Centrifugal Pumps vs Submersible Pumps: Key Differences, Features and Applications

In agricultural irrigation, municipal drainage, industrial circulation, building water supply and even emergency rescue, water pumps are indispensable core equipment. Centrifugal pumps and submersible pumps, as two mainstream pump types, are widely used in different working conditions due to their unique working methods and applicable advantages. So what are their differences? And which occasions are they suitable for? Omron Tech Pumps will systematically sort out their working principles, structural characteristics, application scenarios and selection points for you.

I. Core Common Ground: Basic Understanding of Two Pump Types

Although centrifugal pumps and submersible pumps are significantly different, they share consistent core commonalities, which lay the foundation for their wide application.

• Core Function: Both convert mechanical energy into fluid kinetic energy to realize liquid transportation, lifting or pressurization, solving the demand of "liquid cannot flow independently".
• Basic Advantages: Stable operation, convenient maintenance, long service life, suitable for fluid transportation scenarios in multiple industries.
• Common Misconception: The "size" difference between the two is mainly due to the different connected pipe diameters, which need to be adapted according to transportation requirements.

II. Submersible Pumps: Versatile Underwater Operators with High Convenience and Efficiency

(I) Core Definition and Structural Characteristics

Submersible pumps are widely used water treatment tools. Their core feature is the integrated design of pump body and motor, which can work directly submerged in water. Different from ordinary ground water pumps, this characteristic determines their unique advantages.

(II) Working Principle

Submersible pumps rely on centrifugal force to achieve continuous water pumping, and the steps are clear and easy to understand:

1. Preparation Stage: Before starting the pump, the suction pipe and pump must be filled with liquid to avoid damage to the equipment caused by idling.
2. Rotation and Pressurization: After starting the pump, the impeller rotates at high speed to drive the liquid to rotate synchronously. The liquid flies away from the impeller under the action of centrifugal force.
3. Transportation and Discharge: The flying liquid decelerates and pressurizes in the diffuser chamber of the pump casing, and then is discharged from the pump outlet.
4. Cycle Reciprocation: A vacuum low-pressure area is formed in the center of the impeller, and the liquid in the liquid pool is sucked into the pump under the action of atmospheric pressure for continuous circulation.

(III) Core Functional Advantages

• Submersible Operation: No need to build additional motor brackets, occupying minimal space, suitable for special scenarios such as deep wells and confined spaces.
• Strong Self-priming Performance: No need for additional liquid filling, it can directly extract underwater liquid after startup, with convenient operation.
• High Stability: The motor and pump body are professionally waterproof and sealed, which can adapt to humid underwater environments with many impurities and avoid short circuits.

(IV) Basic Parameters

Core parameters directly determine the transportation capacity and adaptability, which need to be focused on: flow rate, lift, pump speed, supporting power, rated current, efficiency, pipe diameter.

(V) Scope of Application

It is suitable for a wide range of scenarios and can be called an "all-round player", mainly including:

• Construction drainage and agricultural irrigation and drainage
• Industrial water circulation and urban and rural domestic drinking water supply
• Emergency rescue (such as basement and mine waterlogging drainage) and deep well water extraction

(VI) Limitations

• Tedious Maintenance: The pump body needs to be taken out of the liquid, resulting in high maintenance costs.
• Medium Restriction: It is not suitable for liquids containing a large number of hard impurities and strong corrosiveness, which are easy to wear parts.
• High Heat Dissipation Requirements: The motor relies on liquid cooling. Insufficient diving depth and too small flow rate are easy to burn the motor.

III. Centrifugal Pumps: Main Force Pumps for Ground Atmospheric Pressure with Precise Structure and Strong Adaptability

(I) Core Principle: What is "Centrifugation"?

Centrifugation is the embodiment of object inertia (for example, if an umbrella rotates too fast, water drops will break away from the umbrella and fly out). Centrifugal pumps are designed based on this principle, relying on high-speed rotating impellers to throw water out to realize liquid transportation.

