Axial Flow Pumps

Axial flow pumps are dynamic pumps designed to move very large volumes of liquid at relatively low head.

Also known as propeller pumps, they move liquid predominantly parallel to the pump shaft and are commonly used for flood control, drainage, cooling-water circulation, dock and marine applications, irrigation, water treatment and other high-capacity transfer duties.

AxFlow UK supplies axial flow pumps from Gruppo Aturia and FPX Solutions, including vertical, horizontal and submersible configurations for industrial and infrastructure applications.

Our engineers can help select the pump, hydraulic design, installation arrangement, materials and drive around the required flow, total head, water level, NPSH, submergence and site conditions.

What is an axial flow pump?

An axial flow pump is a dynamic pump that moves liquid primarily in the same direction as the pump shaft.

Instead of throwing liquid radially outward like a conventional centrifugal impeller, an axial-flow impeller acts more like a propeller. Its blades generate lift and accelerate the liquid through the pump.

This makes axial flow pumps especially suited to very high flow rates where only a relatively small increase in head is required.

How does an axial flow pump work?

An axial flow pump works through four main stages:

1. Liquid approaches the pump through the intake or suction bell.
2. A rotating propeller-style impeller transfers energy to the liquid.
3. The liquid moves mainly parallel to the pump shaft.
4. Guide or diffuser vanes can straighten the flow and convert part of its velocity into useful pressure.

The result is a pump that can move extremely large quantities of liquid efficiently, but generally develops much less head than a conventional radial centrifugal pump.

Why choose an axial flow pump?

Axial flow pumps are particularly effective when the application requires:

• Very high flow
• Relatively low total head
• Continuous water circulation
• Large-scale drainage or dewatering
• Flood-control pumping
• Cooling-water circulation
• Dock or marine water movement
• Large intake or outfall systems
• Efficient operation at the correct design duty
• Vertical, horizontal or submersible installation

Their main advantage is not simply capacity. It is the ability to move large quantities of liquid without unnecessarily generating high pressure.

Where to use Axial Flow pumps

Axial flow pumps tend to be utilised in applications which require rather high flow rates and a low amount of pressure. They can be used as circulating water pumps in power plants. As well as this, they’re commonly used in the chemical industry for circulating large amounts of fluids in evaporators. Whilst being useful in flood dewatering applications where substantial quantities of water need to be moved over a short distance, for instance over a levee or dyke.  Marine applications include impounding pumps for docks and ports.

How to Select an Axial Flow Pump

Selecting the correct axial flow pump requires balancing hydraulic performance, fluid characteristics, installation layout, and materials to ensure reliable, energy-efficient operation and long service life.

Define Hydraulic Requirements

• Flow rate (Q): Primary selection parameter. Accurately define required discharge flow to avoid oversizing and unnecessary energy consumption.
• Total Dynamic Head (TDH): Typically low (≈ 1–10 m per stage). Include static lift, friction, and minor losses. Select a pump operating near its Best Efficiency Point (BEP).
• NPSH: Ensure available NPSH exceeds required NPSH to prevent cavitation. Vertical or semi-submerged installations improve suction conditions.

Consider Fluid Properties

• Fluid type: Clean water, seawater, slurries, or effluents affect hydraulic design and materials.
• Temperature: Impacts bearing lubrication and thermal expansion.
• Solids content: Abrasive fluids require hardened impellers, wear coatings, or lined casings.
• Corrosiveness: Use stainless steel, duplex, bronze, or coated materials as required.

Select Installation Configuration

• Vertical pumps: Ideal for sumps and intake wells; space-saving and self-venting.
• Horizontal pumps: Suitable for limited headroom but require priming systems.
• Submersible or mixed-flow designs: Used for flood control, drainage, and variable water levels.

Evaluate Mechanical Design

• Impellers: Fixed-pitch (simple, robust) or adjustable-pitch (variable performance).
• Bearings: Water- or grease-lubricated, matched to service conditions.
• Drive options: Vertical motors, gear drives, or diesel engines.
• Column design: Modular sections sized to site depth and support requirements.

Efficiency and Control

• Select the pump with the highest efficiency at the duty point.
• Use adjustable-pitch impellers or VFDs for flow control while minimising throttling losses.
• Operating near BEP reduces vibration, wear, and lifecycle costs

What types of axial flow pump are available?

