Sanitary centrifugal pump for particle-laden liquids: choose an open impeller to pump fruit pieces without damage

In a centrifugal pump, liquid enters at the impeller center and is accelerated outward by the vanes. For clear liquids such as water or thin milk, a closed impeller (dual-disc design) provides high hydraulic efficiency. However, when the liquid contains fruit pieces, coconut flesh, fibers, or fruit pulp, the narrow gaps between the two discs of a closed impeller become points of restriction: particles get trapped, sheared, or cause the pump to vibrate and lose flow rate.

An open impeller removes one or both shroud discs, leaving the vanes exposed and creating a wide passage for solids. Combined with a large inlet port, particle-laden liquids pass through the pump with less impact, thereby preserving the shape of fruit pieces. This is why the CR series is positioned by CSF Inox for particle-laden and pulpy liquids, rather than for high-flow thin liquids.

The CR series is a single-stage volute centrifugal pump, meaning one impeller stage and one volute casing to direct the flow. The single-stage design suits moderate flow rates and low head — matching the majority of particle-laden transfer operations between tanks, through mild heat exchangers, or into filling lines. Because particle integrity is the priority, the CR is not aimed at high head applications; when the process requires long or elevated discharge runs, that section should be handled by a more appropriate pump.

The values above represent the upper limits of the product range; actual operating points depend on pump size, viscosity, and particle size of each specific fluid. When submitting a request, please describe the product type, piece size, flow rate, and discharge head clearly so the correct size can be selected.

Particle-laden liquids appear in many F&B production lines. Open-impeller pumps with large inlet ports are commonly used to convey the following products while maintaining the desired texture:

• Jams and fruit fillings with whole pieces (pineapple, mango, strawberry) for pastries, yogurt, and ice cream.
• Pulpy juices (orange juice with juice sacs, guava juice, aloe vera juice with pieces).
• Chunky tomato sauce, coarsely blended vegetable sauce, chili sauce with seeds.
• Fermented liquid or fiber-rich pulp in food processing.

Within the same plant, thin homogeneous liquids (milk, water, CIP solution) are better suited to closed-casing centrifugal pumps such as the CS series, which deliver higher flow rates and head. Separating the two fluid types allows each process stage to use the right pump type — avoiding product damage in particle-handling stages and avoiding insufficient head in thin-liquid stages. For further reference, see the food and beverage industry solutions page and the sanitary pump solutions for F&B page.

A pump for particle-laden liquids is still a piece of equipment that comes into direct contact with food, so it must comply with hygienic design requirements: AISI 316L stainless steel, low-roughness polished surfaces (typically Ra ≤ 0.8 µm to limit bacterial adhesion), no dead-leg cavities, self-draining design where possible, and quick-release clamp or DIN connections for ease of cleaning. Gaskets must use food-grade materials such as EPDM, FKM, or silicone depending on the product and temperature.

For particle-laden liquids, cleaning in place (CIP) is especially important because fruit residues tend to adhere. Open impellers actually offer one practical advantage in this regard: fewer enclosed gaps mean the CIP solution can more easily reach the hydraulic surfaces. However, turbulent flow conditions and sufficient CIP flow rate must be ensured to flush out remaining fruit fragments. When the process requires higher sterility (aseptic) or steam sterilization (SIP), the gasket temperature limits should be reviewed and the pump assembly should be configured to comply with the EHEDG, 3-A, or FDA standards applicable to the facility.