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An impeller is a driven rotating part (a rotor with vanes or blades) used to increase a fluid's flow and pressure. In simple words: an impeller is like a spinning wheel with blades that pushes liquid or air so it moves faster and can build pressure.
| Language | Word or phrase used | Simple explanation | What it relates to |
|---|---|---|---|
| Hindi | इम्पेलर (Impeller) | पंप के अंदर घूमने वाला पंखा जैसा हिस्सा जो पानी को तेज़ी से धकेलता है। | घर का पानी पंप, मोटर |
| Marathi | इम्पेलर (Impeller) | पंपमधला फिरणारा पातीसारखा भाग जो पाणी बाहेर ढकलतो. | पाण्याचा पंप |
| Tamil | இம்பெல்லர் (Impeller) | பம்பில் உள்ள சுழலும் பாகம், இது திரும்பி தண்ணீரை வேகமாக தள்ளும். | வீட்டுப் பம்ப் |
| Kannada | ಇಂಪೆಲ್ಲರ್ (Impeller) | ಪಂಪಿನ ಒಳಗೆ ತಿರುಗುವ ಬ್ಲೇಡ್ ಭಾಗ, ನೀರನ್ನು ಒತ್ತಡದಿಂದ ಮುಂದೆ ತಳ್ಳುತ್ತದೆ. | ನೀರು ಪಂಪ್ |
| Bengali | ইমপেলার (Impeller) | পাম্পের ভেতরের ঘূর্ণায়মান অংশ, যা জলকে বাইরে ঠেলে চাপ বাড়ায়। | জল তোলার পাম্প |
| Gujarati | ઇમ્પેલર (Impeller) | પંપની અંદર ફરતો બ્લેડવાળો ભાગ, જે પાણીનો પ્રવાહ અને દબાણ વધારે. | ઘર/ખેતર પંપ |
| Telugu | ఇంపెల్లర్ (Impeller) | పంపులో తిరిగే భాగం, ఇది నీటిని బయటకు తోసి ప్రెషర్ పెంచుతుంది. | వాటర్ మోటర్ |
| Malayalam | ഇംപെല്ലർ (Impeller) | പമ്പിനുള്ളിലെ തിരിയുന്ന ഭാഗം, വെള്ളത്തെ പുറത്ത് തള്ളുകയും മർദ്ദം കൂട്ടുകയും ചെയ്യുന്നു. | വീടിലെ പമ്പ് |
Think of an impeller like the fan inside a mixer-grinder jar, but instead of pushing air, it pushes water. When it spins, it throws water outward, so the water moves faster and pressure increases. That is how water can go up a pipe to your overhead tank. In a pump, running without water is dangerous because parts can heat up quickly and get damaged in seconds, so pumps should not be run dry.
An impeller adds energy to the fluid, while a turbine extracts energy from the fluid.
You will see the term "impeller" in:
These are the most common "types" people mean when talking about pump impellers.
| Type | How it looks | Best for | Example use |
|---|---|---|---|
| Open | Vanes exposed on one side | Dirty water, mild solids, easier cleaning | Sump, wastewater |
| Semi-open (semi-closed) | One side shrouded | Mixed conditions, balance of efficiency and solids handling | General industrial |
| Closed (enclosed, shrouded) | Shrouds on both sides | Cleaner fluids, usually better efficiency | Domestic water supply |
For many centrifugal pump applications, backward-curved blades are commonly cited as a high-efficiency choice, but real efficiency still depends on the full pump design, fluid, and operating point.
Here is the most common working sequence:
Why pressure increases: the impeller makes the fluid move faster, and the casing shape helps convert that motion into higher pressure.
KSB describes the same idea as energy transfer by torque through the rotating impeller, converting mechanical power into pump power output.
A common head form of the Euler pump relation is:
H = (U2·Vw2 − U1·Vw1) / g
Where:
Tiny example: if (U2·Vw2 − U1·Vw1) = 98.1 m²/s², then H = 98.1 / 9.81 = 10 m.
Common real-world uses:
EASA notes the three most common causes of surface damage in pump impellers are:
Cavitation often shows up as pitting and erosion marks on the impeller surface over time.
| Cause | What happens | Visible sign | Common symptom |
|---|---|---|---|
| Cavitation | Vapor bubbles collapse and pit metal | Pitting, crater-like marks | Gravel-like noise, vibration, reduced performance |
| Erosion | Abrasive wear from solids | Worn, thinned surfaces | Falling head and efficiency |
| Corrosion | Chemical attack on metal | Rust, material loss | Lower efficiency, leaks |
Running a pump without adequate liquid removes cooling and lubrication. That can destroy components quickly, especially mechanical seals.
There is no universal fixed interval. A practical approach is to replace (or repair) based on inspection and performance.
A useful rule of thumb: if an impeller wears or gets plugged, you often see flow drop, pressure drop, and efficiency drop on the pump curve.
Watch for:
| Observation | Likely reason | Action |
|---|---|---|
| Flow and pressure drop | Wear, clogging | Inspect, clean, measure wear; check for plugging and surface loss |
| Frequent seal failure | Dry running, heat, vibration | Fix priming, ensure pump stays flooded; correct operating conditions |
| Cavitation marks | Suction issues, operating point issues | Review suction conditions and cavitation symptoms; correct root cause |
This is where most people mean "agitator vs impeller".
| Feature | Agitator washer | Impeller washer |
|---|---|---|
| Movement | Central post moves clothes more directly | Low-profile plate moves clothes through water flow |
| Cleaning style | More direct rubbing | More fabric-to-fabric rubbing |
| Space | Usually less capacity | Often more capacity in same drum size |
In industrial mixing language, the impeller is the rotating blade, while the agitator often refers to the overall mixing device or assembly (drive plus shaft plus impeller).
A rotating part with blades that transfers energy to a fluid to increase flow and pressure, commonly inside pumps.
Common designs are open, semi-open (semi-closed), and closed (enclosed/shrouded) impellers.
Dry running can damage pump parts very fast. Some sources warn damage can happen in about 20 to 30 seconds, and seals can fail in as little as 30 seconds in certain cases. Treat it as "avoid completely".
Common causes include cavitation, erosion, and corrosion, each with characteristic surface marks and performance loss.
Failure is usually the end result of damage mechanisms (cavitation, erosion, corrosion), poor operating conditions, clogging, or dry running that overheats components.
No fixed interval. Replace when inspection shows heavy wear or when performance drops. If an impeller wears or gets plugged, flow and pressure typically drop noticeably.
For many centrifugal pump applications, backward-curved blades are commonly cited as a high-efficiency choice, but it depends on design and operating point.
It depends on context. In washing machines they clean differently: agitators use a central post, impeller washers use a low-profile plate to move clothes through water flow.
Common signs include lower pressure, reduced flow, higher noise or vibration, and frequent seal issues. Worn or plugged impellers often cause overall performance drops on the pump curve.