Vertical axial flow pumps

Vertical axial flow pumps are commonly installed in wet wells, sumps, intake structures and pumping stations.

The hydraulic section remains below the liquid level while the motor can be positioned above the installation.

This arrangement is widely used for:

• Flood control
• Drainage
• Cooling water
• Irrigation
• Dock and marine applications
• Large water-transfer systems

Horizontal axial flow pumps

Horizontal axial flow pumps can be incorporated directly into appropriate pipework or circulation systems.

They can be useful where the site layout favours an inline or horizontal arrangement and where sufficiently good inlet conditions can be maintained.

Submersible axial flow pumps

Submersible axial pumps combine the hydraulic section and motor into a submerged pumping unit.

They are particularly useful for:

• Drainage pumping stations
• Stormwater
• Flood protection
• Surface-water transfer
• Wastewater circulation
• Installations where a conventional above-floor drive arrangement is undesirable

Adjustable-pitch axial flow pumps

Some propeller pumps use adjustable blades.

Changing blade pitch alters the hydraulic characteristics of the impeller, allowing the pump to be matched more closely to changing operating conditions.

Depending on the pump design, blade pitch may be fixed during assembly, manually adjustable or controllable during operation.

Which axial flow pump configuration should I choose?

The installation is often as important as the pump itself.

WHY BUY AXIAL FLOW PUMPS FROM AXFLOW

• AxFlow are the UK representatives for Gruppo Aturia, the oldest Italian pump manufacturer who offer a large range of axial flow pumps ranging from materials such as cast iron, stainless steel, bronze, duplex and super suplex stainless steel.
• Gruppo Aturia have supplied axial flow pumps to some of the world’s most prestigious projects including the MOSES scheme designed to stop Venice from flooding.
• AxFlow are experts at both the installation of axial flow pumps and their repair having carried out numerous projects in the maritime and land drainage sectors.

AxFlow GB provide stock available on a standard 2-3 days or express 24-hour delivery.

Axial flow pumps are a type of dynamic (centrifugal) pump that move fluid parallel to the pump shaft, rather than radially as in centrifugal pumps. They are designed for high-flow, low-head applications where large volumes of liquid must be transported efficiently — such as flood control, cooling water circulation, irrigation, and wastewater treatment.

In simple terms, they operate like a propeller in a pipe: the rotating impeller blades impart velocity directly along the flow axis, generating continuous movement of fluid.

Axial Flow Pump Maintenance Overview

Axial flow (propeller) pumps are used in high-flow, low-head applications such as flood control, cooling water circulation, and water transfer. Due to demanding hydraulic conditions, regular inspection and maintenance are essential to maintain efficiency and reliability.

Key Maintenance Practices

• Routine monitoring: Check for leaks, unusual vibration or noise, bearing temperatures, and changes in pressure, flow, or power consumption.
• Performance tracking: Record operating data and compare with baseline or factory test results to detect efficiency loss or wear.
• Bearings & lubrication: Ensure proper lubrication of line shaft and thrust bearings. Monitor oil condition, water flush flow, and bearing temperatures.
• Alignment: Verify shaft and motor alignment, particularly after installation or overhaul, to prevent vibration and premature wear.
• Impellers & columns: Inspect for erosion, corrosion, cavitation, or debris buildup. Maintain correct blade pitch and internal clearances.
• Seals & packing: Inspect mechanical seals or packed glands for leakage. Ensure correct materials and clean seal flush lines.
• Suction system: Keep strainers and suction bells clear and ensure adequate submergence to avoid cavitation and air entrainment.

Scheduled Overhaul & Storage

• Perform major inspections every 6–12 months, replacing worn bearings, seals, and wear components.
• For extended shutdowns, drain the pump, protect metal surfaces, store in dry conditions, and rotate the shaft periodically.

Hydraulic Characteristics

• Flow Direction: Parallel to the shaft (axial).
• Head Range: Typically 1–10 m per stage (can be higher with multi-stage designs).
• Flow Capacity: Very high — up to tens of thousands of cubic metres per hour.
• Efficiency: Excellent in high-volume, low-head service; often 80–90% hydraulic efficiency.
• Specific Speed: Very high (Ns > 10,000 in US units), meaning the pump is optimized for high flow, low head conditions.