Quick answer
Top entry agitators are mounted vertically on the tank roof and can use any impeller type for blending, suspension, reaction or heat transfer across all viscosities and tank sizes. Side entry agitators are mounted horizontally on the tank sidewall using propeller impellers, and are suited only to large tanks above 10,000 litres with low-viscosity liquids below 500 cP. Choose a top entry agitator for chemical reactors, pharmaceutical vessels, water treatment tanks, food processing and any application requiring controlled mixing intensity, solids suspension or high viscosity handling. Choose a side entry agitator for large crude oil storage tanks, petroleum product blending, molasses storage or water storage homogenisation where top entry installation is impractical. Premix Technologies manufactures both top entry and side entry agitators in Ahmedabad for chemical, pharma, oil and gas and water treatment industries across India.
The Most Common Agitator Selection Question
When a process engineer or plant manager needs to specify mixing equipment for a new or existing tank, one of the first decisions is whether to use a top entry or side entry agitator. Both configurations achieve mixing but serve different purposes, suit different tank sizes and have different installation, operating and maintenance characteristics.
What is a Top Entry Agitator?
A top entry agitator is mounted on the top of the tank, with the motor and gearbox sitting above the vessel. The shaft extends downward through a top-mounted nozzle into the liquid, with impellers positioned at the correct elevation for the mixing objective. Top entry agitators are the most versatile configuration — they can accommodate almost any impeller type, shaft length, power level and tank geometry.
When to Use a Top Entry Agitator
- Process tanks from 500 litres to several thousand cubic metres
- Applications requiring precise mixing intensity or specific flow patterns
- High-viscosity mixing requiring anchor, helical ribbon or gate impellers
- Reactor vessels requiring mechanical seals for pressure or vacuum service
- Pharmaceutical, food and chemical processes requiring controlled mixing conditions
- Tanks where the liquid level varies significantly during operation
What is a Side Entry Agitator?
A side entry agitator is mounted on the side wall of the tank, with the motor and gearbox outside the vessel and only the shaft and impeller inside. The shaft enters through a side nozzle, typically angled downward and offset from the tank centreline to create a rotating flow pattern. Side entry agitators almost always use propeller-type impellers to generate high axial flow with low power consumption.
When to Use a Side Entry Agitator
- Large storage tanks and blending tanks above 50,000 litres
- Petroleum product blending and homogenisation in crude oil tanks
- Molasses, ethanol, vegetable oil and liquid food ingredient storage
- Water storage tank blending and temperature uniformity
- Tanks with floating roofs or where top entry installation is not possible
Key Technical Differences
Shaft Orientation and Flow Pattern
A top entry agitator shaft is vertical and generates flow patterns that depend entirely on impeller selection — axial flow for top-to-bottom circulation, radial flow for outward horizontal flow. A side entry agitator shaft is horizontal and deliberately offset from the tank centreline, creating a sweeping rotational flow ideal for blending and preventing stratification but not suitable for suspension, reaction or viscous mixing.
Power and Efficiency
Side entry agitators are highly efficient for low-viscosity blending in large tanks. A pair of side entry propeller agitators can blend a 10,000 m³ crude oil tank using only 30–75 kW of power. For smaller tanks below 50 m³, top entry agitators are more efficient and flexible.
Viscosity Range
Top entry agitators handle the full viscosity range from water-like liquids to thick pastes above 100,000 cP using appropriate impeller types. Side entry agitators are limited to low-viscosity liquids below approximately 500 cP. Above this viscosity, the propeller cannot develop the flow pattern needed for effective blending.
Summary: Which to Choose
- Tank size: Top entry → any size; Side entry → large tanks above 10 m³, typically 50–100,000 m³
- Liquid viscosity: Top entry → full range; Side entry → low viscosity only (<500 cP)
- Impeller type: Top entry → any; Side entry → propeller only
- Mixing objective: Top entry → blending, suspension, reaction, heat transfer; Side entry → blending and stratification prevention
- Typical industries: Top entry → chemical, pharma, water treatment, food; Side entry → petroleum, biofuels, large water storage
Conclusion
Premix Technologies manufactures both top entry and side entry agitators for industrial process applications. Our engineering team selects the correct impeller type, shaft design, sealing arrangement and motor-gearbox combination based on your tank geometry, liquid properties, mixing objective and site conditions. Contact us at sales@premixtechnologies.com or explore our industrial agitator range.
Frequently Asked Questions
How can Premix Technologies help?
Premix supports equipment selection, sizing, MOC, GA drawing, fabrication, testing and quotation.
What data is required?
Share application, liquid properties, tank size, flow rate, pressure, temperature and automation need.
Can Premix customize equipment?
Yes. Premix manufactures customized agitators, dosing skids, metering packages and static mixers.