Pumps and Systems

Open Impeller Stainless Steel Pump: The Right Choice for Liquids with Solids

We explain how pumps with an open impeller and stainless steel casing transfer liquids containing solid particles with a low risk of clogging, and where they are used.

ORFA Technical TeamUpdated: Oct 30, 20263 min read

Open impeller stainless steel centrifugal pump

Not every process liquid is clean: food products with fruit pulp, washing water with residues or cooling liquids carrying particles can clog pumps with closed impellers. An open impeller stainless steel pump passes solid particles more easily thanks to its open impeller, while its stainless steel construction provides resistance to corrosion and chemical attack.

This article explains how open impeller pumps are built, how they differ from closed impeller pumps, where they are used and what to check when selecting one.

What Is an Open Impeller Stainless Steel Pump?

An open impeller pump is a centrifugal pump whose impeller vanes are not enclosed by front and back shrouds. The wide, open passages between the vanes let solid particles pass without getting trapped, which considerably reduces the risk of clogging. Wetted parts made of stainless steel provide corrosion resistance and are easy to clean.

Open vs Closed Impeller

Feature	Open impeller	Closed impeller
Design	Exposed vanes, no shrouds	Vanes between two shrouds
Solids handling	Better, low clogging risk	Limited, may clog with fibres/solids
Hydraulic efficiency	Usually lower	Usually higher
Cleaning and inspection	Easy	More difficult
Typical liquid	Liquids with particles, slightly viscous liquids	Clean liquids

Applications

Clean and dirty water: General water transfer and circulation.
Chemical transfer: Pumping chemicals that are compatible with stainless steel.
Food and beverage: Transfer of products containing solids such as fruit pulp.
Pharmaceuticals and cosmetics: Transfer of liquids containing particles or with moderate viscosity.
Wastewater treatment: Transfer of domestic and industrial wastewater.
Washing systems: Transfer and recirculation of washing water containing residues.
Cooling circuits: Circulation of cooling liquids that may carry particles.

Technical Features and Benefits

Stainless steel casing and impeller: Resistant to corrosion and many chemicals, easy to clean.
Open impeller design: Lets solids pass more easily and reduces the risk of clogging.
Wide temperature range: Suitable for various process temperatures; limits depend on the model and seal material.
Flexible connection options: Easy to integrate into existing pipework.
Easy maintenance: The open impeller simplifies cleaning and inspection.
Long service life: Durable and trouble-free when used with suitable liquids at the right duty point.

Tip: With an open impeller, the clearance between impeller and casing directly affects efficiency. With abrasive particles this clearance grows over time and performance drops; regular inspection and, where needed, adjustment or part replacement keep performance up.

Selection Checklist

Particle size, quantity and abrasiveness
Liquid viscosity and temperature
Chemical compatibility of the stainless steel grade with the liquid (especially chloride-containing liquids)
Required flow and head
Mechanical seal type and material

Frequently Asked Questions

When should an open impeller pump be used?

When the liquid contains solid particles, fibres or residues that could clog a closed impeller. For clean liquids, a closed impeller is usually more efficient.

Is an open impeller stainless steel pump resistant to all chemicals?

No. Stainless steel resists many liquids, but some acids and chloride-containing liquids can cause corrosion. Material compatibility must always be checked for chemical applications.

Why is the efficiency of an open impeller pump lower?

Some liquid leaks back through the gap between the vanes and the casing. This internal leakage reduces hydraulic efficiency slightly compared with a closed impeller.

Conclusion

Open impeller stainless steel pumps are a suitable solution for transferring liquids that contain solids or have moderate viscosity with a low risk of clogging. Selected with materials and seals that match the liquid, they offer reliable, long service. Browse our open impeller stainless steel pumps page for available models, or ask the ORFA sales team for advice on your application.

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