(II) Structural Composition

Centrifugal pumps have precise structures, and the six core components are indispensable, each with a clear role:

• Impeller: The core component with high speed and large output force. The blades are the key. Static balance test must be done before assembly, and the surface must be smooth to reduce friction.
• Pump Body (Pump Casing): The main body of the water pump, which plays a supporting and fixing role, connects the bearing bracket, and provides space for liquid diffusion and pressurization.
• Pump Shaft: The transmission core, which connects the motor through a coupling, transmits the motor torque to the impeller, and transfers mechanical energy.
• Bearing: Supports the pump shaft, divided into rolling bearings (lubricated with grease, the refueling amount is 2/3～3/4 of the volume) and sliding bearings (lubricated with transparent oil, refueled to the oil level line). The operating temperature must be controlled within 85℃ (normally about 60℃).
• Sealing Ring (Leak Reduction Ring): Installed at the junction of the pump casing and the impeller, it controls the gap (0.25～1.10mm), reduces internal leakage and prolongs the service life of parts.
• Stuffing Box: Seals the gap between the pump casing and the pump shaft to prevent water flow from leaking out and air from entering. It is cooled by a water seal pipe, and the packing needs to be replaced after about 600 hours of operation.

(III) Working Principle

It has similarities with the working principle of submersible pumps, but the core points for attention are different:

1. Startup Preparation: The pump body and water inlet pipe must be filled with liquid before startup to prevent "cavitation" (air in the pump cannot form sufficient low pressure, making it impossible to pump water).
2. Rotary Water Extraction: The impeller rotates at high speed to drive the liquid to rotate. The liquid flies out of the impeller under the action of centrifugal force, and a vacuum is formed in the center of the impeller.
3. Continuous Transportation: The water from the water source enters the water inlet pipe under the action of atmospheric pressure (or water pressure), realizing continuous water pumping through cycle reciprocation.

Tip: Cavitation will cause the pump body to heat up, vibrate, reduce water output, and even seriously damage the equipment, which needs to be focused on prevention.

(IV) Core Functional Advantages

• Wide Transportation Range: The flow rate (several to thousands of cubic meters per hour) and lift (several to hundreds of meters) cover a wide range, adapting to different needs.
• Outstanding Pressurization Effect: Suitable for long-distance and high-drop pipeline transportation, such as high-rise secondary water supply and water supply network transportation in waterworks.
• Easy Maintenance: Installed on the ground, daily inspection and parts replacement are convenient, with low maintenance cost.
• Energy Saving and High Efficiency: Variable frequency centrifugal pumps can adjust the speed to reduce power consumption, suitable for liquids from normal temperature to 120℃.

(V) Classification Methods (5 Common Types)

• According to impeller suction mode: single-suction type, double-suction type
• According to the number of impellers: single-stage, multi-stage
• According to impeller structure: open type, semi-open type, closed type
• According to working pressure: low pressure, medium pressure, high pressure
• According to pump shaft position: horizontal type, vertical type

(VI) Scope of Application

• According to application scenarios: civil and industrial pumps
• According to conveying medium: clean water pumps, impurity pumps, corrosion-resistant pumps
• Typical scenarios: factory circulating water supply, high-rise secondary water supply, water supply network transportation in waterworks, etc.

Conclusion

Centrifugal pumps, with their precise multi-component structure, are like rigorous ground mechanics, stably supporting various fixed transportation systems. Submersible pumps, relying on their highly integrated design, are like flexible underwater special forces, solving all underwater transportation problems. Omron Tech Pumps has deeply cultivated the pump field, relying on the precise control of the core characteristics of centrifugal pumps and submersible pumps, to create high-quality pump products suitable for multiple scenarios, empower fluid transportation with professional technology, and help various industries achieve efficient, energy-saving and stable operation goals.