The Ultimate Guide to Marine Pumps

Marine pumps refer to various types of pumps designed for ship use that comply with maritime regulations and technical standards. On board, they are commonly employed to transport seawater, freshwater, sewage, lubricating oil, and fuel oil.

Marine pumps are widely used in modern ships. Generally, a diesel-powered cargo vessel requires 36 to 50 pumps of various types, accounting for 20% to 30% of the total mechanical equipment on board.

Types and Uses of Marine Pumps

Marine pumps are primarily classified by their working principles and usage purposes, with the three common types being positive displacement pumps, centrifugal pumps, and jet pumps. This article by FILIPUSI experts primarily explains how centrifugal marine pumps operate.

1. Vertical Marine Pump

It generates centrifugal force through the high-speed rotation of the impeller. The motor drives the vertical main shaft and impeller to rotate. Liquid enters the impeller center from the bottom suction port, gains kinetic and pressure energy under the action of the blades, and is discharged from the upper outlet after being guided by the volute. The Vertical Marine Pump is highly suitable for medium and high-pressure applications such as seawater cooling, firefighting, and ballast water management.

2. Horizontal Marine Pump

The horizontal marine centrifugal pump adopts a horizontal coaxial integrated layout, with the motor and pump body arranged side by side in a horizontal configuration. During operation, the motor drives the horizontal transmission shaft to rotate the impeller at a constant speed. The medium is drawn axially from the front suction channel of the pump head into the impeller cavity.

The high-speed rotation of the impeller blades flings the medium, creating a centrifugal pressurization effect that converts the mechanical energy of the motor into liquid flow velocity and pressure. After entering the volute cavity, the liquid slows down while its pressure further increases, ultimately being discharged through the radial outlet on the pump body.

The Horizontal Marine Pump features a lower center of gravity, reduced operational vibration, and eliminates the need for elevated disassembly. It can also be adapted for maintenance in low and confined engine room spaces. It is primarily used for bilge water drainage, freshwater circulation supply, auxiliary cooling water circulation in the engine room, onboard washing water supply, and cargo hold water drainage pumping.

3. Marine Double Suction Pump

The marine double suction pump features a symmetrical impeller with dual-side water intake. The motor is connected laterally to a horizontal drive shaft, which powers the impeller rotation. The pump body has independent water intake channels on both sides, allowing seawater or medium to flow synchronously into the blade passages from both ends of the impeller. The axial thrust generated by dual-side water intake cancels each other out, significantly reducing bearing load.

The high-speed rotation of the impeller creates a centrifugal effect, performing synchronized work on the liquid flowing in from both sides, converting mechanical energy into fluid kinetic energy. The liquid converges into the central volute, where velocity decreases and pressure rises, ultimately being discharged uniformly from the top outlet of the pump body.

The Marine Double Suction Pump body adopts a horizontally split, mid-opening structure, enabling access to the impeller and sealing components for maintenance without disassembling the piping system. This design ensures convenient operation and maintenance, with a flow rate far exceeding that of single-stage centrifugal pumps of the same size. It features minimal operational vibration and enhanced stability. It is highly suitable for medium to large flow rate, medium to low-pressure water transportation applications, such as ballast water regulation for large and medium-sized vessels, main engine seawater cooling, high-flow firefighting water supply, centralized bilge drainage, and seawater desalination feedwater delivery.

Technical Comparison of Core Marine Centrifugal Pumps

Selection Criteria for Marine Pumps

The selection of marine pumps must strictly adhere to three core dimensions: medium characteristics, operating conditions, and classification society regulations. Different pump types vary significantly by purpose and are not interchangeable.

• Determine the Medium and Material: For seawater, corrosion-resistant materials against chloride ions (such as nickel-aluminum bronze or duplex stainless steel 2205/2507) must be selected; for fuel/oil, viscosity considerations are necessary, with volumetric pumps preferred for high viscosity; for chemicals, the sealing and flow components must match the corrosion resistance grade.
• Calculate Key Parameters: Determine the rated discharge (Q) and total head (H) based on the system's maximum demand, with a 10% to 15% margin reserved. Avoid selecting pumps with excessively low specific speed (<60) to prevent unstable operating conditions; for high specific speeds (>200), double-suction impellers like the Marine Double Suction Pump are recommended.
• Check the Net Positive Suction Head (NPSH): Ship rolling can cause fluctuations in the suction liquid level, so it is essential to ensure that the available NPSH (NPSHa) is at least 0.5 meters greater than the required NPSH (NPSHr) to prevent cavitation damage to the impeller.
• Compliance Certification: The product must obtain type approval certificates from mainstream classification societies (such as CCS, DNV, ABS) and comply with the requirements of the SOLAS Convention and the "Code for the Statutory Survey of Steel Hulls of Seagoing Vessels."

