficiency and thus reduces the power consumption of the pumps.

l  Seawater centrifugal pumps with integrated vacuum system sharply increased the suction depth of pumps, which enables the pumps to intake sea water from lower places.

l  VFD motors are adopted for centrifugal sea water pumps, which enables the same piece of pump to work at various flow rates and discharge pressures.

Sichuan Zigong Pump & Valve Co., Ltd has an experienced technical team that can provide you with professional and economical pumping solutions.

Contact us by sales@zgpumpvalve.com or wa.me(Whatsapp: +8613738006567)