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Salvatore Robuschi Centrifugal Pump Impeller Guide

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    Salvatore Robuschi is an Italian pump manufacturer that supplies industrial centrifugal pumps that Tapflo proudly distributes as part of our range here in the UK. Their centrifugal pumps have the advantage of being made bespoke for clients to suit specific applications due to the focus on a modular design they feature. The complete range can be built in Cast Iron, Stainless Steel (various grades), as well as custom alloys such as Duplex & Super Duplex Stainless Steel & Hastelloy B & C. Othe modular options, include the type of Centrifugal Pump Impeller required for your application so Tapflo UK have put together this Impeller Guide to help you find your ideal centrifugal pump solution.

    How does Salvatore Rouschi Centrifugal Pumps work?

    The main feature of any Centrifugal Pump is the internal rotors also called impellers that sit within the pump casing. When fluid enters the pump, the impeller begins to rotate causing a force for the velocity of the product to be pushed through to the discharged side. This then allows more fluid to enter and begin the ongoing operation of pumping the desired application.

    The section below gives an overview of the different centrifugal pump impeller types that can be fitted to the Salvatore Robuschi range and where they are best employed to obtain the most efficient and trouble-free operation from your pumping process.

    Centrifugal Pump Impeller Types

    RD: Closed Impeller

    RD Close Impeller Type

    Impeller Vanes are totally enclosed by 2 supports/shrouds at the front and rear.

    Closed Impeller Applications:

    • Generally used for clean fluids with less than 1% non-abrasive solids in suspension with a max size of 5-10mm.
    • No entrained gases.
    • Abrasive solids will reduce efficiency.

    Closed impellers are meant for clean fluids because the impeller will become blocked between the vanes, as well as between the impeller wear ring and impeller nut if the fluid contains solids in a high concentration of solids that are larger than the internal passage between the vanes. This will very quickly stop the pump from functioning and require constant cleaning and flushing.

    RB: Multi-Channel

    RB Multi-Channel Impeller Type Similar to the Closed type impeller, but they feature fewer vanes with larger internal passages.

    Multi-channel impeller applications:

    • Generally used for clean to slightly dirty fluids with less than 3-4% non-abrasive solids in suspension with a max size of 40-50mm.
    • No entrained gases.
    • Abrasive solids will reduce efficiency.

    In comparison to the RD Closed Impeller model, Multi-Channel impellers can be used for dirtier fluids because the impeller nut is internally mounted into the impeller and the internal passage between fewer vanes. This enables small particulates to flow across and through the impeller without clogging.

    RG: Semi-Open

    RG Semi-Open Impeller Type Exposed impeller vanes with a wearing plate fitted to the casing cover.

    Semi-open impeller applications:

    • Generally used for dirty fluids containing non-abrasive solids such as sediments, short fibres and crystals with a max size of 5-10mm in concentrations up to 15%.
    • Can also be used for fluids with entrained gases up to 10-12%.
    • Abrasive solids will reduce efficiency.

    Semi-Open impellers are better suited to dirty fluids as their operation removes any entrained solids and gases from the impeller wear plate and impeller nut. The processes that remove these are the internal circulation of the fluid from discharge back to suction within the pump and the rotation of the impeller blades against the wear plate.

    RC: Recessed Vortex

    RC Recessed Vortex Impeller Type Exposed vanes where the impeller doesn’t extend into the pump casing, essentially resulting in the casing becoming an open flow passage.

    Recessed Vortex impeller applications:

    • Generally used for heavily solids laden fluids or slurries where solids passage up to 150mm and concentration up to 30% are required.
    • Long fibrous and viscous slurries up to 1000 cPs can be transferred.
    • Abrasive particulates up to 5% concentration.
    • Entrained gases up to 20%.

    Recessed Vortex impellers are best suited to dirty/heavily solids laden fluids and slurries. They are capable of passing solids which are <90% of the discharge port ΓΈ. The impeller rotates in an area of the casing volute that is outside of the fluid pathway. This spinning action creates a vortex within the fluid, similar to that which can be seen when you flush the toilet.

    Recessed Vortex Impeller Pump Operation

    85% of the process fluid is transported from the suction port directly to the discharge port whilst only 15% comes into contact with the impeller. As a result, large solids can be easily passed through the pump by rotating the action of the fluid without necessarily coming into contact with either the impeller or mechanical seal


    Efficiencies for Recessed Vortex Centrifugal Pumps are generally lower than their traditional counterparts due to the flow circulation around the impeller and the flow pattern seen during operation. The process fluid rotates numerous times within the casing before eventually discharging out of the pump.

    Impeller Interchangeability

    Thanks to the versatile design of Salvatore Robuschi Centrifugal Pumps, it can be straightforward to re-purpose your existing pump for a different application by changing the impeller type. Careful consideration needs to be made with regards to the installed power and speed of the motor.


    To find out more about the Salvatore Robuschi range we offer at Tapflo UK, take a look at our product page or speak to a member of our sales team to find the ideal centrifugal pump design for your application.

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