Summary of Pump Type Suitability:

• Centrifugal Pump: Suitable for scenarios with high flow rates and medium to low head, such as seawater cooling, ballast water, and firefighting. Depending on space and flow requirements, users can select the space-saving Vertical Marine Pump, the smooth-running Horizontal Marine Pump, or the high-flow Marine Double Suction Pump. Features a simple structure and smooth operation, but lacks self-priming capability (requires a foot valve or vacuum pump).
• Positive Displacement Pumps (Reciprocating/Screw/Gear): Suitable for high viscosity, low flow rate, high pressure, or applications requiring precise metering, such as fuel oil transfer, lubricating oil pumps, and cargo oil pumps (reciprocating pumps are commonly used for tank cleaning in oil tankers).
• Submersible Pump / Magnetic Drive Pump: Suitable for flammable, explosive, toxic, and hazardous media (such as LNG and chemicals), ensuring zero leakage, and must comply with explosion-proof and cryogenic material requirements.
• Self-Priming Pump: Suitable for applications such as bilge drainage where liquid levels fluctuate significantly, frequent starts are required, and no foot valve is present, with the capability for dry suction.

Selecting the appropriate marine pump should not be based solely on the initial installation cost but requires an assessment of the total lifecycle cost (LCC). Under the premise of meeting performance requirements, opt for models with high standardization and readily available spare parts. Conduct a comprehensive evaluation of initial investment, energy consumption, and maintenance frequency, rather than focusing only on the procurement price. It is recommended to provide detailed operating condition specifications to FILIPUSI manufacturers with classification society qualifications, tailored to the specific vessel type and drawings for customized selection.

Application of Marine Pumps

Marine pumps are the core equipment of ship power, safety, and living systems, primarily divided into three major application categories based on the transported medium and functional scenarios:

1. Pumps for Marine Power Plants

• Fuel System: The fuel is delivered from the bunker to the main engine injection system via the fuel transfer pump and booster pump, with some axial-flow supply pumps also featuring fuel refining and heating functions.
• Lubrication System: The oil pump (mostly gear or screw pump) supplies oil to moving parts such as the main engine and bearings, ensuring lubrication and cooling, with requirements for steady flow and no pulsation.
• Cooling System: The seawater pump extracts seawater from the outside of the ship to cool high-temperature components such as diesel engines and gas turbines; The fresh water pump circulates antifreeze or fresh water in a closed circuit to achieve heat exchange.
• Boiler and Refrigeration: The feed pump supplies water to the boiler to produce steam; Cooling water pump maintains stable temperature of condenser in refrigeration unit.

2. Ship Safety and General Operation Pumps

• Ballast System: The ballast pump (large displacement low head centrifugal pump) injects or discharges ballast water, adjusts the ship's draft, trim, list, and stabilizer height to ensure safe navigation when unloaded or fully loaded.
• Cabin Bottom Drainage: The cabin bottom pump (including emergency submersible pump) removes rainwater, leaks, or damaged water accumulated at the bottom of the engine room and cargo hold, preventing the ship from sinking. It often has an automatic start-stop function.
• Fire Fighting System: The fire pump delivers seawater or foam mixture to extinguish the fire, which shall meet the requirements of SOLAS Convention and have high reliability. The emergency fire pump is usually driven by an independent diesel engine.
• Domestic Water Supply: The fresh water pump transports fresh water from the storage tank to the kitchen, bathroom, and drinking water points, and works with a pressure cabinet to achieve constant pressure water supply.

3. Special Ship Specific Pumps

• Liquid Cargo Ships: Cargo oil pumps (mostly large centrifugal pumps or screw pumps) load and unload crude oil or refined oil products; The tank washing pump provides high-pressure water flow to drive the tank washing machine, cleaning the residual oil in the tank.
• Engineering Vessels: Mud pump/cutter suction pump is used for dredgers to transport high concentration sediment mixtures, and the core components need to be made of wear-resistant alloys to cope with severe wear.
• Other Special Uses: Including salvage pumps for salvage ships, propulsion pumps for waterjet propulsion ships (using reactive forces to propel high-speed vessels), fishing pumps for fishing boats, etc.

Real-World Case Studies (FILIPUSI Solutions)

Maintenance of Marine Pumps

The core of marine pump maintenance lies in periodic inspection, lubrication and sealing of key parts, timely troubleshooting, and ensuring that the equipment is always available. Daily attention should be paid to the operation sound, temperature, and leakage situation. Wear parts should be replaced regularly and major repairs should be carried out. Different pump types (such as oil pumps and fire pumps) have special requirements.

Frequently Asked Questions (FAQ)

FILIPUSI Multipurpose Marine Pump

FILIPUSI specializes in manufacturing high-performance Vertical Marine Pumps, Horizontal Marine Pumps, and Marine Double Suction Pumps. Our products comply with international maritime standards and hold major classification society certifications.

Please consult FILIPUSI experts to customize specialized pumps for your vessel, to safeguard your shipping route, and to view relevant qualifications and drawings.