A volute module

A single-stage centrifugal pump comprising a volute module further comprising a body defining at least part of an impeller chamber as well as a volute at least partially surrounding the impeller chamber;

• an unencapsulated impeller rotatable about a drive axis in the impeller chamber, wherein the volute module is configured such that a rotating flow of pump fluid created by the unencapsulated impeller is directed towards the volute which channels the rotating flow of pump fluid towards a pressure outlet of the volute module;
• and an initial-stage impeller housing in the impeller chamber, configured for when the pump housing is used as part of a multi-stage centrifugal pump, wherein the initial-stage impeller housing encapsulates another impeller rotatable about the drive axis and defines guide vanes directing a flow of a pump fluid from the impeller of the initial-stage impeller housing towards a subsequent stage impeller of a subsequent stage of the multi-stage centrifugal pump, wherein the subsequent stage impeller is formed by the unencapsulated impeller or by a further intermediate-stage impeller housing which encapsulates a further impeller rotatable about the drive axis and defines guides vanes;
• and
• a motor housing attached to the volute module, wherein the volute module comprises the unencapsulated impeller but no initial-stage impeller housing and no intermediate stage impeller housing.

A multi-stage centrifugal pump comprising;

• a volute module further comprising a body defining at least part of an impeller chamber as well as a volute at least partially surrounding the impeller chamber;
• an unencapsulated impeller rotatable about a drive axis in the impeller chamber, wherein the volute module is configured such that a rotating flow of pump fluid created by the unencapsulated impeller is directed towards the volute which channels the rotating flow of pump fluid towards a pressure outlet of the volute module;
• and an initial-stage impeller housing in the impeller chamber, configured for when the pump housing is used as part of a multi-stage centrifugal pump, wherein the initial-stage impeller housing encapsulates another impeller rotatable about the drive axis and defines guide vanes directing a flow of a pump fluid from the impeller of the initial-stage impeller housing towards a subsequent stage impeller of a subsequent stage of the multi-stage centrifugal pump, wherein the subsequent stage impeller is formed by the unencapsulated impeller or by a further intermediate-stage impeller housing which encapsulates a further impeller rotatable about the drive axis and defines guides vanes;
• and
• a motor housing, wherein the volute module comprises the unencapsulated impeller and the initial-stage impeller housing, wherein the volute module further comprises one or more intermediate stage impeller housings, wherein each inter-mediate-stage impeller housing encapsulates an impeller rotatable about the drive axis and comprises guide vanes directing a flow of a pump fluid from the impeller of the respective intermediate-stage impeller housing towards an impeller of a sub-sequent stage of the multi-stage pump, wherein the subsequent stage of the multi-stage is formed by the unencapsulated impeller or by another intermediate-stage impeller housing.